Steel Bumper Systems

Front Cover Vehicle Illustrations:

Top Section, Left to Right:Chevy Silverado - stamped facebar, 50XLF steelP/T Cruiser - stamped reinforcing beam, 120XF steelHonda Odyssey - roll formed reinforcing beam, 140T steelLincoln Navigator - stamped reinforcing beam, 80XLF steel

Bottom Section, Left to Right:Dodge Durango - stamped reinforcing beam, 50 XLF steelFord Mustang - roll formed reinforcing beam, M190HT steelFord F-150 - stamped facebar, 50XLF steelJeep Wrangler - roll formed facebar, 120XF steel

Steel Bumper Systems forPassenger Cars and Light Trucks

Revision Number ThreeJune 30, 2006

American Iron and Steel Institute

Copyright © American Iron and Steel Institute

This publication is for general information only. The information in itshould not be used without first securing competent advice withrespect to its suitability for any given application. The publication ofthe information is not intended as a representation or warranty onthe part of American Iron and Steel Institute - or any other personnamed herein - that the information is suitable for any general or particular use or freedom from infringement of any patent or patents.Anyone making use of the information assumes all liability from suchuse.

First Edition, June 1998First Revision, March 15, 2001Second Revision, February 15, 2003Third Revision, June 30, 2006

Contents

Contents i

Figures vi

Tables vii

Preface ix

Introduction x

Objective xiii

1. Bumper systems and components1.1 Bumper systems 1-1

1.1.1 System selection

1.1.2 Metal facebar system

1.1.3 Plastic fascia and reinforcing beam system

1.1.4 Plastic fascia, reinforcing beam and energy absorption system

1.2 Bumper components 1-3

1.2.1 Fascia

1.2.2 Energy absorbers

1.2.3 Facebar

1.2.4 Reinforcing beam

2. Steel materials 2-1

2.1 Introduction 2-1

2.2 Typical properties of steel grades for facebars 2-2

2.3 Typical properties of steel grades for brackets, supports, and reinforcing beams 2-2

2.4 Elongation versus as-shipped (steel mill) yield strength 2-5

2.5 Elongation versus after-fabrication yield strength 2-5

2.6 Yield strength versus strain rate 2-9

2.7 Sheet steel descriptors 2-11

2.8 SAE J2329 Low-carbon sheet steel 2-12

2.8.1 Steel grade

2.8.2 Types of cold rolled sheet

2.8.3 Types of hot rolled sheet

2.9 SAE J2340 Dent resistant, high-strength and ultra high-strength sheet steel 2-13

2.9.1 Steel grade

2.9.2 Steel type

2.9.3 Hot rolled, cold reduced and metallic coated sheet

2.9.4 Surface conditions for cold reduced and metallic coated sheet

2.9.5 Conditions for hot rolled sheet

i

Contents

2.10 SAE J1562 Zinc and zinc-alloy coated sheet steel 2-15

2.10.1 Galvanizing processes

2.10.2 Types of coatings

2.10.3 Coating mass

2.10.4 Surface quality

2.10.5 Coated sheet thickness

2.10.6 Coating designations

2.11 SAE J403 Carbon steel chemical compositions 2-17

2.11.1 Carbon sheet steel

2.11.2 Boron sheet steel

2.12 SAE J405 Wrought stainless steels 2-18

2.13 SAE Specification and ordering descriptions 2-19

2.14 ASTM A463 Aluminized Sheet Steel 2-21

3. Manufacturing processes3.1 Stamping 3-1

3.1.1 Stretching

3.1.2 Drawing

3.1.3 Bending

3.1.4 Bending and straightening

3.1.5 Forming limits

3.2 Roll forming 3-5

3.3 Hydroforming 3-7

3.4 Hot forming 3-8

3.5 Bumper beam coatings 3-9

3.5.1 Zinc or zinc-iron coatings

3.5.2 Aluminum coating

3.5.3 Polishing

3.5.4 Chromium coating

3.5.5 Conversion coating

3.5.6 Electrocoating (E-coating)

3.5.7 Paint coating

3.5.8 Autodeposition coating

3.5.9 Powder coating

ii

Contents

4. Manufacturing considerations4.1 Forming considerations 4-1

4.1.1 Guidelines for roll forming high-strength steel

4.1.2 Guidelines for roll forming ultra high-strength steel

4.1.3 General guidelines for stamping high-strengthand ultra high-strength steels

4.1.4 Guidelines for hat sections stamped from high-strength or ultra high-strength steels

4.1.5 Rules of thumb for high-strength steel stampings

4.2 Welding considerations 4-214.2.1 Steel chemistry

4.2.2 High-strength and ultra high-strength steels

4.2.3 Welding processes

4.2.3.1 Gas metal arc welding (GMAW)

4.2.3.2 Flux cored arc welding (FCAW)

4.2.3.3 Resistance spot welding (RSW)

4.2.3.4 Resistance projection welding (RPW)

4.2.3.5 Resistance seam welding (RSeW)

4.2.3.6 Resistance projection seam welding (RPSeW)

4.2.3.7 High frequency and induction resistance seam welding (RSeW-HF&I)

4.2.3.8 Upset welding (UW)

4.2.3.9 Friction welding (FRW)

4.2.3.10 Laser beam welding (LBW)

4.2.3.11 Laser beam and plasma arc welding (LBW/PAW)

4.2.4 Weldability of bumper materials

4.2.5 Ranking of welding processes

5. Design concepts5.1 Sweep (roll formed sections) and depth of draw (stampings) 5-1

5.2 Tailor welded blanks 5-1

5.3 Leading benchmark bumper beams 5-8

5.4 Bumper weights, materials and coatings 5-16

5.5 Current steel bumper design - North American passenger cars and minivans 5-325.5.1 Typical bumper design for 5mph (8km/h) low speed system

5.5.2 IIHS/CU design path

5.5.3 Canadian/NHTSA design path

5.6 Current steel bumper design - North American pickups, full size vans and sport utilities 5-36 5.6.1 Flow chart for 2.5mph (4 km/h) low speed system


5.6.3 NHTSA design path

5.7 Auto/Steel Partnership high speed steel bumper design - North American passenger cars 5-395.7.1 Quantech design criteria for high speed steel bumper system

5.7.2 Flow Chart for high speed system

iii

Contents

5.8 Bumper design for pedestrian impact 5-42

5.8.1 Impact tests

5.8.2 EuroNCAP leg to bumper impacts with a “leg-form” impactor

5.8.3 Government regulations

5.8.4 Design approaches

5.8.4.1 Cushioning the impact

5.8.4.2 Supporting the lower limb

5.8.5 Design solutions

6. Relevant safety standards in North America and Europe 6-1

6.1 United States National Highway Traffic Safety Administration (49CFR), Part 581 Bumper Standard 6-3

6.1.1 Requirements

6.1.2 Pendulum corner impacts

6.1.3 Pendulum longitudinal impacts

6.1.4 Impacts into a fixed collision barrier

6.2 Canadian Motor Vehicle Safety Regulations Standard 215 6-8

6.2.1 Requirements




6.3 Comparison between United States and Canadian Bumper Regulations 6-9

6.3.1 Requirements




iv

6.4 Insurance Institute for Highway Safety: Low-Speed Crash Test Protocol 6-10

6.4.1 Requirements

6.4.2 Test vehicles

6.4.3 Full-width flat-barrier impact

6.4.4 Right front into 30 degree angle-barrier impact

6.4.5 Rear into pole impact

6.5 Consumers Union bumper-basher tests 6-11

6.5.1 Requirements

6.5.2 Bumper-basher

6.5.3 Center impact

6.5.4 Off-center impact

6.5.5 Corner impact

6.6 Research Council for Automotive Repairs (RCAR) Low-Speed Offset Crash Test 6-12

6.6.1 Requirements

6.6.2 Test vehicle

6.6.3 Front impact

6.6.4 Rear impact

6.6.5 Damageability and repairability

Contents

7. Steel versus aluminum and composite bumper beams 7-1

7.1 Types of bumper beams 7-1

7.2 Cost of bumper beams 7-2

8. Conclusions 8-1

9. References 9-1

v

NORTH AMERICAN BUMPER SYSTEM MARKET SHARE BY UNITS FOR KNOWN SYSTEMS xii1.1 COMMON BUMPER SYSTEMS 1-21.2 COMMON REINFORCING BEAM CROSS SECTIONS 1-52.1 ELONGATION VERSUS YIELD STRENGTH: STEEL AS-SHIPPED FROM THE

STEEL MILL 2-62.2 ELONGATION VERSUS YIELD STRENGTH: STEEL AFTER FABRICATION BY

BUMPER SUPPLIER 2-72.3 INCREASE IN YIELD STRENGTH THROUGH WORK HARDENING AND BAKE

HARDENING 2-82.4 STRESS VERSUS STRAIN AT DIFFERENT STRAIN RATES FOR TRIP 600 2-102.5 STRESS VERSUS STRAIN AT DIFFERENT STRAIN RATES FOR DP 600 2-103.1 TYPICAL CIRCLE GRID PATTERN 3-23.2 REPRESENTATION OF STRAINS BY ETCHED CIRCLES 3-33.3 TYPICAL FORMING LIMIT DIAGRAM 3-63.4 COATINGS: FRONT REINFORCING BEAMS 3-103.5 COATINGS: REAR REINFORCING BEAMS 3-114.1 a) RULES OF THUMB - SPRINGBACK 4-44.1 b) RULES OF THUMB - SPRINGBACK 4-54.1 c) RULES OF THUMB - SPRINGBACK 4-64.2 RULES OF THUMB - DIE FLANGE STEELS 4-74.3 RULES OF THUMB - HAT SECTION 4-84.4 RULES OF THUMB - V-CHANNEL 4-94.5 RULES OF THUMB - RADIUS SETTING 4-104.6 a) RULES OF THUMB

- COMBINATION FORM AND FLANGE DIE 4-114.6 b) RULES OF THUMB

- COMBINATION FORM AND FLANGE DIE 4-124.7 RULES OF THUMB - FORMING BEADS 4-134.8 RULES OF THUMB - FORMING AN EMBOSS 4-144.9 RULES OF THUMB - EDGE SPLITTING 4-154.10 RULES OF THUMB - PART DESIGN 4-164.11 RULES OF THUMB - DIE CONSTRUCTION 4-174.12 RULES OF THUMB - DEVELOPED BLANKS 4-184.13 RULES OF THUMB - TRIMMING 4-194.14 RULES OF THUMB - DIE SHEAR 4-204.15 GAS METAL ARC WELDING (GMAW) 4-254.16 FLUX CORED ARC WELDING (FCAW) 4-284.17 RESISTANCE SPOT WELDING (RSW) 4-304.18 RESISTANCE PROJECTION WELDING (RPW) 4-304.19 RESISTANCE SEAM WELDING (RSeW) 4-344.20 RESISTANCE PROJECTION SEAM WELDING (RPSeW) 4-344.21 HIGH FREQUENCY AND INDUCTION RESISTANCE SEAM WELDING

(RSeW-HF&I) 4-374.22 UPSET WELDING (UW) 4-374.23 FRICTION WELDING (FRW) 4-414.24 LASER BEAM WELDING (LBW) 4-414.25 HARDNESS IN HEAT-AFFECTED ZONE OF ARC WELDS 4-474.26 RESISTANCE SPOT WELDING COMPARISON 4-485.1 DEFINITION OF SWEEP 5-25.2 DEFINITION OF DEPTH OF DRAW 5-55.3 EXAMPLES OF TAILOR WELDED BLANKS 5-65.4 ROLL FORMED BEAMS 5-95.5 STAMPED BEAMS 5-115.6 TYPICAL BUMPER DESIGN FOR 5mph LOW SPEED SYSTEM

NORTH AMERICAN PASSENGER CARS AND MINIVANS 5-35

Figures

vi

5.7 TYPICAL BUMPER DESIGN FOR 2.5mph LOW SPEED SYSTEM NORTHAMERICAN PICKUPS, FULL SIZE VANS AND SPORT UTILITIES 5-38

5.8 AUTO/STEEL PARTNERSHIP BUMPER DESIGN FOR HIGH SPEED SYSTEMNORTH AMERICAN PASSENGER CARS 5-41

5.9 EuroNCAP PEDESTRIAN TESTS 5-455.10 EuroNCAP LEG FORM IMPACTOR 5-465.11 EuroNCAP “LEG FORM” IMPACT CRITERIA (2010) 5-476.1 IMPACT PENDULUM 6-56.2 IMPACT PENDULUM 6-66.3 LOCATIONS OF PLANES A and B 6-76.4 SAMPLE IMPACT APPARATUS 6-76.5 RCAR FRONT CRASH PROCEDURE 6-146.6 RCAR REAR CRASH PROCEDURE 6-15

Figures

vii

2.1 STEEL GRADES FOR POWDER COATED, PAINTED AND CHROME PLATED FACEBARS 2-3

2.2 STEEL GRADES FOR BRACKETS, SUPPORTS AND REINFORCING BEAMS 2-4

2.3 SAE J2329 LOW-CARBON COLD ROLLED SHEET — MECHANICAL PROPERTIES 2-22

2.4 SAE J2329 LOW-CARBON HOT ROLLED SHEET — MECHANICAL PROPERTIES 2-22

2.5 SAE J2329 LOW-CARBON HOT & COLD ROLLED SHEET — CHEMICAL COMPOSITION 2-23

2.6 SAE J2340 DENT RESISTANT SHEET STEEL 2-232.7 SAE J2340 HIGH-STRENGTH SOLUTION STRENGTHENED AND LOW-ALLOY

SHEET STEEL 2-24

2.8 SAE J2340 HIGH-STRENGTH RECOVERY ANNEALED SHEET STEEL 2-24

2.9 SAE J2340 ULTRA HIGH-STRENGTH DUAL PHASE & MARTENSITE SHEET STEEL 2-25

2.10 SAE J1562 COATING MASS FOR GALVANIZED SHEET STEEL 2-26

2.11 SAE J403 CARBON STEEL COMPOSITIONS FOR SHEET 2-27

2.12 SAE J405 CHEMICAL COMPOSITIONS OF WROUGHT STAINLESS STEELS 2-27

4.1 SAE J2340 STEELS AND STRENGTH GRADES. 4-23

4.2 SAE J2340 CHEMICAL LIMITS ON UNSPECIFIED ELEMENTS. 4-23

4.3 RANKING OF WELDING PROCESSES BY BUMPER MATERIAL 4-44

5.1 SWEEP NUMBERS (CAMBER, X, INCHES). 5-3

5.2 SWEEP NUMBERS (CAMBER, X, MILLIMETERS). 5-4

5.3 LEADING BENCHMARK BUMPER BEAMS. 5-14

5.4 ROLL FORMED BUMPER BEAMS - THICKNESS, WEIGHT, MATERIAL, COATINGS AND SWEEP - BEAMS PRODUCED IN THE 2004 CALENDAR YEAR 5-17

5.5 COLD STAMPED BUMPER BEAMS - THICKNESS, WEIGHT, MATERIAL,COATINGS AND DEPTH-OF-DRAW - BEAMS PRODUCED IN THE2004 CALENDAR YEAR 5-25

5.6 HOT FORMED BUMPER BEAMS - THICKNESS, WEIGHT, MATERIAL COATINGSAND DEPTH-OF-DRAW - BEAMS PRODUCED IN THE 2004 CALENDAR YEAR 5-29

6.1 RELEVANT SAFETY STANDARDS IN NORTH AMERICA AND EUROPE. 6-2

7.1 COST OF STEEL FACEBAR SYSTEMS 7-3

7.2 COST OF STEEL REINFORCING BEAM SYSTEMS 7-3

7.3 COST OF REINFORCING BEAMS 7-3

7.4 WEIGHT OF REINFORCING BEAM SYSTEMS 7-4

Tables

viii

Preface

This publication is the third revision of Steel Bumper Systems forPassenger Cars and Light Trucks. It is a living document. Asexperience in its use is gained, further revisions and expansionswill be issued.

This publication brings together materials properties, product designinformation, manufacturing information and cost information. Ithas been prepared to suit the needs of OEM bumper stylists,bumper engineers and bumper purchasers. It is also intended tosuit the needs of the Tier 1 and 2 bumper suppliers and steelindustry marketing personnel.

This publication was prepared by the Bumper Project Group of theAmerican Iron and Steel Institute. The efforts of the followingmembers are acknowledged:

Willie Bernert, ChairpersonDofasco Inc.

Scott BulychA.G. Simpson Co. Limited

Jim CranCran Associates Inc.

DeWayne EgleCosma

Karl HenseleitSKD Automotive Group

Tony HersbergerBenteler Automotive

Chris KantnerMittal Steel USA

Mark KochShape Corporation

Conrad KudelkoFord Motor Company

Michael MihelichDaimlerChrysler Corporation

Raj MohanSeverstal North America Inc.

Scott StokfiszGeneral Motors Corporation

Ming TangFlex-N-Gate

Thomas VikstromPullman Industries, Inc.

Eric WelteAK Steel Corporation

Ben ZabikMeridian Automotive Systems

American Iron and Steel InstituteJune 30, 2006

ix

Introduction

In the 1997 model year, almost 28 million bumper units weresupplied to the North American (Canadian and U.S.) originalequipment manufacturers (OEM’s). Of these, 76% were steel,17.6% composite and 6.4% aluminum (Reference 1.1). About11.5 million steel units were reinforcing beams covered by a plasticfascia, about 5.7 million steel units were chrome-plated facebarsand the remaining 4.0 million steel units were painted facebars. Bymanufacturing process, approximately 60% of the steel units werestamped and 40% roll formed. In total, about 300,000 tons of steelwere consumed in the 1997 model year by the North Americanbumper reinforcing beam and facebar market.

Bumper systems have changed drastically over the last 20 to 30years. More demanding government safety regulations and differentstyling concepts have resulted in new designs. For example,reinforcing beams covered by plastic fascias entered the scene inthe early 1970’s. Styling fashion has changed appearance valuesfrom almost 100% chrome-plated facebars to predominately fasciasystems that are color coordinated with the body. The growth oflight trucks, minivans and sport utility vehicles created two classesof bumper systems in the eyes of the engineering world: one forpassenger cars and one for the broad grouping of light trucks.Safety concerns have resulted in the bumper beam becoming a partof the structural load path.

Materials have also changed dramatically. With emphasis onvehicle performance, especially fuel economy, vehicle weightconsiderations were on top of most automotive engineers’ projectlists. High-strength and ultra high-strength steels were developed.These permitted designers to reduce sheet metal thickness, henceweight.

Business management practices have changed. In the past, thevehicle assemblers (OEM’s) produced most of the bumper systems,with only a handful of relatively small independent stamperssupplementing the market’s total needs. Now, the OEM’s are aminor manufacturing player, relying heavily on a growing industrydevoted in some cases to producing nothing but bumpercomponents and systems. In fact, most of these independentmanufacturers supply all of the design details and verificationtesting. The OEM’s supply the big picture requirements, i.e., howthe bumper system fits into the overall vehicle appearance, how itwill be affixed to the vehicle, weight limitations, outer boundarysize limitations, etc.

Bumper systems, like all automotive components, are still subject toconstant change. The shift to fascia-covered reinforcing beamsystems from facebars continues in the light truck area. The shiftback to steel from more costly aluminum and composite systemscontinues. The trend to higher yield strength steel continues. Thereis more integration with fog lamps, head lights, turning lights andgrills. The OEM’s are increasingly relying on their bumper suppliersto provide technical innovations.

x

For reasons of low cost and light weight, steel is well positioned inthe current bumper system market. Further, even though thismarket is undergoing constant change, steel is strengthening itsposition. As shown in the figure on page xii, steel’s market sharewas forecasted to increase from 76.0% in the 1997 model year to84.2% in the 2001 model year. Over this same period, aluminum’sshare dropped from 6.4% to 1.9% and the share held bycomposites decreased from 17.6% to 13.9%.

The bumper market, at 300,000 tons per year of mainly high-strength steel, is important to the North American steel industry.For this reason, the Automotive Applications Committee of theAmerican Iron and Steel Institute (AISI) established a BumperProject Group. In view of the fact there is little, if any, publishedinformation on bumper systems, the Bumper Project Groupprepared this technical information bulletin to provide fundamentalbackground information on North American bumper systems.

xi

7%

6%

5%

4%

3%

2%

1%

NORTH AMERICAN BUMPER SYSTEM MARKETSHARE BY UNITS FOR KNOWN SYSTEMS

1997 1998 1999 2000 2001

ALUMINUM

18%

15%

12%

9%

1997 1998 1999 2000 2001

COMPOSITES

90%

80%

70%

60%

50%

1997 1998 1999 2000 2001

STEEL

Source: CSM Corporation (Reference 1.1)

xii

Objective

The purpose of this publication is to increase the reader’sunderstanding of passenger car and light truck bumper systems.It is an overview of an automotive component system, which hasundergone significant change in recent years. The informationprovided is aimed at automotive industry design, manufacturing,purchasing and safety related staffs; and steel industry sales andmarketing groups. The emphasis is on materials, design, manufacturing, government regulations and cost. It is a livingdocument and revisions and additions will be made as experienceis gained. The AISI Bumper Project Group hopes this publicationwill increase the reader’s knowledge of bumper systems and helpovercome engineering challenges.

xiii

1-1

1. Bumper systems and components

1.1 Bumper systems

There are several factors that an engineer must consider whenselecting a bumper system. The most important factor is the abilityof the bumper system to absorb enough energy to meet the OEM’sinternal bumper standard. Another important factor is the bumper’sability to absorb energy and stay intact at high-speed impacts.Weight, manufacturability and cost are also issues that engineersconsider during the design phase. Both initial bumper cost andrepair cost are important. The formability of materials is importantfor high-sweep bumper systems. Another factor considered is recyclability of materials, which is a definite advantage for steel.

As shown in Figure 1.1, there are four bumper systems in commonuse today:

1. Metal facebar

2. Plastic fascia and reinforcing beam

3. Plastic fascia, reinforcing beam and mechanicalenergy absorbers

4. Plastic fascia, reinforcing beam and foam or honeycomb energy absorber

1.1.2 Metal facebar system

1.1.1 System selection

A metal facebar system, as shown in Figure 1.1 A, consists of asingle metallic bumper that decorates the front or rear end of avehicle and acts as the primary energy absorber in a collison.

The bumper regulations in the United States require passenger carsto withstand a 2.5 mph (4 km/h) impact at the curb position plus orminus two inches (50mm) with no visual damage and no damageto safety related items. The Canadian passenger car regulations callfor a 5 mph (8 km/h) impact, however limited damage is permitted.The North American OEM’s voluntarily design their passenger carbumpers to withstand a 5 mph (8 km/h) impact with no visualdamage and no damage to safety items. Current facebar systemscan only withstand a 2.5 mph (4 km/h) impact at the curb positionplus or minus 2 inches (50mm) with no visual damage and nodamage to safety items. For this reason, the use of current facebarsystems is restricted to light trucks. The aesthetics of facebarsmatch the styling trend for full size vans, pickups and sportutilities. Thus, most facebars are presently being applied to thesevehicles.

If the design standard for light truck bumpers were to rise to the 5mph (8 km/h) voluntary passenger car standard, then the facebarsystems used on full size vans, pickups and sport utilities wouldhave to be redesigned. For the reason of weight, such redesignswould likely revert to systems that employ a reinforcing beam.

1-2

FIGURE 1.1COMMON BUMPER SYSTEMS

1.1.3 Plastic fascia and reinforcing beam system

This system, as shown in Figure 1.1 B, consists of a plastic fasciaand a reinforcing beam that is fastened directly to the vehicle frameor motor compartment rails. It is primarily used in Europe andJapan, where bumper regulations are less stringent than those inNorth America. On many vehicles in Europe and Japan, thereinforcing beam in this system also serves as the first structuralcross-member. While this arrangement leads to a small sacrifice inbumper performance, it increases vehicle crashworthiness. If thereinforcing beam is part of the body-in-white, the favored materialis steel because of the structural requirements associated with across-member. Also, steel is fully compatible with the body-in-white E-coat and paint systems used by the OEM’s.

1.1.4 Plastic fascia, reinforcing beam and energy absorption system

Bumper systems with a plastic fascia, reinforcing beam and energyabsorption are used primarily in North America. These readily meetthe 5 mph (8 km/h) voluntary bumper standard set by the NorthAmerican OEM’s. While all passenger cars and most minivans inthe United States and Canada have this type of system, the methodof energy absorption varies. Energy can be absorbed by amechanical absorber (Figure 1.1 C), by foam or honeycomb (Figure1.1 D), or by the reinforcing beam itself (Figure 1.1 B).

1.2 Bumper components

Bumper fascias (Figure 1.1) are designed to meet several requirements. They must be aerodynamic to control the flow of theair around the car and the amount of air entering the enginecompartment. They must be aesthetically pleasing to the consumer.Typical fascias are styled with many curves and ridges to givebumpers dimension and to distinguish vehicles from competingmodels. Another requirement of bumper fascias is that they be easyto manufacture and light in weight. Virtually all fascias are madefrom one of three materials: polypropylene, polyurethane orpolycarbonate.

1.2.1 Fascia

Energy absorbers (Figure 1.1) are designed to absorb a portion ofthe kinetic energy from a vehicle collision. Energy absorbers arevery effective in a low speed impact, where the bumper springsback to its original position. Energy absorber types include foam,honeycomb and mechanical devices. All foam and honeycombabsorbers are made from one of three materials: polypropylene,polyurethane or low-density polyethylene. Mechanical absorbersare metallic and resemble shock absorbers. However, mechanicalabsorbers have several times the weight of a foam or honeycombabsorber and receive very limited usage. In some bumper systems,the reinforcing beam itself is designed to absorb energy andseparate energy absorbers are not required.

1.2.2 Energy absorbers

1-3

Facebars (Figure 1.1) are usually stamped from steel with lots ofplastic or stainless steel trim to dress them up. A small volume offacebars is produced from aluminum. Steel facebars, for formabilityreasons, are usually made from steels with a low to medium yieldstrength. Thus, facebars are quite thick. This thickness (plus thefact facebars are deep and have large wrap around ends) givesfacebars a relatively heavy weight. After stamping, steel facebarsare chrome plated or painted for appearance and corrosionprotection reasons.

1.2.3 Facebar

The reinforcing beams (Figure 1.1) are key components of thebumper systems that employ them. Reinforcement beams helpabsorb the kinetic energy from a collision and provide protection tothe rest of the vehicle. By staying intact during a collision, beamspreserve the frame. Design issues for reinforcing beams includestrength, manufacturability, weight, recyclability and cost.

Steel reinforcing beams are stamped, roll formed or made by thePlannja process. Typical cross sections are shown in Figure 1.2.A stamped beam is advantageous in high-volume production andoffers complex shapes. However, the stamping process is capitalintensive and the process itself requires good formability from thesteel. The Plannja process is a hot stamping process, which wasdeveloped in Sweden. While it results in high-strength beams, it isrelatively expensive due to its low production rate. Roll formedbeams account for the majority of the steel reinforcing beams usedtoday. Common cross sections for roll formed beams are box, C orchannel, and hat. Typically, these cross sections are made of ultrahigh-strength steels at very thin gauges. A back plate is sometimeswelded to an open channel or hat section to create a box section.

All steel reinforcing beams receive corrosion protection. Somebeams are made from hot-dip galvanized or electrogalvanizedsheet. The zinc coating on these products provides excellentcorrosion protection. Other beams are protected after fabricationwith a paint system such as E-coat.

1.2.4 Reinforcing beam

1-4

1-5

FIGURE 1.2COMMON REINFORCING BEAM CROSS SECTIONS

2. Steel materials

Flat rolled steels are versatile materials. They provide strength andstiffness with favorable mass-to-cost ratios, and they allow highspeed fabrication. In addition, they offer excellent corrosion resistance when coated, high energy absorption capacity, goodfatigue properties, high working hardening rates, aging capability,excellent paintability, ease of repair and complete recyclability.These characteristics, plus the availability of high-strength and ultrahigh-strength steels, have made sheet steel the material of choice inthe automotive industry.

Numerous steel types and grades offer designers a wide choice forany given application. Bumper steels with elongations up to 60%facilitate forming operations. Bumper steels with yield strengths upto 1420 MPa (205 ksi) facilitate mass reduction.

High-strength steel grades are defined as those having a minimumyield strength greater than or equal to 240 MPa (35 ksi) and/or aminimum tensile strength less than or equal to 550 MPa (80 ksi).Ultra high-strength strength steel grades are defined as those having a minimum tensile strength greater than 550 MPa (80 ksi).

Low-carbon steels have excellent ductility. They are widely usedfor body and underbody components that are formed by stamping,roll forming or hydroforming. However, in order to reduce component mass, low-carbon steels are gradually being replacedby steels of greater strength. As the name implies, dent resistantsteels are commonly used for body panels such as quarter, doorand hood. Their relatively low as-received yield strength facilitatesforming. Cold work of forming and bake hardening during theautomotive paint cycle increase their yield strength and dent resistance. Microalloy steels usually have less ductility than low-carbon and dent resistant steels. However, they can be suppliedwith the necessary ductility to produce most automotive parts.Carbon-boron steel has good formability and high yield strengthafter heat treating. Dual phase steel also offers good formability. Itsstrength increases significantly through cold work during the fabrication process. Recovery annealed and martensitic steels haveultra high yield strengths. However, their formability limits their useto roll formed sections and less severe stampings. Stainless steelsoffer excellent corrosion resistance, excellent formability and highyield strength.

2-1

2.1 Introduction

The steel grades that are commonly used for facebars are shown withtheir typical properties in Table 2.1. Most facebars are made from high-strength steel [minimum yield strength higher than 240 MPa (35 ksi)].

For comparative purposes, Table 2.1 also includes similar SAE grades.It is important to note that the similar SAE grades are not equivalentgrades. That is, there are minor differences between the SAE gradesand the common grades to which they are similar. The differencesmight be significant in some applications.

Facebars, due to their depth of draw and complex shape, are produced by the stamping process. Steels of high formability arerequired and all of the grades shown in Table 2.1 can be supplied tomeet the demanding requirements of a facebar stamping. Facebars areeither powder coated, painted or chrome plated so a high-quality sur-face is required on the steel sheet. The steel mills use special processingfrom casting, slab surfacing, hot rolling and tempering in the productionof facebar steel. In addition, the majority of the sheet steel used for plated facebars is flat polished prior to the stamping operation.

The steel grades that are commonly used for brackets, supports andreinforcing beams, are shown with their typical properties in Table 2.2.Most reinforcing beams are made from ultra high-strength steel [minimum tensile strength greater than 550 MPa (80 ksi)].

For comparative purposes, Table 2.2 also includes similar SAE grades.It is important to note that the similar SAE grades are not equivalentgrades. That is, there are minor differences between the SAE gradesand the common grades they are similar to. The differences might besignificant in some applications.

All of the high-strength steel grades in Table 2.2 can be supplied withsufficient formability for the production of stamped brackets, supportsand reinforcing beams. They can also be readily roll formed into reinforcing beams.

Generally speaking, the ultra high-strength steel grades in Table 2.2have less formability than the high-strength grades listed in Table 2.2.However, they offer significant weight reduction opportunities and arecommonly used for less severe stampings and roll formed reinforcingbeams. Grades 120XF and 135XF have sufficient ductility to producestampings, including reinforcing beams, provided the amount of drawis minimal. Grade 140T has a relatively low as-delivered yield strength,which facilitates stamping and roll forming operations. An advantageof this grade is the fact it work-hardens significantly during forming. Infact, the yield strength after forming approaches 965 MPa (140 ksi).Thus, 140T offers sufficient formability to produce roll formed beamswith a large sweep and it provides high yield strength in the finishedpart. Grades 140XF and M130HT through M220HT have low formabilityand their use is generally restricted to roll formed reinforcing beamssince roll forming is a process of gradual bending without drawing.The Carbon-Boron grades can be used to produce complex partsthrough the hot stamping process. After quenching, the parts haveyield strengths around 1140 MPa (165 ksi). The SS grades are readilystamped or roll formed. Their excellent corrosion resistance obviatesthe need for protective coatings.

2.2 Typical properties of steel grades for facebars

2-2

2.3 Typical properties of steel grades for brackets, supports and reinforcing beams

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MPa (ksi)

480 (69.6) 31 0.17 J2340 340X505 (73.2) 29 0.16 J2340 380X531 (77.0) 27 0.15 J2340 420X600 (87.0) 26 0.13 J2340 490X673 (97.6) 22 0.12 J2340 550X

475 (68.9) 28 0.15 J2340 340X501 (72.7) 27 0.14 J2340 380X527 (76.5) 26 0.14 J2340 420X614 (89.1) 20 0.12 J2340 490X

690 (100.0) 19 0.08 J2340 550X

453 (65.7) 30 0.17 J2340 340X492 (71.4) 28 0.16 J2340 380X531 (77.0) 26 0.15 J2340 420X662 (96.0) 15 0.11 J2340 550X

480 (69.6) 18 N/A J403 10B21

500 (72.5) 27 N/A J403 15B21500 (72.5) 27 N/A J403 15B24

500 (72.5) 27 N/A J403 15B21

883 (128) 12 N/A J2340 830R985 (143) 7.0 N/A --1028 (149) 5.6 N/A --

889 (129) 11 N/A J2340 700R

1055 (153) 5.4 N/A J2340 900M1179 (171) 5.1 N/A J2340 1100M1420 (206) 5.1 N/A J2340 1300M1627 (236) 4.7 N/A J23401500M

1055 (153) 5.4 N/A J2340 900M1179 (171) 5.1 N/A J2340 1100M1420 (206) 5.1 N/A J2340 1300M1627 (236) 4.7 N/A J23401500M

862 (125) 25 0.25 J405 S301001193 (173) 25 0.22 J405 S20400

1034 (150)634 (92)834 (121)

132418

N/AN/AN/A

J2340 950DL––

TABLE 2.2STEEL GRADES FOR BRACKETS, SUPPORTS AND REINFORCING BEAMS

TYPICAL PROPERTIES AS-SHIPPED FROM THE STEEL MILL

NOTES:

HR Hot rolled sheet

CR Cold rolled sheet

HDG (CR) Hot-dip galvanized (cold rolled base) sheet

EG (CR) Electrogalvanized (cold rolled base) sheet

Aluminized (CR) Hot dip aluminized (cold rolled base) sheet

SS Stainless steel

XLF Microalloy quality. Strength is obtained through small quantities of alloying elements such as vanadium and niobium. Designation number (e.g. 50) is mimimum yield strength in ksi.

..B..(M) Carbon-boron quality (Modified). Properties are for the steel as-shipped from the steel mill. Strengthis achieved through heating and quenching. After quenching, the yield strength is about 1140 MPa(165ksi)

..B.. Carbon-boron quality. Properties are for the steel as-shipped from the steel mill. Strength is achievedthrough heating and quenching. After quenching, the yield strength is about 1140 MPa (165ksi)

XF Recovery annealed quality. Strength is achieved primarily through cold work during cold rolling atthe steel mill. Designation number (e.g. 120) is minimum yield strength in ksi.

140T Dual phase quality. Structure contains martensite in ferrite matrix. Properties are for the steel as-shipped from the steel mill. Designation number (e.g. 140) is the minimum tensile strength in ksi.

M...HT Martensitic quality. Strength is determined by carbon content. Designation number (e.g. 130) is theminimum tensile strength in ksi.

N/A Not applicable. The Carbon-Boron steels listed are intended for hot forming. The RecoveryAnnealed and Martensitic steels are primarily used in roll forming operations. However, they may beused for stampings provided the amount of draw is minimal. The “n” value for Dual Phase steels isvery dependent on the range over which it is calculated.

2-4

TYPICAL TYPICAL TYPICAL SIMILAR SAE TENSILE ELONG "n" GRADE

STRENGTH (%) VALUEMPa (ksi)

MPa (ksi)

403 (58.5)439 (63.7)475 (68.9)527 (76.5)587 (85.1)

376 (54.5)418 (60.6)459 (66.5)530 (76.8)592 (85.8)

379 (54.9)415 (60.2)452 (65.5)641 (93.0)

320 (46.4)

330 (47.9)330 (47.9)

330 (47.9)

869 (126)969 (141)

1010 (147)

876 (127)

923 (134)1020 (148)1214 (176)1420 (206)

923 (134)1020 (148)1214 (176)1420 (206)

517 (75)779 (113)

634 (92)371 (54)518 (75)

HIGH-STRENGTH STEEL GRADESHR 50XLF MicroalloyHR 55XLF MicroalloyHR 60XLF MicroalloyHR 70XLF MicroalloyHR 80XLF Microalloy

CR 50XLF MicroalloyCR 55XLF MicroalloyCR 60XLF MicroalloyCR 70XLF MicroalloyCR 80XLF Microalloy

HDG (CR) 50XLF MicroalloyHDG (CR) 55XLF MicroalloyHDG (CR) 60XLF MicroalloyHDG (CR) 80XLF Microalloy

ULTRA HIGH-STRENGTH STEEL GRADES HR 10B21(M) Carbon-Boron

CR 15B21(M) Carbon-BoronCR 15B24 Carbon-Boron

Aluminized (CR) 15B21(M) Carbon-Boron

CR 120XF Recovery AnnealedCR 135XF Recovery AnnealedCR 140XF Recovery Annealed

HDG (CR) 120XF Recovery Annealed

CR M130HT Martensitic CR M160HT Martensitic CR M190HT Martensitic CR M220HT Martensitic

EG (CR) M130HT Martensitic EG (CR) M160HT Martensitic EG (CR) M190HT Martensitic EG (CR) M220HT Martensitic

SS T301 1/4 Hard ConditionSS T204 20% Cold Worked

CRCRCR

140T590T780T

Dual PhaseDual PhaseDual Phase

TYPICALYIELD

STRENGTHMPa (ksi)

MATERIAL GRADE(COMMON

NAME)

DESCRIPTION

AHSS (advanced high-strength steel) Guidelines published by theInternational Iron and Steel Institute (Reference 2.4) provide a comparison between the various families of steel products in theform of as-shipped yield strength versus formability (Figure 2.1).The latter is represented by the total elongation of each materialclass. Each bubble in the graph represents the typical propertiesof all steel products in each category of steels, as produced bymost of the major steel makers around the world. The bubbles are:• IF (interstitial free) products• IS (isotropic) products• Mild (mild steel) products• BH (bake hardenable) products• CMn (carbon-manganese and carbon-boron) products• HSLA (high strength low-alloy) products• TRIP (transformation induced plasticity) products• DP, CP (dual phase, complex phase) products• T204 austenitic stainless steel • MART (martensitic) products

The above bubbles may be placed into three groups: ConventionalHSS (high-strength steel), stainless steel and AHSS.

The purpose of Fig. 2.1 is threefold:a. To visually display the tradeoffs between strength and ductility.b. To provide an indication of the current trends in new steel

product development, andc. To allow for a first-cut material family selection for various

applications.

It is clear from the graph that most of the traditional steel productsobey an inverse relationship between strength and ductility.Bucking this trend are the dual phase and complex phase familiesof steel products. These products, although available for at leasttwenty years, have just recently attracted the attention theydeserve for their excellent combination of higher strength and verygood ductility, making them suitable for energy-absorption applications. Carrying this concept a step further are the TRIP(TRansformation Induced Plasticity) steels. Although the principlesunderlying these steel products were available and understood atleast thirty years ago, only now are these steels becoming availablefor automotive body applications. TRIP steels provide furtherenhanced potential for energy absorption at thinner gauges, thusmaking it possible for a vehicle structure to provide improved safety at lower mass.

The above data are all based on tensile properties obtained fromundeformed materials. In actual service the steel sheets arestrained during fabrication, which is known to increase theirstrength and decrease their ductility. Many of the formed parts arealso subsequently painted and baked to cure the paint. Althoughnot all steels respond to the straining and baking process many ofthem do. Key among them are the so-called Bake Hardening (BH),the Dual Phase (DP) and the TRIP steels. The net effect of this is tofurther shift the bubbles to the right of the chart and a little lower(Figure 2.2). This has no significant effect on forming of the steelbut it can certainly affect its performance in service. The effect isusually beneficial as straining and baking increase the stress levelsat which permanent deformation begins.

2.4 Elongation versus as-shipped (steel mill) yield strength

2.5 Elongation versus after-fabrication yield strength

2-5

FIGURE 2.1ELONGATION VERSUS YIELD STRENTH: STEEL AS-SHIPPED FROM THE STEEL MILL

2-6

2-7

FIGURE 2.2ELONGATION VERSUS YIELD STRENTH: STEEL AFTER-FABRICATION BY BUMPER SUPPLIER

STEEL GRADE

INCREASE DUE TO WH

INCREASE DUE TO BH

TOTAL INCREASE IN YIELD STRENGTH

TRIP 350/600 17% 21% 38%

DP 350/600 32% 13% 45%

HSLA 350/600 6% 0% 6%

Work performed by the member steel companies of the International Iron and SteelInstitute (IISI) quantified the effect of work hardening (WH) and bake hardening (BH)on the yield strength of certain dual phase and TRIP steels and compared it to that ofHSLA 340 material. These results are provided below and shown graphically inFigure 2.3.

Elo

ngat

ion

(%)

Lower Yield Strength ( MPa)

HSLA

T204 Stainless

TRIP

DP, CP

MART

CMn

2-8

FIGURE 2.3INCREASE IN YIELD STRENGTH THROUGH WORK HARDENING (WH)

AND BAKE HARDENING (BH)

More recently, consideration was given to the impact of the rate ofstraining of a particular material or component on its performance.Since steel is a strain rate sensitive material, its yield strengthincreases as the loading rate increases. This provides further benefits in its ability to sustain and absorb higher loads and higherinput energy, such as in the case of deformation of a bumper orother structural component. Again, this is not a new discovery butit was only through the introduction of the advanced vehicle concepts phase of the ULSAB (UltraLight Steel Auto Body) development that this benefit of steel began to be introduced instructural design of automobile components. Considerable effortwas then expended in various laboratories around the world togenerate tensile data at straining rates ranging from quasi-static (10-3 s-1) to 103 s-1 for many of the above steel grades. The effectof the higher strain rate on the strength and ductility for TRIP 600and DP 600 steels is provided in Figures 2.4 and 2.5, respectively.The data for these steels and other products of interest for bumperconstruction are available from many steel producers and can bemade available for use in the design of bumpers and other energy-absorbing components.

2.6 Yield strength versus strain rate

2-9

Use of the tensile properties of steels at higher rates of loading hasbegun in automotive design and is expected to be universally usedas more data for more steel grades become available and as automotive designers become more comfortable with the reliabilityof these data.

2-10

FIGURE 2.4STRESS VERSUS STRAIN AT DIFFERENT STRAIN RATES FOR TRIP 600.

THE DATA AT 1000 s-1 WERE OBTAINED USING THE SPLIT HOPKINSON BAR (SHB) METHOD

FIGURE 2.5STRESS VERSUS STRAIN AT DIFFERENT STRAIN RATES FOR DP 600.

THE DATA AT 1000 s-1 WERE OBTAINED USING THE SPLIT HOPKINSON BAR (SHB) METHOD

Sheet steel is a complex product and there are many methodsused to describe it. The following descriptors are often associatedwith automotive sheet steel:

a) Type Chemical composition, microstructure processing method or end use are all used to describe the type of steel. Examples include low-carbon, dent resistant, microalloy, high-strength low alloy, recovery annealed, dual phase, bainitic and martensitic sheet.

b) Grade Physical properties such as yield strength, tensile strength or elongation are used to denote a grade. Examples include 180 MPa minimum yield strength and 1500 MPa minimum tensile strength.

c) Steel Product The final process that steel receives before shipment from a steel mill is often used to describe a steel product. Examples include hot rolled, cold rolled and coated sheet.

d) Metallic Coating The process used to apply a metallic coating or the type of metal in the metallic coating are used to describe steel. Examples include hot-dip galvanized, electrogalvanized and zinc coated sheet.

e) Surface Condition Surface smoothness is used to describe sheet steel. Examples are exposed, semi-exposed or unexposed body sheet.

In practice, when specifying sheet steel, most (if not all) of theabove descriptors are required to fully describe the desired steelproduct. Published documents, such as those of the Society ofAutomotive Engineers (SAE) greatly facilitate the correct specification of sheet steel. In this context, the relevant SAE documents are:

• Categorization and Properties of Low-Carbon Automotive Sheet Steels, SAE J2329 (Reference 2.1)

• Categorization and Properties of Dent Resistant, High Strength and Ultra High Strength Automotive Sheet Steel, SAE J2340 (Reference 6.4)

• Selection of Galvanized (Hot Dipped and Electrodeposited) Steel Sheet, SAE J1562 (Reference 2.2)

• Chemical Compositions of SAE Carbon Steels, SAE J403 (Reference 2.3)

• Chemical Compositions of SAE Wrought Stainless Steels, SAE J405 (Reference 2.5)

2.7 Sheet steel descriptors

2-11

This SAE Recommended Practice furnishes a categorization procedure to aid in selecting low-carbon sheet steel. The systememploys four characters. The first two alphabetic charactersdenote hot rolled (HR) or cold rolled (CR) method of manufacture.The third character defines grade (one through five) based on yieldstrength range, minimum tensile strength, minimum percent elongation, minimum rm value, and minimum n-value.

The fourth alphabetic character (E,U,R,F,N or M) classifies the steeltype with regards to surface quality and/or aging character. Anoptional fifth character may be used to restrict carbon content to aminimum of 0.015%. If the sheet steel is a metallic coated product, then thE-coating would be specified in accordance withSAE J1562 (see Section 2.10).

Examples of typical specification and ordering descriptions forautomotive sheet steel are given in Section 2.13.

There are five grades of cold rolled sheet and three grades of hotrolled sheet. Mechanical properties are shown in Tables 2.3 and 2.4, while chemical composition is shown in Table 2.5 (pages 2-23and 2-24).

There are two types of cold rolled sheet, either in the bare or coated condition:

• E Exposed. Intended for critical exposed applications where painted surface appearance is of primary importance.

• U Unexposed. Intended for unexposed applications.

There are four types of hot rolled sheet, either bare or in the metallic coated condition:

• R A coiled product straight off the hot mill, typically known as hot roll black band.

• F A processed product in coils or cut lengths. The product may be susceptible to aging and coil breaks.

• N A processed product in coils or cut lengths. The product is non-aging at room temperature but is susceptible to coil breaks.

• M A processed product in coils or cut lengths. This product is non-aging at room temperature and free from coil breaks.

When specifying a hot rolled sheet, the surface condition shouldalso be indicated (E or U as per Section 2.8.2).

2.8 SAE J2329 Low-carbon sheet steel

2-12

2.8.1 Steel grade

2.8.2 Types of cold rolled sheet

2.8.3 Types of hot rolled sheet

This SAE Recommended Practice defines mechanical properties fordent resistant, high-strength and ultra high-strength sheet steel. Theproperties for dent resistant steels are shown in Table 2.6, the properties for high-strength steels in Tables 2.7 and 2.8, and theproperties for ultra high-strength steels in Table 2.9 (pages 2-23 to2-25).

It should be noted that the yield and tensile strength values for theultra high-strength steels covered by J2340 (Table 2.9) are thosecommonly used in Europe. For example, J2340 and Europe use values such as 600, 800, 1000 and 1200. On the other hand, values such as 590, 780, 980 and 1180 are widely used in NorthAmerica and Japan. Currently, SAE’s Iron and Steel TechnicalCommittee is revising J2340 to cover ultra high-strength steelgrades widely used not only in Europe but also in North Americaand Japan.

SAE J2340 also furnishes a categorization procedure to aid inselecting dent resistant, high-strength and ultra high-strength steels.The system employs several characters:

• The first two characters denote hot rolled (HR) or cold rolled (CR) method of manufacture.

• The next three or four characters denote the grade of steel. Minimum yield strength in MPa is used for dent resistant and high-strength steels and minimum tensile strength in MPa is used for ultra high-strength steels. Refer to Tables 2.6 - 2.9. The final set of characters denotes the steel type. Refer to Section 2.9.2.

If the sheet steel is a metallic coated product, then thE-coatingwould be specified in accordance with SAE J1562 (see Section2.10).

Examples of typical specification and ordering descriptions forautomotive sheet are given in Section 2.13.

In Tables 2.6, 2.7 and 2.8 (dent resistant and high-strength steels)grade is the minimum yield strength in MPa. In Table 2.9, (ultrahigh-strength steels) grade is the minimum tensile strength in MPa.

2.9 SAE J2340 Dent resistant, high-strength and ultra high-strength sheet steel

2-13

2.9.1 Steel grade

In Tables 2.6 to 2.9, type is defined by one or two letters as follows:

• A A non-bake hardenable dent resistant steel in which increase in yield strength due to work hardening results from strain during forming.

• B A bake hardenable dent resistant steel in which increase in yield strength due to work hardening results from strain during forming and an additional increase in yield strength that occurs during the paint-baking process.

• AT, BT These types are similar to Types A and B respectively, except that the steel is interstitial free.

• S A high-strength steel, which is solution strengthened using C and Mn in combination with P or Si.

• X A high-strength steel typically referred to as HSLA. It is alloyed with carbide and nitride forming elements (commonly Nb (Cb), Ti and V) in combination with C, Mn, P and Si.

• Y A high-strength steel similar to Type X, except the spread between the minimum yield and tensile strengths is larger (100 MPa versus 70 MPa).

• SF,XF,YF These types are similar to types S, X and Y respectively, except they are sulphide inclusion controlled.

• R A high-strength steel that has been recovery annealed or stress-relief annealed. Its strength is primarily achieved through cold work during cold rolling at the steel mill.

• DL A dual phase ultra high-strength steel. Its microstructure is comprised of ferrite and martensite. The strength level is dictated by the volume of low-carbon martensite. DL dual phase has a low ratio of yield-to-tensile strength (less than or equal to 0.7).

• DH A dual phase ultra high-strength steel similar to Type DL, except it has a high ratio of yield to tensile strength (greater than 0.7).

• M A martensitic ultra high-strength steel whose carbon content determines the strength level.

The steels in Tables 2.6 to 2.9 can be specified as either hot rolledsheet or cold rolled sheet in either the bare or metallic coated condition. Hot-dipped or electrogalvanized coated sheets are covered by SAE J1562 (Section 2.10). All of the steels shown inTables 2.6 to 2.9 may not be commercially available in all types ofcoatings. Consult your steel supplier. Also, hot rolled sheet for thesteels shown in Tables 2.6 to 2.9 may not be commercially available in thicknesses below 1.5-2.5 mm. Again, consult yoursteel supplier.

2-14

2.9.2 Steel type

2.9.3 Hot rolled, cold reduced and metallic coated sheet

2.10 SAE J1562 Zinc and zinc-alloy coated sheet steel

Cold reduced and metallic coated sheet steel is available in threesurface conditions:

• E Exposed. Intended for critical exposed applications where painted surface appearance is of primary importance.

• U Unexposed. Intended for unexposed applications.• Z Semi-exposed. Intended for non-critical exposed

applications.

Four conditions of hot rolled sheet are available:

• P A coiled product straight off the hot mill, typically known as hot roll black band.

• W A processed product in coils or cut lengths. The product may be susceptible to aging.

• N A processed product in coils or cut lengths. The mechanical properties do not deteriorate at room temperature.

• V A processed product in coils or cut lengths. The mechanical properties do not deteriorate at room temperature. The product is free of coil breaks.

When specifying a hot rolled sheet, the desired surface conditionshould also be indicated (E,U or Z as per Section 2.9.4).

This SAE Recommended Practice defines preferred product characteristics for galvanized coatings applied to sheet steel. A galvanized coating is defined as a zinc or zinc-alloy metallic coating.

Two generic processes for metallic coated sheets are currentlyused in the automotive industry:

• Hot-dip process. A coil of sheet steel is passed continuously through a molten metal bath. Upon emergence from the bath, the molten metal coating mass is controlled by air (or other gas) knives or mechanical wipers before the coating solidifies. This process produces a sheet with a coating on two sides.

• Electrodeposition process. This continuous coating process uses cells in which the metallic coating is electrodeposited on a coil of sheet steel. This process can produce a sheet with a coating on either one or two sides.

2-15

2.9.4 Surface conditions for cold reduced and metallic coated sheet

2.9.5 Conditions for hot rolled sheet

2.10.1 Galvanizing processes

The types of commercially produced metallic coatings include:• Hot-dip galvanized. Essentially a pure zinc coating applied by

the hot-dip galvanizing process.• Electrogalvanized. Essentially a pure zinc coating applied by the

electrodeposition galvanizing process.• Galvannealed. A zinc-iron alloy coating applied by the hot-dip

galvanizing process. The coating typically contains 8-12% iron by weight.

• Alloy. Aluminum-zinc silicon alloy (55%, 43% and 2% by weight respectively) and zinc-aluminum alloy (5% aluminum by weight) coatings are applied by the hot-dip galvanizing process. Zinc-iron alloy (<20% iron by weight) and zinc-nickel (<20% nickel by weight) coatings are applied by the electrodeposition process.

Zinc coated sheet (hot-dip galvanized and electrogalvanized) offerssuperior corrosion resistance. Through sacrificial electrochemicalaction, zinc coatings protect bare (cut) edges. Galvanneal, due toits lighter zinc content, has less corrosion resistance than pure zinccoatings. However, its iron content provides enhanced spot weldability and paintability. Hot-dip galvanized, electrogalvanizedand galvanneal are, by far, the most commonly used coatings forvehicle components. Zinc-aluminum and zinc-nickel coatings haveniche applications. For example, zinc-aluminum alloy offersimproved corrosion resistance to acids; hence, it is often used formufflers.

Coating mass is expressed in g/m2. The approximate thickness ofa coating in microns = g/m2 x 0.14. The approximate thickness ofa coating in mils = g/m2 x 0.006. The heavier the coating mass,the greater the corrosion resistance of a metallic coated sheet.However, spot weldability decreases with an increase in coatingmass.

Three surface qualities may be specified:

• Exposed • Semi-exposed• Unexposed

The thickness of metallic coated sheet steel is determined by measuring, as a single unit, the combination of the base sheet steeland all metallic coatings.

2.10.2 Types of coatings

2.10.3 Coating mass

2.10.4 Surface quality

2.10.5 Coated sheet thickness

2-16

SAE J2329 uses a nine-character designation system to identify thegalvanizing process, thE-coating type and mass of each side of thesheet and surface quality.

• The first and second characters denote the galvanizing process:

HD = hot-dip galvanizedEG = electrogalvanized (electrodeposition)

• The third and fourth characters denote the coating mass of the unexposed side in accordance with Table 2.10 (page 2-26).

• The fifth character denotes thE-coating type of the unexposed side:

G = pure zincA = zinc-ironN = zinc-nickelX = other than G, A or N

• The sixth and seventh characters denote thE-coating mass of the exposed side in accordance with Table 2.10

• The eighth character denotes thE-coating type of the exposed side:

G = pure zincA = zinc-ironN = zinc-nickelX = other than G, A or N

• The ninth character denotes surface quality:

E = ExposedZ = Semi-exposedU = Unexposed

Examples of typical specification and ordering descriptions forautomotive sheet steel are given in Section 2.13.

This SAE Recommended Practice provides chemical compositionranges for carbon steels supplied to certified chemical compositionrather than to certified mechanical properties. SAE J403 uses afour or five character system to designate steel grade:

• The first two characters are the number “10”, which indicate that the grade is carbon steel.

• The last two characters represent the nominal carbon content of the grade in points of carbon. One point of carbon is 0.01% carbon by weight. Five points would be shown as “05”, fifteen points as “15”, etc.

• If boron is added to a carbon steel to improve hardenability, the letter “B” is inserted between the first two characters and the last two characters.

Examples of typical specification and ordering descriptions forautomotive sheet are given in Section 2.13.

2.10.6 Coating designations

2-17

2.11 SAE J403 Carbon steel chemical compositions

SAE J403 provides compositions for carbon grade sheet steels.Table 2.11 (page 2-27) shows the compositions for grades 1006through 1025. SAE J403 provides compositions for grades 1006through 1095. However, grades above 1025 have relatively lowformability and weldability due to their relatively high carbon content. Thus, grades above 1025 are seldom used for automotivesheet applications.

It is important to note that sheet steels specified or ordered to SAEJ403 are not supplied with certified mechanical properties. If certified mechanical properties are required, automotive sheetsteel should be specified or ordered in accordance with SAE J2329(Section 2.8) or SAE J2340 (Section 2.9).

The addition of boron to carbon sheet steel improves its hardenability. For this reason, boron sheet steel is an ideal materialfor hot stampings. As an example, 10B21 (Modified) is used forhot stamped bumper reinforcing beams. As received, this steel hasa yield strength in the range 345-515 MPa. Following hot stampingand quenching in liquid-cooled dies, the yield strength is raised toabout 1140 MPa.

Currently, SAE’s Iron and Steel Technical Committee is revisingJ403 to more appropriately cover sheet steel used for hot stampings.

This SAE Standard provides chemical composition requirements forwrought stainless steels supplied to chemical composition ratherthan to certified mechanical properties. The standard uses threeseries to designate stainless steel grades: S20000, S30000 andS40000. S20000 designates nickel-chromium-manganese, corrosion resistant types that are nonhardenable by thermal treatment. S30000 designates nickel-chromium, corrosion resistantsteels, nonhardenable by thermal treatment. S40000 includes botha hardenable, martensitic-chromium steel and nonhardenable, ferritic-chromium steel.

Table 2.12 (page 2-27) shows the chemical compositions for twostainless steel grades that are appropriate not only for bumperfacebars but also for bumper reinforcing beams.

2.11.1 Carbon sheet steel

2.11.2 Boron sheet steel

2-18

2.12 SAE J405 Wrought stainless steels

2-19

2.13 SAE Specification and ordering descriptions

The following examples represent typical specification and ordering descriptions for automotive sheet steel:

a) SAE J2329 CR2E Cold rolled sheet steel, grade 2 (Tables 2.3 & 2.5), exposed surface condition.

b) SAE J2329 HR3MU Hot rolled sheet steel, grade 3 (Tables 2.4 & 2.5), non-aging at room temperature and free from coil breaks, unexposed surface condition.

c) SAE J2329 CR4C EG60G60GE Cold rolled sheet steel, grade 4 (Tables 2.3 & 2.5), minimum carbon 0.015%, each side electrogalvanized coated to 60g/m2, critical exposed surface condition.

d) SAE J2329 HR2M 45A45AU Hot rolled sheet steel, grade 2 (Tables 2.4 & 2.5), non-aging at room temperature and free from coil breaks, each side galvannealed coated to 45g/m2, unexposed surface condition.

e) SAE J2340 CR 180A Cold reduced sheet steel, grade HD70G70GZ 180 non-bake hardenable dent

resistant (Table 2.6), each side hot-dip galvanized coated to 70g/m2, semi-exposed surface condition.

f) SAE J2340 CR 250B Cold reduced sheet steel, grade EG70G70GE 250 bake hardenable dent

resistant (Table 2.6), each side electrogalvanized coated to 70g/m2, critical exposed surface condition.

g) SAE J2340 HR 340XU Hot rolled sheet steel, grade 340 high-strength low-alloy (Table 2.7), unexposed surface condition.

h) SAE J2340 CR 1300MU Cold reduced sheet steel, grade 1300 ultra high-strength martensitic (Table 2.9), unexposed surface condition.

i) SAE J1562 EG70G70GE Electrogalvanized sheet having a 70 g/m2 minimum zinc coating (Table 2.10) on each side for an exposed application.

2-20

j) SAE J1562 HD70G20AE Hot-dip galvanized sheet having a 70g/m2 minimum zinc coating (Table 2.10) on the unexposed side and a 20g/m2 minimum zinc-iron coating (Table 2.10) on the exposed side for an exposed application.

k) SAE J1562 HD90G90GU Hot-dip galvanized sheet having a 90g/m2 minimum coating (Table 2.10) on each side for an unexposed application.

l) SAE J1562 HD45A45AU Hot-dip galvanized sheet having a 45g/m2 minimum zinc-iron coating (Table 2.10) on each side for an unexposed application.

m) SAE J1562 EG30N30NE Electrogalvanized sheet having a 30g/m2 minimum zinc-nickel coating (Table 2.10) on each side for an exposed application.

n) SAE J1562 EG70G00XE Electrogalvanized sheet having a 70g/m2 minimum zinc coating (Table 2.10) on the unexposed side and no coating on the exposed side for an exposed application.

o) SAE J403 HR1010U Hot rolled sheet steel, grade 1010 (Table 2.11), unexposed surface condition.

p) SAE J403 Hot rolled sheet steel, grade HR1008HD90G90GU 1008 (Table 2.11), having a

90g/m2 minimum coating on each side for an unexposed application.

2-21

Aluminized sheet steel is intended principally for heat resistingapplications and for uses where corrosion resistance and heat areinvolved. One application is hot formed bumper beams.Aluminized sheet has an aluminum-silicon alloy on each sideapplied by a continuous hot-dip process. The coated sheet has thesurface characteristics of aluminum with the superior strength andlower cost of steel.

One specification, which describes aluminized steel, is ASTMA463 (Reference 2.6). The quality of the sheet steel can be commercial (CS Types A, B and C), forming (FS), deep drawing(DDS), extra deep drawing (EDDS), structural (SS), high-strengthlow-alloy (HSLAS), high-strength low-alloy with improved formability (HSLAS-F) and ferritic stainless steel (FSS Types 409 and439). Chemical and mechanical properties are given for all qualities. A463 also defines the type of aluminum-zinc coating andcoating weights.

For hot formed bumper beams (see Section 3.4), boron steel witha Type 1 coating is commonly used. The mechanical properties ofthe boron steel are discussed in Section 2.11.2. The Type 1 aluminum coating contains about 10% silicon. The coating weight(total both sides) is typically 120-160 g/m2 (0.4-0.5 oz/ft2).

2.14 ASTM A463 Aluminized sheet steel

TABLE 2.3SAE J2329 LOW-CARBON COLD ROLLED SHEET

MECHANICAL PROPERTIES

GRADE YIELD MINIMUM MINIMUM MINIMUM MINIMUMSTRENGTH TENSILE ELONGATION rm VALUE n-VALUE

(MPa) STRENGTH (%)

(MPa)

1 N/R N/R N/R N/R N/R

2 140-260 270 34 N/R 0.16

3 140-205 270 38 1.5 0.18

4 140-185 270 40 1.6 0.20

5 110-170 270 42 1.7 0.22

N/R = Not Required

TABLE 2.4SAE J2329 LOW-CARBON HOT ROLLED SHEET

MECHANICAL PROPERTIES

GRADE YIELD MINIMUM MINIMUM MINIMUMSTRENGTH TENSILE ELONGATION n-VALUE

(MPa) STRENGTH (%)(MPa)

1 N/R N/R N/R N/R

2 180-290 270 34 0.16

3 180-240 270 38 0.18

N/R = Not Required

2-22

180A 180 310 0.20 215

180B 180 300 0.19 245

210A 210 330 0.19 245

210B 210 320 0.17 275

250A 250 355 0.18 285

250B 250 345 0.16 315

280A 280 375 0.16 315

280B 280 365 0.15 345

TABLE 2.5SAE J2329 LOW-CARBON HOT & COLD ROLLED SHEET

CHEMICAL COMPOSITION

GRADE MAXIMUM MAXIMUM MAXIMUM MAXIMUM MINIMUMCARBON MANGANESE PHOSPHORUS SULPHUR ALUMINUM

(%) (%) (%) (%) (%)

1 0.13 0.60 0.035 0.035 —

2 0.10 0.50 0.035 0.030 0.020

3 0.10 0.50 0.030 0.030 0.020

4 0.08 0.40 0.025 0.025 0.020

5 0.02 0.30 0.025 0.025 0.020

TABLE 2.6SAE J2340 DENT RESISTANT SHEET STEEL

GRADE & AS RECEIVED AS RECEIVED AS RECEIVED YIELD YIELDTYPE YIELD TENSILE n-VALUE STRENGTH STRENGTH

STRENGTH STRENGTH AFTER AFTER(MPa) (MPa) 2% STRAIN STRAIN & BAKE

(MPa) (MPa)

2-23

Type A = Non-bake HardenableType B = Bake Hardenable

GRADE &TYPE

300S

300X

300Y

340S

340X

340Y

380X

380Y

420X

420Y

490X

490Y

550X

550Y

TABLE 2.7SAE J2340 HIGH-STRENGTH SOLUTION STRENGTHENED

AND LOW-ALLOY SHEET STEEL

2-24

Type S = Solution strengthened using C and Mn in combination with P or Si.Type X = HSLA. Alloyed with carbide and nitride forming elements (commonly Nb, Ti and V) in combination with

C, Mn, P and Si.Type Y = Similar to Type X, except the spread between minimum yield and tensile strengths is larger

(100 MPa versus 70 MPa).

MINIMUMYIELD

STRENGTH(MPa)

300

300

300

340

340

340

380

380

420

420

490

490

550

550

MAXIMUMYIELD

STRENGTH(MPa)

400

400

400

440

440

440

480

480

520

520

590

590

680

680

MINIMUMTENSILE

STRENGTH(MPa)

390

370

400

440

410

440

450

480

490

520

560

590

620

650

COLDREDUCEDMINIMUM

ELONGATION(%)

24

24

21

22

22

20

20

18

18

16

14

12

12

12

HOTROLLED

MINIMUMELONGATION

(%)

26

28

25

24

25

24

23

22

22

19

20

19

18

18

GRADE &TYPE

490R

550R

700R

830R

TABLE 2.8SAE J2340 HIGH-STRENGTH RECOVERY ANNEALED SHEET STEEL

Type R = Recovery annealed or stress-relief annealed.

MINIMUMYIELD

STRENGTH(MPa)

490

550

700

830

MAXIMUMYIELD

STRENGTH(MPa)

590

650

800

960

MINIMUMTENSILE

STRENGTH(MPa)

500

560

710

860

MINIMUMELONGATION

(%)

13

10

8

2

2-25

GRADE &TYPE

500 DL

500 DH

600 DL1

600 DL2

700 DH

800 DL

950 DL

1000 DL

800 M

900 M

1000 M

1100 M

1200 M

1300 M

1400 M

1500 M

TABLE 2.9SAE J2340 ULTRA HIGH-STRENGTH DUAL PHASE & MARTENSITE SHEET STEEL

Type DL = Dual phase with a yield-to-tensile ratio less than or equal to 0.7.Type DH = Dual phase with a yield-to-tensile ratio greater than 0.7.Type M = Martensitic.

MINIMUMYIELD

STRENGTH(MPa)

300

500

350

280

550

500

550

700

600

750

750

900

950

1050

1150

1200

MINIMUMTENSILE

STRENGTH(MPa)

500

600

600

600

700

800

950

1000

800

900

1000

1100

1200

1300

1400

1500

MINIMUMELONGATION

(%)

22

14

16

20

12

8

8

5

2

2

2

2

2

2

2

2

MINIMUM MASSPER SIDE1

FOR HOT-DIP ORELECTROGALVANIZED

(g/m2)

00

20

30

40

45

50

55

60

70

90

98

2-26

CATEGORY(DESIGNATION)

00

20

30

40

45

50

55

60

70

90

98

TABLE 2.10SAE J1562 COATING MASS FOR GALVANIZED SHEET STEEL

1. Single spot test. Approximate thickness in microns equals coating mass in g/m2

multiplied by 0.14. Approximate thickness in mils = coating mass in g/m2 multiplied by 0.006.

2. Not applicable.

MAXIMUM MASSPER SIDE1

FOR HOT-DIP(g/m2)

NA2

50

60

70

75

80

85

90

100

120

130

MAXIMUM MASSPER SIDE1 FOR

ELECTROGALVANIZED(g/m2)

00

30

45

55

60

70

75

80

90

110

130

2-27

GRADE

1006

1008

1009

1010

1012

1015

1016

1017

1018

1019

1020

1021

1022

1023

1025

TABLE 2.11SAE J403 CARBON STEEL COMPOSITIONS FOR SHEET

TABLE 2.12SAE J405 CHEMICAL COMPOSITIONS OF WROUGHT STAINLESS STEELS, %

(maximum unless a range is indicated)

Max = Maximum

CARBON(%)

0.08 Max

0.10 Max

0.15 Max

0.08-0.13

0.10-0.15

0.12-0.18

0.12-0.18

0.14-0.20

0.14-0.20

0.14-0.20

0.17-0.23

0.17-0.23

0.17-0.23

0.19-0.25

0.22-0.28

MANGANESE(%)

0.45 Max

0.50 Max

0.60 Max

0.30-0.60

0.30-0.60

0.30-0.60

0.60-0.90

0.30-0.60

0.60-0.90

0.70-1.00

0.30-0.60

0.60-0.90

0.70-1.00

0.30-0.60

0.30-0.60

PHOSPHOROUS(Max %)

0.030

0.030

0.030

0.030

0.030

0.030

0.030

0.030

0.030

0.030

0.030

0.030

0.030

0.030

0.030

SULFUR(Max %)

0.035

0.035

0.035

0.035

0.035

0.035

0.035

0.035

0.035

0.035

0.035

0.035

0.035

0.035

0.035

DESIGNATION

S20400

S30100

C

0.030

0.15

Mn

7.00-9.00

2.00

P

0.040

0.045

S

0.030

0.030

Si

1.00

1.00

Cr

15.00-17.00

16.00-18.00

Ni

1.50-3.00

6.00-8.00

N

0.15-0.10

0.10

3.1 StampingThe art of science of sheet metal stamping processes arechallenged daily to accommodate higher strength and thinnermaterials. Further, these materials must be transformed into morecomplex shapes with fewer dies and increased quality in the finalpart. And, of course, all must be accomplished while reducingcosts. Such pressures require a rigorous approach to assessing thecurrent state of a stamping process. A detailed discussion onstamping operations is given in Reference 4.2. However, anoverview is outlined below.

The concept of major and minor strain can be used to describedifferent kinds of sheet forming processes. In cases where the sheetis stretched over a punch, the major strain is always positive. Forstretching, the minor strain is usually positive as well. Differentpunch and clamping configurations can create a variety of majorand minor strain levels.

For stretching, a pulling load in the major strain direction is pairedwith a zero or positive load applied in the minor strain direction.The minor strain can vary from slightly negative (no applied load inthe minor strain direction, as in stretching a strip by pulling on itsends) to positive strain equal to the level of the major strain. Aminor strain of zero is a special case, which is often called planestrain. In plane strain, all deformation takes place in only twodimensions; the major strain direction and the thickness direction.All stretching is accommodated by thinning of the material.

In circle grid analysis (CGA), small circles are etched on the surface ofthe steel sheet prior to stamping (Figure 3.1). After stamping, thedeformed circles are compared to the original circles (Figure 3.2).For the condition of plane strain, the deformed circle is an ellipsewith the minor strain diameter equal to the original diameter of theunderformed circle. A minor strain equal to the major strain isindicated by an original circle, which remains circular afterdeformation. However, the diameter of the circle after deformationis larger than the diameter before deformation. This condition iscalled equi-biaxial stretch because the amount of the stretch isequal regardless of the direction in the plane of the sheet.

3.1.1 Stretching

3-1

3. Manufacturing processes

3-2

FIGURE 3.1TYPICAL CIRCLE GRID PATTERN

FIGURE 3.2REPRESENTATION OF STRAINS BY ETCHED CIRCLES

3-3

When a sheet is pulled into a die cavity, and must contract to flowinto the cavity in areas such as at a corner or in the flange of acircular cup, the sheet is said to be undergoing drawing. Drawing,also known as deep drawing, generates compressive forces in theflange area being drawn into the die cavity. Negative minor strainsare generated. In contrast to failures in stretching, failures indrawing do not normally occur in the flange area where thecompression and flow of sheet metal is occurring. Instead, neckingand fracture occur in the wall of the stamping near the nose of thepunch. Failure occurs here because the force causing thedeformation in the flange must be transmitted from the punchthrough this region. If the force required to deform the flange is toogreat, it cannot be transmitted by the wall without overloading thewall.

3.1.2 Drawing

Bending differs from drawing and stretching, because thedeformation present in bending is not homogeneous through thethickness of the material. For pure bending, where there is nosuperimposed tension or compression on the bending process, thecenter of the sheet has zero strain. The outer surface is elongated,with a tensile strain equal to t/2r (t=steel thickness, r=bend radius tothe midpoint of the steel thickness). The inner surface iscompressed, with a compressive strain equal to t/2r. The strainvaries from compressive at the inner radius, through zero at themidpoint of the thickness, to tensile at the outside radius. In purebending, the compressive and tensile strains are equal.

Because the strain varies through the thickness, forming limitanalysis (Section 3.1.5) does not directly apply. Materials with verylittle capacity to be formed can frequently undergo bendingoperations successfully. The tendency to thin locally, with neckingand fracture, is not present in bending. Cold working of thematerial does take place. However, the amount of work hardeningdepends on the radius of the bend and the thickness of the material.A sharper radius (smaller r) or thicker material (greater t) causes anincrease in strain at the surface. Bending is a plane strainoperation. The length of the bend does not change during bending,except for localized distortion at the edge of the sheet.

3.1.3 Bending

As material passes through a draw bead or over a die lip, it is bent,straightened, and sometimes re-bent in the opposite direction. Thenet strain at the end of this process is small, although cold work hasoccurred and the material is harder than it was before the processbegan. As a result, the ability to deform the material in subsequentoperations is decreased.

3.1.4 Bending and straightening

3-4

The measurement of strain provides an important tool fordetermining the local deformation that occurs in a complicatedprocess. Sharply changing levels of strain usually indicate alocalization of deformation and a higher likelihood of necking andfailure during forming. For sheet metal, it has been found that alimit to the major strain exists for each level of minor strain. Thisphenomenon has been studied in the laboratory and has resulted inthe creation of forming limit diagrams.

First, flat sheets of a given material are etched with circles as shownin Figure 3.1. The flat sheets are then deformed in a variety ofconfigurations to develop a large range of major and minor strains.If the forming process for any given configuration is continued untilfailure (as defined by localized necking), the major and minorstrains at failure, as shown in Figure 3.2, can be measured for thatconfiguration.

By plotting the failure strains of the various configurations, aboundary line indicating the major strain limit for each minor strainis obtained (Figure 3.3). While this limit is not absolute, there is avery high probability of failure above this boundary line and a lowprobability of failure below this line. The boundary line isfrequently called the forming limit curve, and the entire graph, theforming line diagram (FLD). A second forming limit curve, plottedwith major strains 10% below those of the boundary line, issometimes used to provide a safety factor. Each combination ofmaterial properties and thickness results in a different FLD.

3.1.5 Forming limits

3.2 Roll formingCold roll forming is a process whereby a sheet or strip of metal isformed into a uniform cross section by feeding the stocklongitudinally through a roll forming mill. The mill consists of atrain with pairs of driven roller dies, which progressively form the flatstrip until the finished shape is produced.

The number of pairs of rolls depends on the type of material beingformed, the complexity of the shape being produced, and thedesign of the particular mill being used. A conventional rollforming mill may have as many as 30 pairs of roller dies mountedon individually driven horizontal shafts.

Roll forming is one of the few sheet metal forming processes that isconfined to a single primary mode of deformation. Unlike mostforming operations that have various combinations of stretching,drawing, bending, bending and straightening, and other formingmodes, the roll forming process is nothing more than a carefullydesigned series of bends. In roll forming, metal thickness is notchanged except for a slight thinning at the bend radii.

3-5

FIGURE 3.3TYPICAL FORMING LIMIT DIAGRAM

3-6

The roll forming process is particularly suited to the production oflong lengths of complex shapes held to close tolerances. Largequantities of these parts can be formed with a minimum of handlingand manpower. The process can be continuous by coil feeding andexit cutting to length. Entry material can be pre-painted orotherwisE-coated. Operations such as notching, slotting, punching,embossing and curving can easily be combined with contour rollforming to produce finished parts off the exit end of the roll formingmill. In fact, ultra high-strength steel reinforcing beams, withsweeps up to 50, only need to have the mounting brackets weldedto them before shipment to the assembly line.

3.3 HydroformingThere are two types of hydroforming - sheet and tubular. Sheethydroforming is typically a process where only a female die isconstructed and a bladder membrane performs as the punch. Highpressure fluid (usually water) forces the bladder against the steelsheet until it takes the shape of the female die. Sheet hydroforminghas not been developed to the point it can be effectively utilized bythe automotive industry. It remains a process used for low volume,large parts such as those encountered in aircraft and bus sheetmetal forming.

In tubular hydroforming, a straight or pre-bent tube is laid into alower die. The upper and lower dies are then clamped together.Next, conical nozzles are inserted and clamped into each end ofthe tube. Finally, a fluid (usually water) is forced at a high pressureinto the tube until it takes the shape of the die. While tubehydroforming technology has been around for decades, the massproduction of automotive parts only became cost effective about1984.

The benefits of hydroforming are usually found via partconsolidation and the elimination of engineered scrap. Boxsections, consisting of two hat sections welded together, lendthemselves to cost-effective replacement by a single hydroformedpart. Punches, mounted in the forming dies, are used to pierceholes during forming, eliminating subsequent machine operations.

The structural integrity of a hydroformed part, made from a singlecontinuous tube, is superior to that of a part made from two ormore components. Weight savings of 10 to 20% can be achievedvia both reducing gauge and eliminating weld flanges. If flangesare necessary for attachment, they can be created by pinching thetube during the hydroforming process.

High volume tubular hydroformed parts are currently incorporatedinto automotive components such as axles, exhaust manifolds,suspensions, frames, drive shafts and shock absorbers. Whilehydroforming technology has not been used to date for bumpersystems, it does have potential over the longer term due to themany advantages it offers.

3-7

3.4 Hot formingGenerally speaking, as the strength of steel increases, its ductilitydecreases. One method used to overcome the reduced formabilityof ultra high-strength steel is hot forming. Hot formed bumperbeams have very high strength. They offer not only mass reductionbut also large and compound sweeps. Highly complicated beamscan be produced in one piece. The repeatability of dimensions isvery good and there is no springback, a phenomenon which iscommon with cold forming processes. Weldability is excellent dueto the low carbon content.

The hot forming process involves the following steps:• Blanking/Pre-forming• Heating• Forming/Quenching• De-scaling (if required)

The typical material used for hot stamping is boron steel having0.22% carbon, 0.002% boron, an as-delivered yield strength of330 MPa (47.9 ksi), an as-delivered tensile strength of 500 MPa(72.5 ksi) and a 27% elongation. The boron steel may be bare oraluminized. If aluminized, a hot dip Type 1 coating (10% silicon)and a coating mass of 120-160 g/m2 (0.7-1.0 mils) are common.

After heating and quenching, a hot formed part has very high hardness (470 HV). Thus, it is best to punch any required holesinto the blank. In some processes, a pre-formed section is usedinstead of a developed blank. For example, an open or tubular rollformed section.

The developed blanks or pre-formed parts are continuously fedinto a furnace. They are heated to austenitizing temperatures,approximately 900ºC (1650ºF). If bare steel is used, the furnaceusually has a non-oxidizing atmosphere to suppress scale formation. However, on transfer to the forming/quenching press,some scale will form. If aluminized steel is used, a Fe-Al alloy formsin the furnace on the surface of the steel sheet and scaling isavoided.

In the forming/quenching press, the blank/pre-formed section isformed to its final shape using dies maintained at room temperature. The part is held in the die until it is sufficientlyquenched. Some tempering is usually required. Tempering may beaccomplished by ejecting the part from the forming/quenchingdies while it is still fairly hot or by baking the quenched part in anoven. The yield strength of the final hot formed part has increasedto about 1140 MPa (165 ksi) and the tensile strength to about1520 MPa (220 ksi). Elongation has decreased to less than 12%.

A part made from aluminized sheet has a hard Fe-Al-Si coating system and is scale free, eliminating the need for de-scaling.Further, this coating system provides corrosion protection for thefinished part. A part made from bare sheet does have scale andde-scaling is often employed. De-scaling by blasting with chromi-um shot imparts a thin film of chromium and iron on the part surface, which prevents oxidation.

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3.5 Bumper beam coatingsSteel bumper beams are coated for one or more of the followingreasons: • To improve appearance• To slow or prevent corrosion• To increase resistance to wearThe frontside of a facebar is an exposed automotive part andappearance is critical. However, in addition to appearance, thecoatings applied to facebars made from hot or cold rolled sheetmust also provide adequate corrosion protection and resistance torock chipping. Zinc coated sheet is not commonly used for facebars. One exception, though, is when the thickness of a facebar is less than 1.00 mm (0.039 inches). In such cases, the zincprovides the extra corrosion protection and rock-chip resistanceneeded to meet design requirements. Successful trials have beenconducted on facebars made from stainless steel. An inherentadvantage of such facebars is their corrosion resistance. Thus,stainless steel facebars need only be coated to meet appearanceand rock-chip requirements.

A reinforcing beam is an unexposed part and the main reason forcoating it is to improve corrosion resistance. Sometimes, however,reinforcing beams are given a coating to provide not only corrosion resistance but also appropriate underbody appearance.Steel reinforcing beams are made from hot rolled, cold rolled orzinc coated sheet. Due to its excellent corrosion resistance, stainless sheet in the uncoated condition is a candidate for reinforcing beams.

Bumper beam coatings may be applied by a steel mill, an automotive supplier or an OEM. Steel mills supply sheet withmetallic coatings (e.g., zinc, zinc-iron) that have been applied byhot dipping or electrocoating. Automotive suppliers apply metallic(e.g., chromium), organic (e.g., E-coat, paint), autodeposition andpowder coatings. The OEMs often apply E-coat on their assemblylines.

The coatings applied to current bumper beams are shown inTables 5.4, 5.5 and 5.6. It may be seen that facebars are typicallycoated with chromium or paint, while reinforcing beams typicallyreceive E-coat. The percentage of front or rear reinforcing beamswith a given coating type is given in Figure 3.4 or 3.5. The percentages are calculated by dividing the number of front or rearreinforcing beams with any given coating in Tables 5.4, 5.5 and 5.6by the total number of front or rear reinforcing beams in Tables5.4, 5.5 and 5.6.

These coatings are described in Section 2.10.

This coating is described in Section 2.14.

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3.5.1 Zinc or zinc-iron coatings

3.5.2 Aluminum coating

FIGURE 3.4COATINGS

FRONT REINFORCING BEAMS

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HR/CR Sheet + E-coat (81%)Zn Sheet + E-coat (16%)Zn Sheet (1.5%)AI Sheet + E-coat (1.5%)

FIGURE 3.5COATINGS

REAR REINFORCING BEAMS

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HR/CR Sheet + E-coat (81%)Zn Sheet + E-coat (16%)Zn Sheet (1.5%)AI Sheet + E-coat (1.5%)

In order to achieve a high quality surface after painting or chromium coating, the steel blanks used to stamp facebars mustbe smooth and free of surface defects. Traditionally, hot rolledsheet has been used for facebars and the following steps taken forthe blanks:• Ordering to special surface and flatness requirements • Pickling • Polishing• Phosphating and lubricating

Due to its excellent surface finish, there is a trend to the increaseduse of cold rolled sheet for facebars. In most cases, cold rolled orstainless sheet blanks do not need polishing and they can gostraight to the stamping press line.

Chromium coatings are applied using the electroplating process,which places a thin layer of metal on an object through the use ofelectricity. Although there are variations, the following steps aretypically used to place a chromium coating on a fabricated facebar:• Polishing manually or automatically to remove die marks, orange

peel and shock lines introduced during the stamping process.• Cleaning to remove lubricants, polishing compounds and shop soils.• Pickling to remove oxides, rust, scale and weld smoke.• Rinse.• Semi-bright nickel electroplating.• Rinse.• Bright nickel electroplating.• Rinse.• Decorative chromium electroplating.• Rinse. In the electroplating steps described above, the metal coating isdeposited onto the facebar by applying an electrical potentialbetween the facebar (cathode) and a suitable anode in the presence of an electrolyte. The electrolyte usually consists of awater solution containing a salt of the metal to be deposited andvarious other additions that contribute to the electroplatingprocess. When the metallic salt dissolves in the water, the metalatoms are freed to move about. The atoms lose one or more electrons and become positively charged ions. The metallic ionsare attracted to the negatively charged facebar. They coat thefacebar and regain their lost electrons to become metal once again.

Typical coating thickness applied to the significant (visible) surfaces of steel facebars is:

Total nickel 30 micrometers (1.2 mils) min.

Semi-bright nickel 40-60% of total nickel

Bright nickel 60-40% of total nickel

Chromium 0.25 micrometers (0.01 mils) min. 0.40 micrometers (0.016 mils) max.

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3.5.3 Polishing

3.5.4 Chromium coating

During electroplating, the process is tightly controlled to place therequired thickness of nickel and chromium on the surfaces withhigh visibility. The frontside of a facebar must have excellentappearance and corrosion resistance. Often, a corrosion resistance of 44 hours using the CASS test outlined in ASTM B368is specified. To avoid unnecessary cost, the electroplating processis designed to place an absolute minimum of nickel and chromiumon the hidden surfaces. For this reason, to provide corrosion protection, the backside of facebars, which are hidden, are given apaint coating.

Phosphate conversion coatings are employed to enhance paintadhesion. By enhancing paint adhesion, they indirectly enhancecorrosion resistance. There are several varieties of phosphate coatings (e.g., iron, zinc or manganese).

Prior to the application of a conversion coating, the metal surfacemust be free of shop soils, oil, grease, lubricants and rust. Themetal surface must be receptive to the formation of a uniform,adherent chemical film or coating. Surfaces may be cleaned bymechanical methods or, more commonly, by immersion or spraycleaner systems.

A phosphate coating is applied by immersing a clean metal part ina hot processing solution for 4-6 minutes, depending on bathchemistry. The weight (thickness) of the conversion coating isdependent on the manner in which the part is cleaned, the immersion time, the composition of the processing bath and thecomposition of the metal itself.

E-coat is an organic coating applied by the electrocoating method.Electrocoating has the ability to coat all areas of complex partsincluding recessed areas and edges. E-coat is a durable, lastingcoating. It is used as a primer, top coat or both.

Parts are usually E-coated via a conveyor system in one continuousprocess. Although there are variations, the usual steps in applyingE-coat to a steel part are: alkaline cleaner, water rinse, surface conditioner, zinc phosphate coating (see Section 3.5.4), rinse, sealcoating, de-ionized water rinse, E-coat application, permeate rinse,final de-ionized water rinse, and curing oven.

E-coating systems are known as anodic or cathodic depending onwhether the part is the anode or the cathode in the electrochemicalprocess. Cathodic systems are common since they require lesssurface preparation and they provide better corrosion resistance.

The E-coat process requires a coating tank or bath in which toimmerse the part. The bath, containing water and paint, is given apositive charge (cathodic system). The part, with a negativecharge, when immersed in the bath, attracts the positively chargedpaint particles. The paint particles coalesce as a coating (E-coat)on the part surface. E-coat thickness typically applied to bumperbeams ranges from 20 to 25 micrometers (0.8 to 1.0 mils).

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3.5.5 Conversion coating

3.5.6 Electrocoating (E-coating)

3.5.7 Paint coating

Paint is a cost effective corrosion protection method. It acts as abarrier to a corrosive solution or electrolyte and it prevents, orretards, the transfer of electrochemical charge from a corrosivesolution to the metal beneath the paint.

Paint is a complex mixture of materials designed to protect thesubstrate and to enhance appearance. It is composed of binders,carriers, pigments and additives. Binders provide the major properties to the paint while the carriers (solvents and/or water)adjust the viscosity of the paint for the application. Pigmentsimpart specific properties such as corrosion resistance and color.The type of pigment and its volume are critical to the optimizationof properties such as adhesion, permeability, resistance to blistering and gloss. Additives include thickeners, flow agents, catalysts and inhibitors.

Paints are often identified by the type of polymers employed.Commonly used paint coatings include:• Alkyd and epoxy ester (air dried or baked)• Two-part coatings such as urethane• Latex coatings such as vinyl, acrylic or styrene polymer

combinations• Water soluble coatings (versions of alkyd, epoxy ester or polyester)

Baked enamel basecoat/rigid clearcoat systems are commonlyapplied to the frontside of facebars. The process steps include:• Conversion coating (see Section 3.5.3)• E-coating (see Section 3.5.4)• Enamel basecoating• Enamel clearcoating• Baking.

Autodeposition is a waterborne process that depends on chemicalreactions to achieve deposition. The composition of an autodeposition bath includes a mildly acidic latex emulsion polymer, de-ionized water and proprietary ingredients. The chemical phenomenon consists of the mildly acidic bath attackingthe steel parts being immersed and causing an immediate surfacereaction that releases iron ions. These ions react with the latex insolution causing a deposition on the surface of the steel parts. Thenewly deposited organic film is adherent yet quite porous. Thus,the chemical activators can rapidly diffuse to reach the surface ofthe metal, allowing continued coating formation.

The coating thickness is time and temperature related. Initially, theprocess is quite rapid, but slows down as the film begins to build.As long as the parts being coated are in the bath, the process willcontinue. Typically, film thickness is from 15 to 25 micrometers(0.6 to 0.8 mils).

Autodeposition will coat any metal the liquid touches. Thus, anadvantage of this coating is its ability to coat the inside of tubingand deep cavities. Autodeposition does not require a conversioncoating and the coating cures at a relatively low temperature.

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3.5.8 Autodeposition coating

3.5.9 Powder coating

In the powder coating process, a dry powder is applied to a cleanobject. After application, the coated object is heated, fusing thepowder into a smooth continuous film. Powders are available in awide range of chemical types, coating properties and colors. Themost widely used types include acrylic, vinyl, epoxy, nylon, polyester and urethane. Modern application techniques for applying powders fall into four basic categories: fluidized bedprocess, electrostatic bed process, electrostatic spray process andplasma spray process.

The electrostatic spray process is the most commonly usedmethod for applying powders. In this process, the electrically conductive and grounded object is sprayed with charged, non-conducting powder particles. The charged particles are attracted to the substrate and cling to it. Oven heat then fuses theparticles into a smooth continuous film. Coating thicknesses in therange of 25 to 125 micrometers (1 to 5 mils) are obtained.

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4-1

4. Manufacturing considerations

4.1 Forming considerationsHigh-strength and ultra high-strength steels have less ductility, andhence less formability, than lower strength steels. Thus, care must be taken in part design and forming method selection. In addition,springback increases with yield strength and it must be accountedfor in the process design. Sections 4.1.1 through 4.1.5 provide“Guidelines” and “Rules of Thumb” for the roll forming and stampingprocesses. The Guidelines and Rules of Thumb are based on practicalexperience. Their use will help alleviate formability and springbackissues associated with the roll forming and stamping of high-strengthand ultra high-strength steels.

4.1.1 Guidelines for roll forming high-strength steel

All of the high-strength steels in Table 2.2 can be roll formed, pre-pierced and swept after roll forming.

The following Guidelines apply (Reference 4.3):

Do:• Select the appropriate number of roll stands for the material

being formed. Remember that the higher the steel strength,the greater the number of stands required on the roll former.

• Use the minimum allowable bend radius for the material inorder to minimize springback.

• Position holes away from the bend radius to help achievedesired tolerances.

• Establish mechanical and dimensional tolerances for successful part production.

• Use appropriate lubrication.

• Use a suitable maintenance schedule for the roll forming line.

• Anticipate end flare (a form of springback). End flare iscaused by stresses that build up during the roll formingprocess.

• Recognize that as a part is being swept (or reformed afterroll forming), the compression of metal can cause sidewallbuckling, which leads to fit-up problems.

Don’t:• Do not roll form with worn tooling, as the use of worn tools

increases the severity of buckling.

• Do not expect steels of similar yield strength from different steel sources to behave similarly.

• Do not over-specify tolerances.

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4.1.2 Guidelines for roll forming ultra high-strength steel.

All of the ultra high-strength steels in Table 2.3 can be roll formed,pre-pierced and swept after roll forming.

The following Guidelines apply (Reference 6.1):

1. The minimum bend radius should be four times thethickness of the steel to avoid fracture.

2. Springback magnitude can range from ten degrees for120X steel to 30 degrees for M220HT steel, as comparedto one to three degrees for mild steel. Springbackshould be accounted for when designing the roll forming process.

3. Due to the higher spingback, it is difficult to achieve reasonable tolerances on sections with large radii (radiigreater than 20 times the thickness of the steel).

4. Rolls should be designed with a constant radius and anevenly distributed overbend from pass to pass.

5. About 50% more passes (compared to mild steel) arerequired when roll forming ultra high-strength steel. The number of passes required is affected by themechanical properties of the steel, section depth-to-steelthickness ratio, tolerance requirements, pre-punchedholes and notches.

6. Due to the higher number of passes and higher materialstrength, the horsepower requirement for forming isincreased.

7. Due to the higher material strength, the forming pressure is also higher. Larger shaft diameters should be considered. Thin, slender rolls should be avoided.

8. During roll forming, avoid undue permanent elongationof portions of the cross section that will be compressedduring the sweeping process.

4.1.3 General guidelines for stamping high-strength and ultra high-strength steels.

All of the high-strength streels in Table 2.2 may be stamped intobumper beams. Additionally, some ultra high-strength steels in Table2.3, such as 120X, 135X, 140X and 140T, may be stamped, bendstretched, drawn and flanged.

The following guidelines apply (Reference 6.2):

PRODUCT DESIGN• Avoid designing parts that require a draw forming operation

(i.e., metal must flow or stretch off the binder).

• Maintain gentle shape changes and constant cross sectionswherever possible in part design. These factors becomemore important as material strength is increased.

4-3

• Keep the depth of the part to a minimum when the parthas excessive sweeps in the plan view or elevation.

• Avoid designing parts with closed corners that requiredraw die operations.

• Keep the flanges as short as possible when there is adeep-formed offset flange.

DIE PROCESS• Try to form the parts completely to the depth desired in

the first forming operation.

• Minimize stretch and compression of metal to reduce residual strains that cause springback and twist in the part.

• Use high pressure on the draw binder and balancing blocks.They allow the sheet metal to flow without wrinkling.

• Keep the side walls perpendicular (90 degrees to the baseof the die).

• Avoid open-angle forming. Overbend the flanges 6 to 10degrees.

• On straight channel-shaped parts, consider a solid form die.

• Pre-forming the sheet steel is a method commonly used toaccumulate enough material to ensure that adequatemetal is available for forming without splitting or excessive thinning.

DIE DESIGN• Maintain die forming radii as sharp as possible. Try to

fold the metal rather then stretch it over a radius. Foldingreduces curl of the sidewalls and springback of the weldflanges.

• Maintain an even draw depth and length of line.

• Design robust dies to minimize flexing of the die components.

DIE CONSTRUCTION / TRYOUT• Sidewalls should be as tight as possible to lessen

springback.

• To reduce shock and press tonnage requirements, aminimum shear of four to six times metal thicknesses is required for cutting dies. This minimum shear alsoreduces noise on break through.

• Trim and pierce dies should have 7% to 10% die clearance.

4-4

2

FIGURE 4.1 a)RULES OF THUMB - SPRINGBACK

Refer to Figure 4.1a)

1) Restrike the flange at an overbend angle between 3 and 7 degrees, depending on the material strength and/or thickness.

2) Set up part in die to allow for overbend.

3) Undercut the lower die steel and let the metal overbend.

4) Pre-form the top part surface prior to flanging and flatten the part using the die pad.

The techniques shown in Figures 4.1 a) through 4.1 c) can helpcompensate for springback when forming a 90-degree bend if a sharp radius or a tight flange (see Figure 4.3) is not adequate.

4-5

FIGURE 4.1 b)RULES OF THUMB - SPRINGBACK

Refer to Figure 4.1b)

5) The addition of stiffening darts helps maintain a 90-degree flange.

6) Coining a flange radius as the die bottoms will help maintain form and helps prevent springback.

7) An extension of the upper flange steel allows for extra pressure to be applied on the formed radius. This is a difficult process tocontrol, but it could help in special conditions, particularly onheavier gauge steels.

4-6

FIGURE 4.1 c)RULES OF THUMB - SPRINGBACK

Refer to Figure 4.1c)

8) Providing a vertical step in the flange stiffens and straightens theflange, stopping sidewall curl as well as springback.

9) Rotary benders are used by many manufacturers to control springback, as the metal is rolled around the radius instead of flanging. Positive comments on thismethod promote its ability to overbend the flange.

10) Place a 90 durometer urethane behind flanging steels in a freestate (not compressed). Clearance holes through the flangingsteels allow the screws to hold the urethane in place. Pleasenote the urethane must stay 0.25 inches (6.4 mm) off the bottomof the pocket. This space leaves room for the urethane deflection.Tighten clearance until desired effect is achieved.

11) By adding a horizontal step along the flange, the flange is stiffened,resulting in reduced springback.

4-7

FIGURE 4.2RULES OF THUMB - DIE FLANGE STEELS

Refer to Figure 4.2

1) Flange steel clearance should be 90% of metal thickness, butno greater than metal thickness. Maintaining a tight conditionhelps to prevent springback.

2) Because of the tight clearance, the die steels should be as hardas possible. Therefore, it is recommended that air-hardenedtool steel or harder material be used, and a surface coating beapplied to increase hardness and improve lubricity.

3) Air-hardened tool steel (D2) is recommended for flange steel(Rockwell 58 - 62 on the C-scale). However, other materials maybe used as long as they have a surface coating applied whichresists scoring.

4) All flanging radii should be as sharp as possible without fracturingthe sheet metal during forming. The flange radii should be some-thing less than metal thickness. Start by just breaking the sharpcorner and work from there until you can make the flange withoutsplitting the sheet metal.

4-8

FIGURE 4.3RULES OF THUMB - HAT SECTION

Refer to Figure 4.3

1) Maintain a constant depth on hat sections, if at all possible.

2) The size of the radius is to be kept as small as possible, normallyless than metal thickness.

3) Form 90-degree side walls on the hat section whenever possible.

4) If the sidewall is not 90 degrees, try to balance the forming withthe same angle on the opposite side of the hat section.

5) Unequal residual strain and/or compression on opposite side-walls has a tendency to twist the entire rail.

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FIGURE 4.4RULES OF THUMB - V-CHANNEL

Refer to Figure 4.4

1) Form part so that the V-channel runs with the grain of the steel.This orientation will minimize springback.

2) The inside angle, or upper V-shape, controls the corner radius.The angle of the V-shape is controlled by the lower steel.

3) The outside, lower female shape should have the smaller radius.The side mating surfaces, however, must match those of the anvilexactly in order to control the final angle of the V-shape.

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FIGURE 4.5RULES OF THUMB - RADIUS SETTING

When forming a hat section, the action of the die can aid the retention of shape by setting the corner radii.

Refer to Figure 4.5

1) As the flange steels make contact with the sheet metal blank, aninitial crown is formed.

2) The flange steels then enter over the die-post radii and force themetal to conform to the lower die. The crown remains in thepart. It is best if both sides enter simultaneously.

3) The die is now very close to its home position. The crown remains and the lower flanges are starting to form.

4) As the die is closed, the lower flanges are formed with cornerradii as sharp as possible. The top corners are forced outward as the crown is hit home by the upper die. If the part retains acrown, then a negative crown can be incorporated to minimizespringback.

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FIGURE 4.6 a)RULES OF THUMB - COMBINATION FORM & FLANGE DIE

Refer to Figure 4.6a)

1) The upper pressure pad gives the sheet metal blank its initial contour and holds the blank in location.

2) The lower ring (known also as a lower pressure pad) controlsthe flow of the metal and prevents wrinkling as the part is beingformed (See 5 and 6 on Figure 4.6 b).

Using a combination form-and-flange die is basic to meeting high-strength steel requirements. A general idea of how this dieworks follows.

The die initially forms the contour in the developed blank using theupper pressure pad. The metal is then locked, using the lock beadsto prevent feeding the metal in from the ends. The metal is allowedto flow in freely from the sides without restrictions within the ring,just a metal thickness apart to stop wrinkling.

The flange steels are maintained as sharp as possible, and the sidewalls are tight. This procedure controls the springback and sidewallcurl in order to produce a quality part. If the part is straight, seeFigure 4.5 for more information.

The four-piece form and flange die shown above incorporates features that lend themselves to the production of hat sectionparts. Remember that in order for this type of die to work, the finished part must be off the ring when the part is completelyformed in order to avoid upstroke deformation. The unique features of this die are as follows:

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FIGURE 4.6 b)RULES OF THUMB - COMBINATION FORM & FLANGE DIE

AIR PINS

Refer to Figure 4.6a) and Figure 4.6b)

3) Flange steels should be kept tight to the lower post to help prevent sidewall curl.

4) A smaller-than-metal thickness radius on the lower post helps prevent springback.

5) Restraining beads are used to restrain the flow in at the ends of the rail. The metal must flow off the ring and on to the die post toprevent the panel from being deformed by the upstroke of the die.

6) Metal thickness clearance between the upper and lower ringunder high pressure is needed to allow the metal to flow in fromthe sides without buckling.

7) Balancing blocks (leveling blocks, kiss blocks or spacer blocks) are used to control the clearance between the upper form steelsand the lower ring surfaces in order to adjust for metal flow.

8) If the rail is open-ended, there is no need to restrict metal flowunless stretch is required to help prevent twist.

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FIGURE 4.7RULES OF THUMB - FORMING BEADS

Refer to Figure 4.7

1) Half-round draw beads are used to control metal flow. Theyrestrict the flow and force the metal to stretch or control feed asrequired to produce the draw shape of the part.

2) Lock beads are generally used to stop the metal from moving.This condition is pure stretch. In general, it is recommended thatthis type of bead be avoided in dies used to form high-strengthsteel material.

3) Start lock bead configurations with radii small enough to shear the sheet metal blank. Then uniformly dress the radii to eliminatecutting, but still locking the metal flow. When the beads needreworking, repeat this procedure.

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FIGURE 4.8RULES OF THUMB - FORMING AN EMBOSS

Refer to Figure 4.8

1) This formation is totally within the part’s perimeter and does notextend to the trim.

2) This example shows the formation open to the part’s trim edge.This formation causes excess or loose metal along the edge.Therefore, it is recommended that a short flange and/or small bead be added to stiffen and eliminate this condition.

When forming an emboss or surface formation into a relatively flathigh-strength steel part, the break lines need to be sharp and crisp.You must coin these lines into the part to set them and reduce anyspringback or distortion. Sidewalls of the embossment must be 45 degrees or less from the surface.

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FIGURE 4.9RULES OF THUMB - EDGE SPLITTING

Refer to Figure 4.9

1) When forming an outside corner, the trim edge has a tendencyto wrinkle. In order to minimize this wrinkling condition, it isrecommended that the flange in the area of the wrinkle be asshort as possible.

2) Inside corners have a tendency to split. Therefore, try to makethe trim line as long as possible by scalloping the edge.

A combination of shortening the flange and lengthening the trim line should help stop the splitting.

If not, a formation change has to be made to add material to thesplit area.

It is important that the trim quality be maintained to prevent edge-splitting from work hardening.

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FIGURE 4.10RULES OF THUMB - PART DESIGN

Refer to Figure 4.10

1) The following are general characteristics of high-strength steel(HSS) that should be taken into consideration during the partdesign phase:

· HSS will stretch, generally in the range of 2% to 6%.· HSS will resist compression due to the hardness of the material.

These characteristics of HSS generally require that parts be designedfor form and flange die processes rather than draw dies.

2) In some cases, it is necessary to compensate for these materialcharacteristics by designing in darts and/or notches to equalize the length of line and to help maintain part dimensional integrity.

3) The above diagram shows how these darts and notches could beapplied to an HSS part.

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FIGURE 4.11RULES OF THUMB - DIE CONSTRUCTION


1) Due to the forces exerted during the forming process of high-strength steel, dies must be built with extra strength. Extra strength is necessary to prevent die flexing. The followingare ways to compensate for the unwanted flexing in the die:

• Block in or heel cam drivers. • Use heavy-duty guide pins and bushings.• Key in the sections and use large fasteners.• Provide for positive returns.• Provide heavy-duty die shoes with appropriate reinforcement.

2) Provide for die adjustability during construction. It is importantto provide these adjustments because it is undesirable tomachine the hardened and coated die details.

3) It is of prime importance to balance the forces exerted on thedie during forming. When practical, form two parts at a time, orproduce the right and left hand part in the same die.

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FIGURE 4.12RULES OF THUMB - DEVELOPED BLANKS


1) When using high-strength steel material for BIW (Body-In-White)structural parts, testing has demonstrated that the recommendedtype of forming is with a flange or form die. This type of die utilizesa developed blank.

2) This blank should be as close to finish trim as possible. Only inareas where the trim is critical should a finish trim operation beadded.

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FIGURE 4.13RULES OF THUMB - TRIMMING


1) Because high-strength steel (HSS) is more brittle and harder thanmild steel, and because it is not as ductile as a result of thestrengthening mechanisms in the metallurgy, it is more difficult totrim. HSS requires approximately the same die clearance betweenthe upper and lower trim steels as mild sheet steel. This clearanceis approximately 7% to 10% of metal thickness per side. The rangeof the hardness and the thickness determines the exact amount.

2) Dies must be sharpened more frequently when trimming HSS.They also require rigidity to prevent the die from flexing, whichcan cause dulling of the trim steels.

3) It is recommended that extremely hard cutting edges be providedon trim steels. Therefore, use of S-7 or other shock-resistant steelwith a minimum of 58-62 Rockwell (C-scale) is recommended.

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FIGURE 4.14RULES OF THUMB - DIE SHEAR


1) Due to excessive shock during blanking or trimming of high-strength steel, a full four times (4x) metal thickness shear is recommended to protect both press and die.

In order to prolong the die life of either a blank or trim die, dieshear must be added.

Advantages of the die shear

1) Lessens tonnage requirements.

2) Saves the press; reduces shock on the press.

3) Lengthens the die life between tune-ups and sharpening.

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4.1.4 Guidelines for hat sections stamped from high-strength or ultra high-strength steels.

Basic guidelines for designing and processing hat section parts ofhigh-strength or ultra high-strength steel are (Reference 6.3):

Do:• Form channels as close to finished shape as possible.

• Avoid closed ends on channels.

• Utilize small die radii.

• A combination of low pad pressure and tight clearanceminimizes curl and springback.

• Allow for extra development time.

Don’t:• Assume high-strength and ultra high-strength steel will

behave like mild steel.

• Depend on traditional die design criteria.

4.1.5 Rules of Thumb for high-strength steel stampings.

Common concerns associated with the use of high-strength steel in a stamping operation include springback, splitting, tolerances, diedesign, die life and blank design. The automotive industry routinelyproduces stamped high-strength steel parts. Over the past severalyears, many lessons have been learned through extensive practicalexperience. These lessons have been summarized in the form ofRules of Thumb in Figures 4.1 through 4.14 (Reference 6.2). The application of the Rules of Thumb will alleviate issues associated withhigh-strength steel at the part design and die design stages. They willshorten die development time and help ensure production successin the stamping of high-strength steel parts.

4.2 Welding considerationsHigh-strength and ultra high-strength steels are routinely welded on aproduction basis. Most assemblies can be welded with conventionalequipment using weld cycles similar to conventional ones. In mostapplications, high-strength or ultra high-strength steel is welded tomild steel using gas metal arc or high-frequency welding. Whenwelding ultra high-strength steels, specific weld windows should bedeveloped. With nominal modification to standard weld procedures,weight reduction may be achieved with high-strength and ultra high-strength bumper beam assemblies.

4.2.1 Steel chemistry

Welding procedures must suit the chemistry of the steel grade beingwelded. Steel specifications traditionally set limits on the main elementsin a steel grade (e.g., carbon, manganese). However, most steelgrades contain additional elements that have not been specified.Thus, when selecting suitable welding procedures, it is important toidentify the levels of any unspecified elements in a bumper steelgrade. Recommended Practice, SAE J2340 (Reference 6.4), recognizesthis fact and places limits on unspecified elements. The high-strengthand ultra high-strength steels covered by SAE J2340 are shown inTable 4.1. The unspecified elements permitted in the SAE J2340grades are shown in Table 4.2.

4.2.3 Welding processes

4.2.2 High-strength and ultra high-strength steels.

When welding high-strength and ultra high-strength steels, it isimportant to consider several factors usually not considered whenwelding low-strength steels (e.g., welding process, welding parametersand material combinations). Integration of these considerations canresult in a successful welding system. For instance, a low heat inputresistance seam welding method has been successfully employed forcommercial production of bumper beams made from M190HT steel.

Various welding methods (arc welding, resistance welding, laserwelding and high-frequency welding) all have unique advantages for the welding of specific sheet steel combinations. Factors such as production rate, heat input, weld metal dilution and weld locationaccess may make one welding system more desirable than anothersystem. For instance, a high-strength steel that is problematic forspot welding may not exhibit the same difficulty in arc or high-frequency welding.

It is important to consider material combinations when employingwelding processes that solidify from a molten pool, or that are constrained by thickness ratio. In general, caution should be exercised when spot welding a high-strength or ultra high-strengthsteel to itself because of possible weld metal interfacial fracture tendencies. However, even a problematic higher strength steel canbe spot welded to a mild steel.

On behalf of the Bumper Project of the American Iron and SteelInstitute, David Dickinson, The Ohio State University, conducted a survey on bumper component welding (Reference 4.5). The surveyidentified the welding processes that are currently used in bumper manufacturing, or were used to produce prototype bumpers. Theprocesses are:

1. Gas metal arc welding (GMAW)2. Flux cored arc welding (FCAW)3. Resistance spot welding (RSW)4. Resistance projection welding (RPW)5. Resistance seam welding (RSeW)6. Resistance projection seam welding (RPSeW)7. High frequency and induction resistance seam welding

(RSeW-HF&I)8. Upset welding (UW)9. Friction welding (FRW)

10. Laser beam welding (LBW)11. Laser beam and plasma arc welding (LBW/PAW)

A brief description of each welding process is given in Sections4.2.3.1. to 4.2.3.11.

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Notes: 1) P= phosphorus S= sulphur Cu= copper Ni= nickel Cr= chromiumMo= molybdenum

2) Maximum phosphorus shall be less than 0.050 on grades 180A & 180B.

3) The sum of Cu, Ni, Cr and Mo shall not exceed 0.50% when none of these elements are specified. When one or more of Cu, Ni, Cr or Mo are specified, the sum limit of 0.50% does not apply. However, the individual limits for the unspecified elements apply.

TABLE 4.1 SAE J2340 STEELS AND STRENGTH GRADES

Steel Description Grade Type Available Strength Grade - MPa

Dent Resistant Non Bake Hardenable A 180, 210, 250, 280

Dent Resistant Bake Hardenable B 180, 210, 250, 280

High-Strength Solution Strengthened S 300, 340

High-Strength low-alloy X & Y 300, 340, 380, 420, 490, 550

High-Strength Recovery Annealed R 490, 550, 700, 830

Ultra High-Strength Dual Phase DH & DL 500, 600, 700, 800, 950, 1000

Ultra High-Strength Low Carbon Martensite M 800, 900, 1000, 1100, 1200, 1300, 1400, 1500

Element Type A, B & R Type S Type X & Y Type D & M

P 0.100 0.100 0.060 0.020

S 0.015 0.020 0.015 0.015

Cu 0.200 0.200 0.200 0.200

Ni 0.200 0.200 0.200 0.200

Cr 0.150 0.150 0.150 0.150

Mo 0.060 0.060 0.060 0.06

TABLE 4.2SAE J2340 CHEMICAL LIMITS ON UNSPECIFIED ELEMENTS

Maximum Percent Allowed

This process, schematically illustrated in Figure 4.15a), utilizes adirect current electrical power supply with the electrode positive(DCEP). The positive electrode attracts electrons flowing in the circuit.The electrons act to melt the electrode wire that deposits withinthe weld metal, mixing with molten material from the base metal.Shielding to prevent oxidation of the hot wire and molten weldpool region is provided by an inert shielding gas directed into theweld region by the gas nozzle. The consumable electrode materialis selected to match the strength (and other important characteristics)of the base metal. The wire guide and contact tube must beperiodically replaced in order to maintain good electrical contact.Also, the gas nozzle must be occasionally cleaned of spatteredmaterial.

The welding current is varied by changing the wire feed speed.Higher wire feed speeds produce higher welding currents. The arclength can be varied by changing the voltage setting. Higher voltagesproduce longer arcs.

As illustrated in Figure 4.15b), there are four basic methods inwhich the wire is transferred to the molten weld pool: short-circuiting,globular, pulsed spray and spray transfer. These transfer modeshave been used to describe the GMAW process itself. Terms suchas “short arc”, “dip transfer MIG” and “spray” are all commonnon-standard terms used to describe the GMAW process and themode of operation.

4.2.3.1 Gas metal arc welding (GMAW)

Short-circuiting transfer characteristics At low current and voltage,short circuit transfer occurs. The weld is a shallow, penetrating onewith low heat input. Using GMAW in this mode allows welding inall positions since the weld puddle is small. In comparison to theother three modes of transfer, this method is slowest (low productivity).This mode produces large amounts of spatter if welding variablesare not optimized. This mode, also know as short arc or dip transfer,is used primarily for sheet metal applications.

Globular transfer characteristics This mode of transfer is obtainedat intermediate current and voltage levels or at high current andvoltage levels with 100% CO2 shielding gas. It has higher heatinput and penetration than short circuit transfer. A larger weld poolmakes it more difficult to weld in the over-head position. It producessignificant amounts of spatter.

Pulsed spray and spray transfer characteristics Spray is achievedat higher welding current and voltage with argon or helium basedshielding gas (over 80%Ar). This high-heat, deep-penetrating weldlimits the application to the flat position. This mode produces littleor no spatter and is known for the high deposition rate (higherproductivity). Pulsing the current where spray transfer occursallows for better control for out-of-position welding.

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FIGURE 4.15GAS METAL ARC WELDING (GMAW)

a) SCHEMATIC

b) METHODS OF WIRE TRANSFER

c) EFFECT OF SHIELDING GAS

In GMAW, the shielding gas (used for atmospheric shielding) alsoaffects the type of metal transfer in the process, penetration depth,and the bead shape. These factors are schematically illustrated inFigure 4.15c). The ionization potential of the gas is the ability of thegas to give up electrons and is the characteristic that determines theplasma characteristics of the arc. The ionization potential (IP) of thegas can have an effect on welding characteristics such as arc heat,stability, & starting:

• Helium, with high ionization potential, inhibits spray transfer in steels.

• CO2, with moderate ionization potential also has limited spray transfer.

• Argon, with low IP, promotes the spray mode - particularly at higher currents.

Surface tension of the weld pool and metal droplets are also affectedby the type of shielding gas. Surface tension affects:

• The drop size.• Puddle flow.• Spatter

Argon results in high surface tension with shallower penetration.CO2 results in low surface tension with deeper penetration.

The advantages and limitations of GMAW are:

Advantages Limitations• High deposition rates • Equipment is more expensive and • High Productivity complex than some manual welding • No slag removal processes• Continuous welding • Process variants/metal transfer • Easily automated mechanisms make the process more • Joint fit-up tolerance complex and the process window more

difficult to control• Restricted access (the GMAW gun is

larger than other electrode holders)• Spatter• Porosity (especially with coated materials)• Higher heat input than some processes

In summary, the GMAW process is ideally suited for many bumperbeam applications because of its high deposition rate that results inhigh weld productivity. It is a process that is used on automated andcontinuous welding lines and is often linked with robots and roboticmanufacturing cells. It is tolerant to moderate joint misalignment andthus is suited for welding materials that might experience some forming springback. It is a relatively clean process requiring no slagremoval from the weldment as do other types of welding processes.It requires only occasional tip and gas cap maintenance.

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As illustrated in Figure 4.16a), FCAW uses a tubular wire that isfilled with a flux. The arc is initiated between the continuous wireelectrode and the workpiece. The flux, which is contained withinthe core of the tubular electrode, melts during welding, supplyingsome cleaning action for the weld metal. It resolidifies as a slagbehind the weld shielding the hot weld from oxidation. Vaporformant materials, contained in the flux core, decompose andadditionally shield the weld pool from the atmosphere. Directcurrent, electrode positive (DCEP) is commonly employed as theFCAW process.

There are two basic variants of the FCAW process as shown inFigure 4.16b):

1. Self-shielded (without shielding gas).2. Gas-shielded (with shielding gas).

Each variant uses different agents in the flux core. Usually, self-shielded FCAW contains significant quantities of gas forming powderthat make this variant useful in outdoor conditions where windwould blow away a shielding gas. The fluxing agents in self-shieldedFCAW are designed not only to shield the weld pool and metaldroplets from the atmosphere, but also to deoxidize the weld pool.In gas-shielded FCAW, supplemental shielding gas is provided.Thus, the flux generates only a secondary source of gas shieldingfrom the atmosphere. The main role of the flux is to support theweld pool for out-of-position welds. Gas-shielded FCAW is oftenused to increase the productivity of out-of-position welding and toachieve deeper penetration welds.

The advantages and limitations of FCAW are:

GMAW equipment is more expensive than most manual weldingequipment. The complexity of process variants makes processcontrol more difficult, thus requiring experienced personnel. Theweld gun may have difficulty reaching into restricted spaces; thus,design of parts and supplemental machinery must be considered.Spatter and porosity discontinuities may occur if process parametersare not fairly accurately controlled, leading to the need for weldmentinspection and possibly clean up and post weld repair. Finally,heat input may need to be controlled, particularly when weldinghigh-strength and ultra high-strength bumper steels.

A useful reference document for GMAW is ANSI/AWS/SAESpecification for Automotive and Light Truck Component WeldQuality - Arc Welding (Reference 6.7).

4.2.3.2 Flux cored arc welding (FCAW)

Advantages Limitations• High deposition rates • Slag must be removed • Deep penetration • More smoke and fumes than GMAW• High-quality • Spatter • Less pre-cleaning • FCAW wire is expensive

than GMAW • Equipment is more expensive and• Slag covering helps complex than that for manual

with larger weldingout-of-position welds

• Self-shielded FCAWis draft tolerant

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FIGURE 4.16FLUX CORED ARC WELDING (FCAW)

a) SCHEMATIC

b) PROCESS VARIANTS (Reference 4.6)

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In summary, the FCAW process offers deeper penetration andhigher deposition rates than the GMAW process, particularly inout-of-position welds. Perhaps one of the most important advantagesof FCAW, particularly in bumper welding, is a tolerance for materialthat has not been rigorously cleaned as the flux aids in the cleaningoperation during welding. However, slag must be removed fromthe weldment, and smoke must be removed from themanufacturing environment. If weld parameters are not set properly,spatter on the weldment may become a problem.

A useful reference document for FCAW is ANSI/AWS/SAESpecification for Automotive and Light Truck Component WeldQuality – Arc Welding (Reference 6.7).

4.2.3.3 Resistance spot welding (RSW)

Resistance spot welding is the most common of the resistancewelding processes. It is used extensively in the automotive,appliance, furniture, and aircraft industries to join sheet materials.In this process, water-cooled, copper electrodes, as illustrated inFigure 4.17a), are used to clamp the sheets to be welded intoplace. The force applied to the electrodes insures intimate contactbetween all the parts in the weld configuration. A current is thenpassed across the electrodes through the sheets. The contactresistances, which are relatively high compared to the bulk materialresistance, cause heating at the contact surfaces. The combinationof heat extraction by the chilled electrodes and rapid contactsurface heating causes the maximum temperature to occur roughlyaround the faying surface. As the material near the faying surfaceheats, the bulk resistance rises rapidly while the contact resistancefalls. Again, the peak resistance is near the faying surface, resultingin the highest temperatures in that region. Eventually meltingoccurs at the faying surface, and a molten nugget develops. Ontermination of the welding current, the weld cools rapidly underthe influence of the chilled electrodes and causes the nugget tosolidify, joining the two sheets.

Acceptable-sized weld nuggets can be produced over a range ofcurrents as illustrated in the operating window or “lobe curve” presentedin Figure 4.17b). At the lower end of the current range is the minimumnugget size, which can be found in a resistance-welding manual andis based on the diameter of the electrode face. At the upper endof the current range is the expulsion limit. Expulsion is a conditionin which the weld nugget grows to a size that cannot be containedby the electrode force; molten metal bursts out of the weld seam.

The current range over which an acceptable nugget size isobtained is a measure of the robustness of the welding process. Awide current range indicates that significant variations in theprocess can occur while maintaining some minimum weld quality.A narrow range, on the other hand, indicates that minor variationsin process conditions can result in unacceptable weld quality.

The lobe curve graphically represents the range of acceptablewelding currents as a function of welding time. The minimum andexpulsion currents are determined for a number of welding timesat a particular electrode force. Separate lines are drawn to connectthe minimum weld size currents and the expulsion currents.

The required current level for making a consistently sized weld(presumably just below expulsion) is probably the simplest methodof defining weldability. This measure of weldability is an indicationof the size of welding transformers required to weld the materialsof interest.

FIGURE 4.17RESISTANCE SPOT WELDING (RSW)

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a) SCHEMATIC

b) LOBE CURVE

FIGURE 4.18RESISTANCE PROJECTION WELDING (RPW)

SEQUENCE OF PROJECTION COLLAPSE

RPW, as illustrated in Figure 4.18, is a variation on resistance spotwelding. Basically, a protrusion (projection) is placed on one of thetwo materials to be welded. This projection is then brought intocontact against the second material.

The welding sequence is similar to that for resistance spot welding.The welding electrodes are used to apply both force and currentacross the configuration. The projection constricts current flow (Itis a point of high resistance in the welding circuit, and heatingoccurs preferentially at this point). As the material heats, itbecomes soft, and the projection collapses under the force appliedby the welding electrodes. Due to the amount of plastic flowinvolved, melting is not always necessary to form a sound weld.

The sequence of events during the formation of a projection weldis shown in Figure 4.18. In illustration (a), the projection is shownin contact with the mating sheet. In illustration (b), the current hasstarted to heat the projection to welding temperature. The electrodeforce causes the heated projection to collapse rapidly and fusiontakes place as show in illustration (c). The completed weld isshown in illustration (d).

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The advantages and limitation of RSW are:

Advantages Limitations• High speed, (<0.1 • Higher equipment costs than arc

seconds in automotive weldingspot welds) • Surface indentation

• Excellent for sheet • Nondestructive testingmetal applications • Low tensile and fatigue strength[thickness <6.4 mm • Not portable (0.25 inches)] • Electrode wear

• No filler metal • Lap joint requires additional metal

RSW is widely used in bumper manufacturing because of its highspeed and excellent adaptability for sheet materials. However,RSW requires a sizable investment in equipment and theequipment is mostly non-portable. RSW welds are difficult toinspect nondestructively and they often have lower tensile andfatigue properties than the base metal. Well-maintainedelectrodes are required to ensure the highest quality spot-welds.In addition, surface indentations are often observed at the locationwhere the welds are made. In many applications these are notobjectionable. However, in cases where surface appearance iscritical, the resistance projection welding process should be used.

Two useful references on the evaluation of resistance spot weldsare the Weld Quality Test Method Manual published by theAuto/Steel Partnership (Reference 6.5) and the ANSI/AWS/SAEStandard Recommended Practices for Test Methods for Evaluatingthe Resistance Spot Welding Behavior of Automotive Sheet SteelMaterials (Reference 6.6). It should be noted that these standardtest methods are intended for yield strengths up to 420 MPa (60.9ksi) and modifications may be required for higher yield strengths.

4.2.3.4 Resistance projection welding (RPW)

RPW offers significant production advantages. The welding electrodesare flat and contact a large surface area on the parts being joined.Also, electrode life is improved and the electrodes require lessattention and maintenance that those used in resistance spot welding.

In resistance spot welding, if the welds are too closely spaced, thewelding current is shunted through a previously finished weld. InRPW, multiple welds may be made simultaneously. Thus, shuntingis less of an issue and welds may be more closely spaced than inresistance spot welding. However, if more that three projectionsare welded simultaneously, the height of the projections must beuniform to avoid some projections fusing before others have madecontact. Alternately, ample pressure in conjunction with a doubleweld cycle (one schedule) may be run. The first weld should beshort in time and high in current. The first hit buries and evens outthe projections. The second weld should be longer in time andlower in current. The second hit tempers the welds.

In conventional spot welding, parts may be located by an assemblyfixture and moved to make a second or third spot-weld. Whenusing projection welding, the parts are simply placed in a nest and,with one operation of the machine; all welds are made at once.One part may be located in relation to the other by punching holesin one and matching them with semi-punchings from the other.

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Projection welding is not limited to sheets. Any joint whose projection(contact area) is small compared to the thickness of the parts beingwelded is a candidate for projection welding.

The purpose of a projection is to localize the heat and pressure at aspecific location in a joint. The projection design determines thecurrent density required. Projections in sheet metal parts aregenerally made by embossing, as opposed to projections in solidmetal pieces that are made by either machining or forging. In thecase of stamped parts, projections are generally located on theedge of the stamping.

The advantages and limitations of RPW are:

Advantages Limitations• Satisfactory heat • Requires an additional operation to

balance for welding form projectionsdifficult combinations • Requires accurate control of projection

• Uniform results height and precise alignment of the• Increased output welding dies with multiple welds

because welds are • Requires higher capacity equipment being made than spot weldingsimultaneously • Sheet metal thickness limited by ability

• Longer electrode life to form projections• Welds may be closely

spaced• Parts easily welded in

assembly fixture• Improved surface

appearance• Parts welded that

cannot be resistancespot welded

Small parts, such as brackets or handles, are difficult to locate in aspot welding machine, which results in misplaced spots or extrudedmetal. Neat embossing would be less unsightly and a fitted electrodewould not mark the exposed surface.

RPW has some limitations. The formation of projections mayrequire an additional operation unless the parts are press-formed todesign shape. With multiple welds, accurate control of projectionheight and precise alignment of the welding dies are necessary toequalize the electrode force and welding current. With sheetmetal, the RPW process is limited to the thickness in which projectionswith acceptable characteristics can be formed.

RSeW is a variation on resistance spot welding. In this case, thewelding electrodes are motor driven wheels, which produce a“rolling” resistance or seam weld. There are three independentparameters: power supply and control, welding wheel configurationand sheet configuration.

Power supply and control governs the frequency with which currentis applied to the workpiece. Depending on this frequency and thespeed with which the material is being welded, the weld will be acontinuous seam weld, an overlapping seam weld or a roll spotweld as illustrated in Figure 4.19a).

Seam welds are typically used to produce continuous gas-tight orliquid-tight joints in sheet assemblies, such as automotive fuel tanks.The process is also used to weld longitudinal seams in structuraltubular sections such as bumper beams. In fuel tanks, the use ofoverlapping or continuous seam welds is mandatory. However,bumper beams do not require leak-tight seams and roll spot weldsmay be used.

Typical lobe curves for RSeW are presented in Figures 4.19b) andc)(Reference 4.7). The major variables that control the quality ofseam welds are current (impulse or continuous), speed and force.These variables are plotted for both uncoated and hot-dip galvanizedsteels. It can be noted that as the speed increases, a limit isreached where a non-continuous seam is produced. Likewise, asthe current is increased, a point is reached where surface eruptionsor expulsion occurs and the copper from the electrodes melts andmay cause additional cracking. In general, increased electrodeforce tends to increase the acceptable lobe size and move it tohigher current levels. For coated steels, the speed tends to bereduced and the current increased.

The advantages and limitations of RSeW are:

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4.2.3.5 Resistance seam welding (RSeW)

Advantages Limitations• High Speed • Higher equipment costs than arc welding• Excellent for sheet • Power line demands

metal applications • Nondestructive testing[<6.35mm • Low tensile and fatigue strength(0.25 inches)] • Not portable

• No filler metal • Electrode wear• Ability to produce • Lap joint requires additional metal

leak-tight joints

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FIGURE 4.19RESISTANCE SEAM WELDING (RSeW)

a) SEAM VARIATIONS b) LOBE CURVE FOR UNCOATEDLOW CARBON STEEL

c) LOBE CURVE FOR HOT-DIP GALVANIZED LOW CARBON STEEL

FIGURE 4.20RESISTANCE PROJECTION SEAM WELDING (RPSeW)

a) SCHEMATIC b) SEAM GEOMETRY

Surface Eruption, Cu Contamination Cracking

CU

RREN

T, k

A

CU

RREN

T, k

A

Lower SpeedHigher Current

FORCE N

FORCE lb.

FORCE lb.FORCE N

Non-ContinuousSeam

SPEED, in./min.

SPEED, mm/sec

SPEED, mm/secSPEED, in./min.

Unitsas perb

The advantages of high speed, applicability to sheet materials andno need for filler metal make RSeW ideally suited for the closurewelding of bumper beam tubes in a high speed automated fabricationline. Often these lines consist of a steel coil (slit to the properwidth) being fed from a pay-off reel into a continuous roll formingline. The line forms the required tubular cross section. The seamwelder then closes the open tube. The formed and welded tubularsection may then go through an induction heat-treating device orinto a sweep forming device, and finally into a cutter, which cutsthe beam to length.

The limitations of RSeW include higher initial equipment costscompared to arc welding and higher power costs compared to arcwelding. In addition, electrode wear and maintenance and the lackof non-destructive testing techniques to assure good welds must beaddressed. Finally, because RSeW is suited to lap joints (rather thanbutt joints as used in arc welding), a slight increase in part weightoccurs.

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In conventional projection welding (RPW), the current is concentratedexactly at the weld location. A relatively new process, resistanceprojection seam welding as illustrated in Figure 4.20a), does thesame thing in seam welding (Reference 4.8). In RSeW, a projectionis rolled into one of the sheets to be welded on a roll forming line.The sheet with the projection, and the sheet to which it is to bewelded, are presented into the resistance seam-welding machinewhere current is passed through two opposed rolls. The currentmust flow through the projection thus concentrating its density asin conventional projection welding.

The shape of the projection has been studied and both the continuousprojection geometry and the dimple projection geometry (asillustrated in Figure 4.20b), have been successfully used. Thecontinuous projection makes a continuous weld, but requires moretotal energy input. The dimple projection makes an intermittentseam; but requires less total energy input.

The advantages and limitations of RPSeW are:

4.2.3.6 Resistance projection seam welding (RPSeW)

Advantages Limitations• Satisfactory heat • Requires an additional operation to form

balance for welding projectionsdifficult combinations • Requires accurate control of projection

• Uniform results height and precise alignment of the• Reduced total energy welding dies

consumption • Sheet metal thickness limited by• Longer electrode life ability to form projections• Parts easily welded

in assembly fixturesurface

• Improved surfaceappearance

• Parts welded thatcannot be resistancespot welded

The advantages of RPSeW are: heat balance problems are solved,the welds are uniform, welding speed is increased and total energyconsumption is reduced. The preparation of the projection, however,requires an additional step. This issue may not be too great aconcern if the projection is formed on the same roll forming lineused to make a part. However, control of the projection size anddesign is still an issue.

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High frequency welding includes those processes in which thecoalescence of metals is produced by the heat generated from theelectrical resistance of the work to high frequency current, usuallywith the application of an upsetting force to produce a forgedweld.

There are two processes (Reference 4.9) that utilize high frequencycurrent to produce the heat for welding: high frequency resistancewelding (HFRW), as illustrated in Figure 4.21a), and high frequencyinduction welding (HFIW), sometimes called induction resistancewelding, as illustrated in Figure 4.21b). The heating of the work inthe weld area and the resulting weld are essentially identical withboth processes. With HFRW, the current is conducted into thework through electrical contacts that physically touch the work.With HFIW, the current is induced in the work by coupling with anexternal induction coil. There is no physical electrical contact withthe work. A characteristic of high frequency current is that it travelsas close to the “vee” edge as possible, thus treating only thesurfaces that are to be welded.

Although the welding process depends upon the heat generatedby the resistance of the metal to high frequency current, otherfactors must also be considered for successful high frequency welding.Because the concentrated high frequency current heats only asmall volume of metal (just where the weld is to take place), theprocess is extremely energy efficient, and welding speeds can byvery high. Materials handling, forming and cutting limit themaximum line speed. Minimum line speed is set by materialproperties and weld quality requirements.

The fit of the surfaces to be joined and the manner in which theyare brought together is important if high-quality joints are to beproduced. Flux is not usually used but can be introduced to theweld area in an inert gas stream. Inert gas shielding of the weldingarea is generally needed only for joining reactive metals such astitanium and certain stainless steel products.

The advantages and limitations of high frequency welding processesare:

Advantages Limitations• Produces welds with • Special care must be taken to avoid

very narrow heat- radiation interference in the plant’saffected zones vicinity

• High welding speed • Uneconomical for products requiredand low power in small quantitiesconsumption • Needs proper fit-up

• Able to weld very • Hazards of high frequency currentthin wall tubes

• Minimizes oxidationand discoloration aswell as distortion

4.2.3.7 High frequency and induction resistance seam welding (RSeW - HF&I)

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FIGURE 4.21HIGH FREQUENCY AND INDUCTION RESISTANCE SEAM WELDING (RSeW-HF&I)

a) HIGH FREQUENCY RESISTANCE WELDING b) HIGH FREQUENCY INDUCTION WELDING

FIGURE 4.22UPSET WELDING (UW)

a) SCHEMATIC b) PLATEN MOTION

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High frequency welding processes offer several advantages overlow frequency and direct current resistance welding processes.One characteristic of the high frequency processes is that they canproduce welds with very narrow heat-affected zones. The highfrequency welding current tends to flow only near the surface ofthe metal because of the “skin effect” and along a narrowcontrolled path because of the “proximity effect”. The heat forwelding, therefore, is developed in a small volume of metal alongthe surfaces to be joined. A narrow heat-affected zone is generallydesirable because it tends to give a stronger welded joint than thewider zone produced by many other welding processes. Withsome alloys, the narrow heat-affected zone and absence of caststructure may eliminate the need for post-weld heat treatment toimprove the metallurgical characteristics of the welded joint. Theshallow and narrow current flow path results in extremely highheating rates and therefore, high welding speeds and low-powerconsumption. A major advantage of the continuous high frequencywelding processes is their ability to weld at very high speeds. highfrequency welding can also be used to weld very thin wall tubes.Wall thicknesses down to 0.13mm(0.005 inches) is presently beingwelded on continuous production mills. The processes areadaptable to many steels including low carbon, low-alloy andstainless steels. Because the time at welding temperature is veryshort and the heat is localized, oxidation and discoloration of themetal as well as distortion of the part are minimal.

As with all processes, there are limitations. Because the equipmentoperates in the radio frequency range, special care must be takenin its installation, operation, and maintenance to avoid radiationinterference in the plant’s vicinity. As a general rule, the minimumspeed for carbon steel is about 7.6m/min(25 feet/min). Forproducts that are only required in small quantities, the highfrequency processes may be uneconomical unless the technicaladvantages justify the application. Because the high frequencyprocesses utilize localized heating in the joint area, proper fit-up isimportant. Equipment is usually incorporated into mill or lineoperation and must be fully automated. The process is limited tothe use of coil, flat, or tubular stock with a constant joint symmetrythroughout the length of the part. Any disruption in the currentpath or change in the shape of the vee can cause significantproblems. Special precautions must be taken to protect plantpersonnel from the hazards of high frequency. The high frequencyprocesses have found applications in the seam welding of bumperreinforcement beams on continuous lines.

UW is a resistance welding process that produces coalescenceover the entire area of faying surfaces, or progressively along abutt joint, by the heat obtained from the resistance to the flow ofwelding current through the area where those surfaces are incontact. Usually DC current is used for the heating, with theparts clamped in electrical contacting dies, one stationary andthe other movable as illustrated in Figure 4.22a). Pressure is usedto complete the weld.

The movable clamping die (or platen motion) is presented inFigure 4.22b). At first, the motion brings the parts into intimatecontact. Then the weld current is energized. In joints withnormal fit-up, some thermal expansion may be seen as the partsheat. Joints with poor fit-up tend to experience a joint seatingmotion during this period. At a point in time when sufficientheating has occurred, a rapid forging force is applied and theabutting parts are rapidly forced into each other, causing someoutward material flow.

With this process, welding is essentially done in the solid state.The metal at the joint is resistance heated to a temperaturewhere recrystallizaion can rapidly take place across the fayingsurfaces. A force is applied to the joint to bring the fayingsurfaces into intimate contact and then upset the metal. Upsethastens recrystallization at the interface and, at the same time,some metal is forced outward from this location. This tends topurge the joint of oxidized metal.

Upset welding has two variations:

1. Joining two sections of the same cross section end-to-end (butt joint).

2. Joining of sections with differing cross sections such as a stud to a plate.

The first variation can also be accomplished by flash welding.The second variation is also done with resistance projectionwelding.

The advantages and limitations of UW are:

The upset welding of butt joints is fast and can be automated.There is some flexibility in joint design. However, control of thejoint tolerances is critical. The process requires large amounts ofcurrent so DC rectified current is usually used to improveefficiency. In some applications, the weld flash must beremoved.

The upset butt process involves relatively slow heating and nomeasures are taken to protect the joint from air. Consequently, agenerous upset is required to exude oxidized metal. For this reason,other butt welding processes such as flash, percussion or frictionwelding are often preferred.

4.2.3.8 Upset welding (UW)

4-39

Advantages Limitations• Some flexibility in • Produces unbalance on three-phase

cross section shape primary power lines so often DC• Rapid process, can current is used

be automated • Requires special equipment for• Impurities can be removal of flash metal

removed during • Difficult alignment for workpiecesupset with small cross sections

• Can weld rings and • Requires part cross sectionvarious cross sections consideration

FRW is a process that produces a weld under a compressiveforce (Reference 4.10). As illustrated in Figure 4.23a), the workpieces are brought into contact and rotated very rapidly toproduce heat. Usually one piece is rotated against a stationarypiece to produce the heat at the junction. The rotation time andforce are adjusted until the temperature in the joint reaches theforging temperature of the material at which time the rotation isstopped and an axial force is applied to forge weld the piecestogether. As such, the process is a solid-state bonding process.

Geometries that have a rotational symmetry are particularlysuitable for friction welding. Applications include round bars andtubes to each other, as well as bars or tubes to sheet steel.

Linear friction welding is used for parts with non-rotationalsymmetry. In this application, one part is oscillated back andforth against the other (Figure 4.23b).

The advantages and limitations of FRW are:

FRW is fast and can join many different materials. It is one ofonly a few welding processes that has this material variability. Itis easily automated. However, part geometry can be a limitation;and, in general, the materials to be joined must be hot forgeable.

4.2.3.9 Friction welding (FRW)

“LASER” is an acronym for “light amplification by stimulatedemission of radiation.” A laser beam that becomes highlyfocused is an excellent source of concentrated energy. This energyis used for many welding applications and also for cutting andheat treating.

Two basic types of lasers are used in welding: solid-state and gas(Reference 4.10). Solid-state lasers are made of a single elongatedcrystal rod. Nd:YAG (a doped crystal of neodymium with yttrium,aluminum, and garnet) is the most common solid-state laser usedfor welding today. The end surfaces of the rod are ground flatand parallel. These ends usually have a reflectivE-coating placedon them. While one end is totally reflective, the other end is partiallyreflective, leaving a small area for photons to escape. The Ndions excite their electrons to a higher energy level. By doing this,photons are emitted at a wavelength of 1.06 microns. After thephotons are emitted, the electrons are allowed to return to theiroriginal state.

4.2.3.10 Laser beam welding (LBW)

4-40

Advantages Limitations• Faster than most • Start-up cost is high

other processes • Parts must be able to rotate about an• Can join dissimilar axis of symmetry

material together • Free machining alloys are difficult to(e.g.) Copper to weldsteel • Non-forgeable materials cannot be

• Easily automated friction weldedfor high-volumeproduction

4-41

FIGURE 4.23FRICTION WELDING (FRW)

a) PART ROTATION b) PART OSCILLATION

FIGURE 4.24LASER BEAM WELDING (LBW)

b) BEAM FOCUS

a) CARBON DIOXIDE LASER

4-42

The most common gas laser is the carbon dioxide laser (seeFigure 4.24a). It is also the laser used for most welding applications.An electrical charge excites the carbon dioxide molecules, whichon their return to their normal energy state emit some photons.Much like solid-state lasers, reflective surfaces are placed at theends of the tube in which the gas is contained. The one end istotally reflective, while the other allows a small amount of light topass. This light is emitted at a wavelength of 10.6 microns.

Factors affecting the choice between gas and solid-state lasers are:

Nd:YAG lasers: most metals absorb its wavelength better thanthe CO2 laser wavelength, versatile fiber-optic delivery, easybeam alignment, easier maintenance, smaller equipment, andmore expensive safety measures than CO2 because of its wave-length.

CO2 lasers: higher power, better beam quality in terms of focusability, higher speeds and deeper penetration for materials thatdon’t reflect its light, and lower start-up and operation.

In laser welding, the beam can be focused for different applicationsas illustrated in figure 4.24b). Usually, a small focus size is usedfor cutting and welding, while a larger focus is used for heat treatmentor surface modification. The focal spot of the beam can also bevaried based on the application.

The advantages and limitations of LBW are:

LBW advantages include the very rapid weld travel speed andthe low heat input that results in very little distortion. However,initial equipment costs for laser welding are high. Additionalcosts to assure good part fit-up may be of some disadvantage.Coatings on steel can be a problem in plume formation throughwhich the laser beam cannot adequately penetrate. Fume controlshielding gas may be required.

There have been a number of experimental developments inwelding processes using the laser welding process as a base andcoupling a second welding process (such as plasma arc welding)with it. The benefit is that the high travel speed associated withthe laser process is combined with the metal fill, the less stringentpart fit-up and the favorable bead shape associated with the plasmaarc process. Two variations of the LBW/PAW process aredescribed in two patents (References 4.11 and 4.12).

Advantages Limitations• Single pass weld • High initial start-up costs

penetration in • Part fit-up and joint tracking aresteel up to 19mm critical(0.75 inches) thick • Not portable

• Materials need • High cooling rates may lead tonot be conductive material problems

• No filler metalrequired

• Low heat inputproduces lowdistortion

4.2.3.11 Laser beam and plasma arc welding (LBW/PAW)

The heat of welding causes changes in the microstructures andmechanical properties in a region of heated steel that is referredto as the heat-affected zone (HAZ). The resulting microstructurein the HAZ will depend on the composition of the steel and therate at which the steel is heated and cooled. The degree ofhardening in the HAZ is an important consideration determiningthe weldability of a carbon or low-alloy steel. Weldability andresistance to hydrogen cracking generally decrease with increasingcarbon or martensite in the weld metal or the HAZ, or both.

Although carbon is the most significant alloying element affectingweldability, the effects of other elements can be estimated byequating them to an equivalent amount of carbon. Therefore,the effect of total alloy content can be expressed in terms of acarbon equivalent (CE). One empirical formula that may be usedfor judging the risk of underbead cracking in carbon steel is:

CE = C + Mn + Cr + Mo + V + Ni + Cu

6 5 15

Generally, steels with low CE values (e.g., 0.2 to 0.3) have excellentweldability; however, the susceptibility to underbead crackingfrom hydrogen increases when the CE exceeds 0.40.

David Dickinson, The Ohio State University, used his experienceand the results of a State-of-the-Art Welding Survey (Reference4.5), to rank the suitability of various welding processes for joining bumper steels. His “poor”, “acceptable”, “better” and“best” rankings are given in Table 4.3. Note: The rankings for10B21 Modified were added to the Table by the American Ironand Steel Institute’s Bumper Project Group. The rankings are subjective and should not be taken as absolute. However, theydo provide a starting point for the selection of a welding process.

The welding processes in Table 4.3 were all identified inDickinson’s SOA Survey as ones that are currently used inbumper manufacture, or were used to produce prototypebumpers. The processes, described in Sections 4.2.3.1 to4.2.3.11, are:

1. Gas metal arc welding (GMAW)2. Flux cored arc welding (FCAW)3. Resistance spot welding (RSW)4. Resistance projection welding (RPW)5. Resistance seam welding (RSeW)6. Resistance projection seam welding (RPSeW)7. High frequency and induction resistance seam welding

(RSW-HF&I)8. Upset welding (UW)9. Friction welding (FRW)

10. Laser beam welding (LBW)11. Laser beam and plasma arc welding (LBW/PAW)

4.2.4 Weldability of bumper materials

4-43

4.2.5 Ranking of welding processes

4-44

TABLE 4.3RANKING OF WELDING PROCESSES BY BUMPER MATERIAL

BUMPERMATERIAL1

MATERIALSTANDARD2

WELDING PROCESSES 3, 4

UNCOATED

CQ

DQSK

DQAK

35XLF

50XLF

55XLF

80XLF

120XF

135XF

140T

M190HT

10B21 (Modified)

COATED

HDG/EG

SAEJ2329 (Grade 1)

SAEJ2329 (Grades 2 & 3)

SAEJ2329 (Grades 2 & 3)

SAEJ1392 (035XLF)

SAEJ1392 (050XLF)

SAEJ1392 Modified

SAEJ1392 (080XLF)

SAEJ2340 (830R)

SAEJ2340 Modified

SAEJ2340 (950DL)

SAEJ2340 (1300M)

SAEJ403 (10B21 Modified)

—

B

B

B

B

B

B

B

b

b

b

b

B

b

B

B

B

B

B

B

B

b

b

b

b

B

b

B

B

B

B

B

B

B

B

B

B

b

g

g

B

B

B

B

B

B

B

B

B

B

b

g

g

B

B

B

B

B

B

B

B

B

B

b

b

g

B

B

B

B

B

B

B

B

B

b

b

g

g

B

B

B

B

B

B

B

B

B

B

b

B

g

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

b

p

b

b

b

b

b

b

b

b

b

b

b

b

p

GM

AW

FCA

W

RSW

RP

W

RSe

W

RP

SeW

RSe

W-H

F&1

UW

FRW

LBW

LBW

/PA

W

1. Refer to Section 4.2.5 and Tables 2.1, 2.2, 2.3, 5.4 and 5.5 for bumper material definitions and properties.

2. See References 4.13, 4.14, 4.15 and 6.4.

3. Refer to Section 4.2.3 for welding process definitions.

4. p = poor g = acceptable b = better B = best

All of the materials in Table 4.3 are commonly used for productionbumpers. Examples are given in Tables 5.4 and 5.5 along with adescription of each bumper material. In Table 4.3, the weldingprocesses are ranked for the following materials:

Hot rolled or cold rolled (uncoated) sheet steel

1. CQ Commercial quality2. DQSK Drawing quality, special killed de-oxidation

practice.3. DQAK Drawing quality, aluminum killed.4. 35XLF High-strength low-alloy with sulphide inclusion

control, low carbon, 240 MPa (35 ksi) yield strength.

5. 50XLF High-strength low-alloy with sulphide inclusion control, low carbon, 345MPa (50ksi) yield strength.

6. 55XLF High-strength low-alloy with sulphide inclusion control, low carbon, 380MPa(55ksi) yield strength.

7. 80XLF High-strength low-alloy with sulphide inclusion control, low carbon, 550MPa (80ksi) yield strength.

8. 120XF High-strength low-alloy with sulphide inclusion control, low carbon 830MPa (120ksi) yield strength.

9. 135XF High-strength low-alloy with sulphide inclusion control, low carbon 920MPa (135ksi) yield strength.

10. 140T Dual phase structure contains martensite in ferrite matrix, excellent formability prior to strain aging, 965MPa (140ksi) tensile strength.

11. M190HT Martensitic quality, 1310MPa (190ksi) tensile strength.

12. 10B21 Carbon-boron steel, 1140MPa (165ksi) yield (Modified) strength after hot forming and quenching.

hot-dip galvanized or electrogalvanized sheet steel

13. HDG/EG Includes materials one through 12 (above) that have been hot-dip galvanized or electrogalvanized.The ranking of the welding processes for individual materials (one through 12) in the galvanized condition becomes quite complex because of the dual effect of steel grade and metallic coating on weld ability. Thus, one overall ranking is given for each of materials onethrough 12 in either the hot-dip galvanized or the electrogalvanized condition for each welding process.

4-45

4-46

The following is an overall explanation of the rankings assigned inTable 4.3:

Arc welding (GMAW and FCAW)

In general, all steel bumper materials may be arc welded withoutdifficulty. Selection of an appropriate filler metal with properstrength is all that is required. Welding consumable manufacturerscan assist with this selection.

Consideration should be given to the heat-affected zone in arcwelded joints. The graphs in Figure 4.25 are diagrammaticrepresentations of the heat-affected zone for arc welded steelbumper materials. Actual plots are available from steel suppliersand welding consumable manufacturers.

Figure 4.25 indicates that as the carbon content in the steelincreases, the hardness at the fusion line increases. For example,the carbon content of a martensitic steel depends on its strengthlevel. A higher strength level has a higher carbon content. Figure4.25 indicates that a martensitic steel with a higher carbon contenthas increased hardness at the fusion line. Dual phase steel isanother example. The carbon content of dual phase steel dependson its production process - as rolled, batch annealed or continuousannealed. All three have different carbon levels and differentfusion line hardness.

Figure 4.25 also indicates that some steel materials undergo softeningand a loss of strength in the heat-affected zone (e.g., microalloy,dual phase, recovery annealed and martensitic materials). Lowerheat input during welding helps reduce the degree of softening.

Higher strength materials are slightly more difficult to weld thanlower strength materials because of the springback associated withhigher strength parts. Fixturing, to hold the parts firmly in placeduring welding, is often required to get defect free welds.

Galvanized coatings on steel can cause minor difficulties with arcwelding. For example, zinc has a much lower melting andvaporization point than steel. Thus, during welding, zinc fumes aregenerated. They may be captured by a ventilation system. Also,intermetallic zinc inclusions may be formed during welding.However, inclusions may be minimized by using the FCAWprocess. The flux scavenges the inclusions and they are removedalong with the flux.

Resistance welding (RSW, RPW, RSeW and RPSeW)

A comparison of resistance spot weldabilty is given in Figure 4.26for hot rolled, cold rolled and galvanized sheets. Welding lobesare given for representative bumper materials. The lobes are some-what arbitrary. However, they do allow a rough comparison of thespot weldability of steel materials. For a given material, a weldinglobe is expressed as weld time verses weld current at a constantelectrode force level.

4-47

FIGURE 4.25HARDNESS IN HEAT-AFFECTED ZONE OF ARC WELDS

Distance From Fusion Line

Ha

rdn

ess

4-48

FIGURE 4.26RESISTANCE SPOT WELDING COMPARISON

c) GALVANIZED SHEET

a) HOT ROLLED SHEET

b) COLD ROLLED SHEET

Each lobe is a three dimensional diagram. The larger rectangularplane in a lobe represents the base line of weldability. Thisbase line diminishes into the depth of the page to a smallerplane. The reduction in plane size represents sensitivity tosome weld parameter such as electrode force. Thus, whenthe two planes are almost the same size, the material is weldableover a wide range of parameters. On the other hand, if oneplane is considerably smaller than the other, weldability lossesare expected with a change in parameter. For galvanized sheets,the coating has a marked effect on weldability. To representthe effect of the coating, a square has been placed onto thesmaller plane.

The lobes in Figure 4.26 are sometimes referred to as operatingwindows. Weld current and time must be within an operatingwindow to achieve a sound weld. A small operating windowmeans a high degree of control is required in the weldingprocess. Thus, materials with small operating windows areregarded as less weldable than materials with large windows.

CQ and DQ hot and cold rolled materials are weldable over awide range of welding currents and times. Their excellentweldability is often taken as the base against which othermaterials are compared. CQ and DQ are only minimallyaffected by electrode force (A high electrode force reducescontact resistance. Thus, either more current or a longer weldtime is required). Weld nuggets in CQ and DQ materials areductile and strong.

The hot and cold rolled XLF materials have excellent weldability.They closely match the weldability of CQ and DQ. The XLFmaterials obtain their strength from microalloying elements(precipitation hardening) and controlled rolling (fine grainsize). During welding, loss of precipitation hardening andgrain growth may occur, resulting in strength loss in the heat-affected zone. Usually, the effect is minimal and does not hinderthe application of XLF materials.

120XF and 135XF hot and cold rolled sheets generally obtaintheir strength through cold work and recovery annealing.While there is no problem welding these materials, a reductionin hardness and strength in the heat-affected zone can occur.Using the lowest current and shortest weld time prevents overwelding and improves heat-affected zone strength.

Weldability tests on hot and cold rolled dual phase (e.g. 140T)steels show they respond very similar to other steels at theirstrength level.

Martensitic hot or cold rolled sheet (e.g., M190HT) obtains itsstrength through the quench hardening of somewhat highercarbon steel to martensitic steel. Resistance weld nuggetstend to be brittle and subject to cracking failure. Also,strength loss, through tempering of the base metal, can occurin the heat-affected zone. Regardless, martensitic steels areresistance weldable provided some precautions are taken duringwelding.

4-49

Galvanized coatings add a complexity to welding. In general, asthe strength level of the base steel increases, weldability decreases.Also, as strength increases, the required electrode force increases.The effect of the coating on the electrode, plus the higher weldingforce, cause reduced weldability as indicated by the smalleroperating windows for galvanized materials. Coatings alsoreduce electrode life; thus, the condition of the electrodes mustbe closely monitored during welding. Frequent dressing orreplacement of the electrodes is required.

High-frequency welding (RSeW-HF&I)

All of the current bumper materials are readily joined by highfrequency welding. High frequency welds have only a smallheat-affected zone because the welding current is concentratedon the surfaces to be welded. In addition, the squeeze at thepoint of weld consummation forces any inclusions in the moltenweld metal out of the weld zone. Galvanized coatings have littleaffect on weldability since the heated region of a joint is small.Also, there is little vaporization of the coating and fuming.

Upset and friction welding (UW and FRW)

Upset and friction welding both result in relatively low heating.Thus, the heat-affect zone not only is small but also containsminimal softening. It is very difficult to align sheet steel partswith these processes. Thus, they are mainly used for bar stockand thicker steel.

Laser welding (LBW and LBW/PAW)

A laser beam is finely focused and usually associated with highertravel speed, therefore, a laser weld has a very small heat-affectedzone due to the higher cooling rate. Thus, any loss of strength inthe welded materials, even higher strength ones, is minimal. Thisprocess requires excellent fit-up, which is sometimes difficult toachieve during production, especially with higher strength materialsdue to springback. The vaporization of galvanized coatings cancause a plume, which blocks the laser beam. In such a case, afume control shielding gas may be used.

4-50

5.1 Sweep (roll formed sections) and depth of draw (stampings)The current styling trend for vehicles is toward rounded,aerodynamic shapes. This trend has impacted bumper design andchallenged bumper manufacturers to provide the highly roundedshapes desired by vehicle stylists. Steel bumper manufacturers havemet the challenge and are providing the contours required for bothreinforcing beams and facebars.

A convenient way of defining the degree of roundness for astamped or roll formed reinforcing beam is to use the concept ofsweep. Sweep expresses the degree of curvature of the outerbumper face, or the face farthest removed from the inside of thevehicle. Sweep is defined in Figure 5.1 and Tables 5.1 and 5.2.Sweep in the camber, X, for a 60 inch (1524 mm) chord length, L,of a given circle of radius, R. Sweep in expressed as the number ofone-eighth inches (3.18 mm). For example, if X is 5 inches (127mm) for an L of 60 inches (1524 mm), the sweep would be 40.Tables 5.1 and 5.2 indicate that a sweep number of 40 correspondsto a radius of curvature of 92.5 inches or 2350 mm. Tables 5.1 and5.2 also list the cambers for chord lengths smaller than 60 inches(1524 mm). For example, if the camber is 2.711 inches (68.9 mm)and the chord length is 40 inches (1016 mm), the sweep number is50. The concept of sweep applies well to a reinforcing beambecause it has a near constant radius of curvature and no wraparounds at the end of the reinforcing beam.

Depth of draw is often used to describe the amount of roundingand wrap around on a bumper section, and in particular, a stampedfacebar. As shown in Figure 5.2, depth of draw is the distance, X,between the extreme forward point on a bumper and the extremeaft point on a bumper. This distance has a physical significance inthat it cannot exceed the opening available with a given stampingpress. X is usually stated in inches (millimeters).

5.2 Tailor welded blanksA tailor welded blank is two or more pieces of flat material, havingdissimilar thicknesses, and/or physical properties, joined togetherbefore forming to provide customized qualities in the finishedproduct. Examples are shown in Figure 5.3.

Talor welded blanks are commonly joined using one of thefollowing methods (Reference 7.1):

1. Laser beam butt seam welding2. high frequency induction butt seam welding3. Resistance roller mash lap seam welding4. Electron-beam butt seam welding

5. Design concepts

5-1

FIGURE 5.1DEFINITION OF SWEEP

5-2

TABLE 5.1SWEEP NUMBERS (CAMBER, X, INCHES)

SWEEPNO.

CHORD LENGTH, L, INCHES RADIUS(inches)

30 35 40 45 50 55 60

1

10

15

20

25

30

35

40

45

50

55

60

0.031

0.311

0.466

0.622

0.773

0.926

1.072

1.224

1.373

1.513

1.659

1.790

0.043

0.424

0.635

0.847

1.052

1.263

1.474

1.670

1.872

2.067

2.264

2.449

0.056

0.554

0.830

1.107

1.374

1.652

1.924

2.188

2.455

2.711

2.973

3.218

0.070

0.701

1.050

1.402

1.749

2.095

2.445

2.776

3.167

3.449

3.782

4.103

0.087

0.866

1.297

1.732

2.164

2.592

3.023

3.442

3.867

4.282

4.703

5.106

1.105

1.048

1.569

2.098

2.621

3.143

3.673

4.182

4.701

5.214

5.731

6.236

0.125

1.250

1.875

2.500

3.125

3.750

4.375

5.000

5.625

6.250

6.875

7.500

3600.0

360.6

240.9

181.3

145.6

121.9

104.9

92.5

82.8

75.1

68.9

63.8

5-3

RADIUS(mm)

TABLE 5.2SWEEP NUMBERS (CAMBER, X, MILLIMETERS)

SWEEPNO.

CHORD LENGTH, L, MILLIMETERS

762 889 1016 1143 1270 1397 1524

1

10

15

20

25

30

35

40

45

50

55

60

0.79

7.90

11.8

15.8

19.6

23.5

27.2

31.1

34.9

38.4

42.1

45.5

1.09

10.8

16.1

21.5

26.7

32.1

37.4

42.4

47.5

52.5

57.5

62.2

1.42

14.1

21.1

28.1

34.9

42.0

48.9

55.6

62.4

68.9

75.5

81.7

1.78

17.8

26.7

35.6

44.4

53.2

62.1

70.5

80.4

87.6

96.1

104

2.21

22.0

32.9

44.0

55.0

65.8

76.8

87.4

98.2

109

119

130

2.67

26.6

39.9

53.3

66.6

79.8

93.3

106

119

132

146

158

3.18

31.8

47.6

63.5

79.4

95.3

111

127

143

159

175

191

91440

9159

6119

4605

3698

3096

2664

2350

2103

1908

1750

1619

5-4

FIGURE 5.2DEFINITION OF DEPTH OF DRAW

5-5

FIGURE 5.3EXAMPLES OF TAILOR WELDED BLANKS

5-6

5-7

Tailored blanks are being used in increasingly larger numbers forvarious automotive applications. It has been estimated (Reference7.2) that about 10 million tailored blanks were used in 1997 by theNorth American automotive industry. The potential benefits of tailorwelded blanks are impressive:

Part integration/part eliminationWeight reductionTooling reductionLower manufacturing costImproved structural integrityOptimized material property utilizationReduced material useIncreased offal utilization and reduced scrapImproved crashworthinessReduced design and development timeImproved dimensional accuracy

Increasingly, tailored blanks are being used for bumper reinforcement beams. They allow the automotive designer to placea material having the exact properties required in the exact portionof the part where the properties are required. A good example isthe front reinforcing beam on the 1998 VW Jetta (Figure 5.5 andTable 5.3). This beam is made from a three piece blank similar tothe bumper reinforcement blank shown in Figure 5.3. The blank isjoined using the resistance roller mash lap seam welding process.The middle portion of blank is made from a formable grade of 552MPa (80 ksi) yield strength hot-dip galvanized sheet to give highstrength in the beam where it is needed. However, this sheet steeldoes not have the level of formability required for the sharp wraparound at each end of the stamped beam. Thus, the end portions ofthe blank are made from hot-dip galvanized sheet with a yieldstrength of approximately 207 MPa (30 ksi). It provides the requiredlevel of formability to successfully stamp the wrap arounds andprovides the level of strength required at the wrap arounds. The thickness of all three pieces in the tailored blank is 2.36mm(0.093 inches).

5-8

5.3 Leading benchmark bumper beamsExamples of leading edge bumper beams are given in Table 5.3 andFigures 5.4 and 5.5. The examples clearly illustrate that steel bumperbeams readily meet the challenges faced by bumper designers -styling, weight, cost and structural integrity. Often a designer faces a particular problem with one of these criteria. The examples indicate innovative methods that have been used to overcome a particular design obstacle.

The current styling trend is towards rounded, aerodynamic shapes.The front reinforcing beam on the Chevrolet Cavalier/Pontiac Sunfirehas an impressive No. 50 sweep. The Toyota Camry front reinforcingbeam, with a No. 35 sweep, is also impressive. The Cavalier/Sunfireand Camry beams are roll formed from 140T steel, which provides afinal yield strength of approximately 634 MPa (92 ksi). The CrownVictoria/Grand Marquis front reinforcing beam is roll formed from120XF steel, which has limited formability. Even so, a significant No.34 sweep is achieved. The Ford F150 pickup has an outstanding 559mm (22 inches) depth of draw on its front facebar. The facebar isstamped from 50XLF cold rolled sheet. The rear reinforcing beam ofthe Chrysler NS Voyager is a fine example of a beam stamped from120XF steel. Even with an elongation of 12%, a good 152 mm (6 inches) depth of draw is achieved. The front reinforcing beam forthe Volkswagon Jetta is a most interesting example. A three piecetailored blank (see Section 5.2 for details) is used to provide a sharpwrap around at each end of the stamped beam. The depth of draw is 210 mm (8.25 inches).

For fuel economy reasons, bumper weight is important. Steel, withits high strength and stiffness, offers weight saving opportunities.The Ford Taurus/Mercury Sable is a good example. The front reinforcing beam on the Taurus D186 weighs only 6.08 kg (13.41pounds). It is roll formed from M190HT electrogalvanized steel withan elongation of about 5.1%. A significant property of the beam is its1214 MPa (176.0 ksi) yield strength. Facebars, by nature, are significantlyheavier than reinforcing beams. Also, facebars are highly styled. Inorder to reduce facebar weight while retaining styling, the FordRanger front facebar is made from 50XLF high-strength steel (traditionalfacebars are made from carbon steel).

Cost drives many bumper designs. Significantly, the lowest costbumper systems employ a steel beam. The reasons are twofold. First,steel is the lowest cost bumper material. Secondly, steel bumperbeams have the lowest manufacturing cost, even at volumes as lowas 100,000 parts per year. Even more cost savings are achieved on thefront facebar of the Dodge Ram. The use of a blank incorporating65% of the final trim line reduces material requirements and cost.

Part integration offers cost savings and ease of assembly. Two good examples are the front facebar on the Chevrolet Silverado and the rear reinforcing beam on the Toyota Avalon. The frameattachment detail is incorporated into the facebar on the Silverado.The reinforcing beam design on the Avalon minimizes mountingbracketry.

5-9

FIGURE 5.4ROLL FORMED BEAMS

A.) CROWN VICTORIA/GRAND MARQUISNO. 34 SWEEP IN NON-SYMMETRIC SECTION USING 120XF STEEL

B.) FORD TAURUS/MERCURY SABLENO. 19 SWEEP IN ENCLOSED B SECTION USING M190HT STEEL

5-10

C.) TOYOTA AVALONNO. 43 SWEEP USING 140T STEEL. MINIMAL BRACKETRY

FIGURE 5.4 (continued)ROLL FORMED BEAMS

D.) CHEVROLET CAVALIER/PONTIAC SUNFIRENO. 50 SWEEP IN BOX SECTION USING 140T STEEL

E.) TOYOTA CAMRYNO. 35 SWEEP IN DOUBLE BOX SECTION WITH 140T STEEL

5-11

FIGURE 5.5STAMPED BEAMS

F.) FORD F150 PICK UP559mm (22 inches) DEPTH OF DRAW WITH 50XLF STEEL. AERODYNAMIC STYLING

G.) DODGE RAM152 mm (6 inches) DEPTH OF DRAW WITH 50XLF STEELSTAMPING BLANK INCORPORATES 65% OF TRIM LINE

5-12

H.) CHEVROLET SILVERADO191 mm (7.5 inches) DEPTH OF DRAW WITH 50XLF STEEL

FRAME ATTACHMENT INTEGRATED INTO FACEBAR

I.) VOLKSWAGON JETTA210 mm (8.25 inches) DEPTH OF DRAW WITH 80XLF AND 45XLF STEELS

THREE PIECE TAILORED BLANK

FIGURE 5.5 (continued)STAMPED BEAMS

5-13

FIGURE 5.5 (continued)STAMPED BEAMS

J.) FORD RANGER483mm (19 inches) DEPTH OF DRAW WITH 50XLF STEEL.

ENERGY ABSORBING MOUNTING BRACKETS

K.) CHRYSLER VOYAGER152 mm (6 inches) DEPTH OF DRAW WITH 120XF STEEL

5-14

TAB

LE 5

.3LE

AD

ING

BEN

CH

MA

RK

BU

MPER

BEA

MS

VEH

ICLE

BU

MPE

RPR

OD

UC

TIO

NLE

AD

ING

ED

GE

MA

TER

IAL

THIC

KN

ESS

SWEE

P N

UM

BER

/M

AJO

R

(Mod

el Y

ear

BEA

MM

ETH

OD

FEA

TUR

E[

mm

(in

ches

)]D

EPTH

of D

RA

WA

DVA

NTA

GES

intr

oduc

ed/d

isco

ntin

ued)

[ m

m (

inch

es)]

A. C

row

n V

icto

ria/

Fron

tRo

llLa

rge

swee

p in

UH

SS12

0XF

1.52

(0.0

60)

No.

34

Styl

ing

Gra

nd M

arqu

isRe

info

rcin

gFo

rmin

gno

n-sy

mm

etric

sec

tion.

60G

60G

EG

(199

8/ —

)B

eam

B. F

ord

Taur

us/

Fron

tRo

llLa

rge

swee

p in

UH

SSM

190H

T1.

12 (0

. 044

)N

o. 1

9W

eigh

t Sav

ings

Mer

cury

Sab

leRe

info

rcin

gFo

rmin

gen

clos

ed B

-sec

tion.

30G

30G

EG

Cos

t Sav

ings

(199

5/ —

)B

eam

C. T

oyot

a A

valo

nRe

arRo

llM

inim

al m

ount

ing

140T

1.60

(0.0

63)

No.

43

Part

Inte

grat

ion

(200

0/ —

)Re

info

rcin

g Fo

rmin

gbr

acke

try.

CR

Cos

t Sav

ings

Bea

mEa

se o

f Ass

embl

y

D. C

hevr

olet

Cav

alie

rFr

ont

Roll

Ver

y la

rge

swee

p in

140T

1.50

(0.0

59)

No.

50

Styl

ing

Pont

iac

Sunf

ireRe

info

rcin

gFo

rmin

ga

box

sect

ion.

CR

(199

5/ —

)B

eam

E. T

oyot

a C

amry

Fron

tRo

llLa

rge

swee

p in

a14

0T1.

40 (0

.055

)N

o. 3

5St

ylin

g(1

997/

—)

Rein

forc

ing

Form

ing

doub

le b

ox s

ectio

n.C

RB

eam

F. F

ord

F150

Fron

tSt

ampi

ngA

erod

ynam

ic s

tylin

g.50

XLF

1.98

(0.0

78)

559

(22)

Styl

ing

Pick

up (1

996/

—)

Face

bar

CR

G. T

300

Dod

ge R

amFr

ont

Stam

ping

Dev

elop

ed b

lank

with

50

XLF

2.01

(0.0

79)

152

(6)

Cos

t Sav

ings

Pick

up (1

993/

—)

Face

bar

65%

of t

rim li

ne.

HR

H. G

MT

800

Fron

tSt

ampi

ngFr

ame

atta

chm

ent d

etai

l50

XLF

2.01

(0.0

79)

191

(7.5

)Pa

rt In

tegr

atio

nC

hevr

olet

Silv

erad

oFa

ceba

rin

tegr

ated

into

face

bar.

CR

Cos

t Sav

ings

Pick

up (2

000/

—)

Ease

of A

ssem

bly

I. V

olks

wag

onFr

ont

Stam

ping

Thre

e-pi

ece

tailo

red

80XL

F2.

36 (0

.093

)21

0 (8

.25)

Styl

ing

Jett

a (1

993/

1998

)Re

info

rcin

gbl

ank.

75G

75G

HD

G(m

iddl

e an

dB

eam

(mid

dle

port

ion)

end

port

ions

)45

XLF

75G

75G

HD

G(e

nd p

ortio

ns)

5-15

TAB

LE 5

.3 (

conti

nued

)LE

AD

ING

BEN

CH

MA

RK

BU

MPER

BEA

MS

DEF

INIT

ION

S

UH

SS—

Ultr

a hi

gh-s

tren

gth

stee

l.

XF—

Hig

h-st

reng

th lo

w-a

lloy

(HSL

A) w

ith s

ulph

ide

incl

usio

n co

ntro

l to

impr

ove

form

abili

ty.

Des

igna

tion

num

ber

(e.g

. 50)

is y

ield

str

engt

h in

ksi

.

XLF

—H

igh-

stre

ngth

low

-allo

y (H

SLA

) with

low

car

bon

cont

ent a

nd s

ulph

ide

incl

usio

n co

ntro

l. F

orm

abili

ty

of th

is q

ualit

y is

sup

erio

r to

XF

qual

ity. D

esig

natio

n nu

mbe

r (e

.g. 5

0) is

yie

ld s

tren

gth

in k

si.

T—

Stru

ctur

e co

ntai

ns m

arte

nsite

in fe

rrite

mat

rix.

Exce

llent

form

abili

ty p

rior

to s

trai

n ag

ing.

D

esig

natio

n nu

mbe

r (e

.g. 1

40) i

s m

inim

um te

nsile

str

engt

h in

ksi

.

M..H

T—

Mar

tens

itic

qual

ity.

Que

nche

d m

arte

nsite

str

uctu

re w

ith r

educ

ed fo

rmab

ility

. D

esig

natio

n nu

mbe

r (e

.g. 1

90) i

s m

inim

um te

nsile

str

engt

h in

ksi

.

CR

—C

old

rolle

d sh

eet.

HR

—H

ot r

olle

d sh

eet.

EG—

Elec

trog

alva

nize

d sh

eet.

Des

igna

tion

30G

30G

is a

zin

c co

atin

g on

eac

h si

de o

f the

she

et w

ith a

coa

ting

wei

ght

of 3

0 g/

m2 .

Des

igna

tion

60G

60G

is a

zin

c co

atin

g on

eac

h si

de o

f the

she

et w

ith a

coa

ting

wei

ght o

f 60

g/m

2 .

HD

G—

hot-d

ip g

alva

nize

d sh

eet.

Des

igna

tion

75G

75G

is a

zin

c co

atin

g on

eac

h si

de o

f the

she

et w

ith a

coa

ting

wei

ght

of 7

5 g/

m2 .

Des

igna

tion

45A

45A

is a

zin

c-iro

n al

loy

coat

ing

on e

ach

side

of t

he s

heet

with

a c

oatin

g w

eigh

t of 4

5g/m

2 .

VEH

ICLE

BU

MPE

RPR

OD

UC

TIO

NLE

AD

ING

ED

GE

MA

TER

IAL

THIC

KN

ESS

SWEE

P N

UM

BER

/M

AJO

R

(Mod

el Y

ear

BEA

MM

ETH

OD

FEA

TUR

E[

mm

(in

ches

)]D

EPTH

of D

RA

WA

DVA

NTA

GES

intr

oduc

ed/d

isco

ntin

ued)

[ m

m (

inch

es)]

J. Fo

rd R

ange

rFr

ont

Stam

ping

Ener

gy a

bsor

bing

50XL

F 2.

26 (0

.089

)48

3 (1

9)Pa

rt In

tegr

atio

nPi

ckup

(199

5/ —

)Fa

ceba

rm

ount

ing

brac

kets

.H

RW

eigh

t Sav

ings

Cos

t Sav

ings

K. C

hrys

ler

NS

Rear

Stam

ping

Goo

d de

pth-

of-d

raw

120X

F1.

83 (0

.072

)15

2 (6

)St

ylin

gV

oyag

erRe

info

rcin

gw

ith 1

20XF

ste

el.

45A

45A

HD

G(1

995.

5/20

00)

Bea

m

5-16

5.4 Bumper weights, materials and coatingsBeams produced by the roll forming production method areshown in Table 5.4, beams produced by the cold stampingmethod are shown in Table 5.5 and beams produced by the hotforming method are shown in Table 5.6. These data may be usedto establish bumper beam benchmarks.

In Tables 5.4, 5.5 and 5.6, the bumper beams are grouped bysteel grade. The steel grades are defined in the Notes at the endof each table (see also Tables 2.1 and 2.2). For any given steelgrade, the bumper beams are listed in decreasing order of steelbeam thickness. The vehicle make and model is given for eachbeam. While Tables 5.4, 5.5 and 5.6 are based on the 2004 calendar year, the majority of the beams have been carried forward. However, a vehicle redesign usually involves a bumperredesign. Thus, any vehicle redesigned from 2005 onwards willlikely have a beam differing from that shown in Table 5.4, 5.5 or5.6. The bumper beam location (front or rear of the vehicle) isindicated. The bumper beam is a “facebar” if “frontside” and“backside” coatings are shown. If only one coating is indicated,the bumper beam is a reinforcing beam.

There are five weight columns in Tables 5.4, 5.5 and 5.6. The firstcolumn indicates the weight of the roll formed, cold stamped orhot formed beam itself. For facebars, the weight is that of a painted beam. Chrome facebars are 0.37 kg (1.0 pound) heavier.The second column is the weight of any reinforcements welded tothe plain beam. The third column is the combined weight of theplain beam and attached reinforcements. The fourth column tabulates the weight of mounting brackets. The fifth column is theweight of a plain bumper beam, its reinforcements and its mounting brackets. It should be noted that many spaces in thefive weight columns are left blank. A blank space indicates thatthe weight being tabulated is unavailable.

The steel products used to manufacture the bumper beams arelisted in Tables 5.4, 5.5 and 5.6. Note that both hot rolled (HR)and cold rolled (CR) sheets are delivered in the bare condition.For hot-dip galvanized (HDG) and electrogalvanized (EG) sheets,the coating type and weight are shown. See Section 2.14 for adescription of aluminized (CR) sheet.

Corrosion protection coatings may be applied by the bumper supplier or by the OEM on the assembly line. The corrosion resistance of a bumper beam depends on all of the coatingsapplied to it. Thus, the coatings applied by both the bumper supplier and OEM are included in Tables 5.4, 5.5 and 5.6.

Sweep or curvature is often imparted to bumper beams duringroll forming. For the roll formed beams in Table 5.4, the amount ofsweep is shown. A small sweep radius indicates a large amount ofcurvature to help achieve a high degree of styling.

Depth-of-draw is included in Tables 5.5 and 5.6 for cold stampedand hot formed beams. Depth-of-draw is an indication of theamount of styling imparted to a cold stamped or hot formedbeam. A large depth-of-draw helps achieve a high degree ofstyling.

6120

(241

)

6120

(241

)

N/A

3172

(125

)

0 0

5109

(201

)

5109

(201

)

5109

(201

)

3310

(130

)

2174

(86)

2183

(86)

9679

(381

)

2174

(86)

2174

(86)

2700

(106

)

50X

LF

80X

F

120X

F

WEI

GH

T [k

g (p

ound

s)]

5-17

TAB

LE 5

.4R

OLL

FO

RM

ED B

UM

PER

BEA

MS

THIC

KN

ESS,

WEI

GH

T, M

ATE

RIA

L, C

OA

TIN

GS

AN

D S

WEE

PB

EAM

S PR

OD

UCED

IN

TH

E 2

00

4 C

ALE

ND

AR

YEA

R

STEE

LG

RAD

E1TH

ICK

NES

S[m

m (

inch

es)]

MA

KE

MO

DEL

FRO

NT

OR

REA

RB

UM

PER

Bea

mPe

rfor

man

ceRe

info

rcem

ents

Subt

otal

Mou

ntin

gBr

acke

tsTo

tal

STEE

LPR

OD

UC

TB

UM

PER

SU

PPLI

ERC

OA

TIN

GAS

SEM

BLY

LINE

COAT

ING

SWEE

PN

UM

BER

SWEE

PR

AD

IUS

[mm

(inch

es)]

2.01

(0.

079)

2.01

(0.

079)

4.70

(0.

185)

2.00

(0.

079)

2.01

(0.

079)

2.01

(0.

079)

1.91

(0.

075)

1.91

(0.

075)

1.90

(0.

075)

1.82

(0.

072)

1.80

(0.

071)

1.80

(0.

071)

1.80

(0.

071)

1.80

(0.

071)

1.80

(0.

071)

1.66

(0.

065)

Jeep

Jeep

Do

dge

Dai

mle

rC

hrys

ler

Jeep

Jeep

Mer

cury

Ford

Linc

oln

Ho

nda

Dai

mle

rC

hrys

ler

Dai

mle

rC

hrys

ler

Dai

mle

rC

hrys

ler

Dai

mle

rC

hrys

ler

Dai

mle

rC

hrys

ler

Nis

san

Che

roke

e

Che

roke

e

Dur

ango

300M

/Con

cord

/In

trep

id/L

HS

Wra

ngle

r

Wra

ngle

r

Gra

nd M

arqu

is

Cro

wn

Vic

toria

Tow

n C

ar

Acu

ra C

L

Stra

tus/

Cirr

us

Sebr

ing

Co

nv.

300M

Intr

epid

Co

nco

rde

Fro

ntie

r

fro

nt

rear

rear

fro

nt

fro

nt

rear

rear

rear

rear

rear

fro

nt

rear

rear

rear

rear

fro

nt

7.04

(15.

53)

8.14

(17.

94)

12.8

3(2

8.29

)

6.15

(13.

56)

5.64

(12.

43)

7.92

(17.

46)

7.92

(17.

46)

7.92

(17.

46)

7.04

(15.

53)

8.14

(17.

94)

12.8

3(2

8.29

)

6.15

(13.

56)

5.64

(12.

43)

10.3

0(2

2.71

)

10.3

0(2

2.71

)

10.7

6(2

3.73

)

0.00

0.00

0.00

0.00

0.00

2.38

(5.2

5)

2.38

(5.2

5)

2.84

(6.2

7)

0.00

0.00

7.03

(15.

5)

0.00

1.16

(2.5

6)

0.54

(1.1

8)

0.54

(1.1

8)

0.54

(1.1

8)

7.04

(15.

53)

8.14

(17.9

4)

19.8

6(4

3.79

)

6.24

(13.

76)

6.15

(13.

56)

6.80

(14.

99)

10.8

4(2

3.89

)

10.8

4(2

3.89

)

11.3

0(2

4.91

)

7.63

(16.

82)

6.03

(13.

29)

5.52

(12.1

7)

7.23

(15.

94)

6.61

(14.

57)

6.18

(13.

62)

8.00

(17.6

4)

90G

90G

HD

G

90G

90G

HD

G

HR

HR

45A

45A

HD

G

45A

45A

HD

G

60G

60G

EG

60G

60G

EG

60G

60G

EG

CR

CR

CR

CR

CR

CR

CR

E-co

at p

lus

pain

t

E-co

at p

lus

pain

t

E-C

oat

E-co

at p

lus

pow

der

coat

E-co

at p

lus

pow

der

coat

E-co

at

E-co

at

E-co

at

E-co

at

none

none

none

Prim

er

Dip

B/W

none

none

none

none

none

Prim

er

Dip

B/W

Prim

er

Dip

B/W

Prim

er

Dip

B/W

Prim

er

Dip

B/W

Prim

er

Dip

B/W

Prim

er

Dip

B/W

15 15 N/A 29 0 0 18 18 18 28 43 43 9 43 43 35

5-18

3310

(130

)

2061

(81)

1981

(78) 0 0 0 0

2183

(86)

3509

(138

)

2476

(97)

3400

(134

)

3350

(132

)

3350

(132

)

0 0

120X

F

WEI

GH

T [k

g (p

ound

s)]

STEE

LG

RAD

E1TH

ICK

NES

S[m

m (

inch

es)]

MA

KE

MO

DEL

FRO

NT

OR

REA

RB

UM

PER

Bea

mPe

rfor

man

ceRe

info

rcem

ents

Subt

otal

Mou

ntin

gBr

acke

tsTo

tal

STEE

LPR

OD

UC

TB

UM

PER

SU

PPLI

ERC

OA

TIN

GAS

SEM

BLY

LINE

COAT

ING

SWEE

PN

UM

BER

SWEE

PR

AD

IUS

[mm

(inch

es)]

1.60

(0.

063)

1.60

(0.

063)

1.60

(0.

063)

1.50

(0.

059)

1.50

(0.

059)

1.50

(0.

059)

1.50

(0.

059)

1.50

(0.

059)

1.50

(0.

059)

1.50

(0.

059)

1.46

(0.

057)

1.40

(0.

055)

1.40

(0.

055)

1.30

(0.

051)

1.30

(0.

051)

Ford

Suba

ru

Ford

Che

v.

Cad

illac

Che

v.

Cad

illac

Dai

mle

rC

hrys

ler

Dai

mle

rC

hrys

ler

Dai

mle

rC

hrys

ler

Maz

da

Mits

ubish

i

Chr

ysle

r/D

odg

e

Che

v.

Che

v.

Esca

pe

Lega

cy

Esca

pe

Co

rvet

te

XLR

Co

rvet

te

XLR

Stra

tus/

Cirr

us

Chr

ysle

r/D

odge

Min

ivan

Neo

n

Maz

da 6

Eclip

se

Sebr

ing/

Aven

ger

Co

rvet

te

Co

rvet

te

fro

nt

fro

nt

rear

fro

nt

fro

nt

rear

rear

rear

fro

nt

rear

fro

nt

fro

nt

fro

nt

fro

nt

rear

3.20

(7.0

5)

4.49

(9.9

0)

7.71

(17.

0)

7.71

(17.

0)

9.05

(19.

94)

9.05

(19.

94)

3.20

(7.0

5)

4.49

(9.9

0)

8.84

(19.

49)

8.84

(19.

49)

9.05

(19.

94)

9.05

(19.

94)

0.00

0.00

0.59

(1.3

)

1.3

(1.3

)

0.00

0.00

0.65

(1.4

4)

0.00

0.00

0.00

0.00

0.00

3.85

(8.4

9)

4.49

(9.9

0)

4.15

(9.16

)

8.84

(18.

83)

8.84

(18.

3)

9.05

(19.

94)

9.05

(19.

94)

4.76

(10.

49)

7.04

(15.

52)

5.63

(12.

41)

6.5

(14.

32)

7.76

(17.1

1)

6.74

(14.

86)

5.50

(12.1

3)

7.02

15.4

8)

60G

60G

EG

CR

60G

60G

EG

70G

70G

EG

70G

70G

EG

70G

70G

EG

70G

70G

EG

CR

CR

CR

CR

CR

70G

70G

EG

70G

70G

E-co

at

E-co

at

E-co

at

E-co

at

E-co

at

E-co

at

E-co

at

E-co

at

E-co

at

none

none

none

none

none

none

none

Prim

er

Dip

B/W

Prim

er

Dip

B/W

Prim

er

Dip

B/W

E-co

at

E-co

at

28 46 48 0 0 0 0 43 27 38 26 26 0 0

TAB

LE 5

.4 (

conti

nued

)R

OLL

FO

RM

ED B

UM

PER

BEA

MS

THIC

KN

ESS,

WEI

GH

T, M

ATE

RIA

L, C

OA

TIN

GS

AN

D S

WEE

PB

EAM

S PR

OD

UCED

IN

TH

E 2

00

4 C

ALE

ND

AR

YEA

R

1.30

(0.

051)

1.30

(0.

051)

1.30

(0.

051)

1.20

(0.

047)

1.20

(0.

047)

1.22

(0.

048)

1.20

(0.

047)

1.20

(0.

047)

2.00

(0.

079)

2.00

(0.

079)

2.00

(0.

079)

2.00

(0.

079)

2.00

(0.

079)

2.00

(0.

079)

2.00

(0.

079)

5-19

2668

(105

.0)

2668

(105

.0)

2743

(105

.0)

2623

(103

)

2623

(103

)

3350

(132

)

2400

(94)

2400

(94)

2475

(97)

2470

(97)

2300

(91)

2950

(116

)

1930

(76)

1930

(76)

1930

(76)

120X

F

135X

F

140T

WEI

GH

T [k

g (p

ound

s)]

STEE

LG

RAD

E1TH

ICK

NES

S[m

m (

inch

es)]

MA

KE

MO

DEL

FRO

NT

OR

REA

RB

UM

PER

Bea

mPe

rfor

man

ceRe

info

rcem

ents

Subt

otal

Mou

ntin

gBr

acke

tsTo

tal

STEE

LPR

OD

UC

TB

UM

PER

SU

PPLI

ERC

OA

TIN

GAS

SEM

BLY

LINE

COAT

ING

SWEE

PN

UM

BER

SWEE

PR

AD

IUS

[mm

(inch

es)]

Linc

oln

Ford

Jagu

ar

Bui

ck

Bui

ck

Mits

ubish

i

Nis

san

Nis

san

Ho

nda

Ho

nda

Ho

nda

Ho

nda

Ho

nda

Ho

nda

Ho

nda

LS D

EW98

Thun

derb

ird

M20

5

S-ty

pe X

400

X-ty

pe X

200

LaC

ross

e

LaC

ross

e

Gal

ant

Sent

ra

Sent

ra

Acu

ra T

L

Acu

ra T

L

Acu

ra C

L

Ody

ssey

Ody

ssey

MD

X

MD

X

fro

nt

fro

nt

fro

nt

fro

nt

rear

fro

nt

fro

nt

rear

fro

nt

rear

fro

nt

fro

nt

rear

fro

nt

rear

7.14

(15.

74)

6.88

(15.

16)

6.57

(14.

5)

7.18

(15.

82)

6.92

(15.

24)

6.57

(14.

5)

0.04

(0.0

8)

0.04

(0.0

8)0.

00

0.00

0.00

0.00

7.18

(15.

83)

6.92

(15.

24)

6.57

(14.

5)

6.08

(13.

39)

9.60

(21.1

6)

6.89

(15.1

9)

5.10

(11.2

4)

5.56

(12.

26)

7.32

(16.1

4)

8.57

(18.

89)

8.63

(19.

03)

7.94

(17.5

0)

14.74

(32.

50)

6.94

(15.

30)

15.67

(34.

55)60

G60

G H

DG

60G

60G

HD

G

60G

60G

HD

G

CR

CR

CR

CR

CR

CR

CR

CR

CR

CR

CR

CR

none

none

none

E-co

at

E-co

at

E-co

at

E-co

at

E-co

at

E-co

at

Prim

er

Dip

B/W

Prim

er

Dip

B/W

Prim

er

Dip

B/W

Prim

er

Dip

B/W

Prim

er

Dip

B/W

Prim

er

Dip

B/W

Prim

erD

ip B

/W

35 35 35 36 36 26 39 39 38 38 41 32 50 50 50

TAB

LE 5

.4 (

conti

nued

)R

OLL

FO

RM

ED B

UM

PER

BEA

MS

THIC

KN

ESS,

WEI

GH

T, M

ATE

RIA

L, C

OA

TIN

GS

AN

D S

WEE

PB

EAM

S PR

OD

UCED

IN

TH

E 2

00

4 C

ALE

ND

AR

YEA

R

Pilo

t

Pilo

t

Civ

ic

Acc

ord

Tund

ra

Maz

da 6

Maz

da 6

W

ago

n

Maz

da 3

Mo

nte

Car

lo

Reg

al

Reg

al

Cen

tury

Cen

tury

Civ

ic

Acu

ra E

L

Sien

na

6.68

(14.

73)

15.7

5(3

4.72

)

5.84

(12.

86)

4.19

(9.24

)

7.92

(17.4

6)

8.0

(17.6

3)

7.8 (17.1

9)

6.5

(14.

33)

12.31

(27.1

3)

8.31

(18.

31)

10.7

5(2

3.69

)

8.31

(18.

31)

10.7

5(2

3.69

)

5.16

(11.3

8)

5.38

(11.8

6)

6.18

(13.

62)

CR

CR

CR

CR

CR

CR

CR

CR

CR

CR

CR

CR

CR

CR

CR

Cr

none

E-co

at

none

none

none

none

none

E-co

at

5-20

1930

(76)

1930

(76)

3488

(137

)

1509

(59)

3520

(139

)

2740

(34)

2200

(43)

3000

(31)

9160

(361

)

2597

(102

)

2597

(102

)

2597

(102

)

2597

(102

)

3000

(118

)

3000

(118

)

2943

(116

)

140T

WEI

GH

T [k

g (p

ound

s)]

STEE

LG

RAD

E1TH

ICK

NES

S[m

m (

inch

es)]

MA

KE

MO

DEL

FRO

NT

OR

REA

RB

UM

PER

Bea

mPe

rfor

man

ceRe

info

rcem

ents

Subt

otal

Mou

ntin

gBr

acke

tsTo

tal

STEE

LPR

OD

UC

TB

UM

PER

SU

PPLI

ERC

OA

TIN

GAS

SEM

BLY

LINE

COAT

ING

SWEE

PN

UM

BER

SWEE

PR

AD

IUS

[mm

(inch

es)]

2.00

(0.

079)

2.00

(0.

079)

1.80

(0.

071)

1.80

(0.

071)

1.80

(0.

071)

1.66

(0.

065)

1.66

(0.

065)

1.66

(0.

065)

1.60

(0.

063)

1.60

(0.

063)

1.60

(0.

063)

1.60

(0.

063)

1.60

(0.

063)

1.60

(0.

063)

1.60

(0.

063)

1.60

(0.

063)

Ho

nda

Ho

nda

Ho

nda

Ho

nda

Toyo

ta

Maz

da

Maz

da

Maz

da

Che

v.

Bui

ck

Bui

ck

Bui

ck

Bui

ck

Ho

nda

Ho

nda

Toyo

ta

fro

nt

rear

rear

fro

nt

fro

nt

rear

rear

rear

rear

fro

nt

rear

fro

nt

rear

fro

nt

fro

nt

rear

3.30

(7.2

8)

8.60

(18.

95)

7.13

(15.

71)

7.13

(15.

71)

7.13

(15.

71)

7.13

(15.

71)

0.00

0.90

(1.9

8)

0.00

0.90

(1.9

8)

0.00

0.90

(1.9

8)

0.89

(1.9

6)

2.81

(6.2

0)

1.18

(2.6

0)

2.72

(6.0

0)

1.18

(2.6

0)

2.72

(6.0

0)

Prim

er

Dip

B/W

Prim

erD

ip B

/W

Prim

erD

ip B

/W

E-co

at

E-co

at

E-co

at

E-co

at

E-co

at

E-co

at

Prim

erD

ip B

/W

Prim

erD

ip B

/W

50 50 27 65 26 10 36 36 36 36 31 31 32

3.30

(7.2

8)

9.50

(20.

93)

7.13

(15.

71)

8.03

(17.

69)

7.13

(15.

71)

8.03

(17.

69)

TAB

LE 5

.4 (

conti

nued

)R

OLL

FO

RM

ED B

UM

PER

BEA

MS

THIC

KN

ESS,

WEI

GH

T, M

ATE

RIA

L, C

OA

TIN

GS

AN

D S

WEE

PB

EAM

S PR

OD

UCED

IN

TH

E 2

00

4 C

ALE

ND

AR

YEA

R

5-21

1.60

(0.

063)

1.60

(0.

063)

1.60

(0.

063)

1.60

(0.

063)

1.60

(0.

063)

1.60

(0.

063)

1.60

(0.

063)

1.60

(0.

063)

1.60

(0.

063)

1.60

(0.

063)

1.56

(0.

061)

1.40

(0.

055)

1.40

(0.

055)

1.40

(0.

055)

1.40

(0.

055)

3330

(131

)

2040

(80)

3580

(141

)

3385

(133

)

2240

(88)

3330

(131

)

2194

(86)

2908

(114

.5)

2743

(108

.0)

2668

(108

.0)

2700

(34)

3003

(118

)

2943

(116

)

2290

(90

2185

(86)

)

140T

WEI

GH

T [k

g (p

ound

s)]

STEE

LG

RAD

E1TH

ICK

NES

S[m

m (

inch

es)]

MA

KE

MO

DEL

FRO

NT

OR

REA

RB

UM

PER

Bea

mPe

rfor

man

ceRe

info

rcem

ents

Subt

otal

Mou

ntin

gBr

acke

tsTo

tal

STEE

LPR

OD

UC

TB

UM

PER

SU

PPLI

ERC

OA

TIN

GAS

SEM

BLY

LINE

COAT

ING

SWEE

PN

UM

BER

SWEE

PR

AD

IUS

[mm

(inch

es)]

Toyo

ta

Toyo

ta

Toyo

ta

Toyo

ta

Toyo

ta

Toyo

ta

Toyo

ta

Toyo

ta

Toyo

ta

Toyo

ta

Maz

da

Toyo

ta

Toyo

ta

Toyo

ta

Toyo

ta

Vib

e

Taco

ma

Sola

ra

Cam

ry

Cor

olla

Mat

rix

Ava

lon

Sola

ra

Sequ

oia

120N

Tund

ra

Maz

da 3

Ava

lon

Ava

lon

Cam

ry

Sola

ra

rear

fro

nt

rear

rear

rear

rear

rear

rear

fro

nt

fro

nt

fro

nt

Aus

tral

ian

fro

nt

fro

nt

fro

nt

fro

nt

0.77

(1.7

0)9.

30(2

0.50

)

0.00

0.00

0.00

10.8

9(2

4.0)

6.58

(14.

5)

11.1

1(2

4.5)

6.58

(14.

5)

11.1

1(2

4.5)

0.11

(0.2

4)

1.00

(2.2

0)

6.97

(15.

37)

2.29

(5.0

5)

6.72

(14.

82)

7.76

(17.1

1)

6.75

(14.

88)

6.26

(13.1

8)

8.12

(17.9

0)

6.69

(14.

74)

12.11

(26.

70)

11.6

6(2

5.7)

6.0

(13.

22)

6.40

(14.1

1)

5.68

(12.

52)

6.32

(13.

93)

5.80

(12.

79)

CR

CR

CR

CR

CR

CR

CR

CR

CR

CR

CR

CR

CR

CR

CR

E-co

at

E-co

at

E-co

at

E-co

at

E-co

at

E-co

at

E-co

at

E-co

at

E-co

at

E-co

at

E-co

at

E-co

at

E-co

at

E-co

at

none

none

none

28 47 26 27 42 28 43 32 34 34 30 32 41 43

TAB

LE 5

.4 (

conti

nued

)R

OLL

FO

RM

ED B

UM

PER

BEA

MS

THIC

KN

ESS,

WEI

GH

T, M

ATE

RIA

L, C

OA

TIN

GS

AN

D S

WEE

PB

EAM

S PR

OD

UCED

IN

TH

E 2

00

4 C

ALE

ND

AR

YEA

R

5-22

3500

(138

)

2184

(86)

2591

(102

)

2591

(102

)

2591

(102

)

2184

(86)

2591

(102

)

2591

(102

)

5000

(197

)

5000

(197

)

3558

(140

)

3558

(140

)

1981

(78)

1981

(78)

1981

(78)

140T

M19

0HT

WEI

GH

T [k

g (p

ound

s)]

STEE

LG

RAD

E1TH

ICK

NES

S[m

m (

inch

es)]

MA

KE

MO

DEL

FRO

NT

OR

REA

RB

UM

PER

Bea

mPe

rfor

man

ceRe

info

rcem

ents

Subt

otal

Mou

ntin

gBr

acke

tsTo

tal

STEE

LPR

OD

UC

TB

UM

PER

SU

PPLI

ERC

OA

TIN

GAS

SEM

BLY

LINE

COAT

ING

SWEE

PN

UM

BER

SWEE

PR

AD

IUS

[mm

(inch

es)]

1.40

(0.

055)

1.30

(0.

051)

1.30

(0.

051)

1.30

(0.

051)

1.30

(0.

051)

1.30

(0.

051)

1.30

(0.

051)

1.30

(0.

051)

1.20

(0.

047)

1.20

(0.

047)

1.70

(0.

067)

1.70

(0.

067)

1.60

(0.

063)

1.60

(0.

063)

1.60

(0.

063)

Toyo

ta

Che

v.

Che

v.

Che

v.

Old

s

Pont

iac

Pont

iac

Pont

iac

Toyo

ta

Toyo

ta

Ho

nda

Ho

nda

Ford

Mer

cury

Linc

oln

Co

rolla

Cav

alie

r

Cav

alie

r

Mal

ibu

Ale

ro

Sunf

ire

Sunf

ire

Gra

nd A

M

Vib

e

Mat

rix

Acc

ord

2dr

Acc

ord

4dr

Expl

ore

r

Mo

unta

inee

r

Avi

ato

r

fro

nt

fro

nt

rear

rear

rear

fro

nt

rear

rear

fro

nt

fro

nt

rear

rear

fro

nt

fro

nt-

fro

nt

3.69

(8.1

3)

4.50

(9.9

3)

3.07

(6.7

6)

3.63

(8.0

0)

3.60

(7.9

0)

5.24

(11.

55)

5.94

(13.

10)

3.07

(6.7

6)

3.63

(8.0

0)

3.60

(7.9

0)

1.55

(3.4

2)

1.4

4(3

.17)

0.00

0.00

0.00

1.46

(3.2

2)

1.05

(2.3

1)

0.45

(1.0

0)

0.65

(1.4

3)

1.66

(3.6

6)

5.53

(12.1

9)

5.26

(11.6

0)

5.60

(12.

35)

6.10

(13.

45)

6.05

(13.

34)

5.26

(11.6

0)

6.10

(13.

45)

6.10

(13.

45)

4.97

(10.

96)

4.97

(10.

96)

6.70

(14.

77)

6.99

(15.

41)

3.52

(7.76

)

4.28

(9.4

4)

4.66

(10.

27)

CR

CR

CR

CR

CR

CR

CR

CR

CR

CR

CR

CR

CR

CR

CR

E-co

at

E-co

at

E-co

at

none

none

E-co

at

E-co

at

E-co

at

Prim

erD

ip B

/W

Prim

erD

ip B

/W

Prim

erD

ip B

/W

Prim

erD

ip B

/W

Prim

erD

ip B

/W

Prim

erD

ip B

/W

Prim

erD

ip B

/W

E-co

at

E-co

at

none

none

none

26 43 36 36 36 43 36 36 18 18 26 26 42 42 42

TAB

LE 5

.4 (

conti

nued

)R

OLL

FO

RM

ED B

UM

PER

BEA

MS

THIC

KN

ESS,

WEI

GH

T, M

ATE

RIA

L, C

OA

TIN

GS

AN

D S

WEE

PB

EAM

S PR

OD

UCED

IN

TH

E 2

00

4 C

ALE

ND

AR

YEA

R

5-23

1.50

(0.

059)

1.50

(0.

059)

1.50

(0.

059)

1.12

(0.

044)

1.12

(0.

044)

1.12

(0.

044)

1.14

(0.

045)

1.14

(0.

045)

1.00

(0.

039)

0.99

(0.

039)

0.99

(0.

039)

0.99

(0.

039)

0.94

(0.

037)

1.55

(0.

061)

1.55

(0.

061)

3096

(122

)

3096

(122

)

3096

(122

)

4843

(190

.7)

4843

(190

.7)

4843

(190

.7)

3988

(157

)

3988

(157

)

3700

(146

)

0 0 0 0

3430

(135

)

5109

(201

)

M19

0HT

M19

0HT

WEI

GH

T [k

g (p

ound

s)]

STEE

LG

RAD

E1TH

ICK

NES

S[m

m (

inch

es)]

MA

KE

MO

DEL

FRO

NT

OR

REA

RB

UM

PER

Bea

mPe

rfor

man

ceRe

info

rcem

ents

Subt

otal

Mou

ntin

gBr

acke

tsTo

tal

STEE

LPR

OD

UC

TB

UM

PER

SU

PPLI

ERC

OA

TIN

GAS

SEM

BLY

LINE

COAT

ING

SWEE

PN

UM

BER

SWEE

PR

AD

IUS

[mm

(inch

es)]

Ford

Mer

cury

Linc

oln

Ford

Ford

Ford

Satu

rn

Satu

rn

Nis

san

Ford

Ford

Ford

Ford

Bui

ck

Cad

illac

Cro

wn

Vic

toria

Mar

quis

Tow

n C

ar

Taur

us D

186

Taur

us D

186

Seda

n

Taur

us D

186

Wag

on

VU

E

VU

E

Alti

ma

Focu

s C

170

Seda

n

Focu

s C

170

Wag

on

Focu

s C

170

3 dr

.

Focu

s C

170

LeSa

bre

DeV

ille

fro

nt

fro

nt

fro

nt

fro

nt

rear

rear

fro

nt

rear

fro

nt

rear

rear

rear

fro

nt

rear

rear

10.5

0(2

3.15

)

10.5

0(2

3.15

)

10.5

0(2

3.15

)

6.08

(13.

41)

5.39

(11.

89)

6.80

(15.

00)

5.36

(11.

82)

5.10

(11.

25)

4.80

(10.

58)

4.88

(10.

76)

4.50

(9.9

2)

5.22

(11.

51)

10.5

0(2

3.15

)

10.5

0(2

3.15

)

10.5

0(2

3.15

)

6.46

(14.

25)

5.90

(13.

00)

6.80

(15.

00)

5.89

(12.

98)

5.63

(12.

41)

5.33

(11.

74)

5.70

(12.

56)

4.95

(10.

92)

5.67

(12.

50)

1.89

(4.1

7)

1.89

(4.1

7)

1.89

(4.1

7)

0.00

0.00

0.00

0.83

(1.8

4)

0.73

(1.6

2)

0.78

(1.7

2)

0.00 1.9

(4.1

9)

1.9

(4.1

9)

0.00

0.00

0.00

0.38

(0.8

4)

0.50

(1.1

1)

0.00

0.53

(1.1

6)

0.53

(1.1

6)

0.53

(1.1

6)

0.82

(1.8

0)

0.45

(0.9

9)

0.45

(0.9

9)

12.3

9(2

7.31)

12.3

9(2

7.31)

12.3

9(2

7.31)

6.46

(14.

25)

5.90

(13.

00)

6.80

(15.

00)

3.83

(8.4

4)

3.97

(8.7

5)

5.36

(11.8

2)

7.56

(14.

82)

6.36

(14.

03)

6.11

(13.

46)

5.70

(12.

56)

6.85

(15.1

0)

7.57

(16.

69)C

R

CR

CR

30G

30G

EG

50G

50G

EG

50G

50G

EG

CR

CR

CR

30G

30G

EG

30G

30G

EG

30G

30G

EG

60G

60G

EG

CR

CR

E-co

at

E-co

at

E-co

at

none

none

none

E-co

at

E-co

at

none

none

none

none

E-co

at

E-co

at

none

none

none

E-co

at

E-co

at

E-co

at

Prim

er

Dip

B/W

E-co

at

E-co

at

E-co

at

E-co

at

none

none

30 30 30 19 19 19 23 23 25 0 0 0 0 27 18

TAB

LE 5

.4 (

conti

nued

)R

OLL

FO

RM

ED B

UM

PER

BEA

MS

THIC

KN

ESS,

WEI

GH

T, M

ATE

RIA

L, C

OA

TIN

GS

AN

D S

WEE

PB

EAM

S PR

OD

UCED

IN

TH

E 2

00

4 C

ALE

ND

AR

YEA

R

5-24

DEF

INIT

ION

S:XF

Reco

very

ann

eale

d qu

ality

. Str

engt

h is

ach

ieve

d pr

imar

ily th

roug

h co

ld w

ork

durin

g co

ld ro

lling

at t

he s

teel

mill

. Des

igna

tion

num

ber

(e.g

. 50)

is m

inim

um y

ield

stre

ngth

in k

si.

XLF

Mic

roal

loy

qual

ity. S

tren

gth

is o

btai

ned

thro

ugh

smal

l qua

ntiti

es o

f allo

ying

ele

men

ts s

uch

as v

anad

ium

and

nio

bium

. Des

igna

tion

num

ber

(e.g

. 120

) is

min

i-m

um y

ield

str

engt

h in

ksi

.

TD

ual p

hase

qua

lity.

Str

uctu

re c

ont

ains

mar

tens

ite in

ferr

ite m

atrix

. Des

igna

tion

num

ber

(e.g

. 140

) is

min

imum

tens

ile s

tren

gth

in k

si.

M..H

TM

arte

nsiti

c q

ualit

y. S

tren

gth

is d

eter

min

ed b

y ca

rbo

n co

nten

t. D

esig

natio

n nu

mb

er (

e.g.

19

0)

is m

inim

um t

ensi

le s

tren

gth

in k

si.

CR

Col

d ro

lled

shee

t.H

RH

ot ro

lled

shee

t.EG

Elec

tro

galv

aniz

ed s

heet

. Th

e si

x-ch

arac

ter

des

crip

tor

des

igna

tes

coat

ing

typ

e an

d w

eigh

t. T

wo

num

eric

cha

ract

ers

(e.g

. 60

) d

eno

te c

oat

ing

wei

ght

ing/

m2.

An

alp

hab

etic

cha

ract

er d

eno

tes

coat

ing

typ

e.

“A”

is a

zin

c-ir

on

allo

y co

atin

g.

“G”

is a

zin

c co

atin

g.

The

first

thr

ee c

hara

cter

s d

eno

te c

oat

ing

wei

ght

and

typ

e o

n o

ne

sid

eo

f th

e sh

eet

and

the

last

thr

ee c

hara

cter

s d

eno

te c

oat

ing

wei

ght

and

type

on

the

oppo

site

sid

e of

the

shee

t.

HD

GH

ot-d

ip g

alva

nize

d s

heet

. The

six

-cha

ract

er d

escr

ipto

r d

esig

nate

sco

atin

g ty

pe

and

wei

ght.

Tw

o n

umer

ic c

hara

cter

s (e

.g. 9

0)

den

ote

co

atin

g w

eigh

t in

g/m

2.

An

alp

hab

etic

cha

ract

er d

eno

tes

coat

ing

typ

e.

“A”

is a

zin

c-ir

on

allo

y co

atin

g.

“G”

is a

zin

c co

atin

g.

The

first

thr

ee c

hara

cter

s d

eno

te c

oat

ing

wei

ght

and

typ

e o

n o

ne

sid

eo

f th

e sh

eet

and

the

last

thr

ee c

hara

cter

s d

eno

te c

oat

ing

wei

ght

and

type

on

the

oppo

site

sid

e of

the

shee

t.

NO

TES:

1.A

bla

nk c

ell m

eans

tha

t da

ta a

re u

nava

ilabl

e fo

r th

at c

ell.

2.B

eam

wei

ght

is fo

r a

pain

ted

beam

. Add

0.3

7 kg

(1.

0 po

und)

for

a ch

rom

e be

am.

3.A

ll bu

mpe

r be

ams

are

rein

forc

ing

beam

s.

4.A

zer

o (

0) s

wee

p nu

mbe

r m

eans

the

bea

m is

str

aigh

t/fla

t.

5.Sw

eep

num

bers

are

ro

unde

d to

the

nea

rest

who

le n

umbe

r. Sw

eep

radi

i are

act

ual r

adii.

6. T

he P

rimer

Dip

B/W

co

atin

g w

oul

d be

term

ed E

-Co

at.

TAB

LE 5

.4 (

conti

nued

)R

OLL

FO

RM

ED B

UM

PER

BEA

MS

THIC

KN

ESS,

WEI

GH

T, M

ATE

RIA

L, C

OA

TIN

GS

AN

D S

WEE

PB

EAM

S PR

OD

UCED

IN

TH

E 2

00

4 C

ALE

ND

AR

YEA

R

1.55

(0.

061)

1.55

(0.

061)

2467

(97)

2467

(97)

M22

0HT

WEI

GH

T [k

g (p

ound

s)]

STEE

LG

RAD

E1TH

ICK

NES

S[m

m (

inch

es)]

MA

KE

MO

DEL

FRO

NT

OR

REA

RB

UM

PER

Bea

mPe

rfor

man

ceRe

info

rcem

ents

Subt

otal

Mou

ntin

gBr

acke

tsTo

tal

STEE

LPR

OD

UC

TB

UM

PER

SU

PPLI

ERC

OA

TIN

GAS

SEM

BLY

LINE

COAT

ING

SWEE

PN

UM

BER

SWEE

PR

AD

IUS

[mm

(inch

es)]

Pont

iac

Bui

ck

Bonn

evill

e

Park

Ave

nue

rear

rear

4.91

(10.

83)

4.91

(10.

83)

5.36

(11.

82)

5.36

(11.

82)

2.2

(4.8

5)

1.68

(3.7

1)

0.45

(0.9

9)

0.45

(0.9

9)

7.56

(16.

67)

7.68

(15.

53)

CR

CR

E-co

at

E-co

at

none

none

38 38

5-25

2.29

(0.

090)

2.29

(0.

090)

2.29

(0.

090)

2.29

(0.

090)

2.00

(0.

079)

1.80

(0.

071)

1.80

(0.

071)

1.80

(0.

071)

2.01

(0.

079)

2.01

(0.

079)

1.91

(0.

075)

1.91

(0.

075)

1.91

(0.

075)

1.80

(0.

071)

1008

/10

10

DR2

10

35X

LF

WEI

GH

T [k

g (p

ound

s)]

TAB

LE 5

.5CO

LD S

TAM

PED

BU

MPER

BEA

MS

THIC

KN

ESS,

WEI

GH

T, M

ATE

RIA

L, C

OA

TIN

GS

AN

D D

EPTH

-OF-

DR

AW

BEA

MS

PR

OD

UCED

IN

TH

E 2

00

4 C

ALE

ND

AR

YEA

R

STEE

LG

RAD

E1TH

ICK

NES

S[m

m (

inch

es)]

MA

KE

MO

DEL

FRO

NT

OR

REA

RB

UM

PER

Bea

mPe

rfor

man

ceRe

info

rcem

ents

Subt

otal

Mou

ntin

gBr

acke

tsTo

tal

STEE

LPR

OD

UC

TB

UM

PER

SU

PPLI

ERC

OA

TIN

GAS

SEM

BLY

LINE

COAT

ING

DEP

THO

F D

RAW

[mm

(inc

hes)

]

Che

v.

Che

v.

Che

v.

GM

C

Ford

GM

C

Che

v.

Ford

Che

v.

GM

C

Che

v.

Maz

da

Ford

Ford

Taho

e 41

0/20

Subu

rban

C/K

400

Sier

ra 4

00

Ran

ger

Can

yon

Col

orad

o

F-25

0/F-

350

Expr

ess

600

Sava

na 6

00

S-Se

ries

325

B Se

ries

Pick

up

Ran

ger

F-25

0/F-

350

rear

rear

rear

rear

rear

rear

rear

fro

nt

rear

rear

fro

nt

fro

nt

fro

nt

rear

21.1

9(4

6.71

)

21.1

9(4

6.71

)

21.1

9(4

6.71

)

21.1

9(4

6.71

)

20.2

3(4

4.60

)

20.2

3(4

4.60

)

17.0

5(3

7.59

)

10.9

4(2

4.12

)

10.9

4(2

4.12

)

7.26

(16.

00)

9.83

(21.

67)

1.19

(2.6

2)

6.38

(14.

07)

6.38

(14.

07)

10.8

3(2

3.86

)3.

57(7

.86)

17.0

5(3

7.59)

12.01

(26.

48)

9.83

(21.6

7)

CR

CR

HR

HR

CR

CR

CR

CR

HR

HR

HR

CR

CR

CR

fro

ntsi

de c

hro

me

or

pain

tba

cksi

de n

one

fro

ntsi

de c

hro

me

back

side

no

ne

fro

ntsi

de c

hro

me

or

pain

tba

cksi

de n

one

fro

ntsi

de c

hro

me

or

pain

tba

cksi

de n

one

fro

ntsi

de c

hro

me

or

pain

tba

cksi

de p

aint

or

E-co

at

fro

ntsi

de c

hro

me

or

pain

tba

cksi

de a

cryl

ic c

om

poun

d

fro

ntsi

de c

hro

me

or

pain

tba

cksi

de a

cryl

ic c

om

poun

dfr

ont

side

chr

om

e o

r pa

int

back

side

the

rmo

plas

tics

wat

er b

ased

co

mpo

und

fro

ntsi

de c

hro

me

or

pain

tba

cksi

de n

one

fro

ntsi

de c

hro

me

or

pain

tba

cksi

de n

one

fro

ntsi

de c

hro

me

or

pain

tba

cksi

de a

cryl

ic c

om

poun

d

fro

ntsi

de c

hro

me

or

pain

tba

cksi

de p

aint

or

E-co

at

fro

ntsi

de c

hro

me

or

pain

tba

cksi

de p

aint

or

E-co

atfr

ont

side

chr

om

e o

r pa

int

back

side

the

rmo

plas

tics

wat

er b

ased

co

mpo

und

none

none

none

none

none

none

none

none

none

none

none

none

none

none

135

(5.3

)

135

(5.3

)

135

(5.3

)

135

(5.3

)

165

(6.5

)

165

(6.5

)

203

(8.0

)

132

(5.2

)

132

(5.2

)

140

(5.5

)

99 (

3.9)

117

(4.6

)

165

(6.5

)

CR

CR

CR

CR

CR

CR

CR

CR

CR

CR

CR

60G

60G

EG

CR

CR

CR

CR

5-26

1.80

(0.

071)

1.80

(0.

071)

1.80

(0.

071)

1.80

(0.

071)

1.80

(0.

071)

1.80

(0.

071)

1.80

(0.

071)

1.80

(0.

071)

1.80

(0.

071)

1.40

(0.

055)

2.49

(0.

098)

2.06

(0.

081)

2.01

(0.

079)

2.01

(0.

079)

2.00

(0.

079)

1.91

(0.

075)

35X

LF

40X

LF

50X

LF

WEI

GH

T [k

g (p

ound

s)]

STEE

LG

RAD

E1TH

ICK

NES

S[m

m (

inch

es)]

MA

KE

MO

DEL

FRO

NT

OR

REA

RB

UM

PER

Bea

mPe

rfor

man

ceRe

info

rcem

ents

Subt

otal

Mou

ntin

gBr

acke

tsTo

tal

STEE

LPR

OD

UC

TB

UM

PER

SU

PPLI

ERC

OA

TIN

GAS

SEM

BLY

LINE

COAT

ING

DEP

THO

F D

RAW

[mm

(inc

hes)

]

Ford

Ford

Che

v.

Che

v.

Che

v.

GM

C

GM

C

Toyo

ta

Toyo

ta

Toyo

ta

Maz

da

Suba

ru

Do

dge

Che

v.

GM

C

Ford

F-15

0 Fl

are-

side

F-15

0 Su

perc

rew

Silv

erad

o

Taho

e

Subu

rban

Sier

ra

Yuko

n

Tund

ra

Taco

ma

Taco

ma

B Se

ries

Pick

up

Baha

Ram

2 d

r.

Silv

erad

o

Sier

ra

F150

rear

rear

rear

rear

rear

rear

rear

rear

fro

nt

rear

rear

rear

fro

nt

fro

nt

fro

nt

fro

nt

9.83

(21.

67)

9.83

(21.

67)

8.90

(19.

62)

7.69

(16.

96)

7.69

(16.

96)

8.90

(19.

62)

7.69

(16.

96)

11.7

1(2

5.82

)

7.71

(17.

00)

4.45

(9.8

0)

17.6

8(3

8.98

)

17.2

4(3

8.00

)

17.9

1(3

9.48

)

8.35

(18.

40)

9.83

(21.6

7)

9.83

(21.6

7)

8.90

(19.

62)

7.69

(16.

96)

7.69

(16.

96)

8.90

(19.

62)

7.69

(16.

96)

11.7

1(2

5.82

)

7.71

(17.0

0)

4.45

(9.8

0)

24.6

9(5

4.43

)

8.35

(18.

40)

25.17

(55.

50)

3.01

(6.6

3)

5.67

(12.

50)

fro

ntsi

de c

hro

me

or

pain

tba

cksi

de t

herm

opl

astic

sw

ater

bas

ed c

om

poun

dfr

ont

side

chr

om

e o

r pa

int

back

side

the

rmo

plas

tics

wat

er b

ased

co

mpo

und

fro

ntsi

de c

hro

me

or

pain

tba

cksi

de t

herm

opl

astic

sw

ater

bas

ed c

om

poun

dfr

ont

side

chr

om

e o

r pa

int

back

side

the

rmo

plas

tics

wat

er b

ased

co

mpo

und

fro

ntsi

de c

hro

me

or

pain

tba

cksi

de t

herm

opl

astic

sw

ater

bas

ed c

om

poun

dfr

ont

side

chr

om

e o

r pa

int

back

side

the

rmo

plas

tics

wat

er b

ased

co

mpo

und

fro

ntsi

de c

hro

me

or

pain

tba

cksi

de t

herm

opl

astic

sw

ater

bas

ed c

om

poun

dfr

ont

side

chr

om

e o

r pa

int

back

side

the

rmo

plas

tics

wat

er b

ased

co

mpo

und

fro

ntsi

de c

hro

me

or

pain

tba

cksi

de t

herm

opl

astic

sw

ater

bas

ed c

om

poun

dfr

ont

side

chr

om

e o

r pa

int

back

side

the

rmo

plas

tics

wat

er b

ased

co

mpo

und

fro

ntsi

de c

hro

me

or

pain

tba

cksi

de p

aint

or

E-co

at

none

fro

ntsi

de c

hro

me

or

pain

tba

cksi

de a

cryl

ic c

om

poun

d

fro

ntsi

de c

hro

me

or

pain

tba

cksi

de n

one

fro

ntsi

de c

hro

me

or

pain

tba

cksi

de t

herm

opl

astic

sw

ater

bas

ed c

om

poun

dfr

ont

side

chr

om

e o

r pa

int

back

side

pai

nt

none

none

none

none

none

none

none

none

none

none

none

none

none

none

none

none

165

(6.5

)

165

(6.5

)

200

(7.9

)

180

(7.1

)

180

(7.1

)

200

(7.9

)

180

(7.1

)

200

(7.9

)

147

(5.8

)

191

(7.5

)

119

(4.7

)

150

(5.9

)

TAB

LE 5

.5 (

conti

nued

)CO

LD S

TAM

PED

BU

MPER

BEA

MS

THIC

KN

ESS,

WEI

GH

T, M

ATE

RIA

L, C

OA

TIN

GS

AN

D D

EPTH

-OF-

DR

AW

BEA

MS

PR

OD

UCED

IN

TH

E 2

00

4 C

ALE

ND

AR

YEA

R

4.00

(8.8

2)21

.68

(47.

8)

5-27

1.91

(0.

075)

1.91

(0.

075)

1.91

(0.

075)

1.91

(0.

075)

1.91

(0.

075)

190.

(0.0

75)

1.80

(0.

071)

1.80

(0.

071)

1.80

(0.

071)

1.80

(0.

071)

2.26

(0.

089)

2.26

(0.

089)

2.26

(0.

089)

2.26

(0.

089)

50X

LF

55X

LF

WEI

GH

T [k

g (p

ound

s)]

STEE

LG

RAD

E1TH

ICK

NES

S[m

m (

inch

es)]

MA

KE

MO

DEL

FRO

NT

OR

REA

RB

UM

PER

Bea

mPe

rfor

man

ceRe

info

rcem

ents

Subt

otal

Mou

ntin

gBr

acke

tsTo

tal

STEE

LPR

OD

UC

TB

UM

PER

SU

PPLI

ERC

OA

TIN

GAS

SEM

BLY

LINE

COAT

ING

DEP

THO

F D

RAW

[mm

(inc

hes)

]

Ford

Ford

Ford

Ford

Ford

Che

v.

Do

dge

Do

dge

Do

dge

Do

dge

Che

v.

GM

C

Che

v.

GM

C

F-15

0 St

yles

ide

(500

0 lb

. tow

)

F-15

0 St

yles

ide

(990

0 lb

. tow

)

F-15

0 Fl

ares

ide

(500

0 lb

. tow

)

F-15

0 Fl

ares

ide

(990

0 lb

. tow

)

F-25

0/F-

350

Col

orad

o

Dur

ango

Dur

ango

Dak

ota

Ram

Spo

rt

Subu

rban

Subu

rban

430

Taho

e 41

0/20

Yuko

n 41

0/20

rear

rear

rear

rear

rear

rear

fro

nt

rear

fro

nt

fro

nt

fro

nt

fro

nt

fro

nt

fro

nt

12.2

5(2

7.00

)

9.98

(22.

0)

6.51

(14.

35)

9.34

(20.

59)

6.51

(14.

35)

14.5

2(3

2.01

)

14.2

9(3

1.50

)

14.2

9(3

1.50

)

14.2

9(3

1.50

)

14.2

9(3

1.50

)

13.5

2(2

9.8)

1.54

(3.4

)

3.01

(6.6

4)

8.13

(17.

92)

3.01

(6.6

4)

4.54

(10.

01)

29.9

4(6

6.00

)

38.5

6(8

5.00

)

31.7

5(7

0.00

)

40.3

7(8

9.00

)

25.7

6(5

6.8)

11.5

2(2

5.4)

9.52

(20.

99)

17.4

7(3

8.51

)

9.52

(20.

99)

19.0

6(4

2.02

)

29.94

(66.0

0)

46.04

(101.5

0)

31.75

(70.0

0)

47.85

(101.5

0)

25.76

(56.8

0)

11.52

(25.4

)

11.20

(24.6

9)

11.20

(24.6

9)

0.00

7.48

(16.

50)

0.00

7.48

(16.

50)

0.00

0.00

1.68

(3.7

0)

1.68

(3.7

0)

CR

CR

CR

CR

CR

CR

CR

CR

CR

CR

HR

HR

HR

HR

fro

ntsi

de c

hro

me

or

pain

tba

cksi

de p

aint

fro

ntsi

de c

hro

me

or

pain

tba

cksi

de p

aint

fro

ntsi

de c

hro

me

or

pain

tba

cksi

de p

aint

fro

ntsi

de c

hro

me

or

pain

tba

cksi

de p

aint

fro

ntsi

de c

hro

me

or

pain

tba

cksi

de p

aint

front

side

Zn

+ C

r or Z

n +

pain

tba

cksi

de p

aint

E-co

at

E-co

at

E-co

at

E-co

at

fro

ntsi

de c

hro

me

back

side

no

ne

fro

ntsi

de c

hro

me

back

side

no

ne

fro

ntsi

de c

hro

me

or

pain

tba

cksi

de n

one

fro

ntsi

de c

hro

me

or

pain

tba

cksi

de n

one

none

none

none

none

none

none

none

none

none

none

none

none

none

none

160

(6.3

)

160

(6.3

)

160

(6.3

)

160

(6.3

)

160

(6.3

)

140

(5.5

)

90 (

3.5)

100

(3.9

)

90 (

3.5)

140

(5.5

)

127

(5.0

)

127

(5.0

)

127

(5.0

)

127

(5.0

)

TAB

LE 5

.5 (

conti

nued

)CO

LD S

TAM

PED

BU

MPER

BEA

MS

THIC

KN

ESS,

WEI

GH

T, M

ATE

RIA

L, C

OA

TIN

GS

AN

D D

EPTH

-OF-

DR

AW

BEA

MS

PR

OD

UCED

IN

TH

E 2

00

4 C

ALE

ND

AR

YEA

R

5-28

2.26

(0.

089)

2.26

(0.

089)

1.60

(0.

063)

2.79

(0.

110)

2.06

(0.

081)

1.65

(0.

065)

1.32

(0.

050)

1.91

(0.

075)

1.91

(0.

075)

55X

LF

80X

LF

120X

F

WEI

GH

T [k

g (p

ound

s)]

STEE

LG

RAD

E1TH

ICK

NES

S[m

m (

inch

es)]

MA

KE

MO

DEL

FRO

NT

OR

REA

RB

UM

PER

Bea

mPe

rfor

man

ceRe

info

rcem

ents

Subt

otal

Mou

ntin

gBr

acke

tsTo

tal

STEE

LPR

OD

UC

TB

UM

PER

SU

PPLI

ERC

OA

TIN

GAS

SEM

BLY

LINE

COAT

ING

DEP

THO

F D

RAW

[mm

(inc

hes)

]

Che

v.

GM

C

GM

Satu

rn

Ford

Ford

Ho

nda

Chr

ylse

r

Chr

ysle

r

fro

nt

fro

nt

fro

nt

fro

nt

fro

nt

fro

nt

fro

nt

fro

nt

rear

14.2

9(3

1.50

)

14.2

9(3

1.50

)

9.00

(19.

84)

7.50

(16.

53)

8.50

(18.

74)

6.92

(15.

25)

2.06

(4.5

4)

0.00

3.00

(6.6

1)

0.00

0.00

0.00

9.00

(19.

84)

10.5

0(2

3.15

)

8.50

(18.

74)

6.92

(15.

25)

2.06

(4.5

4)

0.50

(1.1

0)

0.00

4.00

(8.8

2)

0.36

(0.7

9)

2.17

(4.7

9)

9.50

(20.

94)

10.5

0(2

3.15)

12.5

0(2

7.56)

7.28

(16.

04)

4.23

(9.3

3)

5.44

(12.

00)

6.35

(14.

00)

HR

HR

HR

HR

HR

HR

CR

90G

90G

HD

G

90G

90G

HD

G

fro

ntsi

de c

hro

me

or

pain

tba

cksi

de n

one

fro

ntsi

de c

hro

me

back

side

no

ne

E-co

at

E-co

at

E-co

at

E-co

at

none

none

none

none

none

none

none

none

none

E-co

at

E-co

at

none

127

(5.0

)

127

(5.0

)

152

(6.0

)

76 (

3.0)

114

(4.5

)

171

(6.7

)

50.8

(2.

0)

63.5

(2.

5)

C/K

400

Sier

ra 4

00

Ast

ro

LS Expl

orer

Spor

t/Sp

ort T

rac

Expe

ditio

n/N

avU

222/

228

Elem

ent

P/T

Cru

iser

P/T

Cru

iser

TAB

LE 5

.5 (

conti

nued

)CO

LD S

TAM

PED

BU

MPER

BEA

MS

THIC

KN

ESS,

WEI

GH

T, M

ATE

RIA

L, C

OA

TIN

GS

AN

D D

EPTH

-OF-

DR

AW

BEA

MS

PR

OD

UCED

IN

TH

E 2

00

4 C

ALE

ND

AR

YEA

R

NO

TES:

1. A

bla

nk c

ell m

eans

that

dat

a ar

e un

avai

labl

e fo

r th

at c

ell.

2. B

eam

wei

ght i

s fo

r a

pain

ted

beam

. Add

0.3

7 kg

(1.0

pou

nd) f

or a

chr

ome

beam

.3.

Bum

per

beam

s w

here

“fr

onts

ide”

and

“ba

cksi

de”

are

show

n in

“B

umpe

r Su

pplie

r C

oatin

g” c

olum

n ar

e bu

mpe

r fa

ceba

rs. A

ll ot

her

bum

per

beam

s ar

e re

info

rcin

g be

ams.

DEF

INIT

ION

S10

08/1

010

—Lo

w c

arbo

n qu

ality

. Mec

hani

cal p

rope

rtie

s ar

e no

t cer

tifie

d.D

R21

0—

Den

t res

ista

nt q

ualit

y. M

inim

um y

ield

str

engt

h of

210

MPa

(30

ksi)

as-s

hipp

ed fr

om th

e st

eel m

ill. S

tren

gth

incr

ease

s du

e to

wor

k ha

rden

ing

durin

g fo

rmin

g.XF

—Re

cove

ry a

nnea

led

qual

ity. S

tren

gth

is a

chie

ved

prim

arily

thro

ugh

cold

wor

kdur

ing

cold

rol

ling

at th

e st

eel m

ill. D

esig

natio

n nu

mbe

r (e

.g. 5

0) is

min

imum

yie

ldst

reng

th in

ksi

. XL

F—

Mic

roal

loy

qual

ity. S

tren

gth

is o

btai

ned

thro

ugh

smal

l add

ition

s of

allo

ying

ele

men

ts s

uch

as v

anad

ium

and

nio

bium

. Des

igna

tion

num

ber

(e.g

. 50)

is m

inim

um y

ield

str

engt

h in

ksi

. T

—D

ual p

hase

qua

lity.

Str

uctu

re c

onta

ins

mar

tens

ite in

ferr

ite m

atrix

. Des

igna

tion

num

ber

(e.g

. 140

) is

min

imum

tens

ile s

tren

gth

in k

si.

M..H

T—

Mar

tens

itic

qual

ity.

Stre

ngth

is d

eter

min

ed b

y ca

rbon

con

tent

. D

esig

natio

n nu

mbe

r (e

.g. 1

90) i

s m

inim

um te

nsile

str

engt

h in

ksi

. C

R—

Col

d ro

lled

shee

t.H

R—

Hot

rol

led

shee

t.EG

—El

ectr

ogal

vani

zed

shee

t. Th

e si

x-ch

arac

ter

desc

ripto

r de

sign

ates

coa

ting

type

and

wei

ght.

Two

num

eric

cha

ract

ers

(e.g

. 60)

den

ote

coat

ing

wei

ght i

n g/

m2 .

An

alph

abet

ic c

hara

cter

deno

tes

coat

ing

type

. “A

” is

a z

inc-

iron

allo

y co

atin

g. “

G”

is a

zin

c co

atin

g. T

he fi

rst t

hree

cha

ract

ers

deno

te c

oatin

g w

eigh

t and

type

on

one

side

of t

he s

heet

and

the

last

thre

e ch

arac

ters

den

ote

coat

ing

wei

ght a

nd ty

pe o

n th

e op

posi

te s

ide

of th

e sh

eet.

HD

G—

Hot

-dip

gal

vani

zed

shee

t. Th

e si

x-ch

arac

ter

desc

ripto

r de

sign

ates

coa

ting

type

and

wei

ght.

Two

num

eric

cha

ract

ers

(e.g

. 90)

den

ote

coat

ing

wei

ght i

n g/

m2 .

An

alph

abet

ic c

hara

cter

deno

tes

coat

ing

type

. “A

” is

a z

inc-

iron

allo

y co

atin

g. “

G”

is a

zin

c co

atin

g. T

he fi

rst t

hree

cha

ract

ers

deno

te c

oatin

g w

eigh

t and

type

on

one

side

of t

he s

heet

and

the

last

thre

e ch

arac

ters

den

ote

coat

ing

wei

ght a

nd ty

pe o

n th

e op

posi

te s

ide

of th

e sh

eet.

HR

HR

HR

HR

HR

HR

HR

HR

HR

HR

HR

HR

HR

HR

HR

HR

5-29

3.50

(0.

138)

3.00

(0.

118)

3.00

(0.

118)

2.70

(0.

106)

2.70

(0.

106)

2.50

(0.

098)

2.50

(0.

098)

2.50

(0.

098)

2.50

(0.

098)

2.14

(0.

084)

2.14

(0.

084)

2.14

(0.

084)

2.14

(0.

084)

2.00

(0.

079)

2.00

(0.

079)

2.00

(0.

079)

10B2

1(M)

WEI

GH

T [k

g (p

ound

s)]

STEE

LG

RAD

E1TH

ICK

NES

S[m

m (

inch

es)]

MA

KE

MO

DEL

FRO

NT

OR

REA

RB

UM

PER

Bea

mPe

rfor

man

ceRe

info

rcem

ents

Subt

otal

Mou

ntin

gBr

acke

tsTo

tal

STEE

LPR

OD

UC

TB

UM

PER

SU

PPLI

ERC

OA

TIN

GAS

SEM

BLY

LINE

COAT

ING

DEP

THO

F D

RAW

[mm

(inc

hes)

]

VW

VW

VW

VW

VW

VW

VW

VW-C

hina

VW-Se

at

VW

VW

VW

VW/S

koda

Ford

Smar

t

Smar

t

A4

Jett

a U

SA

C1

USA

New

Be

etle

C1

ECE

New

Be

etle

B5 U

SA P

assa

t

B5 U

SA P

assa

t

PQ24

Bra

sil

New

Pol

o

PQ24

A04

New

Pol

o

PQ24

A04

New

Pol

o C

hina

PQ24

S04

New

Ibiz

a

A4

ECE

Gol

f

A4

Jett

a U

SA

A4

ECE

Hin

ten

Fabi

a

C17

0 Fo

cus

W45

6 EC

E Br

asil

form

er (S

UV

)

W45

6 U

SA B

rasil

form

er (S

UV

)

rear

rear

rear

fro

nt

rear

rear

rear

rear

rear

rear

fro

nt

rear

rear

rear

rear

rear

6.00

(13.

23)

6.50

(14.

33)

8.00

(17.

64)

2.00

(4.4

1)

2.80

(6.1

7)

2.80

(6.1

7)

2.80

(6.1

7)

3.50

(7.7

2)

6.00

(13.

23)

6.00

(13.

23)

3.30

(7.2

8)

4.30

(9.4

8)

4.09

(9.0

2)

4.09

(9.0

2)

6.00

(13.

23)

7.20

(15.

87)

8.00

(17.6

4)

5.00

(11.0

3)

5.00

(11.0

3)

5.00

(11.0

3)

5.00

(11.0

3)

6.00

(13.

23)

6.00

(13.

23)

6.00

(13.

23)

5.10

(11.2

4)

4.80

(10.

58)

7.22

(15.

92)

9.19

(20.

26)

0.70

(1.5

4)

3.00

(6.6

1)

2.20

(4.8

5)

2.20

(4.8

5)

2.20

(4.8

5)

2.50

(5.5

1)

1.80

(3.9

7)

0.50

(1.1

0)

3.13

(11.

62)

5.10

(11.

24)

E-co

at

E-co

at

E-co

at

E-co

at

E-co

at

E-co

at

E-co

at

E-co

at

E-co

at

E-co

at

E-co

at

E-co

at

E-co

at

E-co

at

Zin

c co

ated

Zin

c co

ated

none

none

none

none

none

none

none

none

none

none

none

none

none

none

none

none

65 (

2.6)

80 (

3.1)

80 (

3.1)

82 (

3.2)

105

(4.1

)

70 (

2.8)

70 (

2.8)

70 (

2.8)

70 (

2.8)

65 (

2.6)

65 (

2.6)

65 (

2.6)

85 (

3.3)

40 (

1.6)

40 (

1.6)

TAB

LE 5

.6H

OT

FOR

MED

BU

MPER

BEA

MS

THIC

KN

ESS,

WEI

GH

T, M

ATE

RIA

L, C

OA

TIN

GS

AN

D D

EPTH

-OF-

DR

AW

BEA

MS

PR

OD

UCED

IN

TH

E 2

00

4 C

ALE

ND

AR

YEA

R

HR

HR

HR

HR

HR

HR

HR

HR

HR

HR

HR

HR

HR

HR

HR

5-30

2.00

(0.

079)

1.80

(0.

071)

1.80

(0.

071)

1.80

(0.

071)

1.80

(0.

071)

1.80

(0.

071)

1.80

(0.

071)

1.60

(0.

063)

1.60

(0.

063)

1.50

(0.

059)

1.50

(0.

059)

10B2

1(M)

WEI

GH

T [k

g (p

ound

s)]

STEE

LG

RAD

E1TH

ICK

NES

S[m

m (

inch

es)]

MA

KE

MO

DEL

FRO

NT

OR

REA

RB

UM

PER

Bea

mPe

rfor

man

ceRe

info

rcem

ents

Subt

otal

Mou

ntin

gBr

acke

tsTo

tal

STEE

LPR

OD

UC

TB

UM

PER

SU

PPLI

ERC

OA

TIN

GAS

SEM

BLY

LINE

COAT

ING

DEP

THO

F D

RAW

[mm

(inc

hes)

]

PSA

GM

/Ope

l

VW

VW

VW-S

eat

VW-C

hina

VW-S

eat

GM

/Saa

b

GM

/Saa

b

PSA

Smar

t

VW

VW

VW

VW

T5 N

ew 3

07

Zaf

ira

PQ24

Bra

sil

PQ24

A04

N

ew P

olo

PQ24

S04

N

ew Ib

iza

PQ24

A04

New

Pol

o C

hina

SE24

1N

ew C

ordo

ba

602

New

9-5

440

New

9-3

X4 (X

41, X

42)

New

Xan

tia

W45

6 Br

asil

form

er (S

UV

)

C1

USA

New

Beet

le

C1 E

CE N

ewBe

etle

D1

(Pha

eton

)

D1

(Pha

eton

)

rear

rear

fro

nt

fro

nt

fro

nt

fro

nt

rear

fro

nt

fro

nt

rear

fro

nt

fro

nt

fro

nt

fro

nt

rear

4.27

(9.4

2)

3.60

(7.9

4)

2.00

(4.4

1)

2.80

(6.1

7)

2.80

(6.1

7)

2.80

(6.1

7)

2.80

(6.1

7)

3.60

(7.9

4)

3.60

(7.9

4)

2.10

(4.6

3)

2.85

(6.2

8)

7.60

(16.

76)

4.15

(9.1

5)

7.27

(16.

03)

4.40

(9.7

0)

5.00

(11.0

3)

5.00

(11.0

3)

5.00

(11.0

3)

5.00

(11.0

3)

6.00

(13.

23)

10.2

0(2

2.49

)

10.2

0(2

2.49

)

7.27

(16.

03)

10.0

5(2

2.16)

14.6

0(3

2.19)

7.15

(15.

76)

3.00

(6.6

1)

0.80

(1.7

6)

3.00

(6.6

1)

2.20

(4.8

5)

2.20

(4.8

5)

2.20

(4.8

5)

3.20

(7.0

5)

6.60

(14.

55)

6.60

(14.

55)

2.00

(4.4

1)

7.20

(15.

88)

7.00

(15.

43)

3.00

(6.6

1)

E-co

at

Zin

c co

ated

E-co

at

E-co

at

E-co

at

E-co

at

E-co

at

E-co

at

Raw

/CB

-Zin

c

Raw

/CB

-Zin

c

E-co

at

Zin

c co

ated

E-co

at

E-co

at

E-co

at

none

none

none

none

none

none

none

none

yes

yes

none

none

none

none

none

80 (

3.1)

90 (

3.5)

60 (

2.4)

60 (

2.4)

60 (

2.4)

60 (

2.4)

75 (

3.0)

85 (

3.3)

85 (

3.3)

55 (

2.2)

50 (

2.0)

80 (

3.1)

80 (

3.1)

90 (

3.5)

70 (

2.8)

TAB

LE 5

.6 (

conti

nued

)H

OT

FOR

MED

BU

MPER

BEA

MS

THIC

KN

ESS,

WEI

GH

T, M

ATE

RIA

L, C

OA

TIN

GS

AN

D D

EPTH

-OF-

DR

AW

BEA

MS

PR

OD

UCED

IN

TH

E 2

00

4 C

ALE

ND

AR

YEA

R

Alu

min

ized

(CR)

Alu

min

ized

(CR)

5-31

1.2

(0.0

47)

1.2

(0.0

47)

15B2

1(M)

WEI

GH

T [k

g (p

ound

s)]

STEE

LG

RAD

E1TH

ICK

NES

S[m

m (

inch

es)]

MA

KE

MO

DEL

FRO

NT

OR

REA

RB

UM

PER

Bea

mPe

rfor

man

ceRe

info

rcem

ents

Subt

otal

Mou

ntin

gBr

acke

tsTo

tal

STEE

LPR

OD

UC

TB

UM

PER

SU

PPLI

ERC

OA

TIN

GAS

SEM

BLY

LINE

COAT

ING

DEP

THO

F D

RAW

[mm

(inc

hes)

]

Ford

Ford

Mus

tang

Mus

tang

fro

nt

rear

4.3

(9.5

8)

6.02

(13.

29)

5.2

(11.6

)

6.02

(13.

29)

0.92

(2.0

4)no

ne

none

E-co

at

E-co

at

85 (

3.3)

85 (

3.3)

TAB

LE 5

.6 (

conti

nued

)H

OT

FOR

MED

BU

MPER

BEA

MS

THIC

KN

ESS,

WEI

GH

T, M

ATE

RIA

L, C

OA

TIN

GS

AN

D D

EPTH

-OF-

DR

AW

BEA

MS

PR

OD

UCED

IN

TH

E 2

00

4 C

ALE

ND

AR

YEA

R

NO

TES:

1. A

bla

nk c

ell m

eans

that

dat

a ar

e un

avai

labl

e fo

r th

at c

ell.

2. B

eam

wei

ght i

s fo

r a

pain

ted

beam

. Add

0.3

7 kg

(1.0

pou

nd) f

or a

chr

ome

beam

.3.

Bum

per

beam

s w

here

“fr

onts

ide”

and

“ba

cksi

de”

are

show

n in

“B

umpe

r Su

pplie

r C

oatin

g” c

olum

n ar

e bu

mpe

r fa

ceba

rs. A

ll ot

her

bum

per

beam

s ar

e re

info

rcin

g be

ams.

DEF

INIT

ION

S10

B21

(M)

—C

arbo

n-bo

ron

qual

ity (S

AE

10B

21 m

odifi

ed).

Bea

ms

are

hot f

orm

ed. A

fter

quen

chin

g, th

e yi

eld

stre

ngth

is a

bout

114

0 M

Pa (1

65ks

i).15

B21

(M)

—C

arbo

n-bo

ron

qual

ity (S

AE

15B

21 m

odifi

ed).

Bea

ms

are

hot f

orm

ed. A

fter

quen

chin

g, th

e yi

eld

stre

ngth

is a

bout

114

0 M

Pa (1

65ks

i).

5.5 Current steel bumper design - North American passenger cars and minivansThe bumper systems on passenger cars sold in the United Statesmust meet the NHTSA( National Highway Traffic SafetyAdministration), Part 581, Bumper Standard (see Section 6.1).Such bumpers are termed 2.5mph (4km/h) bumpers. Thebumper systems on passenger cars sold in Canada must meet theCanadian Motor Vehicle Safety Regulations Standard 215 (seeSection 6.2). Such bumpers are termed 5mph (8km/h) Canadianbumpers. In practice, the NHTSA and Canadian regulations arenot that far apart. Although Canada has higher test speeds, itsacceptance criteria are less stringent than NHTSA’s. Canadaallows damage to any non-safety or non-functional item. NHTSA,however, restricts damage to the bumper system.

North American OEMs typically place 5mph (8km/h) bumpersystems on their passenger cars. One such system is the 5mph(8km/h) Canadian bumper referred to above. Another system isthe so-called 5mph (8km/h) NHTSA bumper. This system is basedon NHTSA Part 581 in all respects except for test speeds, whichare doubled [5mph (8km/h) longitudinal pendulum and barrierimpacts and 3mph (4.8km/h) corner pendulum impacts]. Itshould be noted that the NHTSA and Canadian bumper standardsapply only to passenger cars. However, most OEMs voluntarilytreat minivans the same as passenger cars from the bumperperspective. Thus, most OEMs place a 5mph (8km/h) bumpersystem on their minivans.

The Insurance Institute for Highway Safety (IIHS) and theConsumers Union (CU) both test bumper systems (see Sections6.4 and 6.5 respectively). Both IIHS and CU publish the “cost ofrepair” for vehicles they have tested. Thus, for marketing reasons,an OEM often sets a target “cost of repair” for a given vehicle.

5-32

As explained above, most North American OEMs place either a5mph (8km/h) NHTSA or a 5mph (8km/h) Canadian bumpersystem on their passenger cars and minivans. For the reason oflow cost with light weight, about 90% of today’s bumper systemshave a steel beam. When designing a 5mph (8km/h) bumper,the secret of success is to allow the steel bumper beam to yieldand deform within the allowable intrusion space.

The Flow Chart in Figure 5.6 outlines a typical design process for5mph (8km/h) low speed bumper systems having a steel beam.It is emphasized that the process shown in Figure 5.6 is a typicalprocess. Other processes are also used to design 5mph (8km/h)low speed bumper systems.

The designer’s first step is to determine the OEM internal acceptance requirements. For example, are the IIHS and CUtests to be included in the design process? Are the Canadian orthe NHTSA criteria to be used? Are there OEM requirementsthat are not incorporated into the Flow Chart? If the answer tothe latter question is yes, then the designer must modify the FlowChart to cover the additional OEM requirements.

5.5.1 Typical bumper design for 5 mph (8 km/h) low speed system

Often, particularly if the IIHS or CU targets are zero or minimal“cost of repair”, the IIHS and CU tests are more demanding thanthe NHTSA or Canadian criteria. Thus, if the IIHS and CU testsare to be included in the design process, it is logical to evaluatethem first. The designer enters the IIHS/CU design path. If theIIHS and CU tests need not be considered, then the designerenters the Canadian/NHTSA design path.

In the IIHS/CU path, the designer follows the front bumperbranch or the rear bumper branch. The first step in either branchis to establish the IIHS “cost of repair” that is acceptable to theOEM. It should be noted that there are two IIHS “cost of repair”targets for either a front or a rear bumper. One is the “cost ofrepair” following the corner or pole impact for the front or rearbumper respectively. The other is the “cost of repair” followingthe barrier impact. Of course, the two targets for a bumpermight well be the same.

The second step is to prepare a Base Design. Often, but notalways, the most demanding IIHS test requirement for a frontbumper is the impact into the corner barrier and for the rearbumper the impact into the pole. Thus, it is suggested that theBase Design for a front bumper be based on the corner impactwhile the Base Design for the rear bumper be based on the poleimpact. After preparing a Base Design that satisfies the “cost ofrepair” target, the designer checks the performance of the frontor rear bumper in the 90degree barrier test. If the “cost ofrepair” under the 90degree barrier test does not meet the target,the designer prepares a new base design. If it does, the designerproceeds to the CU requirements.

First, the designer establishes the CU “cost of repair” desired bythe OEM. It should be noted that the “cost of repair” is calculatedafter the three CU bumper basher tests have been completed.Thus, there is only one “cost of repair” target for either a front ora rear bumper. Next, the designer verifies that the Base Designselected to satisfy the two IIHS “cost of repair” targets for a givenbumper satisfies the CU “cost of repair” target. If it does not,then the Base Design must be modified. If it does, the designercan proceed to the Canadian/NHTSA design path.

By definition, a 5mph (8kh/h) North American bumper systemmust meet either the Canadian or the NHTSA criteria. As a firststep, the designer determines whether the bumper system is tobe a 5mph (8km/h) Canadian one or a 5mph (8km/h) NHTSAone (See the introduction to Section 5.5 above for a descriptionof a 5mph (8km/h) NHTSA bumper.).

If the Canadian criteria are to be used, a base design is prepared.It is reasonable to start with the pendulum impacts and thenmove to the barrier impact because this is the order used intesting. The Canadian damage criteria are evaluated after allimpacts have been completed. That is, the cumulative damageincurred during the longitudinal impacts, the corner impact andthe barrier impact is evaluated. If there is damage to safety andfunctional items, the base design must be modified. If not, thedesigner can move to the next step.


5-33

5.5.3 Canadian/NHTSA design path

At this juncture, the base design meets the regulatoryrequirements for the bumper to be placed on a vehicle for sale inCanada. However, because the Flow Chart applies to NorthAmerican vehicles, the bumper must also meet the regulatoryrequirements for a 2.5mph (4km/h) NHTSA bumper. Then, thebumper and vehicle may also be sold in the United States.Specifically, the base design must be checked to ensure that thereis no non-bumper visual damage and no damage to safety andfunctional items after the accumulated effects of the 2.5mph(4km/h) longitudinal pendulum impacts, the 1.5mph (2.4km/h)corner pendulum impacts and the 2.5mph (4km/h) barrier impact.Also, the vehicle shall not touch the test device, except on theimpact ridge shown in Figures 6.1 and 6.2, with a force thatexceeds 2000 pounds (907kg) on the combined surfaces ofPlanes A and B (see Figure 6.3) of the test device.

If the 5mph (8km/h) NHTSA criteria are to be used, a basedesign is prepared. It is reasonable to start with the pendulumimpacts and then move to the barrier impact because this is theorder used in testing. The NHTSA damage criteria are evaluatedafter all impacts have been completed. That is, the cumulativedamage incurred during the longitudinal pendulum impacts, thecorner pendulum impacts and the barrier impact is evaluated.There must be no non-bumper visual damage and no damage tosafety and functional items. Also, the vehicle shall not touch thetest device, except on the impact ridge shown in Figures 6.1 and6.2, with a force that exceeds 2000 pounds (907kg) on the combined surfaces of Planes A and B (see Figure 6.3) of the testdevice. If these two conditions are met, the designer has reacheda final design. The base design automatically meets the regulatory requirements of a bumper to be placed on a vehicle forsale in the United States because the NHTSA damage criteriahave been applied at speeds twice those required by NHTSA.Also, because the NHTSA damage criteria are more severethan the Canadian damage criteria, and because the impactspeeds used for the base design are the same as the Canadianimpact speeds, the bumper and vehicle may also be sold inCanada.

5-34

5-35

DETERMINE OEMINTERNAL ACCEPTANCE

REQUIREMENTS

IIHS/CONSUMERS UNION

REQUIREMENTS?

FRONTOR

REARBUMPER?

ESTABLISHDESIRED IIHS

COST OFREPAIR

BASE DESIGN

• IIHS 5 mphCorner Barrier

• IIHS 5 mphFront Barrier

• IIHS 5 mphRear Barrier

BASE DESIGN

• IIHS 5 mphInto Pole


COST OFREPAIR

ACCEPTABLECOST OFREPAIR?


ESTABLISH DESIREDCONSUMERS UNION

COST OF REPAIR

• 5 mph Centre Impact• 5 mph Off-Centre Impact• 3 mph Corner Impact

YES

YES

FRONT

NO

REAR

NO

FRONT

NO

REAR

NO

FRONT REAR

YES NO

CANADIAN ORNHTSA

CRITERIA?

BASE DESIGN

• 5 mph Longitudinal Pendulum

• 3 mph Corner Pendulum

• 5 mph Barrier Impact

NHTSA

• 2.5 mph Longitudinal Pendulum

• 1.5 mph Corner Pendulum

• 2.5 mph Barrier Impact

BASE DESIGN

• 5 mph Longitudinal Pendulum

• 3 mph Corner Pendulum

• 5 mph Barrier Impact

CANADIAN NHTSA

YES

NO

NO

ANY DAMAGETO SAFETY &FUNCTIONAL

ITEMS?

FINAL DESIGN

ANYNON-BUMPER

VISUAL OR SAFETY &FUNCTIONAL ITEM

DAMAGE?

CDNYES

NHTSAYES

NO

CDNYES

NHTSAYES

A+BPLANESFORCE

2000 LBS.<

FIGURE 5.6TYPICAL BUMPER DESIGN FOR 5 mph LOW SPEED SYSTEM

NORTH AMERICAN PASSENGER CARS AND MINIVANS

5.6 Current steel bumper design - North American pickups, full size vans and sport utilitiesNeither the United States nor Canada has mandatory bumperregulations for light truck vehicles. However, most NorthAmerican OEMs voluntarily apply the United States (NHTSA)passenger car regulations (see Section 6.1) to pickups, full sizevans and sport utilities with one significant difference. For passengercars, the longitudinal and corner pendulum impacts are conductedat heights from 16 to 20 inches (400 to 500mm). However, thependulum impacts on a light truck bumper are conducted atheights that are associated with the actual bumper height. Abumper system designed in this manner, is termed a modified NHTSA 2.5mph (4km/h) bumper system.

The Insurance Institute for Highway Safety (IIHS) and theConsumers Union (CU) both test bumper systems (see Sections6.4 and 6.5 respectively). Both IIHS and CU publish the “cost ofrepair” for vehicles they have tested. Thus, for marketing reasons,an OEM often sets a target “cost of repair” for a given vehicle.For example, the OEM may wish a “cost of repair” that is near themedian “cost of repair” of the other vehicles in its class.

5-36

As explained above, most North American OEMs place amodified NHTSA 2.5mph (4km/h) bumper system on their pick-ups, full size vans and sport utilities. For the reason of low costwith light weight, about 90% of today’s bumper systems have asteel beam. When designing a modified 2.5mph (4km/h) NHTSAbumper, the secret of success is to allow the steel bumper beamto yield and deform within the allowable intrusion space.

The Flow Chart in Figure 5.7 outlines a typical design process fora 2.5mph (4km/h) low speed bumper system having a steelbeam. It is emphasized that the process shown in Figure 5.7 is atypical process. Other processes are also used to design 2.5mph(4km/h) low speed bumper systems.

The designer’s first step is to determine the OEM internalacceptance requirements. For example, are the IIHS and CUtests to be included in the design process? Are there OEMrequirements that are not incorporated into the Flow Chart? Ifthe answer to the latter question is yes, then the designer mustmodify the Flow Chart to cover the additional OEM requirements.

Often, particularly if the IIHS or CU target is a minimal “cost ofrepair”, the IIHS and CU tests are more demanding than theNHTSA criteria. Thus, if the IIHS and CU tests are to be includedin the design process, it is logical to evaluate them first. Thedesigner enters the IIHS/CU design path. If the IIHS and CUtests need not be considered, then the designer enters theNHTSA design path.

5.6.1 Flow chart for 2.5mph (4km/h) low speed system

In the IIHS/CU path, the designer follows the front bumperbranch or the rear bumper branch. The first step in eitherbranch is to establish the IIHS “cost of repair” that is acceptable tothe OEM. It should be noted that there are two IIHS “cost ofrepair” targets for either a front or a rear bumper. One is the“cost of repair” following the corner or pole impact for thefront or rear bumper respectively. The other is the “cost ofrepair” following the barrier impact. Of course, the two targets fora bumper might well be the same.

The second step is to prepare a Base Design. Often, but notalways, the most demanding IIHS test requirement for a frontbumper is the impact into the corner barrier and for the rearbumper the impact into the pole. Thus, it is suggested thatthe Base Design for a front bumper be based on the cornerimpact while the Base Design for the rear bumper be basedon the pole impact. After preparing a Base Design thatsatisfies the “cost of repair” target, the designer checks theperformance of the front or rear bumper in the 90degreebarrier test. If the “cost of repair” under the 90degree barriertest does not meet the target, the designer prepares a newbase design. If it does, the designer proceeds to the CUrequirements.


5-37

First, the designer establishes the CU “cost of repair” desiredby the OEM. It should be noted that the “cost of repair” iscalculated after the three CU bumper basher tests have beencompleted. Thus, there is only one “cost of repair” target foreither a front or a rear bumper. Next, the designer verifiesthat the Base Design selected to satisfy the two IIHS “cost ofrepair” targets for a given bumper satisfies the CU “cost ofrepair” target. If it does not, then the Base Design must bemodified. If it does, the designer can proceed to the NHTSAdesign path.

It is reasonable to start with the pendulum impacts and thenmove to the barrier impact because this is the order used intesting. As noted in the introduction to Section 5.6 above,the pendulum impacts are conducted at heights associatedwith the vehicle’s bumper height. The NHTSA damage criteriaare evaluated after all impacts have been conducted. That is,the cumulative damage incurred during the longitudinalpendulum impacts, the corner pendulum impacts and thebarrier impact is evaluated. There must be no non-bumpervisual damage and no damage to safety and functional items.Also, the vehicle shall not touch the test device, except onthe impact ridge shown in Figures 6.1 and 6.2, with a forcethat exceeds 2000 pounds (907kg) on the combined surfacesof Planes A and B (see Figure 6.3) of the test device. If thesetwo conditions are met, the final design has been reached.

5.6.3 NHTSA design path

5-38

DETERMINE OEMINTERNAL ACCEPTANCE

REQUIREMENTS

IIHS/CONSUMERS UNION

REQUIREMENTS?

FRONTOR

REARBUMPER?


COST OFREPAIR

BASE DESIGN

• IIHS 5 mphCorner Barrier

• IIHS 5 mphFront Barrier

• IIHS 5 mphRear Barrier

BASE DESIGN

• IIHS 5 mphInto Pole


COST OFREPAIR



ESTABLISH DESIREDCONSUMERS UNION

COST OF REPAIR

• 5 mph Centre Impact• 5 mph Off-Centre Impact• 3 mph Corner Impact

YES

YES

FRONT

NO

REAR

NO

FRONT

NO

REAR

NO

FRONT REAR

YES NO

BASE DESIGN(MODIFIED NHTSA CRITERIA)

• 2.5 mph Longitudinal Pendulum

• 1.5 mph Corner Pendulum

• 2.5 mph Barrier Impact

YES

YES

NO

NO

FINAL DESIGN

ANY

NON-BUMPER

VISUAL OR SAFETY &

FUNCTIONAL ITEM

DAMAGE?

A+B

PLANES

FORCE

2000 LBS.<

FIGURE 5.7TYPICAL BUMPER DESIGN FOR 2.5 mph LOW SPEED SYSTEM

NORTH AMERICAN PICKUPS, FULL SIZE VANS AND SPORT UTILITIES

5-39

Quantech, in consultation with A/SP, established the designcriteria for a high speed bumper system as:

1. No bumper damage or yielding after a 5mph (8km/h)frontal impact into a flat, rigid barrier. Note: This criterion does not apply to low speed bumpers, where controlled yielding and deformation are beneficial.

2. No intrusion by the bumper system rearward of the engine compartment rails for all impact speeds less than 9mph (15km/h).

3. Minimize the lateral loads during impacts in order to reduce the possibility of lateral buckling of the rails.

4. Full collapse of the system during Danner (RCAR), NCAP, and IIHS high speed crash without inducing buckling of the rails.

5. Absorb 1% of the total energy every millisecond.6. Absorb 15% of the total energy in the NCAP crash,

including engine hit.7. Use the front-end crush space efficiently.8. Meet the air bag sensor requirements in low, medium

and high speed impacts.9. No detrimental affect on baseline body-in-white static or

dynamic stiffness.

Bumpers should protect car bodies from damage in lowspeed collisions - the kind that frequently occurs in congestedurban traffic. The IIHS Low Speed Crash Test Protocol (seeSection 6.4) addresses this issue. For marketing reasons,many current bumper systems are designed to ensure no orminimal “cost of repair” after the IIHS 5mph (8km/h) barrierimpact. A/SP believes all future vehicles should meet thisrequirement. Thus, Criterion 1 was set to achieve zero damage and no or minimal “cost of repair” after the IIHS5mph (8km/h) barrier impact.

Criterion 4 addresses three high speed load cases:1. 40%-9mph Danner (RCAR Test - see Section 6.6 and

Reference 6.10). This load is a 9mph (15km/h) impact ata 40% offset into a rigid barrier. The A/SP objective is to have no damage to the radiator and other costly equipment in the front-end and to have no damage to the rail beyond 300mm (12inches).

5.7.1 Quantech design criteria for high speed steel bumper system

5.7 Auto/Steel Partnership high speed steel bumper design - North American passenger carsThe Auto/Steel Partnership (A/SP) commissioned QuantechGlobal Services to conduct a study on the front-end of a 4 door,mid-size sedan. The objective was to reduce the cost and mass ofthe front-end structure through the use of advanced high-strengthsteels. The study included the development of a high speedbumper system.

Current North American passenger cars have low speed bumpersystems. Thus, Quantech’s first task for the high speed bumpersystem was to establish design criteria and a design process.SectionS 5.7.1 and 5.7.2 outline the results of Quantech’s researchinto these two areas.

2. 35 mph NCAP (NHTSA New Car Assessment Program, Reference 5.2). This load is a 35mph (56km/h) impact into a rigid barrier. The A/SP objective is to maximize the energy absorbed in the bumper system.

3. 40%-40mph IIHS (Reference 5.3). This load case is a 40mph (64km/h) impact at a 40% offset into a deformable barrier. The A/SP objective is to ensure the bumper system does not break and is capable of transferring the load to the right rail, thereby minimizing the damage.

A major objective of A/SP is to reduce vehicle weight usingsteel as the material of choice. Criterion 6 addresses thisobjective. Traditional bumper systems absorb about 8-11% ofthe energy in the 35mph (56km/h) NCAP crash. If bumpersystems were to dissipate higher levels, there would be anopportunity for mass savings in the front-end structure. Tocapitalize on this opportunity, A/SP set 15% energy absorptionas a stretch goal for future bumper systems.

5-40

For the reason of low cost with light weight, steel is the materialof choice for future, as well as current, bumper beams. TheFlow Chart in Figure 5.8 outlines the design process developedby Quantech for a high speed bumper system having a steelbeam. The process is a logical route to satisfying the designcriteria outlined in Section 5.7.1.

First, a Base Design is prepared. It is checked against theIIHS low speed [5mph (8km/h)] flat frontal barrier load case.If there is damage or yielding, the Base Design is modified. Ifnot, the three high speed load cases are analyzed in the followingsequence:

1. 40% offset - 9mph (15km/h) Danner.2. 35mph (56km/h) NCAP.3. 40% offset - 40mph (64km/h) IIHS.

The results from the analyses of the three high speed loadcases are compared to the design criteria in Section 5.7.1. Ifall of the criteria are met, the designer assesses the amount ofenergy absorption. Energy absorption should be maximizedbecause the higher the amount, the greater the opportunityto reduce mass in the front-end structure. If the designerbelieves energy absorption has been maximized, a viabledesign has been captured. If not, the learning from the threehigh speed load cases is used to improve the Base Designand reach a viable design.

Usually, three or four viable design alternatives are developedusing the above process. The designer then selects one ofthe alternatives as the Preferred Design. The PreferredDesign should be lightweight and easy to manufacture. Also,it should be easy to assemble and integrate with the rails.Cost is also a consideration when selecting the PreferredDesign.

5.7.2 Flow Chart for high speed system

NO/MINIMUMDAMAGEABILITY

OF RAIL

40%-40 mph (IIHS)

5-41

FIGURE 5.8AUTO/STEEL PARTNERSHIP BUMPER DESIGN FOR HIGH SPEED SYSTEM

NORTH AMERICAN PASSENGER CARS

BASE DESIGN

LOW SPEED5 mph

DANNER40% OFFSET

15 km/h (9 mph)

HIGH SPEED35 mph (NCAP)

USE LEARNINGFOR AN IMPROVED

DESIGN

CAPTURE AVIABLE DESIGN

PREFERREDDESIGN

ACCEPTABLE?

ENERGYABSORPTIONMAXIMIZED?

AIR BAG SENSORREQUIREMENTS

AIR BAG G

Source: Auto/Steel Partnership and Quantech Global Services

YES

YES

NO

NO

5-42

The European Union has been subjecting select vehicles to abattery of tests (frontal, side and pedestrian) as part of itsnew car assessment program (EuroNCAP, Reference 5.5). TheEuroNCAP pedestrian tests (Figure 5.9) consist of:• leg to bumper impacts with a “leg-form” impactor,• upper leg to hood edge impacts with an upper “leg-form”

impactor,• head to hood top impacts with two different “head-form”

impactors.

The European Union typically subjects a vehicle to three legto bumper impacts, three upper leg to hood edge impactsand up to 18 head to hood top impacts. The results arereported with a four-star rating system, similar to that used inthe United States NCAP program.

Japan’s NCAP program includes tests that simulate pedestrianhead to hood top impacts. However, leg to bumper andupper leg to hood edge impacts are not included.

Currently, North American NCAP programs do not includepedestrian requirements. However, the high number ofpedestrian accidents in North America and the trend to global vehicle design, likely mean that pedestrian impactrequirements will come to North America in the longer term.

This test significantly influences bumper design. Thus, a briefdiscussion of the requirements is in order. First, it should bestated that the purpose of this test is to reduce severe lowerlimb injuries in pedestrian accidents. The most commonlower limb injuries are intra-articular bone fractures, ligamentruptures and comminuted fractures.

In this test, a “leg-form” impactor is propelled toward a stationary vehicle at a velocity of 40 km/h (25 mph) parallelto the vehicleís longitudinal axis. The test can be performedat any location across the face of the vehicle, between the30° bumper corners.

5.8.1 Impact tests

5.8.2 EuroNCAP leg to bumper impacts with a “leg-form” impactor

5.8 Bumper design for pedestrian impactPedestrian safety is a globally recognized safety concern. Effortstowards modifying vehicle designs to offer some protection forpedestrians began in earnest in the 1970s. At the same time, testprocedures to evaluate the performance of new designs began tobe developed. Pedestrian safety has improved significantly sincethen.

The American Iron and Steel Institute wished to learn how pedestrian safety might affect steel bumper systems. Thus, itretained Dr. Peter Schuster, California Polytechnic State University,to study this topic. The following information is based on his work(Reference 5.4).

5-43

As of June 2005 world-wide, there were no government regulations for pedestrian impact. However, the EuropeanUnion and major vehicle associations have negotiated anagreement (Reference 5.6). The agreement states that newvehicles will achieve a limited level of pedestrian impact performance starting in 2005, with an increased performancein 2010. The limits shown in Figures 5.9 and 5.11 are the targets for 2010. For 2005, the leg to bumper targets are:• knee bending < 20°,• knee shear < 6mm (0.24 inches),• acceleration < 200g.

There are two general approaches to designing a frontbumper system for pedestrian safety:• Provide front-end vehicle components to cushion the

impact and support the lower limb,• Provide sensors and external airbags to cushion the impact

and support the lower limb.

Cushioning reduces the severity of bone fractures. It is directly related to the acceleration impact criterion shown inFigure 5.11. Limiting the lower limb acceleration to 150grequires a bumper stiffness lower than that usually providedto satisfy the damageability criteria associated with low-speed[8 km/h (5 mph)] vehicle impact. Thus, a pedestrian friendlybumper system must be capable of limiting “leg-form” acceleration without sacrificing vehicle damageability in alow-speed impact.

Supporting the lower limb reduces the risk of knee jointinjuries such as ligament ruptures and intra-articular fractures.It is directly related to the knee bend angle criterion in Figure5.11. Enough support must be provided below the mainbumper to limit the bending angle to 15°. Any support provided must not conflict with styling requirements or resultin unacceptable low-speed [8 km/h (5 mph)] impact damage.

5.8.3 Government regulations

5.8.4 Design approaches

5.8.4.1 Cushioning the impact

5.8.4.2 Supporting the lower limb

The “leg-form” impactor is shown in Figure 5.10. It consists of twosemi-rigid 70mm (27.6 inches) diameter core cylinders (the “tibia”and “femur”) connected by a deformable “knee joint”. This corestructure is wrapped in 25mm (1 inch) of foam “flesh” covered by6mm (0.24 inches) of neoprene “skin”.

The performance criteria proposed for 2010 are shown in Figure5.11. The maximum acceleration of the tibia is intended to prevent fracture of the tibia due to bumper contact. The maximum knee bend angle and shear deformation are intendedto prevent severe knee joint injuries such as ligament ruptures andintra-articular bone fractures.

5-44

As bumper systems meeting the requirements of pedestrianleg impact are only beginning to hit the marketplace inEurope, Australia and Japan, it is too early to identify themost popular designs. However, a thorough review of articlesand patents does indicate the most popular design solutionsfor passenger cars. There is limited production of vehicleswith exposed bumper beams (facebars) in these areas.Hence, there has been little activity devoted to adapting facebars to meet pedestrian impact requirements. For passenger cars with reinforcing beams, the most commonlyproposed design solutions are: 1. Front-End Vehicle Component Solutions a) Lower stiffener. A new component called a stiffener orspoiler may be located below the bumper system to preventthe lower part of the leg form from moving further towardthe vehicle than the knee. The stiffener may be a fixed component or a component that deploys based on impulseor speed.b) Energy absorbers. To cushion impact, an energy absorbermay be placed between the bumper beam and the pedestrian. Alternately, an energy absorber may be placedbehind the bumper beam. The most commonly proposedenergy absorbers are plastic foams (single or multi-density)and molded plastic “egg crates”. However, several proposeddesign solutions incorporate “spring steel”, compositesteel/foam and crush can absorbers. c) Beam design. A tall front-view bumper height may be usedto provide leg support. d) “Bull-bars”. Structures may be added to the front of anexisting bumper system to provide energy absorption and tosupport the lower limb.2. Sensor and Airbag SolutionAny current bumper system may be covered with an airbag.In this way, the energy absorption capability of the bumperbecomes irrelevant. The key disadvantages to this designapproach are cost and sensor capability.

All of the Front End Vehicle Component Solutions listedabove may be used in conjunction with steel reinforcingbeam bumper systems. The Sensor and Airbag Solutionwould appear to have the greatest potential for use with steelfacebar bumper systems such as those used on pickup trucks.

5.8.5 Design solutions

5-45

FIGURE 5.9EuroNCAP PEDESTRIAN TESTS (2010 CRITERIA)

Legto Bumper

Upper Legto Hood Edge

Headto Hood Top

Knee bending < 15°

Knee shear < 6 mm

Tibia acceleration < 150 g

Total load < 5 kN

Bending moment < 300 Nm

HIC < 1000

5-46

FIGURE 5.10EuroNCAP LEG FORM IMPACTOR

5-47

FIGURE 5.11EuroNCAP “LEG FORM” IMPACT CRITERIA (2010)

North American and European safety standards for vehicles aresummarized in Table 6.1. While most of the standards in Table 6.1are enacted by legislation, several of the standards, where soindicated, are voluntarily set by the OEM’s.

The North American bumper performance standards are moresevere than the European ones. Thus, the bumpers on NorthAmerican vehicles are considerably stronger than those onEuropean vehicles. Although the North American bumperstandards are set by legislation at the 2.5 mph (4 km/h) level forpassenger cars, the North American OEM’s voluntarily use a 5 mph(8 km/h) performance standard for passenger cars. At this impactspeed, there must be no visual damage on a vehicle and there mustbe no damage to any safety items. However, damage to hiddencomponents of the bumper system is acceptable.

Currently, there are no bumper performance standards for lighttrucks. Most North American OEM’s use the voluntary 5 mph (8km/h) passenger car standard for their minivans. In general, theOEM’s use a voluntary 2.5 mph (4 km/h) performance standard forthe remainder of the light truck category (full size vans, pickups andsport utilities). At this impact speed, there must be no visualdamage on a vehicle and there must be no damage to any safetyitems. However, damage to hidden components of the bumpersystem is acceptable.

Europe has a greater concern about bumper repair cost than NorthAmerican. Hence, the European insurance industry uses a 9 mph(15 km/h) test (known as the Thatcham test in England and theDanner test in Germany) to evaluate repair costs. This testestablishes insurance collision premiums for the first year of a newmodel introduction. In North America, the Insurance Institute forHighway Safety (IIHS) uses four tests at 5 mph (8 km/h). Europeattaches more importance to the ease of bumper replacementcompared to North American. Thus, the European insurance industrygrants a credit, which is based on ease of replacement. This creditis applied to the bumper repair cost. As a result, European bumperdesigners strive to obtain ease of replacement. For example, theymay use bolts, rather then weldments, to facilitate ease of repair.

In current North American practice, the governing design conditionfor a bumper system is the 2.5 or 5 mph (4 or 8 km/h) low-speedimpact requirement. Current bumper systems are not designed toabsorb energy under high-speed impact. However, systems arebeing developed that can absorb about 15% of the energy underhigh-speed impact.

6. Relevant safety standards inNorth America and Europe

6-1

6-2

TABLE 6.1RELEVANT SAFETY STANDARDS IN NORTH AMERICA AND EUROPE

NORTH AMERICA EUROPE KEY DIFFERENCES

Bumper Performance• U.S. standard for passenger carscalls for no visual damage and nodamage to safety items at 2.5 mph(4 km/h); Canada calls for limiteddamage at 5 mph (8 km/h) for pas-senger cars.• Automakers have combined themore stringent aspects of each stan-dard - no visual damage and nodamage to safety items at 5 mph (8km/h) for passenger cars.

Bumper Performance• No requirement standard, butmost countries follow ECE 42, whichcalls for no serious damage (lightbulbs may be changed) at 2.5 mph(4 km/h).

• 5 mph vs. 2.5 mph (8 km/hvs. 4 km/h).• Law vs. recommendation• Greater damage allowed inEurope.

Insurance Testing• The IIHS (Insurance Institute forHighway Safety) conducts 4 tests at5 mph (8 km/h) which measurerepair costs for the bumper. Thetests are front into barrier, rear intobarrier, front into angle barrier andrear into pole.• Statistics are published in anewsletter.

Insurance Testing• European insurance agencies havea test that measures costs forbumper repair (a credit is given forease of replacement). The test is a 9mph (15 km/h) impact at a 40 per-cent offset. In England, it’s called theThatcham Test, in Germany, it’scalled the Danner Test.

• 5 mph vs. 9 mph (8 km/h vs.15 km/h).• Europe gives credit for easeof replacement.

High-Speed Crash Tests CFR571.208 Occupant CrashProtection• Frontal rigid barrier collisionapplies to passenger cars, MPVs,trucks and buses.• 30 mph (48 km/h) frontal colli-sion. No separation of any loadbearing element of a seatbelt assem-bly or anchorage.• Lateral collision 20 mph (32 km/h)and impact both sides.• FMVSS 301, combination of 30mph (48 km/h) frontal/rear and 20mph (32 km/h) side.

High-Speed Crash Tests• 40% offset driver’s side• Front-end collision• 35 mph (56 km/h)• Deformable barrier/honeycombaluminum structure (proposed)• ECE 33 head-on collision unladenvehicle hits barrier at 30 - 33 mph(48 - 53 km/h)• ECE 32 rear-end collision impactor pendulum 22 - 24 mph (35 - 38km/h)

Pedestrian Safety Proposal• ECE 222 Proposal (2001). 25 mph(40 km/h). Knee angle limited to15°. Thigh (hip) into hood.

• Rigid vs. deformable barrier.• Head-on vs. offset collision.

There is a degree of speculation that the 2.5 mph (4 km/h) voluntarydesign standard used by the North American OEM’s for full sizevans, pickups and sport utilities might rise to 5 mph (8 km/h). Ifthis change were to occur, then the bumper systems on thesevehicles would require a redesign. Such a redesign would likelymean the facebar systems commonly used on these vehicles wouldrevert to reinforcing beam systems.

A pedestrian safety standard currently being proposed in Europe isshown in Table 6.1. If enacted, this standard would have an effecton front-end styling and, in turn, bumper system design.

6-3

6.1 United States National Highway Traffic Safety Administration (49CFR),Part 581, Bumper Standard

This standard is summarized in Sections 6.1.1 through 6.1.4. Thereader is cautioned that these sections are only a summary. Thereader must refer to the actual regulatory document in order toobtain a complete understanding of the standard.

The Bumper Standard only applies to passenger vehicles. Amanufacturer may apply for an exemption of a special usepassenger vehicle if compliance with the standard would reasonablyinterfere with the special use of the vehicle. For example, ashuttle vehicle used within the confines of a retirement complex.

A passenger vehicle is subjected to three impact procedures:1. The pendulum corner impacts - front and rear.2. The pendulum longitudinal impacts - front and rear.3. The impacts into a fixed collision barrier - front and rear.

Following the three impact procedures, the vehicle shall meetthe following damage criteria:

1. Each lamp or reflective device except license plate lamps shall be free of cracks and shall comply with applicable visibility requirements. The aim of each headlamp shall be adjustable to within the beam aim inspection limits.

2. The vehicle’s hood, trunk and doors shall operate in the normal manner.

3. The vehicle’s fuel and cooling systems shall have no leaks or constricted fluid passages and all sealing devices and caps shall operate in the normal manner.

4. The vehicle’s exhaust system shall have no leaks or constrictions.

5. The vehicle’s propulsion, suspension, steering and braking systems shall remain in adjustment and shall operate in the normal manner.

6. A pressure vessel used to absorb impact energy in an exterior protection system by the accumulation of gas or hydraulic pressure shall not suffer loss of gas or fluid accompanied by separation of fragments from the vessel.

6.1.1 Requirements

6-4

7. The vehicle shall not touch the test device, except on the impact ridge shown in Figures 6.1 and 6.2, with a force that exceeds 2000 pounds (907kg) on the combined surfaces ofPlanes A and B (see Figure 6.3) of the test device.

8. The exterior surfaces shall have no separations of surface materials, paint, polymeric coatings, or other covering materials from the surface to which they are bonded, and no permanent deviations from their original contours 30 minutes after completion of each pendulum and barrier impact, except where such damage occurs to the bumper face bar and the components and associated fasteners that directly attach the bumper face bar to the chassis frame.

9. Except as provided in Criterion 8 (above), there shall be no breakage or release of fasteners of joints.

1. See Figure 6.4.2. Impact speed of 1.5mph (2.4km/h).3. Impact one front corner at a height of 20 inches (500mm)

using Figure 6.1 pendulum.4. Impact other front corner at a height from 16 to 20 inches

(400 to 500mm) using Figure 6.2 pendulum.5. Impact one rear corner at a height of 20 inches (500mm)

using Figure 6.1 pendulum.6. Impact other rear corner at a height from 16 to 20 inches

(400 to 500mm) using Figure 6.2 pendulum. 7. The plane containing the pendulum swing shall have a

60 degree angle with the longitudinal plane of the vehicle. 8. Impacts must be performed at intervals not less than

30 minutes. 9. Effective impacting mass of pendulum equals mass of

vehicle.10. Trailer hitches, license plate brackets, and headlamp

washers are removed. Running lights, fog lamps and equipment mounted on the bumper face bar are removed if they are optional equipment.


1. See Figure 6.4.2. Impact speed of 2.5mph (4km/h). 3. Two impacts on front surface, inboard of corner.4. Two impacts on rear surface, inboard of corner. 5. Impact line may be any height from 16 to 20 inches (400 to

500mm). If height is 20 inches (500mm), use Figure 6.1 pendulum. If height is between 20 and 16 inches (500 and 400mm), use Figure 6.2 pendulum.

6. Pendulum Plane A (see Figure 6.3) is perpendicular to the longitudinal plane of the vehicle.

7. For each impact, the impact line must be at least 2 inches (50mm) in the vertical direction from its position in any prior impact, unless the midpoint of the impact line is morethan 12 inches (300mm) apart laterally from any prior impact.

8. Impacts must be performed at intervals not less than 30 minutes apart.

9. Effective impacting mass of pendulum equals mass of vehicle.

10. Trailer hitches, license plate brackets, and headlamp washers are removed. Running lights, fog lamps and equipment mounted on the bumper face bar are removed if they are optional equipment.


SIDE VIEW FRONT VIEW

TOP VIEW

25 R

102 R

Impactridge

Impactline

7878

3 R

13 R15°

5°

6-5

FIGURE 6.1IMPACT PENDULUM

NOTES:1. Dimensions in mm2. Not to scale

UNITED STATES REGULATIONS:a) Longitudinal impact if height is 20 inches (500mm).b) One front and one rear corner impact at a height of 20 inches (500mm).

CANADIAN REGULATIONS:a) One front and one rear corner impact at a height of 500mm (20 inches).

Source: Canada: Motor Vehicle Safety Regulations, Standard 215, 1978

610

406

457

152

305

114

6-6

FIGURE 6.2IMPACT PENDULUM

SIDE VIEW FRONT VIEW

TOP VIEW

25 R

102 R

Impactridge

Impactline

78

3 R

13 R15°

NOTES:1. Dimensions in mm2. Not to scale

UNITED STATES REGULATIONS:a) Longitudinal impact if height is between 20 and 16 inches (500mm and 400mm).b) One front and one rear corner impact at a height from 16 to 20 inches (400 to 500mm).

CANADIAN REGULATIONS:a) Longitudinal impact at height from 500 to 400mm (20 to 16 inches).

Source: Canada: Motor Vehicle Safety Regulations, Standard 215, 1978

5°

610

406

609

305

114

FIGURE 6.3LOCATIONS OF PLANES A and B

6-7

SECTION A-A

PLANE B

PLANE A

A A

IMPACTLINE

FIGURE 6.4SAMPLE IMPACT APPARATUS

Sample impact apparatuswith supports

Sample impact apparatuswithout supports

Plane B

ImpactSurface

Plane A

Weight equalsunloaded vehicleweight +0, -10kg•• •

•NOTES:1. Drawing not to scale.2. The arc described by any point on impact line shall be constant with a minimum

radius of 3.3m and lie in a plane perpendicular to Plane A.

Source: Transport Canada, Safety and Security

1. Impact speed of 2.5mph (4km/h).2. Impact into a fixed collision barrier perpendicular to line of

travel while travelling longitudinally forward.3. Impact into a fixed collision barrier perpendicular to line of

travel while travelling longitudinally rearward. 4. Trailer hitches, license plate brackets, and headlamp

washers are removed. Running lights, fog lamps and equipment mounted on the bumper face bar are removed if they are optional equipment.


6.2 Canadian Motor Vehicle Safety Regulations Standard 215This standard is summarized in Sections 6.2.1 through 6.2.4. Thereader is cautioned that these sections are only a summary. Thereader must refer to the actual regulatory document in order toobtain a complete understanding of the standard.

A passenger vehicle is subjected to three impact procedures:1. The pendulum corner impacts - front and rear.2. The pendulum longitudinal impacts - front and rear.3. The impacts into a fixed collision barrier - front and rear.

Following the three impact procedures, the vehicle shall meetthe following damage criteria:

1. Each lamp or reflective device except license plate lamps shall be free of cracks and shall comply with applicable visibility requirements. The aim of each headlamp shall be adjustable to within the beam aim inspection limits.

2. The vehicle’s hood, trunk and doors shall operate in the normal manner.

3. The vehicle’s fuel and cooling systems shall have no leaks or constricted fluid passages and all sealing devices and caps shall operate in the normal manner.

4. The vehicle’s exhaust system shall have no leaks or constrictions.

5. The vehicle’s propulsion, suspension, steering and braking systems shall remain in adjustment and shall operate in the normal manner.

6.2.1 Requirements

1. See Figure 6.4.2. Impact speed of 4.8km/h (3.0mph).3. Impact one front corner at a height of 500mm (20 inches)

using Figure 6.1 pendulum.4. Impact one rear corner at a height of 500mm (20 inches)

using Figure 6.1 pendulum.5. The plane containing the pendulum swing shall have a

60 degree angle with the longitudinal plane of the vehicle. 6. Impacts must be performed at intervals not less than

30 minutes apart. 7. Effective impacting mass of pendulum equals mass of

vehicle.8. Trailer hitches and license plate brackets are removed.


6-8

1. See Figure 6.4.2. Impact speed of 8km/h (5mph). 3. Two impacts on front surface using Figure 6.2 pendulum,

inboard of corner.4. Two impacts on rear surface using Figure 6.2 pendulum,

inboard of corner. 5. Impact line may be any height from 400mm to 500mm (16

to 20 inches).6. Pendulum Plane A is perpendicular to the longitudinal

plane of the vehicle. 7. For each impact, the impact line must be at least 50mm

(2 inches) in the vertical direction from its position in any prior impact, unless the midpoint of the impact line is more than 300mm (12 inches) apart laterally from any prior impact.

8. Impacts must be performed at intervals not less than 30 minutes apart.

9. Effective impacting mass of pendulum equals mass of vehicle.

10. Trailer hitches and license plate brackets are removed.


1. Impact speed of 8km/h (5.0mph).2. Impact into a fixed collision barrier perpendicular to line of

travel while travelling longitudinally forward.3. Impact into a fixed collision barrier perpendicular to line of

travel while travelling longitudinally rearward. 4. Trailer hitches and license plate brackets are removed.


The United States, but not Canada, has the following requirements:1. A pressure vessel used to absorb impact energy in an

exterior protection system by the accumulation of gas or hydraulic pressure shall not suffer loss of gas or fluid accompanied by separation of fragments from the vessel.

2. The vehicle shall not touch the test device, except on the impact ridge shown in Figures 6.1 and 6.2, with a force that exceeds 2000 pounds (907kg) on the combined surfaces of Planes A and B (see Figure 6.3) of the test device.

3. The exterior surfaces shall have no separations of surface materials, paint, polymeric coatings, or other covering materials from the surface to which they are bonded, and no permanent deviations from their original contours 30 minutes after completion of each pendulum and barrier impact, except where such damage occurs to the bumper face bar and the components and associated fasteners that directly attach the bumper face bar to the chassis frame.

4. Except as provided in Criterion 8 of Section 6.1.1, there shall be no breakage or release of fasteners of joints.

6.3.1 Requirements

6.3 Comparison between United States and Canadian Bumper RegulationsThe reader is cautioned that the comparison in Sections 6.3.1through 6.3.4 is only a summary. The reader must refer to theactual regulatory documents in order to obtain a completecomparison.

The United States and Canada use the same test apparatus. TheUnited States permits running lamps, fog lamps and equipment onthe bumper face bar to be removed if they are optional, whileCanada does not. The United States uses lower test speeds thanCanada. As a generalization, the United States requires no visualdamage to all non-bumper parts, while Canada requires nodamage to safety and functional items.

6-9

1. The United States has an impact speed of 1.5mph (2.4km/h), Canada 4.8km/h (3.0mph).

2. Both the United States and Canada require a front and a rear corner be tested using the Figure 6.1 pendulum. Only the United States requires that the other front and other rear corner be tested (The Figure 6.2 pendulum must be used.).


1. The United States has an impact speed of 2.5mph (4km/h), Canada (5mph).


1. The United States has an impact speed of 2.5mph (4km/h), Canada (8km/h (5.0mph).


Following each of four tests (front into full-width flat-barrier, rearinto full-width flat-barrier, right front into 30 degree angle-barrierand rear into pole), IIHS writes a damage estimate. Minor cosmeticdamage to the exterior bumper surface is excluded, even if there issignificant damage to other bumper parts. Although IIHS wouldlike to see a zero damage estimate, there is no criterion for anacceptable or an unacceptable damage estimate.

6.4.1 Requirements

1. One vehicle is used for the front into full-width flat-barrier and rear into pole impacts. A second vehicle is used for the right front into 30 degree angle-barrier and rear into full-width flat-barrier impacts.

2. Front and rear license plates, front license plate bracket (if provided), and all associated fasteners are removed. The rear license plate bracket (if present) is left in place unless it is bolted or riveted directly to the external face of the rear bumper, in which case both the bracket and fasteners are removed. Bolt-on trailer hitch reinforcement members that are supplied as optional equipment are removed, but their fasteners are reattached to the vehicle where possible.

6.4.2 Test vehicles

1. Two tests - front into barrier and rear into barrier.2. Impact speed of 5mph (8km/h).3. The barrier is a 145.15t (160 tons) block of reinforced

concrete, faced with a steel plate 8.0cm (3 inches) thick. The impact area on the steel plate is covered with 2cm (0.75 inches) thick plywood.

4. The barrier is perpendicular to the vehicle’s line of travel (forward or rearward).

6.4.3 Full-width flat-barrier impact

6.4 Insurance Institute for Highway Safety: Low-Speed Crash Test Protocol (Reference 6.8)

This protocol is summarized in Sections 6.4.1 through 6.4.6. Thereader is cautioned that these sections are only a summary. Thereader must refer to the actual protocol document in order toobtain a complete understanding of the protocol.

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1. Impact speed of 5mph (8km/h).2. A rigid steel fixture is bolted to the floor. It includes a steel

plate 214cm (84 inches) wide, 92cm (36 inches) high and 4.5cm (1.75 inches) thick. The steel plate is covered with 2cm (0.75 inches) thick plywood. The bottom edges of the steel plate and plywood are 18cm (7 inches) above the floor level. Thus, the top edges are 110cm (43 inches) above floor level. The angle between the longitudinal centerline of the vehicle and the plane of the plywood is 60 degrees (90 minus30 degrees).

6.4.4 Right front into 30 degree angle-barrier impact

1. Impact speed of 5mph (8km/h).2. Steel pole is 18cm (7 inches) in diameter and extends 92cm

(36 inches) above the floor. 3. Normally, the longitudinal centerline of vehicle is aligned with

the pole and becomes the target point. However, if some aspect of the bumper design (e.g., a trailer hitch) prevents a general assessment of the bumper’s performance, the longitudinal centerline is moved left or right of the pole. The target point is the midpoint of the span from the vehicle centerline to the inboard edge of the rear frame sidemember end.

4. The actual impact point on the bumper will not be more than 7.5cm (3 inches) either side of the target point.

6.4.5 Rear into pole impact

The front and the rear bumper of a vehicle are each impactedthree times — at the center, off-center and at a corner. Followingthe three tests on a front or rear bumper, the total cost for partsand labor to repair the damage to the body and bumper is estimated.Minor cosmetic damage to the exterior bumper surface is usuallyignored if no other problems are found. Consumers Union doesnot use bumper repair cost as a Ratings factor. However, it doespublish the repair cost for the front bumper, the rear bumper andthe total for both bumpers in Consumer Reports magazine.

6.5.1 Requirements

Consumers Union uses an impact bar similar to that shown inFigure 6.2 for all impacts. However, it is not swung as a pendulum.Rather, it is hydraulically propelled, like a battering ram, in thehorizontal direction. Weights, equal to the weight of the vehicle,are placed on the ram.

6.5.2 Bumper-basher

1. The front bumper is impacted at a height of 20 inches (500mm) and the rear bumper at a height of 16 inches (400mm). An impact bar similar to that shown in Figure 6.2 is used for both impacts.

2. 5mph (km/h) impact at vehicle centerline.

6.5.3 Center impact

6.5 Consumers Union bumper-basher tests (Reference 6.9)

These tests are summarized in Sections 6.5.1 through 6.5.5. Thereader is cautioned that these sections are only a summary. Thereader must refer to actual test documents in order to obtain acomplete understanding of the tests.

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1. The front bumper is impacted on the driver’s side at a height of 20 inches (500mm). The rear bumper is impacted on the passenger’s side at a height of 16 inches (400mm). An impact bar similar to that shown in Figure 6.2 is used for both impacts.

2. 5mph (8km/h) impact with outside edge of impact bar at outboard surface of the body (fender/front bumper cover or quarter panel/rear bumper cover). Thus, the impact point is usually about midway between the vehicle centerline and the outboard surface of the vehicle.

6.5.4 Off-center impact

1. The front bumper is impacted on the driver’s side at a height of 20 inches (500mm). The rear bumper is impacted on the passenger’s side at a height of 16 inches (400mm). An impact bar similar to that shown in Figure 6.2 is used for both impacts.

2. 3mph (4.8km/h) impact at 30 degrees on the corner.

6.5.5 Corner impact

Two impacts are conducted. The first is a 15km/h (9mph) impactby the front of the test vehicle into a fixed barrier with a 40%offset. The second is a 15km/h (9mph) impact by a mobile barrier,with a 40% offset, into the rear of the test vehicle. After eachimpact, the replacement parts required to reinstate the vehicle toits pre-accident condition are recorded. Also, the number of hoursrequired to replace the damaged parts and to repair those itemscapable of repair, such that the vehicle is reinstated to the pre-accidentcondition are recorded. The cost of the replacement parts and thenumber of hours are estimated. Thus, the results of the crash testindicate the repairability and damageability status of the test vehicle.

6.6.1 Requirements

The test vehicle is previously undamaged and representative of theseries production. The test vehicle for the rear impact may be thesame vehicle used for the front impact, provided the damagesustained during the front impact has no effect on the results of therear impact.

6.6.2 Test vehicle

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6.6 Research Council for Automotive Repairs (RCAR) Low-Speed Offset Crash Test (Reference 6.10)

This test is summarized in Sections 6.6.1 through 6.6.5. The readeris cautioned that these sections are only a summary. The readermust refer to the actual test document in order to obtain a complete understanding of the test.

RCAR states its standard insurance test reflects the typical low-speed impact, and provides the average level of damage,insurers are paying for every day.

1. One impact into a non-deformable barrier/former (see Figure 6.5). The former can be adjusted laterally to accommodate various vehicle widths. The former may be secured to a fixed barrier or placed on the ground with arresting devices to restrict its movement. The front face of the former is perpendicular to the direction of travel of the test vehicle. The mass of the barrier/former exceeds twice that of the test vehicle. The steering column side of the vehicle contacts the former. The test vehicle overlaps the former by 40%.

2. The test vehicle impact speed is 15km/h (9mph).

6.6.3 Front impact

1. One impact by a mobile barrier into the test vehicle (Figure 6.6). The mobile barrier has a mass of 1000kg (2205 pounds).

2. The mobile barrier contacts the side of the vehicle opposite to the steering column side. The barrier overlaps the test vehicle by 40%. The barrier impact speed is 15km/h (9mph).

6.6.4 Rear impact

RCAR’s objective is “to improve the level of safety, security, quality,design and method of repair of motor vehicles in order to reducecosts to the insurance industry and to the motoring public”. To thisend, RCAR has prepared a Design Guide (Reference 6.11) aimed atreducing the damageability and repairability cost incurred in low-speed impacts.

Damageability is the measure of a vehicle’s ability to withstand theforces of a low-speed impact. It denotes which body structure andother components are damaged as a result of the impact.

Repairability measures how easily, quickly and cost-effectively thedamaged structure and components can be repaired or replaced.

The RCAR Design Guide lists optimum damageability andrepairability features of a bumper system as:

1. The system plays an important role in energy management during vehicle accidents.

2. The system withstands impacts up to 15km/h (9mph) without initiating damage to the body structure beyond the body mounting system.

3. The main bumper mountings are capable of transmitting impact forces into the rails for maximum energy absorption. They are not an integral part of the bumper, but separate items that can be replaced easily in the event of damage.

4. Any side mountings are of the quick-release type.5. Bumper covers are thermoplastic. Hot air welding or

adhesives may repair them.6. Wrap-around bumpers afford much greater protection during

minor parking incidents.

6.6.5 Damageability and repairability

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FIGURE 6.5RCAR FRONT CRASH PROCEDURE

6-14

The height of the barrier shall exceed the height of the front of the test vehicle.The test vehicle shall be free of any additional or propelling device at the moment of impact.Test Vehicle Mass: Net curb weight +75 kg for driver and a full fuel tank or equivalent ballast.

Left Hand Drive vehicle shown

KEY:

U = Offset 40%B = Overall width of test vehicleVF = 15.0 + 1.0 - 0 km/hR = 150mm constant radiusF = Test vehicle

FIGURE 6.6RCAR REAR CRASH PROCEDURE

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Test Vehicle Mass: Net curb weight + 75 kg for driver and a full fuel tank or equivalent ballast.

KEY:

MB = Mobile barrierMMB = 1000 kg ± 5 kg massH = 700mm barrier height ± 10mmh = 200mm barrier ground clearance ± 10mmF = Test vehicler = 50mm constant radius

KEY:

MB = Mobile barrierU = Offset 40%B = Overall width of test vehicleVMB = 15.0 + 1.0 - 0 km/hVF = 0 km/h (handbrake off)R = 150mm constant radiusF = Test Vehicle

Left hand drive vehicle shown

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7. Steel versus aluminum and compositebumper beams

7.1 Types of bumper beams

a) Steel Reinforcing BeamsSteel reinforcing beams are produced using the cold stamping, hotforming or roll forming processes. The tensile strength of coldstamped and roll formed beams ranges from 900-1500 MPa (130-218 ksi). The tensile strength of hot stamped beams, afterheating and quenching, ranges from 1200-1400 MPa (174-203 ksi).All steel beams have an elastic modulus of 207,000 MPa (30,000ksi). Steel reinforcing beams are protected from corrosion by zinccoatings, aluminum coatings or electrocoatings. After mountingto a vehicleís frame, reinforcing beams are covered by cosmetic orenergy absorbing fascias.

b) Steel FacebarsSteel facebars are typically cold stamped from low-carbon andhigh-strength steels having tensile strengths from 350-500 MPa(50-72 ksi) and an elastic modulus of 207,000 MPa (30,000 ksi).They are either chrome plated or painted for corrosion protectionand appearance before being mounted to a vehicle’s frame. Mostfacebars are dressed up with plastic trim.

c) Plastic Reinforcing BeamsThere are two types of plastic beams — glass reinforced plastic orunreinforced plastic. Examples of glass reinforced plastic beamsinclude polypropylene (compression molded), unsaturated polyester (compression molded) and polyurethane (reaction injection molded). Examples of unreinforced plastic beamsinclude polycarbonate/polybutylene (injection or blow molded),polyethylene (blow molded) and polypropylene (blow molded).Plastic beams have tensile strengths up to 275 MPa (40 ksi) andflexural moduli up to 15,000 MPa (2,200 ksi).

d) Aluminum Reinforcing BeamsTypically, aluminum beams are made by stretch or press formingextruded shapes made from the 6000 and 7000 aluminum series.After forming and heat treating, the beams have tensile strengthsup to 550 MPa (80 ksi) and an elastic modulus of 69,000 MPa(10,000 ksi).

Tables 7.1 and 7.2 provide typical costs for steel facebar andreinforcing beam bumper systems. The systems in both Tablesmeet low-speed [8km/h (5mph)] impact test requirements.However, it should be noted that the facebar system costs inTable 7.1 should not be compared to the reinforcing beam system costs in Table 7.2. The facebar systems in Table 7.1 areused on pickups while the reinforcing beam systems in Table 7.2are used on passenger cars. Pickups have up to twice theweight of passenger cars. Thus, in an 8km/h (5mph) impact, thefacebar systems in Table 7.1 receive up to twice the force thatthe reinforcing beam systems in Table 7.2 receive. Tables 7.1 and7.2 indicate that the steel beam itself represents only 15 - 20% ofthe bumper system cost.

Table 7.3 shows cost ranges for steel, plastic and aluminum reinforcing beams. It may be seen that steel reinforcing beamsare $10- $15 less expensive than plastic beams and $15 -$20 lessexpensive than aluminum beams.

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7.2 Cost of bumper beams

$15 - 25

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TABLE 7.1COST OF STEEL FACEBAR SYSTEMS

8km/h (5mph) Bumpers for Midsize and Full-size Pickups(U.S. dollars per facebar)

Steel BeamStamping

$15 - 25

Painting

$25 - 35

ChromePlating

$10 - 50

PlasticTrim

$10 - 30

EnergyAbsorbingBrackets

$50 - 130

System Cost(PaintedFacebar)

$60 - 140

System Cost(Chrome

PlatedFacebar)

$15 - 20

TABLE 7.2COST OF STEEL REINFORCING BEAM SYSTEMS8km/h (5mph) Bumpers for Passenger Cars

(U.S. dollars per beam)

SteelReinforcing

Beam

$5 - 15

EnergyAbsorber

$80 - 100

PaintedFascia

$100 - 135

System cost

Steel

Unreinforced Plastic

Reinforced Plastic

Aluminum

TABLE 7.3COST OF REINFORCING BEAMS

8km/h (5mph) Bumpers for Passenger Cars(U.S. dollars per beam)

ReinforcingBeam

Material

$15 - 20

$25 - 35

$25 - 30

$30 - 40

BeamCost

Reinforcing Beam

PP 7.03 (15.5)

Aluminum 5.76 (12.7)

Steel 5.76 (12.7)

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TABLE 7.4WEIGHT OF REINFORCING BEAM SYSTEMS8km/h (5mph) Beams for Passenger Cars

[kg (lbs.)]

Vehicle

Mazda 626

Buick Park Ave.

Pontiac Sunfire

Absorber

None 0.00 (0.0)

PUR 3.40 (7.5)

EVA 2.86 (6.3)

Fascia

TPO 5.44 (12.0)

TPO 4.99 (11.0)

PUR 5.40 (11.9)

Total

12.47 (27.5)

14.15 (31.2)

14.02 (30.9)

Source: Phillip Townsend Associates, Inc.

PP = polypropylene

TPO = thermoplastic olefin

EVA = ethylene vinyl acetate elastomers

PUR = polyurethane

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8. Conclusions

1. Weighta) Steel reinforcing beams, especially ultra high-strength steelbeams, are fully weight competitive with aluminum and plasticbeams.b) Vehicle weight reduction is being achieved by utilizing the frontbumper as a frame crossmember. Further weight savings may beachieved by optimizing the front bumper to absorb up to 15% ofhigh-speed crash energy. Steel is the best material for both of thesedesign options.

2. StylingToday’s steel bumpers provide the large sweeps and wrap-aroundsdesired by stylists. Production stamped bumper beams havedepths-of-draw as large as 203 mm (8.0 in.). Production rollformed beams have sweep numbers as high as 60.

3. Costa) For normal production volumes, steel reinforcing beams aremore cost effective than aluminum or plastic beams.b) For low production volumes, utilizing the same steel beam onseveral vehicles reduces tooling cost.

1.1 North American Bumper System Market, 1997-2001 Model Years,September 19, 1997, private study, CSM Corporation, 2365Woodlake Drive, Suite 150, Okemos, MI 48864.

2.1 SAE J2329, Categorization and Properties of Low-CarbonAutomotive Sheet Steels, Society of Automotive Engineers, Inc., 400Commonwealth Drive, Warrendale, PA 15096-0001.

2.2 SAE J1562, Selection of Zinc and Zinc-Alloy (Hot-Dipped andElectrodeposited) Coated Sheet Steel, Society of AutomotiveEngineers, Inc., 400 Commonwealth Drive, Warrendale, PA 15096-0001.

2.3 SAE J403, Chemical Compositions of SAE Carbon Steels, Society ofAutomotive Engineers, Inc., 400 Commonwealth Drive, Warrendale,PA 15096-0001.

2.4 www.worldautosteel.org., AHSS Guidelines, AHSS Descriptions,Definitions

2.5 SAE J405, Chemical Compositions of SAE Wrought Stainless Steels,Society of Automotive Engineers, Inc., 400 Commonwealth Drive,Warrendale, PA 15096-0001.

2.6 www.astm.org, ASTM A463, Standard Specification for Sheet Steel,Aluminum-Coated, by the Hot Dip Process.

4.1 Sheet Steel Availability and Property Guide, insert to High-StrengthSteel Bulletin, Edition 10, Auto/Steel Partnership, 2000 Town Center,Suite 320, Southfield, MI 48075-1123.

4.2 Automotive Steel Design Manual, American Iron and Steel Institute,2000 Town Center, Suite 320, Southfield, MI 48075-1199.

4.3 High-Strength Steel Bulletin, Edition 5, Auto/Steel Partnership, 2000Town Center, Suite 320, Southfield, MI 48075-1123.

4.4 Inland Ultra-High-Strength Steels Selection Guide, Inland Steel, UltraHigh-Strength Steel Marketing, telephone 1-800-422-9422.

4.5 David W. Dickinson, Final Report to AISI Bumper Group, BumperComponent Welding, State-of-the-Art Survey, December 31,2000.

4.6 Linnert, Welding Metallurgy, American Welding Society, 1994.

4.7 American Welding Society, Welding Handbook, Volume 4, 1998.

4.8 Peterson High Speed Seam Welding, American Welding SocietyMetal Welding Conference VI, 1994.

4.9 Appreciating high-frequency welding, Welding Journal, July 1996.

4.10 American Welding Society, Welding Handbook, 8th Edition, Volume 2.

4.11 Walduck, R., Enhanced Laser Beam Welding, U.S. Patent 5886870,February 2, 1999.

4.12 Dykhno, I., et al, Combined Laser and Plasma Arc Welding Torch, U.S.Patent 5700989, December 23, 1997.

4.13 Categorization and Properties of Low-Carbon Automotive SheetSteels, SAE J2329, Society of Automotive Engineers, Inc., 400Commonwealth Drive, Warrendale, PA 15096-0001.

4.14 Steel, High Strength, Hot Rolled Sheet and Strip, Cold Rolled Sheetand Coated Sheet, SAE J1392, Society of Automotive Engineers, Inc.,400 Commonwealth Drive, Warrendale, PA 15096-0001.

4.15 Chemical Compositiions of SAE Carbon Steels, SAE J403, Society ofAutomotive Engineers, Inc., 400 Commonwealth Drive, Warrendale,PA 15096-0001.

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9. References


5.2 NHTSA New Car Approval Program, Frontal-crash Test, web siteNHTSA.gov/NCAP.

5.3 Crashworthiness Evaluation of Offset Barrier Crash Test Protocol,(Versioin IX), May, 2002, Insurance Institute for Highway Safety, website carsafety.org

5.4 Schuster, Dr. Peter, “Current Trends in Bumper Design for PedestrianImpact”, December 31, 2004, www.autosteel.org

5.5 EuroNCAP (European New Car Assessment Program), www.euroncap.com

5.6 European Union/Vehicle Associations Pedestrian Safety Agreement,www.acea.be/ACEA/11072.001.pdf


6.2 High-Strength Steel (HSS) Stamping Design Manual, Auto/SteelPartnership, 2000 Town Center, Suite 320, Southfield, MI 48075-1123.


6.4 SAE J2340, Categorization of Dent Resistant, High-Strength andUltra High-Strength Automotive Sheet Steel, Society ofAutomotive Engineers, Inc., 400 Commonwealth Drive,Warrendale, PA, 15096-0001.

6.5 Weld Quality Test Method Manual, Auto/Steel Partnership, 2000Town Center, Suite 320, Southfield, MI 48075-1123.

6.6 ANSI/AWS/SAE Standard D8.9-97, Standard Recommended Practicesfor Test Methods for Evaluating the Resistance Spot Welding Behaviorof Automotive Sheet Steel Materials, Society of AutomotiveEngineers, Inc. 400 Commonwealth Drive, Warrendale, PA, 15096-0001.

6.7 ANSI/AWS/SAE Standard D8.8-97, Specification for Automotive andLight Truck Component Weld Quality - Arc Welding, Society ofAutomotive Engineers, Inc. 400 Commonwealth Drive, Warrendale,PA, 15096-0001.

7.1 Tailor Welded Blank Design and Manufacturing Manual, Auto/SteelPartnership, 2000 Town Center, Suite 320, Southfield, MI 48075-1123.

7.2 Stuart F. Brown, Welding’s Big New Bag of Tricks, Fortune Magazine,January 13, 1997

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American Iron and Steel Institute2000 Town Center, Suite 320Southfield, Michigan 480751-877-STEELINDUSTRYwww.autosteel.org

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