EFFECTS OF WHEEL/RAIL CONTACT PATTERNS andCONTACT …

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EFFECTS OF WHEEL/RAIL CONTACT PATTERNS andCONTACT PATTERNS and VEHICLE PARAMETERS on LOADED CAR HUNTINGLOADED CAR HUNTING

Nicholas Wilson, Huimin Wu, Harry Tournay, Curtis UrbanNicholas Wilson, Huimin Wu, Harry Tournay, Curtis UrbanTransportation Technology Center, IncPueblo, CO, USA

MARTS Chicago September 2009 - 1© Transportation Technology Center, Inc., a subsidiary of the Association of American Railroads, 2009

Background

In 2006, failures of primary suspension adapter pads were reported on a particularwere reported on a particular type of grain car:

Loaded high capacity (286k )lbs) grain hoppers

Truck hunting: loaded hunting is unusualhunting is unusualM-976 trucks with improved tracking Routes with specific rail wear patterns and tighter gage

© TTCI/AAR, 2009, MARTS Chicago, September 2009 p2®

gage

Primary Suspension Adapter PadsP l d i lPolymer pads improve axle steering, reduce W/R forces and rolling resistancegLoaded Hunting motions appeared to cause failures:

P i i dPrimary suspension padsIf a pad does fail, it is typically only 1 out of 8typically only 1 out of 8 in a car

Constant contact sidecontact side bearings (CCSB)


Initial Lateral Stability (Hunting)Tests

50 mph Tests performed at TTC


Initial Lateral Stability (Hunting)Tests

Tests performed at TTC

Wheel Loaded Hunting Threshold SpeedWheel Profile

and Conicity

Empty ~ Standard Pads

Loaded Hunting Threshold Speed

Summer Standard

Pads

Winter Standard

PadsStiffer Pads

Standard Steel

Adaptersy Pads Pads Adapters

Wornλ>0.6

65 mph 47.5 mph 55.5 mph 65 mph 70 mph

KRλ>0.2

80 mph 65 mph 75 mph 80 mph

AAR1Bλ 0 05

>80 mph 75 mph 80 mph 80 mphλ>0.05

p p p p


Initial Hunting Test Conclusions

Loaded car hunting a function ofCar body mass and inertial propertiesHigh W/R Conicity

Worn wheelsWorn rail profile in straight track

Adapter pad stiffness

Loaded car hunting also a function of:Center plate friction

Steel center plates reduced hunting Side bearing friction restraint


Grain Car Wheel Wear and Effects on Conicity

96,000 miles160,000 mile

Relatively low wear in this

New AAR-1B 35,000 milesregion

Higher wear in this tread region

Conicity (λ)Average Conicity, RTT 34 Rail

0.796 000 ilConicity (λ)

on TTCI Hunting t t

0.4

0.5

0.6

nici

ty

New AAR-1B

96,000 miles

test zone

0

0.1

0.2

0.3

Con Avg

Max

Min35,000 miles

160,000 miles


00 40 80 120 160 200

Mileage (*1000)

High Conicity W/R Contact Conditions

Increased conicity on tangent track after ~ 160,000 kmTangent rail head profiles:Tangent rail head profiles:

Certain new rail sections New Rail

Tight gauge

New Rail

“Flattened” crowns &

Fl t thFlow to the gauge corner Flat railhead &

plastic flow


Wheel / Rail Profiles

Average Wheel Flange Width

36m)

Accelerated initial flange wear

34

35

36ng

e Width

(mm

330 50 100 150 200 250

Mileage (*1000)

Flan

Associated ith

1mm gap

New AAR1-B WheelAssociated with initial mismatch & 2-point contact

≅12 mm RRD

Worn rails from 2 degree, 4, degree,

between new wheel & worn high rail in curves


and 6 degree curveshigh rail in curves

Wheel / Rail Profiles

Average Wheel Flange Width

Reduced flange wear after ~ 50,000 miles

34

35

36

eW

idth

(mm

)

33

34

0 50 100 150 200 250

Mileage (*1000)

Flan

ge

g ( )

Associated with single point contact & a largepoint contact & a large radius differential generated on the high


rail in curves

W/R Conicity as a Function of Mileage, Car and Truck ArrangementTruck Arrangement

Car/Truck typesGen I: Grain car with steel adapterssteel adaptersGen II: Grain car with polymer adaptersCoal: Coal car with steelCoal: Coal car with steel adaptorsCoal HD: Coal car with polymer adapters

Root causes for differences are still unknown but suspected to be a function of:

Curving ability


Curving abilityVehicle stability

W/R Conicity as a Function of Rail Profiles for a Particular Grain Car RouteParticular Grain Car Route

Analysis of conicity for 108 axles on 25,000 measured rail profiles from 19 miles of tangent track

s Conicity ≅ 0 1s Conicity ≅ 0 1

asur

ed R

ails Conicity ≅ 0.1

Rails producing lower conicityas

ured

Rai

ls Conicity ≅ 0.1

Rails producing lower conicity

age

of M

ea Conicity ≅ 0.4Rails producing higher conicity

conicity

Mainly dueage

of M

ea Conicity ≅ 0.4Rails producing higher conicity

conicity

Mainly due

Perc

enta Mainly due

to worn wheels

Perc

enta Mainly due

to worn wheels


Percentage of Exception (Wheels) Percentage of Exception (Wheels)

Tangent Track W/R Conicity Summary

New AAR-1b wheels produce low conicity on all rail profiles

Rail profile pair from the high conicity group

Rail profile pair from the low

i irail profiles

Rails with a low rail shoulder produce lower conicities

conicity group

Rail profile pair from the high produce lower conicities,

high shoulder gives high conicity

conicity groupRail profile pair from the low conicity group

Conformal contact tends to produce low conicity λ = 0.05

Flattened rails, gauge flow and narrow gauge produce

λ > 0 35


high conicities λ > 0.35

Tangent Track W/R Conicity Summary (cont.)

Tight gauge is highly correlated to high conicity in tangent track

57

30

60

90

eeda

nce

of W

heel

s (%

)

56.356.456.556.656.756.856.957

Gag

e (in

)

Conicity Exceedance Wheelset % Gage Spacing inches

012200 12220 12240 12260 12280 12300 12320 12340 12360 12380 12400

Distance (feet)

Exce

5656.156.2

High conicity was found on only 10% of trackRail grinding to relieve reduce flattened rails, relieve the gauge corner and remove metal flow in thethe gauge corner and remove metal flow in the gauge corner could reduce conicityA more conformal new wheel profile could change


the rapid initial wear pattern of new wheels

Truck Hunting and Warp Dynamics

Loaded hunting tests revealed:

Predominantly in-phasePredominantly in-phase motion (warp) of the wheelsets & truck bolsterbolsterLittle longitudinal deflection of the adapter padsadapter padsDependence on moments due to the adapters / adapter pads & truck rotation on stability


Truck Warp Test Results

A tiff 140 klb i / d A tiff 12 5 klb i d

High warp restraint similar to previous tests

Warp stiffness reducedby factor of about 11 due

Avg. stiffness = 140 klb-in/mrad Avg. stiffness = 12.5 klb-inmrad

similar to previous testsof the same truck typewhen friction wedges

to friction saturationwith large wedge motionsfrom combined body


have little motion from combined bodyvertical/lateral motions

NUCARS ® simulations to evaluate W/R forces and effects of Carbody and Suspension Parameterseffects of Carbody and Suspension Parameters

40 000 lbs40,000 lbs net lateral axle force


W/R Forces due to Loaded Hunting

NUCARS® simulations of loaded grain car hunting show potential for very high W/R forcesL N tLarge Net Axle L/V ratios could

t kcause track panel shift

Large truckside L/V could causecould cause gauge widening and rail rollover


rail rollover

Progression to Loaded Car Hunting

Accelerated wheel wear occurs in curves as a result of a “mismatch” between the high rail profile & that on tangent tracktangent track

2-point contactHigh rail “conditions” the wheel of a car making flangeHigh rail conditions the wheel of a car making flange contact to a conformal profile

“Conditioning” results in high conicity, especially onConditioning results in high conicity, especially on particular sections of tangent track

New rail of particular section“Flattened” rail with material flow to the gauge cornerSections of track with tight gauge


Progression to Loaded Car Hunting (cont.)

High conicity on tangent trackOn sections where higher speeds occurHigh creep forces under load excite the wheelsets

to yaw/warp the truck frameto yaw within the truck frame on soft adapter padsto yaw within the truck frame on soft adapter pads

Wheelset & truck yaw excite particular (longer) car bodies in a yaw-dominated mode (includes roll)y ( )Car body yaw and coupled roll motions saturate the truck wedge system, reducing the warp restraintReduced warp restraint results in resonance between wheelset, truck & car body yaw above certain threshold speeds


p

Progression to Loaded car Hunting (cont.)

Truck warp restraint breaks-down almost completelyWheelset hollowing (& conicity) increases as a consequence of the hunting motionLoaded car hunting occurs:

At progressively lower speedsAt progressively lower speedsOn increasingly longer sections of tangent track

Pad failure results together with degradation ofPad failure results together with degradation of constant contact side bearing elements


Loaded Car Hunting: Conclusions

Loaded car hunting is a system problem:Only certain car types – many cars with trucks do

hnot huntDepends on truck center spacing, car body inertial characteristics (centers of gravity & moments ofcharacteristics (centers of gravity & moments of inertia associated with high capacity cars for low density bulk products)Wheelset and truck constraints (adapter pad stiffnesses, loss of warp restraint due to friction wedge motion)wedge motion)Track (rail profile mismatch, rail deformation, tight gauge)


g g )

Loaded Car Hunting: Conclusions (cont.)

Many types of car with these trucks do not experience loaded car hunting:

N d “ ” h d k iNeed “tune” the car and truck suspension parameters to the specific car body characteristics:

Truck spacing inertial parameters (CG height yawTruck spacing, inertial parameters (CG height, yaw and roll moments of inertia)Wheelset and truck constraints (adapter pad ( p pstiffnesses, truck warp restraint)

Loaded hunting may lead to very high W/R forcesLoaded hunting may lead to very high W/R forcesPossibility for increased risk of track damage and

derailment (Oct 2009 tests will measure forces w/IWS)


Way Forward: Standards and Testing

Primary Suspension Pad Durability StandardsAAR MSRP, Volume H, Section 4.3.2

Develop M-976 and Chapter 11 Loaded Hunting Test/Analysis Requirements (2009)

What wheel profile?What car body and inertial parameters? (M-976)What performance criteria?

Loaded Hunting Tests at TTCI (Oct/Nov 2009)g ( )Support development of loaded hunting testsIWS to measure W/R forces while hunting


Way Forward: Wheel and Rail Profiles

Rail grinding to relieve reduce flattened rails, relieve the gauge corner and remove metal flow in the gauge corner could reduce conicitythe gauge corner could reduce conicity

A more conformal new wheel profile could change th id i iti l tt f h lthe rapid initial wear pattern of new wheels

A new wheel profile design for freight cars is being evaluated at TTCI to replace the AAR-1bevaluated at TTCI to replace the AAR 1bBased on worn wheel shapesMore conformal to existing rail profiles in curves and g pstraight trackNarrower flange for more gage clearance


Way Forward: Car and Truck DesignI di tImmediate:

Replace adapters & pads with standard adaptersConsequent reduction in curving performanceConsequent reduction in curving performance (increased wheel wear & wheel RCF)

Intermediate:Intermediate:Stiffer padsPartial improvement in tracking performance (reduced p g p (wheel wear & wheel RCF)

Long term:Improved freight truck with reduced stiffness pads & increased warp restraintReduced wheel wear & eliminated RCF


Reduced wheel wear & eliminated RCF

Thank you for your attention!

Nicholas Wilson

Transportation Technology Center IncTransportation Technology Center Inc.PuebloColoradoUSA

MARTS Chicago September 2009 - 27© Transportation Technology Center, Inc., a subsidiary of the Association of American Railroads, 2009

USA

EFFECTS OF WHEEL/RAIL CONTACT PATTERNS andCONTACT …

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