UNIVERSITY OF NAIROBI

FINAL YEAR PROJECT

PROJECT NO: MFO/03/2012

TITLE: DEVELOPMENT OF A MATERIALS SELECTION PROCESS IN

ENGINEERING DESIGN AND MANUFACTURING

A final year project submitted in partial fulfillment of the requirements for the award of the degree of Bachelor of Science in Mechanical Engineering

WRITTEN BY:

MOGAKA DAVIDSON ONCHANA F18/1735/2007

&

MOMANYI GODFREY MARAMBE F18/1869/2007

SUPERVISED BY: PROF. M. F. ODUORI

May 2012

DEPARTMENT OF MECHANICAL AND

MANUFACTURING ENGINEERING

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DECLARATION

We certify that the information presented in this report, except where indicated and acknowledged, is our original effort and has not been presented before to the best of our knowledge. MOGAKA DAVIDSON ONCHANA F18/1735/2007 Signature…………………………………………………………………………………… Date…………………………………………………………………………………………... MOMANYI GODFREY MARAMBE F18/1869/2007 Signature…………………………………………………………………………………… Date…………………………………………………………………………………………... This project has been submitted with the approval of the supervisor Project supervisor: Prof. ODUORI, M. F. Signature…………………………………………………………………………………… Date of Submission ……………………………………………………………………

© Copyright 2012 Mogaka & Marambe

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DEDICATION

To my Dad, Mom (R.I.P), and brother Paul for your continued support. God bless you all.

Mogaka Davidson

To my parents, brothers and sisters who have accorded me with endless support during

my undergraduate studies, to my girlfriend Assumpter with love, to my lecturers in the

department of mechanical and manufacturing engineering for the knowledge they have

imparted in me in my undergraduate studies and from whom I have learnt so much.

Marambe Godfrey

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TABLE OF CONTENTS

Declaration………………………………………………………………………………………………………………...i

Dedication…………………………………………………………………………………………………………………ii

Contents…………………………………………………………………………………………………………………...iii

Acknowledgements……………………………………………………………………………………………………v

Abstract……………………………………………………………………………………………………………………vi

Objectives………………………………………………………………………………………………………….........vii

Chapter One ....................................................................................................................................... 1

1.1 Introduction .................................................................................................................................... 1

1.2 Standards And Codes .................................................................................................................. 2

Chapter Two ...................................................................................................................................... 3

Review Of Literature On Design, Materials Selection And Manufacturing Processes ......... 3

2.1 Introduction .................................................................................................................................... 3

2.2 Overview Of The Engineering Design Process .................................................................. 4

2.3 Material Selection ......................................................................................................................... 6

2.3.1 Materials Selection Process ............................................................................................. 7

2.3.2 Factors Influencing Materials Selection ...................................................................... 9

Chapter Three ................................................................................................................................. 17

Literature Review On Engineering Materials, Their Properties And Categories ................ 17

3.1 Introduction .................................................................................................................................. 17

3.2 Material Properties .................................................................................................................... 17

3.3 Categories Of Engineering Materials................................................................................... 18

3.3.1 Metallic Materials .............................................................................................................. 19

3.3.2 Non-Metallic Materials .................................................................................................... 24

Chapter Four ................................................................................................................................... 27

4.1 Introduction .................................................................................................................................. 27

4.1.1 Rank Order: Pair Wise Comparison Charts.............................................................. 27

4.1.2 Relative Order: Analytic Hierarchy Process (AHP) .............................................. 28

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4.2 Information Processing ............................................................................................................ 29

Chapter Five .................................................................................................................................... 31

Case Study: Selection Of A Material For A Reverted Two Stage Compound Gear Train... 31

5.1 Introduction .................................................................................................................................. 31

5.1.1 Classification Of Gears...................................................................................................... 31

5.1.2 Gearing Terminology ........................................................................................................ 34

5.1.3 Design Considerations For A Gear Train .................................................................. 35

5.1.4 Modes Of Gear Failure ...................................................................................................... 36

5.2 Reverted Compound Gear Train Design ............................................................................ 36

5.2.1 The Design Constraints .................................................................................................... 38

Chapter Six ....................................................................................................................................... 46

6.1 Material Ranking Indices ......................................................................................................... 46

6.2 Support Information ................................................................................................................. 48

6.3 Materials Selection System ..................................................................................................... 48

6.3.1 Database Structure ............................................................................................................ 49

6.3.2 Material Selection System .............................................................................................. 51

Chapter Seven: Closure ............................................................................................................... 59

7.1 Discussion ...................................................................................................................................... 59

7.2 Conclusion ..................................................................................................................................... 61

7.3 Recommendations...................................................................................................................... 61

7.4 References and Appendices .................................................................................................... 62

References ............................................................................................................................ 62

Appendices ........................................................................................................................... 63

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ACKNOWLEDGEMENTS

A project such as this could not have been accomplished without the assistance of a

large number of individuals. First and foremost we would like to sincerely thank Prof.

F.M. Oduori our project supervisor, and a senior lecturer at the Department of

Mechanical and Manufacturing Engineering - University of Nairobi; for the continued

guidance and support he gave us through relevant literature material and helpful

information to undertake this project.

We are grateful to Mr. Enoch Kimanzi for criticizing our work and providing us with

relevant information without which it would be difficult to accomplish our work. We

would also like to extend our hand of appreciation to Prof. S. Mutuli, chairman -

Department of Mechanical and Manufacturing Engineering for his efforts to ensure good

working conditions as well as support through departmental facilities especially the

departmental library.

We would like to acknowledge the staff of East African Foundry Ltd and Kensmetal Ltd

for providing us with meaningful information on engineering materials.

Finally, we would like to thank our families for their support and encouragement.

God bless.

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ABSTRACT

The selection of proper materials is fundamental to engineering design. Engineering

materials are many hence a formalized selection process is required to select a reliable

material for a product. The objective of this project was to develop an online material

selection process based on principles of decision theory and implement it as an

information processing routine on a computer system. A case study was undertaken

that involved selection of a material in the design of a reverted two stage compound gear

train. Selection was done in two stages: screening followed by ranking. The first stage

reduces the large material database to a small candidate list which are locally available

and meets the critical property limits such as strength. The second stage involves

ranking the candidate materials using indices formulated from availability, cost and

machinability. Supporting information is then sought and used to narrow down the

ranked materials to a final choice allowing a definite match to be made between design

requirements and material attributes. This material selection system helps the designer

perform the rigorous process of material selection for the gear train at fast speeds thus

saving time and money during design.

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OBJECTIVES

• To develop an online materials selection process that will be based on the principles of decision theory.

• To develop a knowledge intensive methodology for screening and ranking

engineering materials.

• To implement the materials selection process so developed as an information processing routine on a computer system.

• To document and evaluate the materials selection process so developed by

means of a case study (A Reverted two stage compound gear train)

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1 CHAPTER ONE

1.1 INTRODUCTION

The selection of a material for machine part or structural member is one of the most

important decisions the engineering designer has to make. Poor material choice can

lead to failure of a part or system or to unnecessary cost. The process of materials

selection is difficult one and typically involves multiple conflicting material

characteristics as well as large number of constraints.

A good material selection process considers the limiting factors for a particular design

exercise which include material properties, material processing, material cost and

material availability. Through systematic and optimizing approach, one can list all the

limiting factors associated with the design e.g. strength, hardness, cost and availability.

Weighting measure can be used to prioritize on what materials are more important than

others after which all available materials are listed and ranked.

For ranking purposes, indices like cost and availability of the various materials are

computed. After this task a list of the materials meeting the limiting requirements is

produced in which the materials are ranked from the one with the highest composite

index to the one with the least. In this case, the material with the highest composite

index based on cost and availability is taken as the best for the application. Materials for

other engineering applications can be selected in the same way.

With the advent of the internet, utilization of an online material selection process is a

major advancement in the selection of a material for a particular product. The process

gives accurate information at fast speeds thus saving time and money during design.

The computer can play a major role in storing information (database) on materials

properties. In addition a computer code is created using PHP (recursive acronym for

hypertext preprocessor) in which the information in the database can be accessed and

retrieved. Thus entering the machine part specifications in the program, the computer

searches for the qualified materials in the database and displays them to the user.

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1.2 STANDARDS AND CODES

A standard is set of specifications for parts, materials, or processes intended to achieve

uniformity, efficiency, and a specified quality. One of the most important purposes of a

standard is to place a limit on the number of items in the specifications so as to provide

a reasonable inventory of tooling, sizes, shapes, and varieties.

A code is set of specifications for the analysis, design, manufacture and construction of

something. The purpose of a code is to achieve a specified degree of safety, efficiency,

and performance or quality. However, it’s important to observe that safety codes do not

imply absolute safety1.

This project and the case study identify materials to Unified Numbering System (UNS)

standards. An ideal case of choice of standards should be based on such factors as the

location where the product is applicable and acceptability of the standard under the

applicable design/construction code. In this case therefore, Kenyan Standards (KS)

would have been preferred.

In order to provide a consistent basis for basic specifications of the materials, only UNS

standards for the materials have been used. In some cases where the material’s

common name is available, then the material’s common name is given.

1Shigley’s Mechanical Engineering Design

3

2 CHAPTER TWO

REVIEW OF LITERATURE ON DESIGN, MATERIALS SELECTION

AND MANUFACTURING PROCESSES

2.1 INTRODUCTION

To design is either to formulate a plan for the satisfaction of a specified need or to solve

a problem. If the plan results in the creation of something having a physical reality, then

the product must be functional, safe, reliable, usable, manufacturable and marketable.

Design establishes and defines solutions to, and pertinent structures, for problems not

solved before, or new solutions to problems which have previously been solved in a

different way (Dieter, George., 1983).

Design is an innovative highly iterative, and a decision making process. Decisions

sometimes have to be made with too little information, occasionally with just the right

amount of information, or with an excess of partially contradictory information. These

decisions are made tentatively, with the right reserved to adjust as more becomes

known.

A designer’s personal resources of creativeness, communicative ability, and problem

solving skill are intertwined with knowledge of technology and first principles.

Engineering tools (such as mathematics, statistics, computers, graphics and languages)

are combined to produce a plan that, carried out, produces a product that is functional

safe, reliable, competitive, usable, manufacturable, and marketable, regardless of who

builds it or who uses it.

The selection of proper materials is a key step in the design process because is a crucial

decision that links computer calculations and lines on an engineering drawing with a

real or working design. The enormity of this decision process can be appreciated when

it’s realized that there are over forty thousand metallic alloys and probably close to that

number of non-metallic engineering materials, currently in use (Ashby, M., 1999)

Improper selection of a material, may lead not only to failure of the material but also to

unnecessary cost. Selecting the best material for a part involves more than selecting a

material that has the properties to provide the necessary service performance; the

processing of the material into a finished part also has a key role to play. This is because

the properties of the part may be altered by processing resulting to a change in the

service performance of the part.

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2.2 OVERVIEW OF THE ENGINEERING DESIGN PROCESS

There is no particular step categorization or step nomenclature universally accepted,

but generally the complete design process is outlined in below:

Iteration

Fig. 2.1: Phases in Engineering Design Process (Adapted from: Madara Ogot & Gul Kremer,

Engineering Design: A Practical Guide).

It must be emphasized that engineering design is an iterative process requiring the

repetition of most steps based on what is learned at a later stage. The primary iterations

occur between the conceptual design and preliminary design steps.

2.2.1 Recognition of need

The need for a product typically arises from these three distinct scenarios.

• The need to design a new product or process that will solve a particular problem

or need where none exists.

• The need to redesign: to design a product or process that improves on an

existing one. Improvements include lower cost, highier efficiency, lower

pollution and better ergonomics.

• The need for technology-push product or process: to design a new product or

process and generate need for it. For example , a company develops a new

technology and then seeks a market to apply it.

Problem definition

Recognition of need

Conceptual design

Preliminary design

Detailed design

Production

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2.2.2 Problem definition

It’s a crucial part in the design process and includes;

• Condensed formal problem statement clearly stating objective of the design

process.

• Listing of technical and non-technical design constraints.

• Breakdown of the problem into smaller manageable sub-problems.

• Compilation and ranking of customer needs. What exactly does the customer

expect in final product or process?

• Definition of criteria to be used to evaluate the design.e.g testing of prototypes

developed in preliminary design step.

2.2.3 Conceptual design

A concept is a very preliminary description of the form, required principles and

technology for the solution. This stage is divided into two phases: external and internal

searches. An internal search entails the design team developing several concepts from

which the best suited to the need is selected. The stage is creative, inventive and most

difficult in engineering design process. The external search includes performing

literature searches, looking at previous patents, talking with experts, and benchmarking

similar product. The conclusion of this stage results in the generation and selection of

few promising concepts that warrant further development.

2.2.4 Preliminary design and evaluation

Feasible concepts are further developed by evaluating; leading to selection of one

concept. Selection is based on all design criteria specified during problem definition, as

well as cost estimates. System and component design requirement that will dictate the

detailed design specifications are established. During this stage, working prototypes

(where appropriate) are constructed and evaluated. Based on test results, parts of the

design or the entire design may need to be redone (iteration).

2.2.5 Detailed design

This stage of the design processes develops part geometry, technical drawings, and

tolerances. During this stage:

• All hitherto undefined system specifications and design requirements are

defined such as operating parameters, test requirements, design life, material

requirements, and reliability requirements.

• Detailed manufacturing drawings are produced.

• Detailed assembly drawings are generated.

• Testing is performed to evaluate components, validate computer models and the

design itself. Evaluation ensures all the conclusions reached during preliminary

testing stage are accurate. If errors are found or if components do not meet

anticipated design requirements, a redesign is initiated (Iteration).

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2.2.6 Production

Prior to production, production process planning is carried out. This involves

• Design drawings and specifications interpretation.

• Production processes and machines selection.

• Stock material selection.

• Determination of production sequence of operations.

• Determination of processing time.

The implementation involves successful testing of prototypes after which the final

solution is developed and preceded with full production.

2.2.7 Design Reviews

Design review (DR) is system that involves gathering and evaluating objective

knowledge about the product design quality and the concrete plans for making it a

reality , suggesting improvements at each point, confirming that the process is ready to

proceed to the next phase.-JUSE2 Design Review Committee, 1976 (Ichida, 1996).

Design review ensures design meets all requirements, and product quality is within cost

and time constraints. DRs should include:

• Collecting and compiling relevant information.

• Defining quality target.

• Evaluating product and process designs and supporting operations.

• Proposing improvements.

• Defining subsequent actions and confirm readiness for the next stage.

2.3 MATERIAL SELECTION

Selecting materials usually begins in the preliminary design stage. The problem of

material selection usually involves the selection of materials for a new product or new

design, and re-evaluation of an existing product or design to reduce cost, increase

reliability and improve performance. In selecting the appropriate material one must

consider:

1. Material properties which affects the part perfomance.

2. Material processing which affects manufacturing costs and therefore the final

part cost.

3. Material cost.

4. Availability. Is the material available in desired quantity and time frame?

5. Regulatory properties; Code acceptance and repairability

The relative importance of the above factors depends on the applications. For example

in military and aerospace applications, pushing the materials properties to the limits

takes precedence over cost. For consumer products, lowering cost typically plays the

2Japanese union of scientists and engineers.

7

leading role. For an engineering project on a tight schedule, material availability is

important.

2.3.1 MATERIALS SELECTION PROCESS

Usually, a problem of material selection involves either selection of materials for new

product or design; or re-evaluation of an existing design/product to increase reliability,

reduce cost and improve performance. Materials selection process, being a problem

solving process, is achieved through the following steps:

1. Determination of required critical properties from the design operating

conditions and enviroment. Material selection occurs at every step of design

process. At conceptual stage a wider spectrum of materials should be considered

to inspire more innovative designs. In the material screening process , material

properties considered will depend on possible failure modes likely to be

encountered during service, as well as other desired characteristics. By

establishing all the possible failure modes for each particular component and

matching them with the associated material properties, a list of material

properties for the screening process can be established. Table 2.1 below lists

some of common failure modes and associated influencing material properties.

Table 2.1: Adapted from Engineering Design by Madara Ogot., Gul Kremer

KEY

US-Ultimate strength E- Modulus of elasticity

YS-Yield strength CR-Creep rate

CS-Compressive yield strength HD-Hardness

SS-Shear yield strength CE-Coeffient of expansion

FP-Fatigue properties

2. Screening of large material database for candidate materials that meet the

critical material properties is determined in steps. These critical properties

can be divided into three groups

a) Non-discriminating parameters are those that must be met if material is to be

used at all. Examples include availability and corrosion resistance.

Mode of failure US YS CS SS FP E CR HD CE

Fatigue(High cycle) • •

Fatigue(Low cycle) • • •

Yielding •

Buckling • •

Wear •

Thermal fatigue • •

Creep •

Gross deformation •

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b) Go/no-go parameters. These are minimum or maximum property values

which candidate materials must meet. Excess or under values of these fixed

parameters don’t make up for other deficiencies in other properties.

Examples include cost and strength.

c) Discriminating parameters. These are minimum or maximum property values

which candidate materials must meet, and where any excess or under values

can make up for other deficiencies in other areas. Includes cost, density and

strength.

Depending on material application, a characteristic that is considered a

go/no-go parameter for one application may be considered discriminating or

non-discriminating parameter in another. For example in aerospace

applications cost is a discriminating parameter, whereas in consumer

products, cost is a go/no-go parameter.

3. Selecting the final material based on a trade-off of discriminating

parameters. This is done using desicion tools such as pairwise comparison

charts(ranking method), analytic hierarchy process (AHP) and decision matrices.

These tools will be discussed later in the decision making section.

All materials

Non-discriminating parameters

go/no-go parameters

discriminating parameters

Final material

Fig. 2.2: Three general steps in material selection

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2.3.2 FACTORS INFLUENCING MATERIALS SELECTION

There are several important factors that need to be considered during material

selection. These are commercial properties (Cost and Availability), material

properties(mechanical , physical, and environmental resistance), material processing,

and regulatory properties.

2.3.2.1 MATERIAL PROPERTIES

2.3.2.1.1 Mechanical properties

Mechanical properties of materials are those related to its ability to withstand external

mechanical forces such as tensile forces, compression forces, twisting, bending, and

sudden impact.

A. Strength

Strength is a measure of how a material withstands a heavy load without breaking.

Material strength information is used in engineering design in order to prevent the

failure of a product component by rapture. Following are parameters of strength:

• Elastic Limit: This is the force required to produce permanent deformation.

• Yield Point: This refers to the level of the load at which strain continues at a

constant stress.

• Yield Strength: The amount of tensile force required to just cause a well-defined

permanent deformation in a material.

• Ultimate Tensile Strength (UTS): This is the maximum strength of a material and

corresponds to the maximum load stress a structural member can withstand

before fracture.

• Compressive Strength: This is the ability of a material to resist a gradually applied

compressive load.

Yield strength and tensile strength are the most significant values in many engineering

applications. Appreciable permanent deformation occurs before the stress reaches the

UTS value. Therefore, to guard against permanent deformation in engineering

components, information on elastic limit of the candidate materials should be used in

design. For ductile materials, yield point information should be used instead of elastic

limit value. For this project, yield strength and compressive strength of materials have

been used as screening properties in the materials selection process.

B. Rigidity

This is the resistance of a material to deflection under a bending force. Its specified by

the elastic modulus of a material .Modulus of elasticity is the ratio of the applied stress

to the corresponding strain in the elastic limit of a material. The higher the value of the

elastic modulus the more rigid the material is.

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C. Resistance to fatigue:

Fatigue is defined as the progressive and localized structural damage of a material

under cyclic loading. Thus, fatigue strength, expressed in terms of the fatigue limit or

endurance limit of a material means the stress below which a material will not fail in

fatigue. This value is used in design of parts subjected to repeated alternating stresses

over an extended period of time. Since the strength of a material under cyclic loading is

less than the strength of the same material under static loading, resistance to fatigue

forms the basis for the design of components that are subjected to cyclic loading.

D. Ductility

Ductility is a measure of the degree of plastic deformation that has been sustained at

fracture. A material that experiences very little or no plastic deformation upon fracture

is termed brittle.

E. Resilience

Resilience is the capacity of a material to absorb energy when it is deformed elastically

and then, upon unloading, to have this energy recovered. The associated property is the

modulus of resilience, which is the strain energy per unit volume required to stress a

material from an unloaded state up to the point of yielding.

F. Toughness

Toughness is a mechanical term that is used in several contexts; basically, it is a

measure of the ability of a material to absorb energy up to fracture. Specimen geometry

as well as the manner of load application are important in toughness determinations. A

related property is fracture toughness which is indicative of a material’s resistance to

fracture when a crack is present

G. Hardness

Another mechanical property that may be important to consider is hardness, which is a

measure of a material’s resistance to localized plastic deformation (e.g., a small dent or a

scratch. Quantitative hardness techniques have been developed over the years in which

a small indenter is forced into the surface of a material to be tested, under controlled

conditions of load and rate of application. The depth or size of the resulting indentation

is measured, which in turn is related to a hardness number; the softer the material, the

larger and deeper the indentation, and the lower the hardness index number.

H. Damping capacity

The damping capacity of a material is defined as energy dissipated as heat by a unit

volume of the material during a completely reversed cycle of stress. It is related to

internal friction in the material and depends on maximum stress. The critical value

suggested for engineering design is the value at the endurance limit. High damping

capacity is desirable in most machine parts to reduce accumulation of harmful resonant

stresses, vibration, and to decrease noise in machine tools.

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I. Friction

Surface friction is an energy dissipative process which takes place with relative

tangential displacement of contacting solids in zones of real contact between them,

formed by the action of an external load. It is that component of the load which resists

lateral (tangential) motion of solid surfaces, fluid layers or material elements in contact.

Friction is described by a ratio of friction force to normal load, termed the coefficient of

friction, µ. This value depends not only on the surface finish but also on the contacting

materials. It thus occurs that, in the process of engineering design, decisions must

always be made as to which materials and what processes can be used according to the

friction requirements of the component.

J. Formability

Formability can be defined as the relative ease with which a metal can be shaped

through plastic deformation while avoiding machining operations. Usually, shaping of

the component is achieved by stretching it using mechanical force. Formability

determines the amount the material in question can be stretched or drawn without

necking and failing3 . Forming limit is thus defined as the extent to which the metal can

be stretched before failure occurs.

2.3.2.1.2 Mechanical failure modes

A. Fracture

Fracture refers to the local separation of an object or material into two or more pieces

under the action of stress. Fracture toughness is a property which describes the ability

of a material containing a crack to resist fracture, and is one of the most important

properties of any material for virtually all design applications.

B. Fatigue

Fatigue is the progressive and localized structural damage that occurs when a material

is subjected to cyclic loading. It occurs when a material is subjected to repeated loading

and unloading. If the loads are above a certain threshold, microscopic cracks will begin

to form at the surface. Eventually a crack will reach a critical size, and the structure will

suddenly fracture.

C. Wear

Wear is erosion or sideways displacement of material from its "derivative" and original

position on a solid surface performed by the action of another surface. It is related to

interactions between surfaces and more specifically the removal and deformation of

material on a surface as a result of mechanical action of the opposite surface.

D. Creep

Creep is a slow or progressive deformation of a material with time under constant

3 Ashby, M.F., 1999

12

stress. It is triggered via thermal activation and is more severe in materials that are

subjected to heat for long periods near the melting point.

E. Corrosion

Corrosion is the disintegration of an engineering material into its constituent atoms due

to chemical reactions with its surroundings. It involves electrochemical oxidation of

metals in reaction with an oxidant such as oxygen. A well-known example of

electrochemical corrosion is formation of an oxide iron due to oxidation of the iron

atoms in solid solution.Effects of corrosion are magnified by stress concentration and

cyclic loading.

F. Hydrogen embrittlement

Hydrogen embrittlement is the process by which various metals, most importantly high-

strength steels, become brittle and fracture following exposure to hydrogen. It results

from unintentional introduction of hydrogen into susceptible metals during forming or

finishing operations

2.3.2.1.3 Physical properties

A. Density

Density is commonly defined as mass per unit volume. It is the weight of a material per

unit volume and is measured by weighing it in air and in a fluid of known density.

Different engineering applications demand different density requirements from

materials. Low density materials may be preferred in some applications like in aircraft

components (fuel economy). On the contrary, weight is found to be advantageous in

some cases such as while making foundations and flywheels.

B. Electrical properties

Typical electrical properties include;

• Resistivity which is the measure a materials ability to resist the flow of

electricity. The higher its value, the higher the resistance of the material.

Resistivity changes with temperature.

• Dielectric strength. Materials can be categorised in terms their electrical

properties as conductors, semiconductors or insulators. For an insulator, the

dielectric strength is the voltage required to break down the insulation ( i.e.,

allow electrical conduction ) through a unit thickness of the material.

C. Thermal properties

Typical thermal properties include

• Thermal conductivity- Measure of the rate at which heat can be conducted

through a material. It’s measured with the coefficient of thermal conductivity, k.

13

The higher the coefficient, the better the thermal conductivity. For cases where

thermal insulation is required, materials with low thermal conductivity are used.

• Specific heat- is the amount of thermal energy required to increase a unit mass of

a material’s temperature by 1 degree.

• Coefficient of thermal expansion- it gives a measure of an object’s change in

length per degree change in temperature.

2.3.2.2 MANUFACTURING PROCESS

The manufacturing process influences amount of material wasted, surface defects of the

product, cost and to some extent material properties of finished products. The material

manufacturing process selected is determined largely by its cost and properties of the

material to be used. Typical material processes considered during material selection

process are:

A. Machining

Machining operations can be classified as the ones in which material is removed in chip

form by means of a cutting tool or an abrasive wheel or block. Some of the machining

operations include: turning, grinding, drilling, boring, reaming, milling, planing, shaping

and broaching.

The designer differentiates the machining processes mainly on the basis of the cost to

achieve a certain shape, accuracy and surface finish. The processes are usually costly

and produce scrap and should therefore be avoided if possible. The designer will specify

abrasive methods when he/she seeks high accuracy and surface finish or when the

material is too hard for other cutting tools.

B. Casting

Metal casting is the process by which a metal or metal alloy is poured into a mould and

hardened in the shape of the mold cavity. The casting process involves:

• Melting the metal.

• Pouring the molten metal into the mold.

• Allowing the metal to cooland solidify.

• Removing the finished part from the mold.

This manufacturing process allows the creation of complex parts and can be used to

make small or large parts. In addition, it is well suited for mass production. The types of

casting processes available are sand casting, pressure die casting, investment casting

and ingot casting. The choice of any of these processes depend mainly on the material,

size, tolerances involved and more importantly, on the number of pieces to be produced.

C. Forging

Forging involves plastic deformation of material between two dies to achieve the

desired configuration. Depending upon complexity, forging is carried out as open die

forging and closed die forging. In open die forging, the metal is compressed by repeated

blows using a mechanical hammer and its shape is manipulated manually. In closed die

14

forging, the desired configuration is obtained by squeezing the work piece between two

shaped and closed dies. On squeezing the die cavity gets completely filled and excess

material comes out around the periphery of the die as flash which is later trimmed. Both

open and closed die forging processes are carried in hot as well as in cold state. In

forging, favorable grain orientation of metal is obtained.

D. Rolling

Rolling is the most extensively used metal forming process. The material to be rolled is

drawn by means of friction into the two revolving roll gap. The compressive forces

applied by the rolls reduce the thickness of the material or changes its cross sectional

area. The geometry of the product depends on the contour of the roll gap. Roll materials

are cast iron cast steel and forged steel because of high strength and wear resistance. In

rolling the crystals get elongated in the rolling direction. In cold rolling, the crystal more

or less retains the elongated shape but in hot rolling they start reforming after coming

out from the deformation zone.

E. Extrusion

In extrusion, the material is compressed in a chamber and the deformed material is

forced to flow through a die. The die opening corresponds to the cross section of the

required product. It is basically a hot working process; however, for softer materials

cold extrusion is also performed. In direct extrusion metal flows in the same direction as

that of the ram. Because of the relative motion between the heated billet and the

chamber walls, friction is severe and is reduced by using a lubricant. In indirect

extrusion, the metal flows in the opposite direction of the ram. It is more efficient since

it reduces friction losses considerably.

F. Drawing

Large quantities of wires, rods, tubes and other sections are produced by drawing

process which is basically a cold working process. In this process the material is pulled

through a die in order to reduce it to the desired shape and size. In a typical wire

drawing operation, one end of the wire is reduced and passed through the opening of

the die, gripped and pulled to reduce its diameter. By successive drawing operation

through dies of reducing diameter the wire can be reduced to a very small diameter.

Annealing before each drawing operation permits large area reduction.

G. Case Hardening

The purpose of case hardening is to produce a hard outer surface on a specimen of low

carbon steel while at the same time retaining the ductility and toughness in the core.

This is done by increasing the carbon content at the surface by using solid, liquid, or

gaseous carburizing materials. The process consists of introducing the part to be

carburized into the carburizing material for a stated time, and temperature depending

upon the depth of case desired and the composition of the part. The part may then be

quenched directly from the carburization temperature and tempered, or in some cases

it must undergo a double heat treatment in order to ensure that both the core and the

15

case are in proper condition. Some of the more useful case-hardening processes are

pack carburizing, gas carburizing, nitriding, cyaniding, induction hardening, and flame

hardening.

H. Powder Metallurgy

The powder metallurgy process is a quantity–production process that uses powders

from a single metal, several metals, or a mixture of metals and non-metals. Essentially it

consists of mechanically mixing the powders, compacting them in dies at high pressures

and heating the compacted part at a temperature less than the melting point of the

major ingredient. Waste material and machining operations are reduced significantly.

However, the cost of materials and dies are high. Parts commonly made by this process

are: Oil impregnated bearings, incandescent lamp filaments, cemented carbide tips for

tools and permanent magnet.

I. Plastic Injection Molding

Plastic injection is the most common process for manufacturing plastic products. It

involves:

• Heating a polymer to a molten state.

• Forcing the molten polymer to flow into a mold.

• Cooling and removing the molded part.

This process is suitable for large scale production. In such production scale, the

expenditure on tooling cost is high, and therefore it’s important that the designer

consults the manufacturer at an early stage in design.

2.3.2.3 COMMERCIAL PROPERTIES (COST AND AVAILABILITY)

These properties involve aspects of both direct cost of materials and availability of

materials. This is because availability of a material greatly determines its cost. A

material is selected bearing in mind the cost of manufacture using available methods.

Other costs include:

• The cost of labour required to produce the finished product from that material.

• Cost of indirect materials (processing chemicals and cleaning materials).

• Cost of services incurred (electric power, gas, air, water, coal, and fuel).

• Tool replacement cost.

• Depreciation of plant and machinery.

2.3.2.4 REGULATORY PROPERTIES

A. Code Acceptance

Professional Engineering oganisations provide performance oriented codes, standards

and evaluation procedures by which a product can be tested and evaluated for

compliance.This helps provide a uniform and widely recognised basis for acceptance of

new products.After the new product has been tested to indicate conformance to the

16

code, a technical report is issued describing the new system, the information and the

tests submitted , and the recommended usage.

B. Reparability

This is the ability of the of the damaged or failed equipment, machine or system to be

restored to acceptable operating condition within a specified time. This property should

be taken into account to avoid losses that would be suffered if replacement was to be

done for whole component or equipment. The spare parts should be available and

affordable.

17

3 CHAPTER THREE

LITERATURE REVIEW ON ENGINEERING MATERIALS, THEIR

PROPERTIES AND CATEGORIES

3.1 INTRODUCTION

Many at times, a materials problem is really one of selecting that material which has the

right combination of characteristics for a specific application. This necessitates that the

engineering designers have some familiarity with the general characteristics of a wide

variety of materials.

Engineering materials are classified on the basis of their chemical, physical and

mechanical properties. They include metallic materials (metals and their alloys) and

non-metallic materials (polymers, ceramics and composites).

3.2 MATERIAL PROPERTIES

A material property is the measured magnitude of its response to a standard test

performed according to a standard procedure in a given environment. An

understanding of material properties and behavior puts a designer in a position to

choose a proper material for a given product. Material properties are usually formalized

through specifications namely,

• Performance specifications which delineate the basic functional requirements of

the product and sets out the basic parameters from which the design can be

developed.

• Product specifications which define conditions under which components of the

designs are purchased or manufactured.

3.2.1 MECHANICAL PROPERTIES

Mechanical properties of materials are those related to its ability to withstand external

mechanical forces such as tensile forces, compression forces, twisting (torque), bending

and sudden impact. They include; strength and rigidity, resistance to fatigue, resilience

and toughness, hardness, ductility, damping capacity, friction, and formability. These

were discussed in detail in chapter 2.

3.2.1.1 RELATIONSHIP BETWEEN FAILURE MODES AND MECHANICAL

PROPERTIES

In most modes of failure two or more mechanical properties interact to control the

material behavior. In addition, the service conditions met by the material in general use

are more complex than the test conditions under which the material properties are

usually measured.

The service condition may consist of a complex superposition of environments such as

fluctuating stress (fatigue) at high temperature (creep) in a highly oxidizing atmosphere

18

(corrosion). Specialized simulation tests are developed to” screen materials” for

complex service conditions.

3.3 CATEGORIES OF ENGINEERING MATERIALS

Engineering materials can be classified into two major categories: Metallic materials

and Non- metallic material. These are further subdivided into various classes as

illustrated in the diagram below:

Note: HSLA –High Strength Low Alloy

Fig. 3.2: Categories of engineering materials

ENGINEERING MATERIALS

Metal & Alloys Non-Metals

Aluminium

Non Ferrous Composites Ceramics Polymers

Ferrous

Copper Titanium Nickel Cast irons Steels

Alloy steels

High alloy Stainless HSLA

Austenitic Ferritic Martensitic

Carbon steels

High Carbon Low Carbon

Medium Carbon

Magnesium

Duplex

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3.3.1 METALLIC MATERIALS

These consist of metals and metal alloys. In this category we have ferrous and non

ferrous metals. They have vast application due to their good electrical and thermal

conductivity. They can be classified into ferrous and non ferrous metals.

3.3.1.1 FERROUS ALLOYS

Ferrous alloys contain iron as the prime constituent. Their widespread use is accounted

for by three factors:

• Iron-containing compounds exist in abundant quantities within the earth’s crust

• Metallic iron and steel alloys may be produced using relatively economical

extraction, refining, alloying, and fabrication techniques.

• Ferrous alloys are extremely versatile, in that they may be tailored to have a

wide range of mechanical and physical properties. The principal disadvantage of

many ferrous alloys is their susceptibility to corrosion.

3.3.1.1.1 STEELS

Steels are iron–carbon alloys that may contain appreciable concentrations of other

alloying elements. The mechanical properties are sensitive to the content of carbon,

which is normally less than 1.0 wt%. Steels are classified according to carbon

concentration, namely, into low, medium, and high carbon types.

A. Low-Carbon Steels

Have carbon content of less than 0.25 wt%. Microstructures consist of ferrite and

pearlite constituents. As a consequence, these alloys are relatively soft and weak, but

have outstanding ductility and toughness; in addition, they are machinable, weldable. A

sub group of low-carbon alloys are the high-strength, low-alloy (HSLA) steels. They

contain other alloying elements such as copper, vanadium, nickel, and molybdenum in

combined concentrations as high as 10 wt%, and possess higher strengths.

B. Medium-Carbon Steels

Have carbon concentrations between about 0.25 and 0.60 wt%. These alloys may be

heat treated by austenitizing, quenching, and then tempering to improve their

mechanical properties. They are most often utilized in the tempered condition, having

microstructures of tempered martensite. The plain medium-carbon steels have low

hardenabilities and can be successfully heat treated only in very thin sections and with

very rapid quenching rates.

C. High-Carbon Steels

Have carbon contents between 0.60 and 1.4 wt%. They are the hardest, strongest, and

yet least ductile of the carbon steels. Used in a hardened and tempered condition and, as

such, are especially wear resistant and capable of holding a sharp cutting edge. The tool

and die steels are high-carbon alloys, usually containing chromium, vanadium, tungsten,

20

and molybdenum. These alloying elements combine with carbon to form very hard and

wear-resistant carbide compounds.

3.3.1.1.2 STAINLESS STEELS

The stainless steels are highly resistant to corrosion. Their predominant alloying

element is Chromium with a concentration of at least 11 wt%. Corrosion resistance may

also be enhanced by nickel and molybdenum additions. They are divided into three

classes:

• Ferritic steels: contain 12-27% chromium.

• Martensitic steels: contain 12% chromium and no nickel.

• Austensitic steels: contain 18% chromium and 8% nickel

3.3.1.1.3 CAST IRONS

Generically, cast irons are a class of ferrous alloys with carbon content above 2.14 wt %.

However, most cast irons contain between 3.0 and 4.5 wt% C and, other alloying

elements. They are easily melted and amenable to casting. Cast irons are grouped into:

A. Gray cast Iron

The carbon content varies between 2.5 - 4.0 wt %, with Silicon content varying between

1.0 - 3.0 wt%. The graphite exists in the form of flakes (similar to corn flakes), which

are normally surrounded by ferrite or pearlite matrix. It’s weak and brittle in tension as

a consequence of its microstructure; the tips of the graphite flakes are sharp and

pointed, and may serve as points of stress concentration when an external tensile stress

is applied. Strength and ductility are much higher under compressive loads. They are

very effective in damping vibration energy.

B. Ductile (or Nodular) Iron

It is formed by adding a small amount of magnesium and/or cerium to the gray iron

before casting. Graphite forms as nodules or sphere-like particles instead of flakes. The

matrix phase surrounding these particles is either pearlite or ferrite, depending on heat

treatment. It is normally pearlite for a cast piece. However, heat treatments for several

hours at about 700 0C will yield a ferrite matrix .Castings are stronger and much more

ductile than gray cast iron. Ductile cast iron has mechanical characteristics approaching

those of steel.

C. White cast Iron and Malleable cast Iron

White cast iron contains low-silicon (less than 1.0 wt% Si) and undergoes rapid cooling

rates. Carbon exists as cementite instead of graphite. It is extremely hard but also very

brittle, to the point of being virtually unmachinable. White iron is used as an

intermediary in the production of malleable iron. Heating white iron at temperatures

between 800- 9000C for a prolonged time period and in a neutral atmosphere (to

prevent oxidation) causes a decomposition of the cementite, forming graphite, which

21

exists in the form of clusters or rosettes surrounded by a ferrite or pearlite matrix,

depending on cooling rate. The microstructure of malleable iron is similar to that for

nodular iron hence it’s relatively high strength and appreciable ductility or malleability.

3.3.1.2 NON-FERROUS ALLOYS

Steel and other ferrous alloys are consumed in exceedingly large quantities because

they have such a wide range of mechanical properties, may be fabricated with relative

ease, and are economical to produce. However, they have some distinct limitations,

chiefly:

• Relatively high density,

• Comparatively low electrical conductivity, and

• An inherent susceptibility to corrosion in some common environments.

Thus, for many applications it is advantageous or even necessary to utilize other alloys

having more suitable property combinations. Alloy systems are classified either

according to the base metal or according to some specific characteristic that a group of

alloys share.

3.3.1.2.1 COPPER AND ITS ALLOYS

Copper and copper-based alloys, possessing a desirable combination of physical

properties, have been utilized in quite a variety of applications since antiquity.

A. Copper

Unalloyed copper has excellent thermal and electrical conductivity. It is soft, ductile, and

has an almost unlimited capacity to be cold worked. It is highly resistant to corrosion in

diverse environments including the ambient atmosphere, seawater, and some industrial

chemicals. The mechanical and corrosion-resistance properties of copper may be

improved by alloying. Most copper alloys cannot be hardened or strengthened by heat-

treating procedures; consequently, cold working and/or solid-solution alloying must be

utilized to improve these mechanical properties.

B. Copper alloys

Brasses

Zinc is the predominant alloying element. α brasses are relatively soft, ductile, and

easily cold worked. Brass alloys having higher zinc content contain both α and β phases

at room temperature. The β phase has an ordered body centred cubic (BCC) crystal

structure and is harder and stronger than α phase; consequently, α+β alloys are

generally hot worked. Some of the common brasses are yellow, naval, and cartridge

brass, muntz metal, and gilding metal.

Bronze

The bronzes are alloys of copper and several other elements, including tin, aluminum,

silicon, and nickel. These alloys are somewhat stronger than the brasses, yet they still

22

have a high degree of corrosion resistance. Generally they are utilized when, in addition

to corrosion resistance, good tensile properties are required.

Beryllium coppers

They possess a remarkable combination of properties: tensile strengths as high as 1400

MPa, excellent electrical and corrosion properties, and wear resistance when properly

lubricated; they may be cast, hot worked, or cold worked. High strengths are attained by

precipitation-hardening heat treatments. These alloys are costly because of the

beryllium additions, which range between 1.0 and 2.5 wt%. Applications include jet

aircraft landing gear bearings and bushings, springs, and surgical and dental

instruments.

3.3.1.2.2 ALUMINIUM AND ITS ALLOYS

Aluminium and its alloys are characterized by a relatively low density (2700Kg/m3),

high ductility, high electrical- thermal conductivities, and a resistance to corrosion.

Since aluminium has a face centred cubic (FCC) crystal structure, its ductility is retained

even at very low temperatures. The chief limitation of aluminium is its low melting

temperature, which restricts the maximum temperature at which it can be used.

Principal alloying elements include copper, magnesium, silicon, manganese, and zinc.

Aluminium alloys are classified as either cast or wrought. Some of the more common

applications of aluminum alloys include aircraft structural parts, beverage cans, bus

bodies, and automotive parts (engine blocks, pistons, and manifolds).Recent attention

has been given to alloys of aluminum and other low-density metals (e.g. Mg and Ti) as

engineering materials for transportation, to effect reductions in fuel consumption. An

important characteristic of these materials is specific strength, which is quantified by

the tensile strength–specific gravity ratio.

A generation of new aluminum-lithium alloys has been developed recently for use by

the aircraft and aerospace industries. These materials have relatively low densities

(between 2500–2600 Kg/m3), high specific moduli (elastic modulus specific gravity

ratios), and excellent fatigue and low-temperature toughness properties.

3.3.1.2.3 MAGNESIUM AND ITS ALLOYS

The most outstanding characteristic of magnesium is its density (1700 Kg/m3); hence

its alloys are used where light weight is an important consideration (e.g. in aircraft

components).It is relatively soft, and has a low elastic modulus. At room temperature

magnesium and its alloys are difficult to deform. Consequently, most fabrication is by

casting or hot working. It has a moderately low melting temperature. Chemically,

magnesium alloys are relatively unstable and especially susceptible to corrosion in

marine environments. On the other hand, corrosion or oxidation resistance is

reasonably good in the normal atmosphere (due to impurities). Fine magnesium

powder ignites easily when heated in air; consequently, care should be exercised when

handling it in this state.

23

These alloys are also classified as either cast or wrought, and some of them are heat

treatable. Aluminum, zinc, manganese, and some of the rare earths are the major

alloying elements. These alloys are used in aircraft and missile applications.

3.3.1.2.4 TITANIUM AND ITS ALLOYS

Titanium and its alloys are relatively new engineering materials that possess an

extraordinary combination of properties. The pure metal has a relatively low density

(4500 Kg/m3), a high melting point [16680C], and an elastic modulus of 107 GPa.

Titanium alloys are extremely strong, with room temperature tensile strengths as high

as 1400 MPa. Furthermore, the alloys are highly ductile, easily forged and machined.

The major limitation of titanium is its chemical reactivity with other materials at

elevated temperatures. This property has necessitated the development of

nonconventional refining, melting, and casting techniques; consequently, titanium

alloys are quite expensive. In spite of this high temperature reactivity, the corrosion

resistance of titanium alloys at normal temperatures is unusually high; they are

virtually immune to air, marine, and a variety of industrial environments

They are commonly utilized in airplane structures, space vehicles, surgical implants,

and in the petroleum and chemical industries.

3.3.1.2.5 THE SUPER ALLOYS

The super-alloys have superlative combinations of properties. Most are used in aircraft

turbine components, which must withstand exposure to severely oxidizing

environments and high temperatures for reasonable time periods. Mechanical integrity

under these conditions is critical; in this regard, density is an important consideration

because centrifugal stresses are diminished in rotating members when the density is

reduced. These materials are classified according to the predominant metal in the alloy,

which may be cobalt, nickel, or iron. Other alloying elements include the refractory

metals (Nb, Mo, W, and Ta), chromium, and titanium. In addition to turbine applications,

these alloys are utilized in nuclear reactors and petrochemical equipment.

3.3.1.2.6 MISCELLANEOUS ALLOYS NONFERROUS

The discussion above covers the vast majority of non-ferrous alloys; however, a number

of others are found in a variety of engineering applications. These include:

Nickel and its alloys are highly resistant to corrosion in many environments, especially

those that are basic (alkaline). Nickel is often coated or plated on some metals that are

susceptible to corrosion as a protective measure. Monel, a nickel based alloy containing

approximately 65 wt% Ni and 28 wt% Cu (the balance iron), has very high strength and

is extremely corrosion resistant; it is used in pumps, valves, and other components that

are in contact with some acid and petroleum solutions.

24

Lead, tin, and their alloys find some use as engineering materials. Both are

mechanically soft and weak, have low melting temperatures, are quite resistant to many

corrosion environments, and have re-crystallization temperatures below room

temperature. Many common solders are lead–tin alloys, which have low melting

temperatures. Applications for lead and its alloys include x-ray shields and storage

batteries. Tin is used as a very thin coating on the inside of plain carbon steel cans (tin

cans) that are used for food containers; this coating inhibits chemical reactions between

the steel and the food products.

Zinc is a relatively soft metal having a low melting temperature and a re-crystallization

temperature. Chemically, it is reactive in a number of common environments and,

therefore, susceptible to corrosion. Galvanized steel is just plain carbon steel that has

been coated with a thin zinc layer; the zinc preferentially corrodes and protects the

steel .Typical applications of galvanized steel are familiar (sheet metal, fences, screen,

screws, etc.). Common applications of zinc alloys include padlocks, automotive parts

(door handles and grilles), and office equipment.

Zirconium and its alloys are ductile and have other mechanical characteristics that are

comparable to those of titanium alloys and the austenitic stainless steels. However, the

primary asset of these alloys is their resistance to corrosion in a host of corrosive media,

including superheated water. Furthermore, zirconium is transparent to thermal

neutrons, so that its alloys have been used as cladding for uranium fuel in water-cooled

nuclear reactors.

3.3.2 NON-METALLIC MATERIALS

These are the materials that do not exhibit metallic characteristics in their properties.

Examples are composites, ceramics, rubbers, plastics and polymers.

3.3.2.1 POLYMERS

These are compounds of high molecular weight derived by the addition of smaller

molecules (monomers) or by the condensation of smaller molecules with the

elimination of water, alcohol and other solvents. There are many different polymeric

materials that are familiar to us and find a wide variety of applications.

3.3.2.1.1 Plastics

They have a wide variety of combinations of properties. Some plastics are very rigid and

brittle; others are flexible, exhibiting both elastic and plastic deformations when

stressed, and sometimes experiencing considerable deformation before fracture. Plastic

materials may be either thermoplastic or thermosetting.

A. Thermoplastics

These are also known as thermo softening plastics. They have very weak Van Der Waals

forces. They are polymers that liquefy on heating and when cooled, they form a very

25

glassy state. They are easily molded and extruded into films, fibers and packaging

materials. E.g. Polyvinylchloride, polyethylene

B. Thermosetting plastics

These are polymers that cure irreversibly. Once cooled and hardened, they return to

their shapes but cannot return to their original form. The curing is by heating or

through a chemical reaction. They can be used for automobile parts, aircraft parts and

tyres. Example are vulcanized rubber and epoxy resins.

3.3.2.1.2 Elastomers

They have a cross linked structure with a looser mesh than thermosets. Thus they have

the ability to be deformed to quite large deformations, and then elastically spring back

to their original form. Their moduli of elasticity are quite small. They are to produce

automobile tyres. Example is Natural poly-isoprene (natural rubber)

3.3.2.1.3 Fibers

Fibers are capable of being drawn into long filaments (100: 1 length-to-diameter ratio).

Fiber polymers are utilized in the textile industry, being woven or knit into cloth or

fabric. While in use, fibers may be subjected to a variety of mechanical deformations:

stretching, twisting, shearing, and abrasion. Consequently, they must have a high tensile

strength (over a relatively wide temperature range) and a high modulus of elasticity, as

well as abrasion resistance.

3.3.2.2 CERAMICS

These are inorganic non-metallic materials made up of two or more elements bonded

together. They can be dense or light in weight but with excellent strength and hardness

properties. Typical properties of ceramics include:

• Ceramics are brittle, wear resistant, hard and oxidation-resistant.

• They are very strong in compression but very weak in tension due to presence of

minute cracks.

• They are also widely applicable in positions involving chemicals because they are

inert.

• Ceramics are hard and strong.

Ceramics are divided into four sections of application, namely:-

• Structural application ceramics e.g. bricks, roof and floor tiles.

• Refractory applications: These are the ceramics used as kiln linings and gas fire

radiant.

• Technical engineering applications: These include fire ceramics used in space

shuttle programmers.

• Whiteware applications ceramics: Become white after the high-temperature

firing. E.g. porcelain, pottery, tableware, china, and plumbing fixtures (sanitary

ware).

26

3.3.2.3 COMPOSITES

These are engineering materials made from two or more materials with significantly

different chemical and physical properties and these materials remain separate or

distinct on the microscopic level within a finished structure. The constituent material is

either a matrix or reinforcement.

The matrix, usually a polymer matrix, surrounds and supports the reinforcement by

maintaining their relative positions. The reinforcement; usually fibers, metals, ceramics

and polymers impart their mechanical and physical properties to enhance the matrix

properties. Composites have special properties like:-

• Fire resistance.

• Light weight.

• Chemical and weathering resistance.

• Good electrical properties.

• High strength to weight ratio.

Composites fail by: Shock, impact and repeated cyclic loading causing separation of the

layers (de-lamination). Some composites are brittle and have little reserve strength

beyond initial onset of failure while others have reserve energy absorbing capacity past

the onset of damage. In comparison with other materials, composites have poor bearing

strength.

27

4 CHAPTER FOUR

REVIEW OF LITERATURE ON DECISION MAKING AND

INFORMATION PROCESSING

4.1 INTRODUCTION

Engineering design is inherently a decision making process where choices are

constantly being made between alternatives, such as selection of concepts, components,

or the rating of client needs. The tools used in solving these problems depend largely on

the type of data available (deterministic, probabilistic, or uncertain)4.

Numerous methods have been developed to help design teams make the correct choices

by using structured approaches. The two widely used tools include:

i. Rank order: Pairwise comparison charts (PCCs)

ii. Analytic hierarchy process(AHP)

4.1.1 RANK ORDER: PAIR WISE COMPARISON CHARTS

Dym and Little (2003) proposed using of PCCs based on the premise that it is easier to

differentiate between pairs of alternatives e.g. A is better than B or A is similar to B.

PCCs use a matrix structure to compare each alternative individually with every other

(Pair wise comparison). The results from the comparison are summed to obtain an

overall rank order.

PCCs can be generated using the following steps:

1) In a table, the n items to be compared are listed as row and column headings in

an n×n matrix. An additional column is added at the end of the matrix to record

the total score for each item.

Table 4.1- Structure of PCCs; Adapted from: Madara Ogot & Gul Kremer, Engineering

Design: A Practical Guide.

Comparison criteria

Evaluated A B C D E F Total A -1 -1 -1 -1 -1 -5 B 1 -1 1 -1 0 0 C 1 1 1 1 1 5 D 1 -1 -1 0 -1 -2 E 1 1 -1 0 -1 0 F 1 0 -1 1 1 2

4Taha, A., 2008

28

Key

A-Size E-Availability

B-Weight F-Manufacturability

C-Strength

D-Cost

2) The first row is compared individualy to all other column items. Scores of 1, 0,

and -1 are assigned if the row item is better, similar, or worse, respectively than

the column item.

3) The row scores are totalled, yielding the overall score of thr first alternative.

4) Steps 2 and 3 are repeated for all alternatives.

5) The ranking order for alternatives is compiled. The higher the overall score, the

higher the alternative’s rank. From the table above, strength (C) is ranked

highest.

4.1.2 RELATIVE ORDER: ANALYTIC HIERARCHY PROCESS (AHP)

It is used when a relative score is required for a set of qualitative alternatives.AHP

determines by how much each alternative is better (or worse) than the others. It is

based on the fundamental scale which captures individual preferences with respect to

qualitative or quantitative attributes.

Example

Consider two choices of materials all of which meet the basic properties desired for a

particular product. To select one material, the designer specifies three main criteria: its

availability, cost, and the manufacturing process. Giving a weight of approximately 45%

to availability, 35% to cost and 20% to manufacturing process, the designer uses a

systematic analysis to rank these two materials. The table below ranks the three criteria

for the two materials:

Table 4.2: Criteria ranking for the three materials

Criterion Manufacturing process (20%)

Cost (35%)

Availability (45%)

Composite weights

Index Estimates

Material A

0.63 0.42 0.33 0.4215

Material B

0.37 0.58 0.67 0.5785

The problem involves a single hierarchy (level) with three criteria (manufacturing

process, cost, and availability) and two decision alternatives (Material A and material

B). The ranking of each material is based on computing the following composite

weights:

29

Material A=0.2*0.63+0.35*0.42+0.45*0.33=0.4215

Material B=0.2*0.37+0.35*0.58+0.45*0.67=0.5785

Material B has the highest composite weight, and is therefore the best material choice

for the application.

4.2 INFORMATION PROCESSING

4.2.1 Hypertext Pre-Processor (PHP)

PHP is a server-side scripting language. A server- side scripting language allows the

user to embed little programs (scripts) into the HTML of a web page. When executed,

such scripts allow the user to control what will actually appear in the browser window

with more flexibility than is possible using straight HTML. Although to some extent PHP

is similar to JavaScript, the key difference between the two is that JavaScript is

interpreted by the web browser once the web page that contains the script has been

downloaded whereas PHP is interpreted by the web server before the page is sent to the

browser. Once interpreted, the results of the script replace the PHP code in the Web

page so that all the browser sees is a standard HTML file. The script is processed

entirely by the server, hence the designation: server-side scripting language.

Some of the merits of PHP include:

• Access to server-side resources.

• Interpretation of scripts by the Web server thus eliminating browser

compatibility issues.

• Reduced load on client.

• PHP syntax is similar to that of C, C++, Java, or any other C-derived language.

4.2.2 Definitions

The following definitions are commonly associated with PHP:

a) Constant:- This is an identifier (name) for a simple value and does not change

in the execution of the script. Constant identifiers are always in upper case.

b) Expression:- This is anything that has value. The basic forms of expressions are

constants and variables.

c) Operator:- An operator is anything that you feed with one or more values (or

expressions) which yields another value. Examples of operators are unary

operators operating on one value and ternary operator which select between

two expressions depending on a third one.

d) Open database connectivity (ODBC) is an application programming interface

(API) that allows one to connect to data source.

e) A web server is a computer program that delivers (serves) content, such as

web pages, using the Hypertext Transfer Protocol (HTTP) over the World Wide

Web (WWW). The primary function of a web server is to deliver web pages

which are basically HTML documents to clients (i.e. a web browser). A full

implementation of HTTP also includes a way of receiving content from clients.

This feature is used for submitting web forms, including uploading of files. A

30

client initiates communication by making a request for a specific resource using

HTTP and the server responds with the content of that resource, or an error

message if unable to do so.

f) Mysql:- Mysql is a relational database management system (RDBMS) that runs

as a server providing multi-user access to a number of databases. Many web

applications use mysql as a database component. PhpMyadmin, a free web

based protocol widely installed by web hosts worldwide, can connect to

local/remote MySQL servers to manage databases, tables, column structure and

individual data records. MySQL can be built and installed manually from source

code, though it is more commonly installed from binary package - unless

customizations are required.

g) Data base:- This is a collection of data typically describing activities of one or

more related organizations.

h) Data base management system (DBMS):- Software designed to assist in

maintaining and utilizing large collections of data.

i) Variables in PHP are represented by a dollar sign followed by the name of the

variable. It is possible to access Microsoft server from PHP on a windows

machine by simply using ODBC support and the correct ODBC drive. Variables in

PHP are always assigned by value i.e. when you assign an expression to a

variable, the entire value of the original expression is copied into the destination

variable.PHP also allows for the assignment of value to a variable by reference.

This means that the new variable simply references to the original variable.

Changes in the new variable affects the original variable and vice versa.

4.2.3 How php Works

When a client visits a page on a database – driven website, the client’s web browser

requests for the web page using a standard URL. The web server software (Apache)

recognizes that the requested file is a PHP script and so the server interprets the file

using its PHP plug-in before responding to the page request. Certain PHP commands

connect to the MySQL database and requests the content that belongs to the web page.

The MySQL database responds by sending the requested content to the PHP script. The

PHP script stores the content into one or more PHP variables and then uses the “echo”

function to output the content as part of the web page. The web server sends the HTML

to the web browser as it would for a plain HTML file except that instead of coming

directly from an HTML file, the page is the output provided by the PHP plug-in.

31

5 CHAPTER FIVE

CASE STUDY: SELECTION OF A MATERIAL FOR A REVERTED

TWO STAGE COMPOUND GEAR TRAIN

5.1 INTR0DUCTION

Gears are machine elements that transmit motion by means of successively engaging

teeth. This form of transmission is possible because of the rigidity of the material from

which the gear wheels are made. From kinematical point of view, gear wheels may be

assumed to be completely rigid, such that there is no deformation whatsoever when the

gear wheel is subjected to force. Thus the kind of transmission of motion that occurs in

gear drives is known as a positive drive in which there should be no loss of motion at all.

This is as opposed to belt drives, for instance, in which loss of motion may occur due to

creep, slip or both creep and slip of the belt relative to the pulleys.

5.1.1 CLASSIFICATION OF GEARS

Gears are generally classified according to the orientation of the teeth; as follows:

• Spur gears: The teeth are lengthwise parallel to the axis of rotation of the gear

wheel. The overall form of the gear wheel is actually cylindrical.

Fig. 5.1: Spur gears

• Helical gears: Similar to spur gears except that the teeth of a helical gear are

cut at an angle (known as the helix angle) to the axis. Helical gears are made in

both right and left hand configurations.

32

Fig. 5.2: Helical gears

• Bevel gears:The teeth lie upon a cone rather than a right cylinder. Variants of

the bevel gears are the straight bevel, spiral bevel and the hypoid gears.

Fig. 5.3: Straight bevel

Fig. 5.4: Spiral bevel

33

Fig. 5.5: Hypoid bevel

• Worm and worm wheel: A worm is a type of gear with one or more cylindrical

threads or “starts” (that resemble screw threads) and a face that is usually wider

than its diameter. A worm wheel, on the other hand, is a helical gear that meshes

with the worm.

Fig. 5.5: Worm and wheel gears

Gear drives have a number of advantages compared to the other mechanical power

transmission devices such as belt drives and chain drives. The major advantages are the

following:

• They provide a constant speed ratio.

• They don’t exhibit chordal action, as in chain drives.

• They are more compact as compared to belt and chain drives.

• The range of speeds and loads with which gear drives may be used is far broader

than with belt and chain drives.

34

5.1.2 GEARING TERMINOLOGY

Fig. 5.6: Illustration of gearing terminology; Adapted from Boston-Gear

The following defined terms are generally applicable to gears:

Pitch circle is an imaginary circle that corresponds to the circumference of the friction

wheel that corresponds to the gear. The pitch circle of meshing gears roll on each other

without slipping.

Pitch circle diameter (D) is the diameter of the pitch circle of a gear or pinion.

Addendum (a) is the radial distance from the pitch circle to the top of the tooth.

Dedendum (d) is the radial distance from the pitch circle to the bottom of the tooth

space.

Outside diameter (D�) is the diameter of the addendum circle. Thus �� � � � 2

Root diameter (D�) is the diameter of the root circle.5 Thus �� � � 2�

Whole depth (h�) is the total height of the tooth or the total depth of the tooth space.

Thus �� � � �

Working depth (h�) is the distance that a tooth that projects into the mating tooth

space. Thus �� � 2

5 The root circle is also known as the dedendum circle

35

Clearance (c) is the distance between the top of the tooth and the bottom of the mating

tooth space. Thus; � � �

Circular pitch (p) is the distance, along the pitch circle, from a point on one tooth to a

corresponding point on adjacent tooth. Therefore � � ��/�(z is the number of teeth).

Module (m) is the ratio of the pitch circle diameter of a gear wheel to the number of

teeth on the gear wheel. Thus � � �/�. It therefore follows that � � �� and that the

circular pitch and the module are really measures of the same quantity, to different

scales.

Pressure angle or “tooth shape” (Ф) is the angle at which the pressure from the tooth

of one gear is passed on to the tooth of another gear. Spur gears come in two pressure

angles: 14 !"#

and 20⁰.

Diametral pitch (P) is the ratio of the number of teeth on a gear wheel to the pitch

circle diameter of the gear wheel. Thus % � �/� � 1/�

Backlash (B) of a pair of meshing teeth is the amount by which the width of a tooth

space exceeds the thickness of a mating tooth on the pitch circle. A small amount of

backlash is usually desirable, or necessary. But if it is excessive the gears will rattle

under light loads or when running idle.

Face width (b) is the lengthwise width of the teeth in the direction parallel to the axis of

rotation of the gear wheel

Gear ratio (G) is the mathematical ratio of a pair of spur gears determined by dividing

the number of teeth on the larger gear with the number of teeth on the pinion.

5.1.3 DESIGN CONSIDERATIONS FOR A GEAR TRAIN

Prior to the design of a gear train, the following data is usually required:

• The power to be transmitted

• The speed of the driving gear

• The speed of the driven gear or the gear ratio

• The centre distance

Also the following requirements must be met in design of a gear train:

• The gear teeth should have sufficient strength so that they will not fail under

static loading or dynamic loading during normal running conditions.

• The gear teeth should have wear characteristics so that their life is satisfactory.

• The use of space and material should be economical.

• The alignment of the gears and deflections of the shafts must be considered

because of their effect on the performance of gears.

• The lubrication of the gears must be satisfactory.

36

5.1.4 MODES OF GEAR FAILURE

Gear failure occurs as a result of a material having or lacking particular attributes

closely related to its mechanical properties. The following are the various modes of

gear failure common in practice, and possible remedies:

• Bending failure: Every gear tooth acts as a cantilever. If the total dynamic load

acting on the gear tooth is greater than its beam strength, failure due to bending

will occur i.e. the tooth will break. To avoid such failure, the module and face

width is adjusted such that the beam strength is greater than the dynamic load.

• Pitting: It’s surface fatigue failure which occurs due to many repetition of

Hertz 6contact stresses. The failure occurs when the surface contact stresses are

higher than the endurance of the material. It starts with formation of pits which

continue to grow resulting in the rupture of the tooth. To avoid pitting, the

dynamic load must be less than the wear strength of the gear tooth.

• Scoring: Excessive heat is generated when there is an excessive surface

pressure, high speed, or failure of lubrication system. This causes a stick- slip

phenomenon in which shearing and welding takes place rapidly. To avoid

scoring, proper design of parameters such as speed, pressure and proper flow of

the lubricant should be carried out.

• Abrasive wear: Foreign particles in the lubricant such as dirt, dust or burr can

cause loss of material from contacting surfaces of teeth. This type of failure can

be avoided by providing filters for lubricating oil or by using high viscosity oil

which forms a thicker film and permits easy passage of such particles without

damaging the gear surface.

• Corrosive wear: Corrosion of teeth surface is mainly caused due to the presence

of corrosive elements such as additives present in lubricating oils. In order to

avoid this type of wear, proper anti-corrosive additives should be used.

5.2 REVERTED COMPOUND GEAR TRAIN DESIGN

A reverted compound gear train is a type of parallel axis gear train. Gears (Only spur

and bevel gears are used in this case ), in the various stages of speed transformation,

though not being rigidly mounted on a single shaft; do have a common axis of rotation.

In a two stage reverted gear train, the input and the output gears have a common axis of

rotation. They are more compact than non-reverted compound gear trains. Reverted

gear trains find applications in speed reducers, machine tools and automotive

transmissions.

6Contact stress was originally conceived by “Hertz” (1896) in whose name it is often referred.

37

Fig. 5.7: A reverted two stage compound gear train in a manual winch

For the reverted compound gear train, the input and output shafts must be co-axial and

therefore:

C1=C3 (5.1)

Moreover, it is common practice to make meshing gear wheels be of equal face widths.

In that case:

&'( � ')'* � '+, (5.2)

b2 b3

Z2 Z3

C1 C3

Z1

Z4

b1 b4

Fig. 5.8: Schematic of a reverted compound gear train

38

In figure 5.8, the numbers of teeth on the gear wheels are denoted -(, z2, z3 and z4.

Further, the corresponding gear wheel pitch diameters are D1, D2, D3 and D4.

Then the modules of the gear wheels can be determined as follows:

.( � /(-( ; .) � /)-) ; .* � /*-* ; .+ � /+-+ (5.3)

As is well known, the modules of meshing gear wheels must be equal. Therefore:

&.( � .).* � .+0 (5.4)

The intra-stage gear ratios can be determined as follows:

1( � 2)2( � /(/) � -(-) (5.5)

1* � 2+2* � /*/+ � -*-+ (5.6)

Introducing the following notation for normalized face widths, as a matter of

convenience:

'3( � '(.( ; '3* � '*.( (5.7)

5.2.1 THE DESIGN CONSTRAINTS

The design must satisfy all geometrical, kinematical and strength constraints:

5.2.1.1 Geometric Constraints

According to Juvinall (1983), the face width of a gear wheel should lie between 9-14

times its module. This constraint may be expressed mathematically, as follows:

&4 5 '3( 5 (+4 5 '3* 5 (+, (5.8)

Furthermore, according to Juvinall (1983), gear wheels with standard pressure angle of

20⁰ should not have less than 18 teeth. This is the condition for avoiding undercutting

for gear wheels that are produced by a generation process. However, according to

Budynas and Nisbett (2008), the number of teeth on a pinion that will avoid

interference is determined as follows:

39

-6 7 )891:;)<=:3)ф ?( � @( � 91:) � )1:<=:3)фA (5.9)

Where, BC is the speed ratio for a pair of meshing gear wheels, k is a factor that is equal

to 1 for standard full-depth teeth and 0.8 for stub teeth, ф is the pressure angle and DE is

the number of teeth on the pinion. For full-depth teeth, if we make BC=1 /6 and ф=20⁰,

we find that DE≥16.

Mathematically, this constraint may be stated as follows:

&-( 7 (F-* 7 (F, (5.10)

5.2.1.2 Kinematic Constraints

Budynas and Nisbett (2008) recommend that the speed reduction ratio in a single stage

of a compound gear train should not exceed 1:10. Oonishi (1988) recommends limiting

the speed reduction in a single stage as shown in table below.

Table 5.1: Recommended maximum gear ratio in single stage

Type of gear Low speed High speed

Spur 7:1 5:1

Bevel 5:1 3:1

We shall limit the maximum speed reduction in a single stage to be 1: 6. Bearing in mind

that the gear train being designed is a speed reducer, this leads to constraints that may

be stated mathematically as follows:

&1( 7 G. (FI1* 7 G. (FI, (5.11)

The intra-stage gear ratios must take on such values as to obtain the required overall

gear ratio of the train. This constraint may be expressed as follows:

1(1* � 1 (5.12)

40

5.2.1.3 Strength Constraints

The load carrying capacity of any gear drive is limited by the heat of operation, beam

strength of teeth and wear-load capacity of gear materials. In other words, a satisfactory

gear drive must have the ability to dissipate the friction heat of operation, must have

teeth sufficiently strong to carry the dynamic loads without breaking or shearing and

must be made of materials whose surface-endurance properties are adequate to carry

the dynamic loads without excessive wear.

A. Beam Strength

In studying the beam strength of gear teeth, Buckingham modeled the teeth to be

cantilever beams with the most severe condition of loading assumed to be when the full

load acting on the gear wheel is carried at the tip of a single tooth. To reduce impact

between meshing gear teeth, as well as minimize noise, gears are normally designed in

such a way that a pair of teeth begins contact before the previously engaged pair of

teeth end contact. This nature of tooth contact is characterized by the contact ratio,

which is the average number of teeth in contact at any given time. However, when the

requirement of weight and size of gears are not critical, a condition that includes the

great majority of gears used in machine design, it is safer to assume that the load is

carried at the tip of a single gear tooth.

Gear tooth bending stress is given by the Lewis equation7:

J' � KL'6M (5.13)

Where:

• N� is the transmitted force (newtons)

• b is the face width of the gear (mm)

• � is the circular pitch(mm)

• O is known as the tooth form factor or Lewis form factor.

The value of y, in terms of the number of gear teeth is expressed as:

y� G. (P+ G.4()Q ___________ 20⁰ full depth involute profile

y� G. (IP G.S+(Q ___________ 20⁰ stub system

Now, from their definitions, the circular pitch and the module are related as follows:

6 � T. (5.14)

7 In 1892, Wilfred Lewis investigated for the strength of gear teeth. He derived an equation which is now

extensively used by industry in determining the size and proportions of gear.

41

Therefore, from equations (5.13) and (5.14), the following can be readily obtained:

KL � T'.MJ' (5.15)

Now, let us introduce the following notation:

U � TM (5.16)

Then, from equations (5.15) and (5.16) the following can be readily obtained:

KL � '.UJ' (5.17)

Figure 5.9, shows the pitch circles of a pinion and a gear in mesh, along with the forces

and torques acting upon the two gear wheels. V! is the input torque at the pinion shaft

and V" is the load torque acting upon the shaft carrying the driven gear. Therefore:

W( � KL(/() (5.18)

The tangential and radial components are given by:

KL( � K( XYZ Ф ; Fr1 � K( Z[\ Ф (5.19)

F1

F1

T2

D1

T1

Ft1Fr1

Ft1

Ft1

D2

ø

Fig. 5.9: Forces Acting Between Two Meshing Gear Wheels

42

The power input at the pinion shaft is denoted by ]! and can be expressed as follows:

^( � W(2( (5.20)

Let us denote the pitch line velocity of the input pinion by _!. Then we can write the

following: `( � 2(/() (5.21)

From equations (5.18), (5.20) and (5.21), we can write the following:

KL( � ^(`( (5.22)

From equations (5.7), (5.17) and (5.22), we can write the following:

^(`( � '(.(U(J' � '3(.()U(J' (5.23)

Similarly, for the output stage pinion gear, we can write the following:

^(`* � '*.*U*J' � '3*.*)U*J' (5.24)

If we denote the allowable bending stress of the gear material by abc , then we can write

the following: J'd 7 ^('3(.()U(`( (5.25)

Similarly, assuming that all the gear wheels in the train are made of the same material,

we can write the following:

J'd 7 ^('3*.*)U*`* (5.26)

The pitch-line velocities, _! and _e , may be expressed in terms of the input

shaftrotational velocity as follows:

& `( � 2(/() � 2(.( -() `* � 2*.* -*) � 2(1(.* -*)f (5.27)

43

Thus, from equations (5.25), (5.26) and (5.27), we can write the following:

& J'd 7 )^('3(.(*U(2(-(J'd 7 ^('3*1(.**U* 2(-*f (5.28)

B. Wear Strength

The contact conditions between spur-gear-tooth profile are similar to those between

two cylinders – except that on the gear tooth profiles the radius of curvature is

constantly changing. If use is made of the contact and pressure conditions between two

cylinders as measure of the stress on the surface of the gear teeth, it is necessary to first

select some definite part of the gear tooth for use as a basis of comparison.

In many cases, wear on gear teeth first becomes apparent at or near the pitch line.

Possibly one contributing cause for this effects is the fact that one pair of teeth is usually

carrying the entire load. When contact takes place near the top or the bottom of the

active profile, two pairs of mating teeth are usually sharing the load. Again the impact or

dynamic load is usually imposed on the gear near the pitch line area. It is the intensity of

this dynamic load that is largely responsible for the surface fatigue of the gear materials.

Hence the radius of the curvature of the gear tooth profile at the pitch line is selected as

the one to use as a basis of comparison with the Hertz equation (for cylinders).

The Hertz equation was modified to give the expression for the limiting wear load for

gear teeth by Buckingham and was presented by Oonishi as follows

KL � 88g/6'6 h )-i-6;-ij (5.29)

Where:

• k is the contact stress factor (N/mm2) and is given by:

8 � Jk) Z[\ ф(.+ l)mn where Jk8 is the compressive strength of the material.

• kv is the velocity factor. For medium speed, surface finished gears it is given by:

8g � F.(F.(;`6 where `6 is the pitchline velocity of the pinion.

• Dp is the pitch circle diameter of the pinion (mm) in the meshing pair of gears

• bp is the face width of the pinion (mm) in the meshing pair of gears

8For metals Jk is the same as the yield strength

44

• zg, zp are the numbers of teeth of the gear and the pinion, respectively, in the

meshing pair of gears

Adapting this equation to the load on the input stage pinion, we can write the following:

KL( 5 88g/('( l )-)-(;-)n (5.30)

By using equations (5.3), (5.5), (5.22) and (5.30), it follows that:

^(`( 5 88g-(.('( l )1(;(n (5.31)

Similarly, for the output stage pinion, we can write the following:

^(`* 5 88g-*.*'* l )1*;(n (5.32)

From equations (5.7), (5.31) and (5.32), we can write the following:

^(`( 5 88g-(.()'3( l )1(;(n (5.33)

^(`* 5 88g-*.*)'3* l )1*;(n (5.34)

The contact stress for the pinions in the input and output stages can be expressed as:

8 7 ^(91(;(<) `(8g-(.()'3( (5.35)

8 7 ^(91*;(<) `*8g-*.*)'3* (5.36)

Denoting the allowable contact stress factor of the material by 8c , and assuming that

all the gear wheels in the train are made of the same material, it follows that:

&8d 7 ^(91(;(<) `(8g-(.()'3( 8d 7 ^(91*;(<) `*8g-*.*)'3* f (5.37)

45

Thus, from equations (5.27) and (5.37), we can write the following:

& 8d 7 ^(91(;(<8g.(*'3( 2( -()8d 7 ^(91*;(< 8g.**'3* 2( -* ) 1(f (5.38)

46

6 CHAPTER SIX

THE PROCESS OF MATERIAL SELECTION FOR THE REVERTED

COMPOUND GEAR TRAIN

6.1 MATERIAL RANKING INDICES

In ranking of candidate materials for the gear train, the following factors were

considered: availability, material cost and manufacturing cost.

6.1.1 Availability Index

Availability of a material plays an important role in the selection process. In obtaining

the availability index we considered such factors as availability of material in desired

quantity and time frame, and the form in which the material is supplied.

For the purposes of the selection process, indices of 5, 3 and 1 were allocated for the

locally available materials, not readily available materials and locally unavailable

materials respectively.

6.1.2 Material Cost Index

The prices of materials were obtained from local suppliers9 and are tabulated in table

7.110. Since low cost of a material is desirable, the cost index was obtained as follows:

pq=L r3stu � pq=L qv Lwt xtd=L tu6t3=:gt .dLty:dxpq=L qv tdkw .dLty:dx

HSLA Steel was the least expensive material at Kshs 290 and thus it had a cost index of

1.

Example, for UNS S40500 ( 405 Stainless steel) the cost index is:

pq=L r3stu � )4GI+G = 0.39189

6.1.3 Manufacturing Index

Manufacturing index was obtained on basis of hardness. A material with low Brinell

hardness number (BHN) is easier to machine than one with a high BHN. An average

BHN of 60 for Electrolytic tough pitch (ETP) Copper was chosen and given an index of 1,

being considered to have the best machinability. The other materials were then ranked

on this basis.

zd3`vdkL`y:3i r3stu � {^| FG{^| qv tdkw .dLty:dx

9 East African Foundries Ltd, Kensmetal Ltd and other local suppliers in Industrial Area, Nairobi. 10 See appendix.

47

Example, for UNS S40500 ( 405 Stainless steel) the manufacturing index is:

zd3`vdkL`y:3i r3stu � FG()+ � G. +S*SI

Thus the material that can be machined easily will have a higher manufacturing index.

6.1.4 Composite index

The Composite index was obtained by multiplying the availability index by a weight of

0.55, the cost index by weight of 0.35 and manufacturing index by 0.1. Thereafter,

summing was done for the weighted indices of availability, cost of material and

manufacturing cost for individual materials.

Example, for UNS 40500 (405 Stainless steel) the composite index is:

pq.6q=:Lt r3stu � G. PP } P � G. *P } G. *4(S � G. ( } G. +S*SI � ). 4*PPP

Since the idea in all the indices was to maximize the individual index ranking number,

the material with the highest composite index would then be preferred. To achieve this,

all the candidate materials were ranked on the basis of the composite index and then

sorted to get the top fifteen candidate materials. The material with the highest

compound index was selected as the best candidate for the design of a gear train based

on the chosen materials’ selection criteria. The list of the top fifteen candidate materials

based on their composite index is shown in Table 5.3 below:

Table 5.3: List of Top Fifteen Materials Based On their Composite Index

UNS

Number Material Name

Cost

Index

Manufacturing

Index

Availability

Index

Composite

Index

K11576 HSLA Steel 1 0.387096774 5 3.13870968

K02801 A285-C Steel 0.76316 0.555555556 5 3.07266082

K02100 A516-60 Steel 0.76316 0.491803279 5 3.06628559

K02401 A516-60 Steel 0.76316 0.483870968 5 3.06549236

K01800 A515-70 Steel 0.725 0.550458716 5 3.05879587

K02002 A515-55 Steel 0.725 0.508474576 5 3.05459746

K02403 AL516-65 Steel 0.725 0.45112782 5 3.04886278

K02800 A515-60 Steel 0.725 0.45112782 5 3.04886278

K02700 A516-70 Steel 0.725 0.413793103 5 3.04512931

K01800 A516-55 Steel 0.65909 0.491803279 5 3.02986215

C89520 EnviroBrass2 0.28019 0.882352941 5 2.93630293

S40500 405 SS 0.39189 0.483870968 5 2.93554926

S41000 410 SS 0.39189 0.483870968 5 2.93554926

S40900 409 SS 0.31522 0.458015267 5 2.90612761

S44600 446 SS 0.31183 0.416666667 5 2.90080645

48

6.2 SUPPORT INFORMATION

Support Information gives a detailed profile of each candidate material. The data

requirements for support information differ greatly from those for the screening or

ranking step. Typically, it is the non-quantifiable information which is sought. An

example of Support Information is11:

UNS K02002 A515-55 Steel:

• Material Composition: Iron 98%, Carbon 0.2%, Manganese 1.03%, Phosphorous

0.04%, Sulphur 0.05%, Silicon 0.28%, Copper 0.20%.

• Maximum plate thickness is 63.4mm.

• Much stronger and tougher than ordinary carbon steels.

• Ductile with elongation at failure equal to 22% for a 50mm specimen.

• Characterized by good corrosion resistance and high hardness.

• Machinability is characterized by long, gummy chips . It can be machined in the

annealed condition.

• It’s welded by common fusion and resistance methods, but should not be joined

by oxyacetylene welding.

• Available in many forms e.g. plate, round bar, forgings, tubings.

6.3 MATERIALS SELECTION SYSTEM

The selection system consists of a server application (WAMP) and database (Material

Selection). The database stores information on a sample of materials and their

properties. Pertinent database server software is MySQL. The server application

comprises of Apache (server), MySQL and PHP applications on a windows platform

(operating system). Server applications’ purpose include: data retrieval, updating the

database, enabling multiple client support and performing administrative tasks.

11 Adopted from www.matweb.com

49

6.3.1 Database Structure

The database should be structured such that it is easy to retrieve and update

information in it. The database structure used is as shown in the Tables below:

Table Field Type Description

1.Materials Properties

Id int Unique identifier of the

material.

UNS No varchar Holds value of UNS number

Material Name varchar Holds material name

Form varchar Holds material form

Yield Strength int Holds value of yield strength

of the material

Tensile Strength int Holds value of tensile

strength of the material

Density int Holds value of density of the

material

Elastic Modulus int Holds value of elastic

modulus of the material

Hardness int Holds value of hardness of the

material

Availability Index int Holds value of availability

index of the material

Cost Index int Holds value of cost index of

the material

Manufacturing

Index

int Holds value of the

manufacturing index of the

material

Composite Index int Holds the value of composite

index value of the material

2.Login(Administration

login Purpose)

Id int Unique identifier of the table

Username varchar Holds the username for the

administration login.

Password varchar Holds the password for the

administration login.

50

Below is the implemented database using MySql relational database. It shows two tables

for materials properties and login (for administrators’ login details):

The materials properties table is shown below:

51

6.3.2 Material selection system

To start the materials selection system, run the local server (WAMP) on a windows

operating platform. Then, key in the URL address http://localhost/material selection

system/ to display the homepage as shown below:

The homepage has three menu items: select material, material database, and

administration. On the select material menu item, the “spur” link enables the user to

start the process of material selection for the gear train. The material database has links

for viewing and searching the material database. The third item, administration, allows

the user to add to and edit material in the database.

52

Clicking on the “spur” link, a list of locally available materials is displayed. This is done

by screening the material database using availability as the non-discriminating

parameter (if the material is not available it cannot be used and therefore it’s dropped

in the first stage of selection i.e. it’s not displayed).

On selecting the “calculate stresses” option, a page for capturing properties specified by

the user is displayed. This page allows one to input the design specifications for the

gear.

53

The “calculate” button is used to compute the bending and contact stresses as defined

by equations (5.28) and (5.38) respectively. If the user selects the “calculate” button

without filling any fields an error report is displayed highlighting the empty text fields

in the html form as shown below:

Filling the form with gear specifications e.g. data considered for our selection process, it

would appear as below:

54

On selecting the “calculate” button after successfully filling in all the text fields, a new

page loads showing the parameters used in calculating the design stresses and a list of

the qualified materials. The qualified materials are ranked using composite index in a

descending order (starting with the one having the highest composite index to the one

with the least composite index).

This is the second stage in material selection where screening is done using go/no-go

parameters (These are minimum/maximum properties values which candidate

materials must meet). In selecting a candidate material for the gear train, the bending

stress was compared with the materials yield strength (go/no-go parameter) while the

contact stress was compared with the materials contact stress factor (go/no-go

parameter). For any material to qualify it had to meet these two conditions:

• Material yield strength ≥ bending stress(calculated) &

• Material contact stress factor ≥ contact stress(calculated)

From the list of qualified materials above, UNS K11576 HSLA Steel was ranked the

highest with a composite index of 3.1387 while UNS S20910 22-13-5 Stainless Steel was

the lowest ranked with an index of 2.8678.

55

Other than selecting materials, the system has interfaces for viewing and searching the

database. To view materials in the database, click on the “view database” link to retrieve

and display all materials in the database as shown below:

To search for a particular material in the database, click on the “search database” link in

the “material database” menu item and a form for entering the material specifications to

aid in the search is displayed. For example, using density as the search field and

entering a value of 7850Kg/m3 , materials in the database matching this value are

retrieved and displayed.

56

The application also allows the administrator to manage the database by:

• Adding new materials and,

• Editing existing materials in the database

These two tasks require the administrator to log in (Logging in prevents unauthorized

users from altering contents in the database).To add new materials to the database click

on the “add materials” link and after a successful login the form for entering materials

properties value is displayed:

Enter the material properties values and click the save button.

57

To edit materials in the database click on the “edit materials” link and after a successful

login the “Administration Materials View” page is displayed with the “edit” and “delete”

options:

Select “edit” link and the html form to edit materials properties is displayed:

58

The user is required to enter values in all the fields. In case no change is to be effected in

a given field the previous value should be entered. Note that the Id is a unique identifier

of a material; therefore use the previous Id as the new Id for the material when editing:

Click on “save’ button to save the edited material properties in the database.

Finally, to remove any material from the database click on the “delete” link in the

administration materials view.

59

7 CHAPTER SEVEN: CLOSURE

7.1 DISCUSSION

The selection of a material for machine part or structural member is one of the most

important decisions the engineering designer has to make. Poor material choice can

lead to failure of a part or system or to unnecessary cost. The process of materials

selection is difficult one and typically involves multiple conflicting material

characteristics as well as large number of constraints.

A good material selection process considers the limiting factors for a particular design

exercise which include material properties, material processing, material cost and

material availability. The selection of candidate materials for the gear train was done in

two stages; screening of the large material database and ranking of qualified materials.

Screening was done in two steps. In the first step, using availability as the non-

discriminating parameter all locally unavailable materials were eliminated from further

consideration in the selection. The second step used go/no-go parameters as the basis

for screening. In this case, the materials’ yield strength and the contact stress factor

were considered as the go/no-go parameters. Therefore, for any material to qualify it

had to meet these two conditions: material yield strength had to be greater than the

calculated bending stress and the material contact stress factor had to be greater than

the calculated contact stress.

After screening, the second stage involved ranking the qualified materials using

composite index. The composite index for a given material, by using the Analytic

hierarchy process (AHP), was obtained by multiplying the availability index by a weight

of 0.55, the cost index by a weight of 0.35, and the manufacturing index by a weight of

0.1 and thereafter summing the weighted indices12. The material with the highest

composite index was ranked the best by the material selection system.

Different materials scored differently in the different indices (i.e. availability, cost and

manufacturing). No particular material was exclusively favored by all factors. Some

scored high on some indices and poorly on others while others were just fair. For

example, Low Carbon Steels and Low alloy Steels scored highly in the availability index

as well as cost index. On the other hand, Aluminium alloys scored well in the availability

index but poorly in the cost index.

From the list of the five qualified materials, UNS K11576 HSLA Steel was ranked the

highest with a composite index of 3.1387. Considering the first three materials and

eliminating UNS S43600 436 Stainless Steel on the basis that it’s in sheet form and

hence it cannot be used in gear manufacture, the decision on which material to use

12

Weighted index= weight *index.

60

relied on supporting information. The supporting information for the two materials is

given below:

UNS K11576 High Strength Low Alloy Steel

• Material Composition: Fe 95-97%, C (0.1-0.2%), Mn (0.6-1%), P (0.035%), S

(0.04%), Si (0.15-0.35%), Cr (0.4-0.65%), Ni (0.7-1%), Mo (0.4-0.6%), V (0.03-

0.08%), Cu (0.15-0.5%), B (0.002-0.006%).

• Maximum plate thickness is 64 mm.

• Ductile with elongation at failure equal to 18% for a 50mm specimen.

• Much stronger and tougher than ordinary carbon steels.

• Highly resistant to corrosion.

• Available in many forms e.g. bar, plate, tube.

UNS K02002 A515-55 Steel:

• Material Composition: Iron 98%, Carbon 0.2%, Manganese 1.03%, Phosphorous

0.04%, Sulphur 0.05%, Silicon 0.28%, Copper 0.20%.

• Maximum plate thickness is 63.4 mm.

• Much stronger and tougher than ordinary carbon steels.

• Ductile with elongation at failure equal to 22% for a 50mm specimen.

• Characterized by good corrosion resistance and high hardness.

• Available in many forms e.g. plate, round bar, forgings, tubings.

From the supporting information, the two materials had almost similar attributes, and

thus UNS K11576 HSLA Steel was chosen as the best material for the gear train design

because of its higher composite index.

This online material selection system helps the designer perform the rigorous process

of material selection for the gear train by giving accurate information at fast speeds thus

saving time and money during design. However, several challenges were encountered

during the development of this selection system. Among them were lack of easy access

to comprehensive and accurate information on the availability of the different materials

and their local cost.

61

7.2 CONCLUSION

Optimal selection of engineering materials is done in two stages: screening followed by

ranking. The first stage reduces the large material database to a small candidate list

which meets the critical property limits as defined by the design equations. The second

stage involves ranking the candidate materials using composite index. Supporting

information is then sought and used to narrow down the ranked materials to a final

choice allowing a definite match to be made between design requirements and material

attributes.

The selection of a suitable material for the gear train was successfully implemented as

an information processing routine on a computer system. Only data input was required,

the application developed did the data manipulation and output a list of suitable

materials ranked in order of preference. The selection of UNS K11576 HSLA Steel was

therefore not based on past experience but on stepwise selection from first principles,

considering the design problem was new.

7.3 RECOMMENDATIONS

1. Documentation of concise and accurate information on the materials available in

the local market and their costs.

2. Future students to approach a local gear manufacturing industry to test and

check the workability of this materials selection system.

3. Future students to ensure full realization of an online materials selection portal

for all types of gears (bevel, worm and wheel).

4. Future students to develop this application further to incorporate other

engineering designs other than gear design so as to ensure that we have a one-

stop universal materials selection system.

62

7.4 REFERENCES AND APPENDICES

7.4.1 REFERENCES

1. MADARA OGOT and GÜL KREMER, Engineering Design. A Practical

Guide, Trafford Publishing Co., Inc, 2004.

2. RICHARD G. BUDYNAS AND J. KEITH NISBETT, Shigley’s Mechanical Engineering

Design, 8th edition, McGraw Hill, 2008.

3. ODUORI, M.F, Class notes on gears for FME 212 Mechanics of Machines.

4. MICHAEL F. ASHBY, Materials Selection in Mechanical Design, 2nd Edition,

Butterworth-Heinemann, 1999.

5. RADING, G. O, Concise Notes on Materials Science and Engineering, Trafford

Publishing, 2007.

6. WILLIAM D. CALLISTER, DAVID G. RETHWISCH, Materials Science and

Engineering: An Introduction, 7th Edition, John Wiley and Sons, 2007.

7. TAHA, A. H, Operations Research. An introduction, 8th Edition. Prentice Hall of

India Private Ltd, 2008.

8. POPOV, E, Mechanics of Materials, Upper Saddle River Prentice-Hall, 1976.

9. A Metals Handbook, 9th Edition. Vol.3: Properties & Selection: Stainless Steels,

Tool Materials & Special Purpose Metals, American Society Of Manufacturing

Engineers (ASME).

10. Matweb.com, http://www.matweb.com

11. Metals Bank website, http://www.metalsbank.com

12. http://en.wikipedia.org/wiki/Failure_causes

13. Metals Handbook Desk Edition, Second Edition, American Society for Metals (ASM), 1998.

63

7.4.2 APPENDICES

7.4.2.1 Tables

Table 7.1: Local Cost of Materials in Kshs per Kg

UNS Number Material Name Form Cost per kg

K11576 HSLA Steel Bar 290

K02801 A285-C Steel Plate 380

K01800 A515-70 Steel Plate 400

K02100 A516-60 Steel Bar 380

K02401 A516-60 Steel Bar 380

K02002 A515-55 Steel Bar 400

K02403 AL516-65 Steel Plate 400

K02800 A515-60 Steel Plate 400

K01800 A516-55 Steel Plate 440

K02700 A516-70 Steel Bar 400

S40500 405 Stainless Steel Tube 740

S41000 410 Stainless Steel Tube 740

S40900 409 Stainless Steel Plate 920

S44600 446 Stainless Steel Tube 930

S40300 403 Stainless Steel Plate 930

S43600 436 Stainless Steel Sheet 980

S30200 302 Stainless Steel Plate 920

S44200 442 Stainless Steel Plate 940

S34700 347 Stainless Steel Bar 940

S32100 321 Stainless Steel Bar 940

S31725 317LM Stainless Steel Bar 940

S31635 316Ti Stainless Steel Plate 940

S43400 434 Stainless Steel Plate 980

S30500 305 Stainless Steel Plate 1020

S31726 317L4 Stainless Steel Bar 1000

S34800 348 Stainless Steel Plate 1035

S21000 201 Stainless Steel Plate 1090

S20910 22-13-5 Stainless Steel Bar 1150

C89520 EnviroBrass2 Casting 1035

C89510 EnviroBrass1 Casting 1150

C61300 Aluminium Bronze 7% Sheet 1780

C60800 Aluminium Bronze 6% Tube 1670

C61300 Aluminium Bronze 7% Tube 1700

A95154 Aluminium 5154 Tube 2010

C11000 ETP Copper Sheet 2010

C10200 Oxygen free Copper Sheet 2025

64

C89320 - Casting 1610

C12200 DHP Copper Tube 2010

A96061 AL6061 Tube 2070

C14200 DPA Copper Tube 2010

A95086 Aluminium 5086 Tube 2130

A95083 Aluminium 5083 Tube 2130

A96063 Aluminium 6063 Tube 2050

C61400 Aluminium Bronze D Sheet 1700

A92024 Aluminium 2024 Tube 2010

A92014 Aluminium 2014 Tube 2025

A97075 Aluminium 7075 Tube 2540

Table 7.2: Materials Ranking Indices

UNS

Number Material Name

Cost

index

Manufacturing

index

Availability

Index

Composite

Index

K11576 HSLA Steel 1 0.387096774 5 3.13870968

K02801 A285-C Steel 0.7631579 0.555555556 5 3.07266082

K01800 A515-70 Steel 0.725 0.550458716 5 3.05879587

K02100 A516-60 Steel 0.7631579 0.491803279 5 3.06628559

K02401 A516-60 Steel 0.7631579 0.483870968 5 3.06549236

K02002 A515-55 Steel 0.725 0.508474576 5 3.05459746

K02403 AL516-65 Steel 0.725 0.45112782 5 3.04886278

K02800 A515-60 Steel 0.725 0.45112782 5 3.04886278

K01800 A516-55 Steel 0.6590909 0.491803279 5 3.02986215

K02700 A516-70 Steel 0.725 0.413793103 5 3.04512931

S40500 405 SS 0.3918919 0.483870968 5 2.93554926

S41000 410 SS 0.3918919 0.483870968 5 2.93554926

S40900 409 SS 0.3152174 0.458015267 5 2.90612761

S44600 446 SS 0.311828 0.416666667 5 2.90080645

S40300 403 SS 0.311828 0.416666667 5 2.90080645

S43600 436 SS 0.2959184 0.408163265 5 2.89438776

S30200 302 SS 0.3152174 0.387096774 5 2.89903576

S44200 442 SS 0.3085106 0.387096774 5 2.8966884

S34700 347 SS 0.3085106 0.387096774 5 2.8966884

S32100 321 SS 0.3085106 0.387096774 5 2.8966884

S31725 317LM SS 0.3085106 0.387096774 5 2.8966884

S31635 316Ti SS 0.3085106 0.387096774 5 2.8966884

S43400 434 SS 0.2959184 0.382165605 5 2.89178799

S30500 305 SS 0.2843137 0.387096774 5 2.88821948

S31726 317L4 SS 0.29 0.36809816 5 2.88830982

S34800 348 SS 0.2801932 0.375 5 2.88556763

65

S21000 201 SS 0.266055 0.307692308 5 2.8738885

S20910 22-13-5 SS 0.2521739 0.295566502 5 2.86781752

C89520 EnviroBrass2 0.2801932 0.882352941 5 2.93630293

C89510 EnviroBrass1 0.2521739 0.909090909 3 1.82916996

C61300 AL Bronze 7% 0.1629213 0.612244898 3 1.76824696

C60800 AL Bronze 6% 0.1736527 0.75 3 1.78577844

C61300 AL Bronze 7% 0.1705882 0.659340659 3 1.77563995

A95154 AL5154 0.1442786 1.034482759 1 0.70394579

C11000 ETP Copper 0.1442786 1 1 0.70049751

C10200 Oxygen free Cu 0.1432099 0.967741935 1 0.69689765

C89320 - 0.1801242 0.923076923 1 0.70535117

C12200 DHP Copper 0.1442786 0.923076923 1 0.6928052

A96061 AL6061 0.1400966 0.923076923 1 0.69134151

C14200 DPA Copper 0.1442786 0.895522388 1 0.69004975

A95086 AL5086 0.1361502 0.857142857 1 0.68336687

A95083 AL5083 0.1361502 0.779220779 1 0.67557466

A96063 AL6063 0.1414634 0.731707317 1 0.67268293

C61400 AL Bronze D 0.1705882 0.631578947 1 0.67286378

A92024 AL2024 0.1442786 0.5 1 0.65049751

A92014 AL2014 0.1432099 0.444444444 1 0.6445679

A97075 AL7075 0.1141732 0.4 1 0.62996063

Table 7.3: Materials properties

UNS

Number

Yield

Strength

(MPa)

Tensile

Strength

(MPa)

Density

(Kg/m3)

Elastic

Modulus

(GPa)

Hardness

(BHN)

Contact

stress

(MPa)

K11576 690 795 7850 193 155 1.2053

K02801 205 380 7850 200 108 0.10267

K01800 260 485 7850 200 109 0.16515

K02100 220 415 7850 200 122 0.11824

K02401 220 414 7850 200 124 0.11824

K02002 415 550 7850 200 118 0.42075

K02403 240 450 7850 200 133 0.14072

K02800 240 450 7850 200 133 0.14072

K01800 205 380 7850 200 122 0.10267

K02700 290 485 7850 200 145 0.20546

S40500 205 415 7870 170 124 0.12078

S41000 405 415 7870 180 124 0.44524

S40900 240 450 7800 200 131 0.14072

S44600 275 485 7870 200 144 0.18475

S40300 205 485 7870 190 144 0.10807

S43600 365 530 7870 190 147 0.3426

S30200 205 515 7860 193 155 0.10639

66

S44200 275 515 7870 190 155 0.19448

S34700 205 515 8030 190 155 0.10807

S32100 205 515 8030 190 155 0.10807

S31725 205 515 8030 198 155 0.1037

S31635 205 515 7860 193 155 0.10639

S43400 365 530 7800 200 157 0.32547

S30500 240 585 8000 193 155 0.14582

S31726 240 550 8030 198 163 0.14214

S34800 240 620 8000 195 160 0.14432

S21000 260 655 8000 200 195 0.16515

S20910 380 690 8030 200 203 0.35277

C89520 121 176 7890 115 68 0.06221

C89510 119 185 7890 115 66 0.06017

C61300 240 540 7890 115 98 0.24472

C60800 130 345 8170 121 80 0.06824

C61300 193 447 7890 115 91 0.15826

A95154 75 205 2660 70 58 0.03926

C11000 105 250 8890 120 60 0.04489

C10200 180 205 8940 115 62 0.13766

C89320 125 241 7890 115 65 0.06639

C12200 205 250 8940 117 65 0.1755

A96061 145 241 2700 69 65 0.14888

C14200 205 250 8910 115 67 0.17855

A95086 117 262 2660 71 70 0.0942

A95083 110 270 2660 71 77 0.08327

A96063 195 225 2700 69 82 0.26926

C61400 205 485 7890 115 95 0.17855

A92024 290 440 2780 73 120 0.56289

A92014 414 483 1800 73 135 1.14718

A97075 455 530 2810 72 150 1.40489

Table 7.4: Expressions for evaluating the velocity factor for different applications

Application Pitch line

Velocity, g6

Velocity

Factor, 8g

Type of Finish

Low

speed

Cut gear ~E ≤ 5 �� � 3.053.05 � ~E Machining

Medium speed

Surface finished gear

5~10 �� � 6.16.1 � ~E Shaping

Medium speed

Surface finished gear

10 ~ 20 �� � 1515 � ~E Machined and ground

67

Fig. 7.1: Chart for obtaining the modified Lewis form factor (Y)

68

7.4.2.2 THE CODE

A. Code of the Index page

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"

"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">

<head>

<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />

<title>Materials Selection</title>

<link href="css/styles.css" rel="stylesheet" type="text/css" />

<style type="text/css">

<!--

.style1 {font-size: 36px; color:#FFFFFF;}

.style4 {font-size: 36px; color: #000000; }

-->

</style>

</head>

<body>

<body bgcolor="#CC0000" background="vlcsnap-2012-03-21-11h06m27s26.png">

<div id="container">

<div id="topPan">

<div id="title" class="style1" align="center">

<h4>MATERIALS SELECTION SYSTEM </h4>

</div>

</div>

<div id="content">

<table width="639" height="50" border="0" style="background-color:#C6C6FF" align="center";

border:solid 4px #990000;-moz-opacity:0.75;opacity:1.75;filter:alpha(opacity=75);" >

<tr>

<td>

<div id="menu">

<ul>

<li>

<h2>Select Material</h2>

Reverted Compound Gear Train </h2>

<ul>

<li><a href="availablematerials.php">Spur</a>

</li>

<li><a href="">Helical</a></li>

</li>

</ul>

</li>

</ul>

<ul>

<li>

<h2> Material Database</h2>

<ul>

<li><a href="MaterialsProperties.php"> View Database </a>

69

</li>

<li><a href="SearchMaterial.php"> Search Database </a>

</li>

</ul>

</li>

</ul>

<ul>

<li>

<h2> Administration</h2>

<ul>

<li><a href="login.php">Add Materials</a></li>

<li><a href="login2.php">Edit Materials</a>

</li>

</ul>

</li>

</ul>

</div>

</td>

</tr>

<tr>

</tr>

<tr>

</tr>

</table>

</div>

</div>

</body>

</html>

B. Code to connect to the database

<?php

$DbConn = mysql_connect("localhost","projectmech","wazito");

$Db = mysql_select_db("materialsselection",

$DbConn);

if(!$Db)

{

echo "Connection to DB was not successful";

}

else

{

}

?>

70

C. Code to display locally available materials

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"

"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">

<head>

<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />

<title>Materials Properties</title> <link href="css/styles.css" rel="stylesheet" type="text/css"

/>

<style type="text/css">

<!--

.style1 {font-size: 36px; color:#FFFFFF;}

.style4 {font-size: 36px; color: #000000;} -->

</style>

</head>

<body><body bgcolor="#CC0000" background="vlcsnap-2012-03-21-11h06m27s26.png">

<div id="container">

<div id="topPan">

<div id="title" class="style1" align="center"> <h4>

<a href="index.php" >

<img name="" src="images/2.png" width="33" height="20" alt="" />

</a> MATERIALS SELECTION SYSTEM </li>

<li> Locally Available Materials</a>

</div>

</div>

<div id="content">

<table width="100%" height="100%" border="0" align="center"style="background-

color:#C6C6FF";

border:solid 4px #990000;-moz-opacity:1;opacity:1;

filter:alpha(opacity=75);" >

<thead>

<tr>

<td colspan="8" align="center">

<a href="GetProperties.php"><strong>CLICK HERE TO CALCULATE STRESSES</strong></a>

<?php

include 'DB.php';

$get_details="select * from materialproperties WHERE AvailabilityIndex > '1'";

$get_details_res=mysql_query($get_details) or die(mysql_error());

if (mysql_num_rows($get_details_res)<1)

{

//print message

$display_block = "<p>There are no details for material properties in the database try checking

later.</p>";

}

else

71

{

// get info and build display table

$display_block ="

<table cellpadding=3 cellspacing=2 border=1 width=98% font=medium> <tr>

<td >

<strong>Id</strong> </td> <td>

<strong>UNS Number </strong></td> <td>

<strong>Material Name</strong> </td> <td>

<strong>Form</strong></td> <td>

<strong>Yield Strength</strong></td> <td>

<strong>Tensile Strength</strong></td> <td>

<strong>Density</strong></td> <td>

<strong>Elastic Modulus</strong></td> <td>

<strong>Hardness</strong></td> <td>

<strong>Availability index</strong></td> <td>

<strong>Cost index</strong></td> <td>

<strong>Manufacturing index</strong></td> <td>

<strong>Composite index</strong></td>

</tr>";

while($info=mysql_fetch_array($get_details_res))

{

$id=$info['Id'];

$UNSNo=$info['UNSNo'];

$matN=$info['MaterialName'];

$Form=$info['FormId'];

$Yst=$info['YieldStrength'];

$Tst=$info['TensileStrength'];

$ava=$info['AvailabilityIndex'];

$cost=$info['CostIndex'];

$manu=$info['ManufacturingIndex'];

$compo=$info['CompositeIndex'];

$elas=$info['ElasticModulus'];

$had=$info['Hardness'];

$de=$info['Density'];

$display_block.="<tr>

<td align=centre>$id<br></td>

<td align=centre>$UNSNo<br></td>

<td align=centre>$matN<br></td>

<td align=centre>$Form<br></td>

<td align=centre>$Yst<br></td>

<td align=centre>$Tst<br></td>

<td align=centre>$de</td>

<td align=centre>$elas</td>

<td align=centre>$had</td>

<td align=centre>$ava</td>

<td align=centre>$cost</td>

<td align=centre>$manu</td>

72

<td align=centre>$compo</td>

</tr>";

}

$display_block.="</table>";

}

print "$display_block";

?>

</td>

</thead>

</table>

<div id="searchreport">

</tr>

<tr>

</tr>

</thead>

</table>

</div>

</div>

</body>

</html>

D. Code to enter gear specifications

<?php include 'DB.php';?>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"

"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">

<head>

<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />

<title>Materials Properties</title> <link href="css/styles.css" rel="stylesheet" type="text/css"

/>

<script language="javascript" type="text/javascript" src="xmlhttprequest.js"> </script>

<script language="javascript" type="text/javascript" src="functions.js"> </script>

<script type="text/javascript" > function validateGetProperties

{

var reduction1 = document.getElementById('reduction1').value;

var reduction2 = document.getElementById('reduction2').value;

var speed = document.getElementById('speed').value;

var putpower = document.getElementById('power').value;

var teethpinion = document.getElementById('teethpinion').value;

var facewidth = document.getElementById('facewidth').value;

var length = document.getElementById('length').value;

var Error = "The following field(s) need to be attended to.\n";

var ErrorCounter = 0;

if( putpower == '') { Error += '-Please enter the Input power.\n'; ErrorCounter +=1; }

if( speed == '') { Error += '-Please enter the Input speed.\n'; ErrorCounter +=1; }

if( teethpinion == ''){ Error += '-Please enter the number of teeth in pinion.\n';

ErrorCounter +=1; }

73

if( reduction1 == '') { Error += '-Please enter the reduction 1.\n'; ErrorCounter +=1; }

if( reduction2 == '') { Error += '-Please enter the reduction 2.\n'; ErrorCounter +=1; }

if( length == '') { Error += '-Please enter the module.\n'; ErrorCounter +=1; }

if( facewidth == '') { Error += '-Please enter the Normalized facewidth.\n'; ErrorCounter +=1; }

if (ErrorCounter !=0)

{

alert(Error); return false;

}return true;

}

</script> <style type="text/css">

<!--

.style1 {font-size: 36px; color:#FFFFFF;}

.style4 {font-size: 36px; color: #000000; }

->

</style>

</head>

<body><body bgcolor="#CC0000" background="vlcsnap-2012-03-21-11h06m27s26.png">

<div id="container">

<div id="topPan">

<div id="title" class="style1" align="center">

<h4><a href="index.php" ><img name="" src="images/2.png" width="31" height="22" alt="" />

</a>MATERIALS SELECTION SYSTEM </h4> </div>

</div> <div id="content">

<table width="800" height="315" border="0" align="center"style="background-

color:#C6C6FF";border:solid4px #990000;-moz-

opacity:0.5;opacity:0.5;filter:alpha(opacity=75);"

<formid="GetProperties"name="GetProperties"method="POST"action="getbestMaterials.php"

onsubmit="return validateGetProperties()">

<thead>

<tr>

<td colspan="2">

<strong>CALCULATE BENDING AND CONTACT STRESSES</strong>

</td>

</tr>

</thead>

<tbody >

<tr>

<td>Input Power </td>

<td><input type="text" name="power" id="power" /> kW</td>

</tr>

<tr>

<td>Input Speed</td>

<td><label> <input type="text" name="speed" id="speed" /> rpm</label></td>

</tr>

<tr>

<td>Number of teeth Pinion</td>

<td><label> <input type="text" name="teethpinion" id="teethpinion" /> </label>

74

</td>

</tr>

<td width="185" >Gear Ratio </td>

<td width="399" >

<label>

<input type="text" name="reduction1" id="reduction1" size="10"/> : <input type="text"

name="reduction2" id="reduction2" size="10"/>

</label></td>

<tr>

tr> <tr>

<td>Module </td>

<td><label><input type="text" name="length" id="length"/> mm</label></td>

</tr>

<tr>

<td>Normalized Face Width </td>

<td>

<label><input type="text" name="facewidth" id="facewidth"/></label> </td>

</tr>

<tr>

<td>Preference </td>

<td> <select name="preference" id="preference"> <option value="0">All</option>

</select>

</td>

</tr> <tr> <td colspan="2" align="center">

<label>

<input type="submit" name="Submit" id="Submit" value="Calculate" />

</label></td>

</tr>

</tbody>

</form>

</table>

</div>

</div>

</body>

</html>

E. Code to calculate design stresses and display qualified materials

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"

"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">

<head> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />

<title>Get best materials</title>

<link href="css/styles.css" rel="stylesheet" type="text/css" />

<script type="text/javascript" >

</script>

<style type="text/css"> <!--

.style1 {font-size: 36px; color:#FFFFFF;}

75

.style4 {font-size: 36px; color: #000000; }

-->

</style>

</head>

<body><bodybgcolor="#CC0000"background="vlcsnap-2012-03-21 11h06m27s26.png">

<div id="container">

<div id="topPan">

<div id="title" class="style1" align="center">

<h4> <a href="index.php" >

<img name="" src="images/2.png" width="33" height="26" alt="" /></a>MATERIALS

SELECTION SYSTEM </h4> </div>

</div>

<div id="content">

<table width="100%" height="320" border="0" align="center style="background-

color:#C6C6FF":solid4px #990000;-moz-opacity:0.75;opacity:0.75;filter:alpha(opacity=75);" >

<tr>

<td>

<table width="647" border="1" >

<?php include 'DB.php';

?>

<?php

if(count($_POST))

{

$g1 = $_POST['reduction1'];

$g2 = $_POST['reduction2'];

$N = $_POST['speed'];

$h = $_POST['power'];

$b = $_POST['facewidth'];

$z = $_POST['teethpinion'];

$m = $_POST['length'];

if(count($_POST))

{

if (!$g1 | !$g2 | !$N | !$h | !$b | !$z | !$m)

{

echo "Ensure all fields are filled and try!.";

}

else

{

$g3 = $g1 / $g2; //gear ratio

$y = (0.154 - (0.912 / $z));

//start the expression for modified form Factor

$Y = (3.142 * $y);

$M = ($m * $m * $m / 1000000000);

//start the expression for Facewidth

$fw = $b * $m ;

//start conversion of speed from rpm into rads/sec

$w = (($N *2*3.142) / 60);

76

//start main formula

$D = ($b*$g3*$M*$Y*$w*$z); // Denominator of the formula

//real formula

$YIELD = $h*1000 / $D;

//for convenience, we divide the value above by 1000000 to match what we recorded in the

database.

$MATCHEDYIELD = $YIELD/1000000;

//echo "$MATCHEDYIELD";

//start calculating for contact stress

//we start by finding (velocity factor)kv needed in the formula

//denominator for kv is

$Dkv = (12.2 + ($w * $z * 0.001*$m));

//velocity factor(kv) is then given as

$kv = (12.2 / $Dkv);

//this will soon be needed

$g4 = ($g3 + 1);

//we will need the value of z as a square

$z2 = ($z*$z);

//now we embark on getting the value of the contact stress ka

//the numerator is given as

$Nka = ($h * $g4*1000);

// The denominator for ka is

$Dka = ($kv*$M*$b*$w*$z2);

//the contact stress is given as

$ka = ($Nka / $Dka);

//divide by 1000000 for consistency with the database

$Mka = ($ka / 1000000);

//work out some formula needed for selection of materials

//check in the database for values that meet this condition

$res = "SELECT * FROM materialproperties WHERE YieldStrength >='$MATCHEDYIELD' AND

ContactStress >='$Mka' AND AvailabilityIndex > '1' ORDER BY CompositeIndex DESC";

$result = mysql_query($res) or die(mysql_error());

}

?>

<tr>PARAMETERS USED</tr>

<tr><td align="center">Bending Stress(MPa)</td><td align="center">Contact Stress(MPa)

</td><td align="center"> Modified Formfactor(Y)</td><td align="center">Velocity

Factor(Kv)</td><td align="center">Gear Ratio (G)</td><td align="center"> Face width(mm)

</td><td align="center">Module(mm)</td><td align="center">Speed(rads/s)</td><td

align="center">Power(kW)</td></tr>

<tr><td align="center"><?php echo "$MATCHEDYIELD"; ?> </td><td align="center"><?php

echo "$Mka"; ?></td><td align="center"><?php echo "$Y"; ?></td><td align="center"><?php

echo "$kv"; ?></td><td align="center"><?php echo "$g3"; ?></td><td align="center"><?php

echo "$fw"; ?></td><td align="center"><?php echo "$m"; ?></td><td align="center"><?php

echo "$w"; ?></td><td align="center"><?php echo "$h"; ?></td></tr>

77

</table>

</td> </tr> <tr>

<td>

<table>

<div id="searchreport">

<thead>

<td>

<?php

if (mysql_num_rows($result)<1)

{

//print message

$display_block = "<p>No results were found for your search.</p>";

}

else

{

// get info and build display table

$display_block ="

<table cellpadding=3 cellspacing=2 border=1 width=98%>

<tr>QUALIFIED MATERIALS</tr>

<tr>

<td>

<strong>Id</strong> </td> <td>

<strong>UNS Number</strong> </td> <td>

<strong>Material Name </strong></td> <td>

<strong>Form</strong></td> <td>

<strong>Yield Strength</strong></td> <td>

<strong>Tensile Strength</strong></td> <td>

<strong>Density</strong></td> <td>

<strong>Elastic Modulus</strong></td> <td>

<strong>Hardness</strong></td> <td>

<strong>Availability index</strong></td> <td>

<strong>Cost index</strong></td> <td>

<strong>Manufacturing index</strong></td> <td>

<strong>Composite index</strong></td>

</tr>";

while($info=mysql_fetch_array($result))

{

$id=$info['Id'];

$UNSNo=$info['UNSNo'];

$matN=$info['MaterialName'];

$Form=$info['FormId'];

$Yst=$info['YieldStrength'];

$Tst=$info['TensileStrength'];

$ava=$info['AvailabilityIndex'];

$cost=$info['CostIndex'];

$manu=$info['ManufacturingIndex'];

$compo=$info['CompositeIndex'];

78

$elas=$info['ElasticModulus'];

$had=$info['Hardness'];

$de=$info['Density'];

$display_block.="<tr>

<td align=centre>$id<br></td>

<td align=centre>$UNSNo<br></td>

<td align=centre>$matN<br></td>

<td align=centre>$Form<br></td>

<td align=centre>$Yst<br></td>

<td align=centre>$Tst<br></td>

<td align=centre>$de</td>

<td align=centre>$elas</td>

<td align=centre>$had</td>

<td align=centre>$ava</td>

<td align=centre>$cost</td>

<td align=centre>$manu</td>

<td align=centre>$compo</td>

</tr>";

}

$display_block.="</table>";

}

print "$display_block";

}

}

?>

</tbody>

</table>

</td>

</tr>

</table>

</div>

</div>

</body>

</html>

F. Code to view the material database

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"

"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">

<head>

<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />

<title>Materials Properties</title> <link href="css/styles.css" rel="stylesheet" type="text/css"

/>

<style type="text/css">

<!--

.style1 {font-size: 36px; color:#FFFFFF;}

79

.style4 {font-size: 36px; color: #000000; }

-->

</style>

</head>

<body><body bgcolor="#CC0000" background="vlcsnap-2012-03-21-11h06m27s26.png">

<div id="container">

<div id="topPan">

<div id="title" class="style1" align="center"> <h4>

<a href="index.php" >

<img name="" src="images/2.png" width="33" height="20" alt="" />

</a>MATERIALS SELECTION SYSTEM </h4>

</div>

</div>

<div id="content">

<table width="100%" height="100%" border="0" align="center"style="background-

color:#C6C6FF";

border:solid 4px #990000;-moz-opacity:1;opacity:1;

filter:alpha(opacity=75);" >

<thead>

<tr>

<td colspan="8" align="center">

<strong>MATERIALS PROPERTIES </strong>

<?php

include 'DB.php';

$get_details="select * from materialproperties";

$get_details_res=mysql_query($get_details) or die(mysql_error());

if (mysql_num_rows($get_details_res)<1)

{

//print message

$display_block = "<p>There are no details for material properties in the database try checking

later.</p>";

}

else

{

// get info and build display table

$display_block ="<table cellpadding=3 cellspacing=2 border=1 width=98% font=medium>

<tr>

<td >

<strong>Id</strong> </td> <td>

<strong>UNS Number </strong></td> <td>

<strong>Material Name</strong> </td> <td>

<strong>Form</strong></td> <td>

<strong>Yield Strength</strong></td> <td>

<strong>Tensile Strength</strong></td> <td>

<strong>Density</strong></td> <td>

<strong>Elastic Modulus</strong></td> <td>

<strong>Hardness</strong></td> <td>

80

<strong>Availability index</strong></td> <td>

<strong>Cost index</strong></td> <td>

<strong>Manufacturing index</strong></td> <td>

<strong>Composite index</strong></td>

</tr>";

while($info=mysql_fetch_array($get_details_res))

{

$id=$info['Id'];

$UNSNo=$info['UNSNo'];

$matN=$info['MaterialName'];

$Form=$info['FormId'];

$Yst=$info['YieldStrength'];

$Tst=$info['TensileStrength'];

$ava=$info['AvailabilityIndex'];

$cost=$info['CostIndex'];

$manu=$info['ManufacturingIndex'];

$compo=$info['CompositeIndex'];

$elas=$info['ElasticModulus'];

$had=$info['Hardness'];

$de=$info['Density'];

$display_block.="<tr>

<td align=centre>$id<br></td>

<td align=centre>$UNSNo<br></td>

<td align=centre>$matN<br></td>

<td align=centre>$Form<br></td>

<td align=centre>$Yst<br></td>

<td align=centre>$Tst<br></td>

<td align=centre>$de</td>

<td align=centre>$elas</td>

<td align=centre>$had</td>

<td align=centre>$ava</td>

<td align=centre>$cost</td>

<td align=centre>$manu</td>

<td align=centre>$compo</td>

</tr>";

}

$display_block.="</table>";

}

print "$display_block";

?>

</td>

</thead>

</table>

<div id="searchreport">

</tr>

<tr>

81

</tr>

</thead>

</table>

</div>

</div>

</body>

</html>

G. Code to search materials

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"

"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">

<head> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />

<title>search for materials</title>

<link href="css/styles.css" rel="stylesheet" type="text/css" />

<script type="text/javascript" >

</script>

<style type="text/css"> <!--

.style1 {font-size: 36px; color:#FFFFFF;}

.style4 {font-size: 36px; color: #000000; }

-->

</style>

</head>

<body><body bgcolor="#CC0000" background="vlcsnap-2012-03-21-11h06m27s26.png">

<div id="container">

<div id="topPan">

<div id="title" class="style1" align="center">

<h4> <a href="index.php" >

<img name="" src="images/2.png" width="33" height="26" alt="" /></a>MATERIALS

SELECTION SYSTEM </h4> </div>

</div>

<div id="content">

<table width="100%" height="320" border="0" align="center"style="background-

color:#C6C6FF"; border:solid 4px #990000;-moz-

opacity:0.75;opacity:0.75;filter:alpha(opacity=75);" >

<tr>

<td>

<table width="647" >

<?php include 'DB.php';

?>

<form id="searchMaterials" name="searchMaterials" method="POST"

action="SearchMaterial.php">

<tr>

<td colspan="4"><strong>SEARCH MATERIALS DATABASE </strong>

</td> </tr>

<tr>

82

<td width="136" >UNS Number</td>

<td width="181" ><input type="text" name="UNSNo" id="UNSNo" />

</td>

<td width="143" >Yield Strength</td>

<td width="167" ><label> <input type="text" name="ystrength" id="ystrength" />

</label></td>

</tr> <tr>

<td>Material Name </td>

<td><input type="text" name="material" id="material" /></td>

<td>Tensile Strength </td>

<td><label>

<input type="text" name="tstrength" id="tstrength" />

</label></td>

</tr>

<tr>

<td>Form</td>

<td><label>

<input type="text" name="formId" id="formId" />

</label></td>

<td>Density</td>

<td>

<input type="text" name="density" id="density" /></td>

</tr>

<tr>

<td>Elastic Modulus </td>

<td><input type="text" name="elastic" id="elastic"/></td>

<td>Hardness</td>

<td><label> <input type="text" name="hardness" id="hardness"/> </label>

</td>

</tr>

<tr>

<td>&nbsp;</td>

<td>&nbsp;</td>

<td><input type="submit" name="Submit" id="Submit" value="Search" /></td>

<td><label></label></td>

</tr> <tr>

<td colspan="4" align="center"><label></label></td>

</tr> </form> </table>

</td> </tr> <tr>

<td>

<table>

<div id="searchreport">

<?php

if(count($_POST))

{

$UNSNo = $_POST['UNSNo'];

$material = $_POST['material'];

83

$formId = $_POST['formId'];

$ystrength = $_POST['ystrength'];

$tstrength = $_POST['tstrength'];

$density = $_POST['density'];

$hardness = $_POST['hardness'];

$elastic = $_POST['elastic']; }

$search_parts="";

$Sql="";

$counter =0;

$res = "SELECT * FROM materialproperties";

if(count($_POST))

{

if ($UNSNo !='')

{

if ($counter==0)

{

$search_parts=" WHERE UNSNo LIKE '%$UNSNo%'";

}

else

{

$search_parts.=" AND UNSNo LIKE '%$UNSNo%'";

}

$counter ++;

}

if

($material !='')

{

if ($counter==0)

{

$search_parts=" WHERE MaterialName LIKE '%$material%'";

}

else { $search_parts.=" AND MaterialName LIKE '%$material%'";

}

$counter ++; }

if ($formId !='')

{

if ($counter==0)

{

$search_parts=" WHERE FormId LIKE '%$formId%'";

}

else

{ $search_parts.=" AND FormId LIKE '%$formId%'";

}

$counter ++;

}

if ($ystrength !='')

{

84

if ($counter==0)

{

$search_parts=" WHERE YieldStrength LIKE '%$ystrength%'";

}

else

{

$search_parts.=" AND YieldStrength LIKE '%$ystrength%'";

}

$counter ++;

}

if ($tstrength !='')

{

if ($counter==0)

{

$search_parts=" WHERE TensileStrength LIKE '%$tstrength%'";

}

else

{

$search_parts.=" AND TensileStrength LIKE '%$tstrength%'";

} $counter ++; } if ($density !='')

{

if ($counter==0)

{

$search_parts=" WHERE Density LIKE '%$density%'";

}

else

{

$search_parts.=" AND Density LIKE '%$density%'";

}

$counter ++;

}

if ($hardness !='')

{

if ($counter==0)

{

$search_parts=" WHERE Hardness LIKE '%$hardness%'"; }

else

{

$search_parts.=" AND Hardness LIKE '%$hardness%'";

}

$counter ++;

}

if ($elastic !='')

{

if ($counter==0)

{

$search_parts=" WHERE ElasticModulus LIKE '%$elastic%'";

85

}

else

{

$search_parts=" AND ElasticModulus LIKE '%$elastic%'";

}

$counter ++;

}

$search_order="ORDER BY CompositeIndex DESC";

$Sql= $res."".$search_parts."".$search_order;

}

else

{

$Sql=$res;

}

$result = mysql_query($Sql) or die(mysql_error());

//Execute the SQL query

?>

<thead>

<td>

<?php

if (mysql_num_rows($result)<1)

{

//print message

$display_block = "<p>No results were found for your search.</p>";

}

else

{

// get info and build display table

$display_block ="

<table cellpadding=3 cellspacing=2 border=1 width=98%>

<tr>

<td>

<strong>Id</strong> </td> <td>

<strong>UNS Number</strong> </td> <td>

<strong>Material Name </strong></td> <td>

<strong>Form</strong></td> <td>

<strong>Yield Strength</strong></td> <td>

<strong>Tensile Strength</strong></td> <td>

<strong>Density</strong></td> <td>

<strong>Elastic Modulus</strong></td> <td>

<strong>Hardness</strong></td> <td>

<strong>Availability index</strong></td> <td>

<strong>Cost index</strong></td> <td>

<strong>manufacturing index</strong></td> <td>

86

<strong>Composite index</strong></td>

</tr>";

while($info=mysql_fetch_array($result))

{

$id=$info['Id'];

$UNSNo=$info['UNSNo'];

$matN=$info['MaterialName'];

$Form=$info['FormId'];

$Yst=$info['YieldStrength'];

$Tst=$info['TensileStrength'];

$ava=$info['AvailabilityIndex'];

$cost=$info['CostIndex'];

$manu=$info['ManufacturingIndex'];

$compo=$info['CompositeIndex'];

$elas=$info['ElasticModulus'];

$had=$info['Hardness'];

$de=$info['Density'];

$display_block.="<tr>

<td align=centre>$id<br></td>

<td align=centre>$UNSNo<br></td>

<td align=centre>$matN<br></td>

<td align=centre>$Form<br></td>

<td align=centre>$Yst<br></td>

<td align=centre>$Tst<br></td>

<td align=centre>$de</td>

<td align=centre>$elas</td>

<td align=centre>$had</td>

<td align=centre>$ava</td>

<td align=centre>$cost</td>

<td align=centre>$manu</td>

<td align=centre>$compo</td>

</tr>";

}

$display_block.="</table>";

}

print "$display_block";

?>

</tbody>

</table>

</td>

</tr>

</table>

</div>

87

</div>

</body>

</html>

H. Code for login1 to Add materials properties

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"

"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">

<head> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />

<title>login-addmaterials</title>

<link href="css/styles.css" rel="stylesheet" type="text/css" />

<script type="text/javascript" >

</script>

<style type="text/css">

<!--

.style1 {font-size: 36px; color:#FFFFFF;}

.style4 {font-size: 36px; color: #000000; }

-->

</style>

</head>

<body><body bgcolor="#CC0000" background="vlcsnap-2012-03-21-11h06m27s26.png">

<div id="container">

<div id="topPan">

<div id="title" class="style1" align="center">

<h4> <a href="index.php" >

<img name="" src="images/2.png" width="33" height="26" alt="" /></a>MATERIALS

SELECTION SYSTEM LOGIN FORM </h4> </div>

</div>

<div id="content">

<table width="100%" height="320" border="1" align="center"style="background-

color:#C6C6FF"; border:solid 4px #990000;-moz-

opacity:0.75;opacity:0.75;filter:alpha(opacity=75);" >

<tr>

<td>

<table width="647" >

<tr><tr><p>Hi, to add materials, you must be logged in. fill the form below</p></td></tr>

<?php include 'DB.php';

?>

<form method="POST" action="engineer.php"><table border="1" align="center" ><tr>

<td><span class="style5"><label for="email"><strong>Username</strong></

</span><input type="text" name="username" id="search-text" size="30" /></td> <td><span

class="style5">

<label><strong>Password</strong></label></span>

<input type="password" name="password" id="password"/></td><td>

<input type="submit" id="search-submit" value="login" /></td></tr></table>

</form></table></td> </tr>

<tr>

88

<td>

<table>

<div id="searchreport">

<thead>

<td>

</tbody>

</table>

</td>

</tr>

</table>

</div>

</div>

</body>

</html>

I. Code for login 2( Editing materials)

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"

"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">

<head> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />

<title>login-remove_materials</title>

<link href="css/styles.css" rel="stylesheet" type="text/css" />

<script type="text/javascript" >

</script>

<style type="text/css"> <!--

.style1 {font-size: 36px; color:#FFFFFF;}

.style4 {font-size: 36px; color: #000000; }

-->

</style>

</head>

<body><body bgcolor="#CC0000" background="vlcsnap-2012-03-21-11h06m27s26.png">

<div id="container">

<div id="topPan"> <div id="title" class="style1" align="center">

<h4> <a href="index.php" >

<img name="" src="images/2.png" width="33" height="26" alt="" /></a>MATERIALS

SELECTION SYSTEM LOGIN FORM </h4> </div>

</div>

<div id="content">

<table width="100%" height="320" border="1" align="center"style="background-

color:#C6C6FF";border:solid4px#990000;-moz-

opacity:0.75;opacity:0.75;filter:alpha(opacity=75);" >

<tr>

<td>

<table width="647" >

<tr><tr><p>Hi, to add materials, you must be logged in. fill the form below</p></td></tr>

<?php include 'DB.php';

?>

89

<form method="POST" action="engineer2.php"><table border="1" align="center" ><tr>

<td><span class="style5"> <label for="email"><strong>Username</strong></label>

</span><input type="text" name="username" id="search-text" size="30" /></td>

<td><span class="style5">

<label><strong>Password</strong></label></span><input type="password"

name="password" id="password"/></td><td>

<input type="submit" id="search-submit" value="login" /></td></tr></table>

</form></table></td> </tr>

<tr>

<td>

<table>

<div id="searchreport">

<thead>

<td>

</tbody>

</table>

</td>

</tr>

</table>

</div>

J. Code to link the login 1 with the database

<?php

//ensure that all fields have been filled

include 'DB.php';

if($_POST['username']!="" | $_POST['password']!="")

{

$username = $_POST['username'];

$password = $_POST['password'];

$querytrylogin = "select * from login where username = '$username' And password =

'password' ";

$resultlogin = mysql_query($querytrylogin) or

die ( mysql_error() );

$row = mysql_fetch_row($resultlogin);

if(isset($row[0]))

{

header ("location: AddMaterials.php");

exit;

}

else

{

die('Wrong username or password');

exit;

}

}

else

90

{

die('Wrong username or password');

}

?>

K. Code to link the login2 with the database

<?php

//ensure that all fields have been filled

include 'DB.php';

if($_POST['username']!="" | $_POST['password']!="")

{

$username = $_POST['username'];

$password = $_POST['password'];

$querytrylogin = "select * from login where username = '$username' And password =

'$password' ";

$resultlogin = mysql_query($querytrylogin) or

die ( mysql_error() );

$row = mysql_fetch_row($resultlogin);

if(isset($row[0]))

{

header ("location: AddMaterials.php");

exit;

}

else

{

die('Wrong username or password');

exit;

}

}

else

{

die('Wrong username or password');

}

?>

L. Code to add materials in the database

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"

"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type"

content="text/html; charset=iso-8859-1" />

<title>Adding Materials</title>

<link href="css/styles.css" rel="stylesheet" type="text/css" />

<script type="text/javascript" > function validateAddProperties()

{

var UNSNo = document.getElementById('UNSNo').value;

var material = document.getElementById('material').value;

var formId = document.getElementById('formId').value;

91

var ystrength = document.getElementById('ystrength').value;

var tstrength = document.getElementById('tstrength').value;

var density = document.getElementById('density').value;

var hardness = document.getElementById('hardness').value;

var elastic = document.getElementById('elastic').value;

var Error = "The following field(s) need to be attended to.\n";

var ErrorCounter = 0;

if( UNSNo == '')

{

Error += '-Please enter the UNSNo number.\n'; ErrorCounter +=1;

}

if( material == '')

{

Error += '-Please enter the material name.\n'; ErrorCounter +=1;

}

if( formId == '') { Error += '-the form field is empty.\n'; ErrorCounter +=1;

}

if( ystrength == '') { Error += '-the yield strength field is empty.\n'; ErrorCounter +=1;

}

if( tstrength == '') { Error += '-the tensile strength field is empty.\n'; ErrorCounter +=1;

}

if( density == '') { Error += '-the density field is empty.\n'; ErrorCounter +=1;

}

if( hardness == '') { Error += '-the hardness field is empty.\n'; ErrorCounter +=1;

}

if( elastic == '') { Error += '-elasticity field is empty.\n'; ErrorCounter +=1;

}

if (ErrorCounter !=0)

{

alert(Error); return false;

}

return true;

} </script> <style type="text/css">

<!--

.style1 {font-size: 36px; color:#FFFFFF;}

.style4 {font-size: 36px; color: #000000; }

-->

</style>

</head>

<body bgcolor="#CC0000" background="vlcsnap-2012-03-21-11h06m27s26.png">

<div id="container">

<div id="topPan">

<div id="title" class="style1" align="center">

<h4> <a href="index.php" >

<img name="" src="images/2.png" width="33" height="26" alt="" />

92

</a>MATERIALS SELECTION SYSTEM </h4>

</div>

</div>

<div id="content">

<table width="639" height="315" border="0" align="center"style="background-

color:#C6C6FF";border:solid 4px #990000;-moz-

opacity:0.75;opacity:0.75;filter:alpha(opacity=75);" >

<?php include 'DB.php';

?>

<form id="AddMaterials"

name="AddMaterials"

method="POST"

action="Save.php" onsubmit="return validateAddProperties()">

<tr>

<td colspan="2">

<strong>ADD MATERIALS PROPERTIES</strong>

</td>

</tr>

<tr>

<td width="185" >UNS Number</td>

<td width="399" ><label>

<input type="text" name="UNSNo" id="UNSNo" />

</label></td>

</tr>

<tr>

<td>Material Name </td>

<td>

<label><input type="text" name="material" id="material" /></label>

</td>

</tr>

<tr>

<td>Form</td>

<td>

<select name="formId" id="formId">

<option> Please Select </option>

<option> Plate </option>

<option> Sheet </option>

<option> Tube </option>

<option> casting </option>

<option> Bar </option>

<option> ANN </option>

</select>

</td>

</tr>

<tr>

<td>Yield Strength(MPa) </td>

<td>

93

<label> <input type="text" name="ystrength" id="ystrength" />

</label>

</td>

</tr>

<tr>

<td>Tensile Strength(MPa) </td>

<td><label> <input type="text" name="tstrength" id="tstrength" />

</label></td>

</tr>

<tr>

<td>Density (Kg/M^3)</td>

<td><label> <input type="text" name="density" id="density" /> </label>

</td>

</tr>

<tr>

<td>Young's Modulus(GPa) </td>

<td><label> <input type="text" name="elastic" id="elastic"/> </label>

</td>

</tr>

<tr>

<td>Hardness</td>

<td><label>

<input type="text" name="hardness" id="hardness"/> </label></td>

</tr>

</tr>

<tr>

<td>Availability index</td>

<td><label>

<input type="text" name="availabilityindex" id="availabilityindex"/> </label></td>

</tr>

</tr>

<tr>

<td>Cost index</td>

<td><label>

<input type="text" name="costindex" id="costindex"/> </label></td>

</tr>

</tr>

<tr>

<td>Manufacturing index</td>

<td><label>

<input type="text" name="manufacturingindex" id="Manufacturingindex"/>

</label></td>

</tr>

</tr>

<tr>

<td>Composite index</td>

<td><label>

94

<input type="text" name="compositeindex" id="Compositeindex"/> </label></td>

</tr>

<tr>

<td colspan="2" align="center"><label>

<input type="submit" name="Submit" id="Submit" value="Save" /> </label></td>

</tr>

<tr>

<td colspan="2" align=centre><a href="adminMaterialsProperties.php">Edit

materials</a></td>

</tr>

</form>

</table>

</div>

</div>

</body>

</html>

M. Code to save materials in the database

<title>Save materials to db</title><?php

include 'DB.php';

$UNSNo = $_POST['UNSNo'];

$material = $_POST['material'];

$formId = $_POST['formId'];

$ystrength = $_POST['ystrength'];

$tstrength = $_POST['tstrength'];

$density = $_POST['density'];

$hardness = $_POST['hardness'];

$elastic = $_POST['elastic'];

$availability = $_POST['availabilityindex'];

$cost = $_POST['costindex'];

$manufacturing = $_POST['manufacturingindex'];

$composite = $_POST['compositeindex'];

//calculate for allowable contact stress

$Yst2 = ($ystrength*$ystrength);

$allowableka = 0.0004886 *$Yst2 / $elastic;

$sql= mysql_query("INSERT INTO

materialproperties(UNSNo,MaterialName,FormId,YieldStrength,TensileStrength,Density,Elastic

Modulus,Hardness,AvailabilityIndex,CostIndex,ManufacturingIndex,CompositeIndex,ContactStr

ess)

VALUES('$UNSNo','$material','$formId','$ystrength','$tstrength','$density','$elastic','$hardness',

'$availability','$cost','$manufacturing','$composite','$allowableka')")

or die(mysql_error());

if(!$sql) {

echo "error in saving";

95

}

else

{

echo "Material details were successfully saved in the database";

}

?>

N. Code to Administrations’ materials view

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"

"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">

<head>

<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />

<title>Admin for Materials Properties</title> <link href="css/styles.css" rel="stylesheet"

type="text/css" />

<style type="text/css">

<!--

.style1 {font-size: 36px; color:#FFFFFF;}

.style4 {font-size: 36px; color: #000000; } -->

</style>

</head>

<body><body bgcolor="#CC0000" background="vlcsnap-2012-03-21-11h06m27s26.png">

<div id="container">

<div id="topPan">

<div id="title" class="style1" align="center"> <h4>

<a href="index.php" >

<img name="" src="images/2.png" width="33" height="20" alt="" />

</a>MATERIALS SELECTION SYSTEM </h4>

</div>

</div>

<div id="content">

<table width="100%" height="100%" border="0" align="center"style="background-

color:#C6C6FF;

border:solid 4px #990000;-moz-opacity:1;opacity:1;

filter:alpha(opacity=75);" >

<thead>

<tr>

<td colspan="8" align="center">

<strong>ADMIN'S MATERIALS VIEW </strong>

<?php

include 'DB.php';

$get_details="select * from materialproperties";

$get_details_res=mysql_query($get_details) or die(mysql_error());

if (mysql_num_rows($get_details_res)<1)

{

//print message

96

$display_block = "<p>There are no details for material properties in the database try checking

later.</p>";

}

else

{

// get info and build display table

$display_block ="

<table cellpadding=3 cellspacing=2 border=1 width=98%>

<tr>

<td>

<strong>Id</strong> </td> <td>

<strong>UNS Number</strong> </td> <td>

<strong>Material Name </strong></td> <td>

<strong>Form</strong></td> <td>

<strong>Yield Strength</strong></td> <td>

<strong>Tensile Strength</strong></td> <td>

<strong>Density</strong></td> <td>

<strong>Elastic Modulus</strong></td> <td>

<strong>Hardness</strong></td> <td>

<strong>Availability index</strong></td> <td>

<strong>Cost index</strong></td> <td>

<strong>Manufacturing index</strong></td> <td>

<strong>Composite index</strong></td> <td>

<strong>Edit</strong></td> <td>

<strong>Remove</strong></td>

</tr>";

while($info=mysql_fetch_array($get_details_res))

{

$id=$info['Id'];

$UNSNo=$info['UNSNo'];

$matN=$info['MaterialName'];

$Form=$info['FormId'];

$Yst=$info['YieldStrength'];

$Tst=$info['TensileStrength'];

$ava=$info['AvailabilityIndex'];

$cost=$info['CostIndex'];

$manu=$info['ManufacturingIndex'];

$compo=$info['CompositeIndex'];

$elas=$info['ElasticModulus'];

$had=$info['Hardness'];

$de=$info['Density'];

$display_block.="<tr>

<td align=centre>$id<br></td>

<td align=centre>$UNSNo<br></td>

<td align=centre>$matN<br></td>

97

<td align=centre>$Form<br></td>

<td align=centre>$Yst<br></td>

<td align=centre>$Tst<br></td>

<td align=centre>$de</td>

<td align=centre>$elas</td>

<td align=centre>$had</td>

<td align=centre>$ava</td>

<td align=centre>$cost</td>

<td align=centre>$manu</td>

<td align=centre>$compo</td>

<td align=centre><a href=\"edit_material.php?id=$id\">Edit</a></td>

<td align=centre><a href=\"remove_material.php?id=$id\">Delete</a></td>

</tr>";

}

$display_block.="</table>";

}

print "$display_block";

?>

</td>

</tr>

<tr>

</tr>

</thead>

</table>

</div>

</div>

</body>

</html>

O. Code to edit materials in the database

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"

"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type"

content="text/html; charset=iso-8859-1" />

<title>Edit db Materials</title>

<link href="css/styles.css" rel="stylesheet" type="text/css" />

<script type="text/javascript" > function validateAddProperties()

{

var UNSNo = document.getElementById('UNSNo').value;

var material = document.getElementById('material').value;

var formId = document.getElementById('formId').value;

var ystrength = document.getElementById('ystrength').value;

var tstrength = document.getElementById('tstrength').value;

var density = document.getElementById('density').value;

var hardness = document.getElementById('hardness').value;

var elastic = document.getElementById('elastic').value;

98

var Error = "The following field(s) need to be attended to.\n";

var ErrorCounter = 0;

if( UNSNo == '')

{

Error += '-Please enter the UNSNo number.\n'; ErrorCounter +=1;

}

if( material == '')

{

Error += '-Please enter the material name.\n'; ErrorCounter +=1;

}

if( formId == '') { Error += '-the form field is empty.\n'; ErrorCounter +=1;

}

if( ystrength == '') { Error += '-the yield strength field is empty.\n'; ErrorCounter +=1;

}

if( tstrength == '') { Error += '-the tensile strength field is empty.\n'; ErrorCounter +=1;

}

if( density == '') { Error += '-the density field is empty.\n'; ErrorCounter +=1;

}

if( hardness == '')

{ Error += '-the hardness field is empty.\n'; ErrorCounter +=1;

}

if( elastic == '') { Error += '-elasticity field is empty.\n'; ErrorCounter +=1;

}

if (ErrorCounter !=0)

{

alert(Error); return false;

}

return true;

} </script> <style type="text/css">

<!--

.style1 {font-size: 36px; color:#FFFFFF;}

.style4 {font-size: 36px; color: #000000; } -->

</style>

</head>

<body bgcolor="#CC0000" background="vlcsnap-2012-03-21-11h06m27s26.png">

<div id="container">

<div id="topPan">

<div id="title" class="style1" align="center">

<h4> <a href="index.php" >

<img name="" src="images/2.png" width="33" height="26" alt="" />

</a>MATERIALS SELECTION SYSTEM </h4>

</div>

</div>

<div id="content">

99

<table width="639" height="315" border="1" align="center"style="background-

color:#C6C6FF"; border:solid 4px #990000;-moz-

opacity:0.75;opacity:0.75;filter:alpha(opacity=75);" >

<?php

include 'DB.php';

if($_GET['id']!="")

{

$select_row ="select * from materialproperties where Id=$_GET[id]";

$rows=mysql_query($select_row) or die(mysql_error());

if (mysql_num_rows($rows)<1)

{

echo "No items were selected for editing";

}

else

{

while($info=mysql_fetch_array($rows))

{

$id=$info['Id'];

$UNSNo=$info['UNSNo'];

$matN=$info['MaterialName'];

$Form=$info['FormId'];

$Yst=$info['YieldStrength'];

$Tst=$info['TensileStrength'];

$ava=$info['AvailabilityIndex'];

$cost=$info['CostIndex'];

$manu=$info['ManufacturingIndex'];

$compo=$info['CompositeIndex'];

$elas=$info['ElasticModulus'];

$had=$info['Hardness'];

$de=$info['Density'];

}

}

?>

<form id="AddMaterials"

name="AddMaterials"

method="POST"

action="Save2.php" onsubmit="return validateAddProperties()">

<tr> <td colspan="2">

<strong>EDIT MATERIAL PROPERTIES FOR ID (<?php echo $id; ?>) IN THE

DATABASE</strong>

</td><td>Previous values</td>

</tr>

<tr>

<td width="185" >Id</td> <td width="399" ><label><input type="text" name="Id" id="newId"

/>(Use default Id)<td>

<?php

100

echo $id; ?></td></label></td> </tr>

<tr>

<td width="185" >UNS Number</td>

<td width="399" ><label>

<input type="text" name="UNSNo" id="UNSNo" /> </label></td>

<td><?php echo $UNSNo; ?></td></tr>

<tr>

<td>Material Name </td> <td>

<label><input type="text" name="material" id="material" />

</label>

</td> <td><?php echo $matN; ?></td>

</tr>

<tr>

<td>Form</td>

<td>

<select name="formId" id="formId">

<option> Please Select </option>

<option> Plate </option>

<option> Sheet </option>

<option> Tube </option>

<option> casting </option>

<option> Bar </option>

<option> ANN </option>

</select>

</td> <td><?php echo $Form; ?></td>

</tr>

<tr>

<td>Yield Strength(MPa) </td>

<td>

<label> <input type="text" name="ystrength" id="ystrength" />

</label>

</td><td><?php echo $Yst; ?></td>

</tr>

<tr>

<td>Tensile Strength(MPa) </td>

<td><label> <input type="text" name="tstrength" id="tstrength" />

</label></td><td><?php echo $Tst; ?></td>

</tr>

<tr>

<td>Density (Kg/M^3)</td>

<td><label> <input type="text" name="density" id="density" /> </label>

</td><td><?php echo $de; ?></td>

</tr>

<tr>

<td>Young's Modulus(GPa) </td>

<td><label> <input type="text" name="elastic" id="elastic"/> </label>

</td><td><?php echo $elas; ?></td>

101

</tr>

<tr>

<td>Hardness</td>

<td><label>

<input type="text" name="hardness" id="hardness"/> </label></td> <td><?php echo

$had; ?></td>

</tr>

</tr>

<tr>

<td>Availability index</td>

<td><label>

<input type="text" name="availabilityindex" id="availabilityindex"/>

</label></td><td><?php echo $ava; ?></td>

</tr>

</tr>

<tr>

<td>Cost index</td>

<td><label

<input type="text" name="costindex" id="costindex"/> </label></td>

<td><?php echo $cost; ?></td>

</tr>

</tr>

<tr>

<td>Manufacturing index</td>

<td><label>

<input type="text" name="manufacturingindex" id="Manufacturingindex"/>

</label></td><td><?php echo $manu; ?></td>

</tr>

</tr>

<tr>

<td>Composite index</td>

<td><label>

<input type="text" name="compositeindex" id="Compositeindex"/>

</label></td><td><?php echo $compo; ?></td>

</tr>

<tr>

<td colspan="2" align="center"><label>

<input type="submit" name="Submit" id="Submit" value="Save" /> </label></td>

<td colspan="2"><label>

<a href="adminMaterialsProperties.php">Back</label></td>

</tr>

<tr>

<td colspan="2" align=centre>Use previous values if no change is to be made.</td>

</tr>

</form>

<?php } ?>

</table>

102

</div>

</div>

</body>

</html>

P. Code to save edited materials

<title>Save materials to db</title>

<?php

include 'DB.php';

$id = $_POST['Id'];

$UNSNo = $_POST['UNSNo'];

$material = $_POST['material'];

$formId = $_POST['formId'];

$ystrength = $_POST['ystrength'];

$tstrength = $_POST['tstrength'];

$density = $_POST['density'];

$hardness = $_POST['hardness'];

$elastic = $_POST['elastic'];

$availability = $_POST['availabilityindex'];

$cost = $_POST['costindex'];

$manufacturing = $_POST['manufacturingindex'];

$composite = $_POST['compositeindex'];

//calculate for allowable contact stress

$Yst2 = ($ystrength*$ystrength);

$allowableka = 0.0004886 *$Yst2 / $elastic;

//Density=$density,ElasticModulus=$elastic,Hardness=$hardness,AvailabilityIndex=$availabilit

y,CostIndex=$cost,ManufacturingIndex=$manufacturing,

//CompositeIndex=$composite,ContactStress=$allowableka

// WHERE Id=$id;

//

$sql=mysql_query("REPLACE INTO materialproperties

(Id,UNSNo,MaterialName,FormId,YieldStrength,TensileStrength,Density,ElasticModulus,Hardne

ss,AvailabilityIndex,CostIndex,ManufacturingIndex,CompositeIndex,

ContactStress)

VALUES('$id','$UNSNo','$material','$formId','$ystrength','$tstrength','$density','$elastic','$hardn

ess','$availability','$cost','$manufacturing','$composite','$allowableka')")

or die(mysql_error());

if(!$sql) {

echo "error in saving";

}

else

{

echo " properties for the row selected were updated in the database.";

}

?>

103

Q. Code to delete materials in database

<?php

include 'DB.php';

if($_GET['id']!="")

{

$delete_item="delete from materialproperties where Id=$_GET[id]";

mysql_query($delete_item) or die(mysql_error());

header("location: adminMaterialsProperties.php");

exit;

}

else

{

header("location: login.php");

exit;

}

?>

R. Code for cascading style sheet

/* CSS Document */

body{padding:0px; margin:0px; background:#31DDCC 0 0 repeat-x; color:#000033

font:10px/14px Trebuchet MS, sans-serif;}

#container{width:100%; margin:0 auto; position:relative; border-right-color:#660000; border-

bottom-color:#660000; border-left-color:#660000; outline-color:#000099;}

#incontent{width:632px; position:relative;}

#content{width:100%; height:100%; position:relative; background:url(../images/gear7.jpg); }

#heading{width:678px; position:relative; clear:both; height:50px; background:#FEE7EB;

background-image:url(../images/transbg.gif); 0 0 no-repeat}

#title{width:632px; position:relative; margin:0 auto}

.button a{font:10px/14px Tahoma, sans-serif; color:#FFFFFF; text-decoration :underline; }

#topPan{width:100%; position:relative; clear:both; height:80px}

#logo{position:absolute; top:107px; right:29px}

/*menu*/

#menu {

width: 100%;

background: #eee;

float: left;

}

#menu ul {

list-style: none;

margin: 0;

padding: 0;

width: 12em;

float: left;

}

#menu a, #menu h2 {

104

font: bold 11px/16px arial, helvetica, sans-serif;

display: block;

border-width: 1px;

border-style: solid;

border-color: #ccc #888 #555 #bbb;

margin: 0;

padding: 2px 3px;

}

#menu h2 {

color: #fff;

background: #000;

text-transform: uppercase;

}

#menu a {

color: #000;

background: #efefef;

text-decoration: none;

}

#menu a:hover {

color: #a00;

background: #fff;

}

#menu li {position: relative;}

#menu ul ul ul {

position: absolute;

top: 0;

left: 100%;

}

#menu ul ul {

position: absolute;

z-index: 500;

}

div#menu ul ul {

display: none;

}

div#menu ul li:hover ul

{display: block;}

div#menu ul ul,

div#menu ul li:hover ul ul,

div#menu ul ul li:hover ul ul

{display: none;}

div#menu ul li:hover ul,

div#menu ul ul li:hover ul,

div#menu ul ul ul li:hover ul

{display: block;}