materials selection aspects(2005) - fkm.utm.myfkm.utm.my/~ourdjini/materials_selection_aspects.pdf · MATERIALS SELECTION Faculty of Mechanical Engineering Ali Ourdjini, UTM -2005

MATERIALS SELECTION

Ali Ourdjini, UTM - 2005Faculty of Mechanical Engineering

MATERIALS SELECTION


Chapter One

Introduction

MATERIALS SELECTION


IIntroductionntroduction

�� Materials selection is an important part of a larger process of Materials selection is an important part of a larger process of creating creating

new solutions to problems. This larger process is called new solutions to problems. This larger process is called ““Engineering Engineering

DesignDesign””

�� Design of engineering components is limited by the available Design of engineering components is limited by the available

materials, and new designs are made possible by new materialsmaterials, and new designs are made possible by new materials

�� To see how important is the material selection in the design, coTo see how important is the material selection in the design, consider nsider

the definition of the definition of ““engineeringengineering”” used by ABET in the U.S.Aused by ABET in the U.S.A

MATERIALS SELECTION


”Engineering is the profession in which knowledge Engineering is the profession in which knowledge

of the mathematical and natural sciences gained of the mathematical and natural sciences gained

by study, experience, and practice is applied with by study, experience, and practice is applied with

judgement to develop ways to utilise, judgement to develop ways to utilise,

economically, the economically, the materialsmaterials and forces of nature and forces of nature

for the benefit of mankindfor the benefit of mankind”

MATERIALS SELECTION


Issues includeIssues include

�� PropertiesProperties

�� Physical & MechanicalPhysical & Mechanical

�� Manufacturing Manufacturing

considerationsconsiderations

�� CastabilityCastability / formability/ formability

�� MachinabilityMachinability / / CoatabilityCoatability

�� Heat treatment / Heat treatment / WeldabilityWeldability

�� Failure & Failure & repairabilityrepairability

�� Cost analysisCost analysis

�� AvailabilityAvailability

�� Materials life & Materials life & maintenancemaintenance

�� Environmental issuesEnvironmental issues

�� Ergonomic & safety Ergonomic & safety

�� RecyclingRecycling

FFactors actors IInfluencing nfluencing MMaterials aterials SSelectionelection

MATERIALS SELECTION


1.1. When the product is new (never produced before), the decision toWhen the product is new (never produced before), the decision toselect a new material is obviousselect a new material is obvious

2.2. With existing products (Material Substitution), selecting a newWith existing products (Material Substitution), selecting a new material material is due to the following:is due to the following:

�� Reduce material costReduce material cost

�� Reduce production costReduce production cost

�� Accommodate some changes in functionAccommodate some changes in function

�� Solve some material processing problemsSolve some material processing problems

�� Take advantage of new materials or processing methodsTake advantage of new materials or processing methods

�� Incorporate failure analysis recommendationsIncorporate failure analysis recommendations

WWhyhy do we need to select a new do we need to select a new MMaterial ?aterial ?

MATERIALS SELECTION


Engineering Engineering

MaterialsMaterials

Ceramics

Composites

Metals

Polymers

Natural Mats

SteelCu alloys

Al alloys

Cast AlloysCast Alloys

Wrought AlloysWrought Alloys

2000 series2000 series






WWhich hich MMaterial ?aterial ?

?

?

?

?

MATERIALS SELECTION


WWhyhy do we need do we need MMaterial aterial SSelection?election?

�� Mechanical design creates Mechanical design creates

products to meet products to meet functional functional

needsneeds

�� The design process is limited by The design process is limited by

materials capabilitiesmaterials capabilities

�� The type of material affects:The type of material affects:

�� Processing methodProcessing method

�� Shape attained (available)Shape attained (available)

MaterialsMaterials

Attributes: Physical Attributes: Physical Mechanical, Economic, Mechanical, Economic, Thermal, Electrical, Thermal, Electrical, EnvironmentalEnvironmental

Function

Shape

Process

Casting

Extrusion

Sheet

3-D

MATERIALS SELECTION


Source: A. F. Ashby, “Materials

Selection in Mechanical Design”

MATERIALS SELECTION


� Engineering design is the process of devising a system, component,

or process to meet desired needs

�� The design process consists of several steps, each has certain The design process consists of several steps, each has certain

characteristics and certain tasks to be performed:characteristics and certain tasks to be performed:

�� RecongnisingRecongnising a need (problem)a need (problem)

�� Defining the problemDefining the problem

�� Establishing specificationsEstablishing specifications

�� Gathering informationGathering information

TThehe DDesignesign PProcessrocess

MATERIALS SELECTION


�� Generating concept solutionsGenerating concept solutions

Material selectionMaterial selection usually occurs at this stageusually occurs at this stage

�� Analysis and optimisationAnalysis and optimisation

Preliminary layout of designPreliminary layout of design

Detail designDetail design

�� EvaluationEvaluation

�� Presenting resultsPresenting results

�� Approval and release for manufacturingApproval and release for manufacturing

TThehe DDesignesign PProcessrocess

MATERIALS SELECTION


1.1. Original DesignOriginal Design

�� New idea (from scratch)New idea (from scratch)

2.2. Development DesignDevelopment Design

�� Improvements of existing productImprovements of existing product

�� Cars, consumer products (mobile phones, cameras etcCars, consumer products (mobile phones, cameras etc……))

3.3. Variant DesignVariant Design

�� Change in scale or dimensions without changing the functionChange in scale or dimensions without changing the function

�� e.g; desktop PC to laptop computere.g; desktop PC to laptop computer

TTypesypes ofof DDesignesign

MATERIALS SELECTION


Materials EngineeringMaterials EngineeringMechanical EngineeringMechanical Engineering

Increasing detailsIncreasing detailsIncreasing complexityIncreasing complexity

Source: M. F. Ashby, “Materials

Selection in Mechanical Design”

MATERIALS SELECTION


ALL MATERIALSALL MATERIALS SHORT LIST SHORT LIST SPECIFIC SPECIFIC

MATERIALSMATERIALS

ROUGH DATAROUGH DATA ACCURATE DATAACCURATE DATA

METALS, METALS, CERAMICS, CERAMICS, POLYMERS, POLYMERS,

COMPOSITESCOMPOSITES

STEEL, STEEL, ALUMINIUM, ALUMINIUM, TITANIUM, TITANIUM,

COPPERCOPPER

Cast Al alloy 356 Cast Al alloy 356

T6 conditionT6 condition

MATERIALS DATA IN THE DESIGN PROCESSMATERIALS DATA IN THE DESIGN PROCESS

MATERIALS SELECTION


1.1. The clarification of the need involves analysing and clearly The clarification of the need involves analysing and clearly

stating the problemstating the problem

The designer collects and writes down all:The designer collects and writes down all:

�� RequirementsRequirements

�� ConstraintsConstraints

�� The standards to be adhered toThe standards to be adhered to

�� The projected date of completion of the designThe projected date of completion of the design

2.2. The objective of the The objective of the conceptual designconceptual design is to generate possible is to generate possible

solutions, methods to solve the problemsolutions, methods to solve the problem

All ideas are accepted and evaluated according to their meritsAll ideas are accepted and evaluated according to their merits

MATERIALS SELECTION


•• In this stage, all information and previous knowledge are put toIn this stage, all information and previous knowledge are put together gether so that a proper decision can be madeso that a proper decision can be made

•• Information and knowledge include:Information and knowledge include:

�� Engineering science principlesEngineering science principles

�� Previous experiencesPrevious experiences

�� Production methodsProduction methods

�� CostsCosts

•• The output of this stage should be The output of this stage should be two or three solutionstwo or three solutions that have the that have the greatest chance of achieving the desired objectivegreatest chance of achieving the desired objective

MATERIALS SELECTION


3. 3. Embodiment design embodies and evaluate the two or three Embodiment design embodies and evaluate the two or three conceptual solutions selected in greater detail and makes a finaconceptual solutions selected in greater detail and makes a final l choicechoice

•• The output of this stage should be drawings, specifications and The output of this stage should be drawings, specifications and compliance to the needs of specifications of the productcompliance to the needs of specifications of the product

4. The 4. The detail designdetail design stage considers all the large number of small but stage considers all the large number of small but important details to manufacture the productimportant details to manufacture the product

• The work done at this stage must be of very high quality, otherwise delays, higher costs and failure may occur

•• The output of this stage is a set of:The output of this stage is a set of:

�� Very detailed drawings andVery detailed drawings and

�� Final specifications including: Final specifications including: tolerance, precision, joining methods, finishingtolerance, precision, joining methods, finishing

MATERIALS SELECTION


• When selecting materials, current engineering designers choose to

meet three general criteria:

1. Property profile

� Mechanical properties factor

� Life of component factors

2. Processing profile

� Physical factors

� Processing factors

� Cost / availability

3. Environment

� Codes, statutory and other factors

MATERIALS SELECTION


•• The selection of the material is done with all 3 criteria considThe selection of the material is done with all 3 criteria considered at the ered at the

same time with the same time with the PERFORMANCE & COSTPERFORMANCE & COST as the most important as the most important

factorfactor

1. Properties profile1. Properties profile

•• Material selection based on properties profile is the process ofMaterial selection based on properties profile is the process of

matching matching the numerical valuesthe numerical values of the of the properties of the materialproperties of the material to the to the

requirements and constraintsrequirements and constraints

2. Processing profile:2. Processing profile:

• Material selection based on processing profile is aimed at identifying

the process that will form the material into the desired final shape

including joining and finishing at the minimum cost

MATERIALS SELECTION


3. Environmental profile:3. Environmental profile:

•• Relates to the impact of the material (its manufacture, use, reuRelates to the impact of the material (its manufacture, use, reuse and se and

disposal) on the environment. This added constraint increases thdisposal) on the environment. This added constraint increases the cost e cost

of the productof the product

•• Designing for the environment is an excellent philosophy becauseDesigning for the environment is an excellent philosophy because it it

can be a good marketing tool to environment conscious customerscan be a good marketing tool to environment conscious customers

•• Assessment of the impact of materials on the environment is doneAssessment of the impact of materials on the environment is done by by

several approaches. The most popular is the several approaches. The most popular is the ““lifelife--cycle analysiscycle analysis”” or or

““LCALCA””

MATERIALS SELECTION


•• Selecting a Selecting a materialmaterial is a difficult task due to: is a difficult task due to:

1. Large number of materials available

2. Large number of processes available

3. Complex relationship between selection parameters

� The problem of material selection is further made difficult by:

1. Insufficient and inaccurate property data

2. Multiple constraints

MATERIALS SELECTION


•• To realise the full potential of a new material the product mustTo realise the full potential of a new material the product must be be

redesigned to exploit both the redesigned to exploit both the propertiesproperties and the and the manufacturing manufacturing

characteristicscharacteristics of the material.of the material.

•• The essence of materials selection process isThe essence of materials selection process is notnot that one material that one material

compete against another, rather, it is that thecompete against another, rather, it is that the processes associated with processes associated with

the production or fabrication of one material compete with the the production or fabrication of one material compete with the

processes associated with the other. processes associated with the other.

MATERIALS SELECTION


•• Several quantitative selection procedures have been developed toSeveral quantitative selection procedures have been developed to

analyse the large amount of data in the selection processanalyse the large amount of data in the selection process

•• No single correct solution: Material selection requiresNo single correct solution: Material selection requires

1.1. Consideration of conflicting advantages & limitationsConsideration of conflicting advantages & limitations

2.2. Compromise and tradeCompromise and trade--offoff

•• Similar parts which perform similar functions are produced by diSimilar parts which perform similar functions are produced by different fferent

manufacturers, from different materials and different manufacturmanufacturers, from different materials and different manufacturing ing

processesprocesses

MATERIALS SELECTION


Initial Screening of Materials (new product)Initial Screening of Materials (new product)

•• Answer questions on the nature of product, its function etc. Answer questions on the nature of product, its function etc.

•• Need to specify Performance RequirementsNeed to specify Performance Requirements

•• Outline Materials Performance and Processing RequirementsOutline Materials Performance and Processing Requirements

•• Certain materials will be eliminated and other short become candCertain materials will be eliminated and other short become candidatesidates

1.1. Analysis of Materials Performance RequirementsAnalysis of Materials Performance Requirements

�� Can be divided into five categories:Can be divided into five categories:

1.1. Functional Requirements (Materials Properties)Functional Requirements (Materials Properties)

2.2. ProcessabilityProcessability RequirementsRequirements

MATERIALS SELECTION


3.3. Cost & AvailabilityCost & Availability

4.4. ReliabilityReliability

5.5. Resistance to Service Conditions (environment)Resistance to Service Conditions (environment)

2. Classification of Materials Requirements2. Classification of Materials Requirements

�� Materials Properties can be:Materials Properties can be:

�� QuantitativeQuantitative or or QualitativeQualitative

�� EssentialEssential (strength, toughness) or (strength, toughness) or DesirableDesirable ((processabilityprocessability, ,

weight, corrosion, reliability)weight, corrosion, reliability)

MATERIALS SELECTION


�� Some of the methods used to classify the functional requirementsSome of the methods used to classify the functional requirements

include:include:

1. Limit on Materials Properties

�� Rigid or Rigid or ““go go –– no no –– gogo”” requirements (nonrequirements (non--negotiable)negotiable)

�� Soft requirements (negotiable)Soft requirements (negotiable)

2. Cost per Unit Property

3. Ashby’s Method (selection charts)

MATERIALS SELECTION


Materials Selection Chart

MATERIALS SELECTION


3. Development of alternative solutions3. Development of alternative solutions

�� Search for the material(s) that best meet the Search for the material(s) that best meet the requirement requirement elected in the elected in the previous stageprevious stage

�� Selection from alternative solutions requires decisions. ExperieSelection from alternative solutions requires decisions. Experience and nce and judgment are sufficient to permit a sound decision without a forjudgment are sufficient to permit a sound decision without a formal mal processprocess

1.1. This is true when a candidate material possess some outstanding This is true when a candidate material possess some outstanding characteristics or all except one has some serious deficiencycharacteristics or all except one has some serious deficiency

2.2. When there is no obvious choice, a formal process or procedure When there is no obvious choice, a formal process or procedure can be used. At the end of this stage, the number of candidate can be used. At the end of this stage, the number of candidate materials is narrowed downmaterials is narrowed down

MATERIALS SELECTION


4. Evaluation of alternative materials

�� Having narrowed down the number of possible materials to those Having narrowed down the number of possible materials to those

that satisfy the rigid requirement, the search starts for the that satisfy the rigid requirement, the search starts for the

material(s) that best meet the soft requirementsmaterial(s) that best meet the soft requirements

�� Several quantitative methods can be used to further narrow the Several quantitative methods can be used to further narrow the

field of possible materials and matching processes to a few field of possible materials and matching processes to a few

optimum candidatesoptimum candidates..

�� Each candidate material must at least minimally satisfy all the Each candidate material must at least minimally satisfy all the

requirements.requirements.

MATERIALS SELECTION


•• However, it is also more likely that each material will possess However, it is also more likely that each material will possess some some

characteristics that exceed the minimum requirements. characteristics that exceed the minimum requirements.

•• Therefore, a formal method for rating how well each material meeTherefore, a formal method for rating how well each material meets ts

the requirements is needed because some requirements are more the requirements is needed because some requirements are more

important than others.important than others.

�� One of these methods is the One of these methods is the ““weighted Properties Methodweighted Properties Method””

•• Greater weight should be given to the more important requirementGreater weight should be given to the more important requirement..

•• Often, the properties we are comparing cannot be placed on Often, the properties we are comparing cannot be placed on

comparable terms. comparable terms.

MATERIALS SELECTION


MATERIALS SELECTION


Another example. Weight is 4 times as important as strength, strAnother example. Weight is 4 times as important as strength, strength is 4 ength is 4 times as important as cost, corrosion is 2 /3 the importance of times as important as cost, corrosion is 2 /3 the importance of strength, etcstrength, etc

Weighting of attributes

Property 1/2 1/3 1/4 1/5 ratio weight

Strength 1 20 60 50 80 1.0 .14

Density 2 80 4.0 .58

Corrosion 3 40 0.66 .10

Colour 4 50 1.0 .14

Cost 5 20 .25 .04

Total 6.91 1.00

MATERIALS SELECTION


5. Decisions

•• Selecting a material from among alternatives requires Selecting a material from among alternatives requires decisionsdecisions

•• Sometimes experience and judgment are sufficient to make a soundSometimes experience and judgment are sufficient to make a sound

decision decision without a formal process. without a formal process. This is true when a candidate This is true when a candidate

material possesses outstanding characteristics, ormaterial possesses outstanding characteristics, or

•• All except one material has serious deficiencyAll except one material has serious deficiency

Documents

materials selection aspects(2005) - fkm.utm.myfkm.utm.my/~ourdjini/materials_selection_aspects.pdf · MATERIALS SELECTION Faculty of Mechanical Engineering Ali Ourdjini, UTM -2005