Material SelectionMaterial Selection
SKMV4792 AUTOMOTIVE PRODUCTION SKMV4792 AUTOMOTIVE PRODUCTION
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IntroductionIntroductionGoal of manufacturing: to create products and
components that perform properly. Due to advances in materials science, there is a
wide array of available materials◦The increase in the number of choices has often
led to improper or poor materials selection◦Sometimes, a more expensive alloy is chosen
when a cheaper alloy would have been sufficientDesign and material engineers have the
responsibility of proper materials selection.
IntroductionIntroductionMaterial selection processes should be
constantly reevaluatedMaterials selection concerns are always
changing◦Environmental pollution◦Recycling◦Energy ◦Health or safety constraints◦Geopolitical issues
IntroductionIntroduction
Materials in many products have changed over the years
Figure 9-2 a) (Left) A traditional two-wheel bicycle frame (1970s vintage) made from joined segments of metal tubing,
b) (Right) a top-of-the-line (Tour de France or triathlon-type) bicycle with one-piece frame, made from fiber-reinforced polymer-matrix composite. (Courtesy of Trek Bicycle Corporation, Waterloo, WI.)
Material Selection and Material Selection and Manufacturing ProcessesManufacturing Processes Material and
manufacturing processes are extremely interdependent
Change in a material will likely cause a change in the manufacturing process needed
A successful product has gone through both proper material selection and processing selection
Figure 9-4 Schematic showing the interrelation among material, properties, processing, and performance.
(Material)
Material Selection and Material Selection and Manufacturing ProcessesManufacturing Processes Material and
manufacturing processes are extremely interdependent
Change in a material will likely cause a change in the manufacturing process needed
A successful product has gone through both proper material selection and processing selection
Figure 9-4 Schematic showing the interrelation among material, properties, processing, and performance.
(Material)
The Design ProcessThe Design ProcessDesign is the first stage in
manufacturing processes◦What it is◦What properties must it possess◦What material◦How to make it◦How many to make◦What conditions will it see during use
Steps for DesignSteps for Design
1. Conceptual◦Several concepts may be considered
2. Functional◦Workable designs are developed◦Detailed plan for manufacturing◦Prototyping
3. Production◦Full production◦Production speeds and quantities
Procedures for Material SelectionProcedures for Material Selection
General sequence of product design◦design→material selection→process
selection→production→evaluation→redesignCase-history method
◦Evaluates what has been done in the pastModification of an existing product
◦Evaluates the current product and manufacturing techniques
◦Changes or improves upon features of the existing product
Development of a new product◦Follows the full sequence of product design above
Geometric ConsiderationsGeometric ConsiderationsRelative sizeShape complexitySpecified dimensionsPrecisionComponent interactionSurface-finishesTolerances
◦Tolerances due to environmental or usage concernsMinor changes to improve manufacture or
performance
Mechanical PropertiesMechanical Properties
Static strengthBrittle fracturePlastic deformationAllowable bend, stretch, twist, or
compressImpact loadingsVibrations or cyclic loadingsWear resistanceOperating temperatures
Example: Cantilever Beam DesignExample: Cantilever Beam Design
design: equal strength
design: equal cross section
Physical Properties (Electrical, Physical Properties (Electrical, Magnetic, Thermal, and Optical)Magnetic, Thermal, and Optical)Electrical requirements
◦Conductivity, resistivityMagnetic Thermal conductivityThermal expansionOptical requirementsWeightAppearance (color, texture, feel)
Environmental ConsiderationsEnvironmental ConsiderationsOperating temperaturesCorrosionErosionLifetimeFatigueExpected level of maintenanceDisassemblyRepairabilityRecyclability
Manufacturing ConcernsManufacturing Concerns
QuantityProduction rateLevel of qualityQuality control and inspectionAssembly concernsSection thicknessStandard sizes and shapesLiability if product failure occursEnd-of-use disposal
Proper Materials SelectionProper Materials SelectionAll factors and service conditions must be
metAbsolute requirements
◦No compromise possibleRelative requirements
◦Compromises can be made◦Good, better, best are all acceptable
Additional Factors to ConsiderAdditional Factors to ConsiderHandbook data is valuable in determining
materialsNote the conditions under which values for
materials were obtainedCost is often one of the biggest additional factors
◦Often, compromises between material properties and cost must be made
Material availabilityAre there any possible misuses on the part of the
consumer?Have there been failures for similar products?Material’s usage historyMaterial standardization
Consideration of the Consideration of the Manufacturing ProcessManufacturing ProcessOverall attractiveness
◦Physical properties◦Mechanical properties◦Formability
Economical concernsAll processes are not compatible with all
materials
Ultimate ObjectiveUltimate Objective
Develop a combination of material and processes that is the best solution
Material or manufacturing selection normally imposes restrictions or limitations on the other
Economics, environment, energy, efficiency, recycling, inspection, and serviceability are important deciding factors
Decision ModelsDecision Models
Figure 9-5 Sequential flow chart showing activities leading to the production of a part or product.
Figure 9-6 Alternative flow chart showing parallel selection of material and process.
Decision ModelsDecision Models
Figure 9-5 Sequential flow chart showing activities leading to the production of a part or product.
Figure 9-6 Alternative flow chart showing parallel selection of material and process.
CompatibilityCompatibility
Figure 9-7 Compatibility chart of materials and processes. Selection of a material may restrict possible processes. Selection of a process may
restrict possible materials.
Materials SubstitutionMaterials Substitution
Care should be taken so that all requirements are still met
The total picture should be considered so that any possible compromises can be determined◦Aluminum sheets have replaced steel for
weight reduction, but vibration problems require special design considerations
Material SubstitutionsMaterial Substitutions
Material SubstitutionsMaterial SubstitutionsCauses of product failure
◦Failure to know and use the best materials information
◦Failure to account for all reasonable material uses
◦Use of materials with insufficient data◦Inadequate quality control◦Material selection made by unqualified people
Aids to Material SelectionAids to Material SelectionThere is an enormous amount of resources
available for materials selectionMetals Handbook, published by ASM
InternationalASM Metals Reference BookHandbooks are available for specific classes of
materialsAmerican Metal Market provides material costsMaterials Selection in Mechanical Design by M.
F. AshbyComputer software
Select a Material with Rating Select a Material with Rating ChartChart
1. List all required material properties for a product to be designed.
2. Screen all required properties and identify those absolute properties that must be considered for the product as “Go-No-Go” properties.
3. Rate each candidate material on a scale such as 1 to 5 or 1 to 10 for each required property.
4. Define weighted factor for each required property based on its significance.
5. Multiply property rating by its weighted factor and sum the results for each materials
6. Select the material that satisfies the “Go-No-Go” screen and has the highest sum of the relative rating numbers.
Select a Material with Rating ChartSelect a Material with Rating Chart
Material Go-No-Go Relative rating number - R (=rating number x weighting factor)
R r R/r
Weldability Stiffness Stability Fatigue Tensile
1 4 5 4 14
A 14
B 14
C 14
Select a Material with Rating Select a Material with Rating ChartChart
Advantages: Potential materials can be compared in
a uniform, unbiased manner The best candidate can often be
selected There is less chance to overlook a
major requirement by placing all the requirement on a single sheet.
Example: Selection of a Material:Example: Selection of a Material:
Solution:Solution:• Finding “Go-No-Go” property: weldability
• - S: satisfactory• - U: unsatisfactory
• Calculating: R = Relative rating number, and r = weighting factor.Relative rating number R = property rating number x
weighting factor
• Set material’s property rating number (1 – 5):excellent = 5, very good = 4, good = 3, fair = 2, poor = 1
• weighted factor for each material’s property: • - Stiffness : 1• - Stability: 4• - Fatigue: 5• - Tensile strength: 4
Solution (cont.)Solution (cont.)
Weldability Stiffness Stability Fatigue Tensile Strength
R r R/r
Go-No-Goscreening
(1) (4) (5) (4)
X S 3x1 3x4 2x5 3x4 37 14 2.64
Y U 3x1 5x4 3x5 5x4 58 14 4.14
Z S 3x1 3x4 5x5 2x4 48 14 3.43
Rating chart for selecting material
Conclusion:Conclusion:
Based on the chart below, material Y has the highest rating number. However, because it does not have satisfactory weldability and this is an "absolute" requirement, it should not be selected. Material Z should be used.
SummarySummaryProper materials selection is vital to a
product’s successThe design engineer and materials
engineer are responsible for materials selection
Materials and process selection go hand-in-hand
Data should be used to validate materials selection