material selection skmv4792 automotive production fkm.utm.my/~jinhoe

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  • Material Selection

    SKMV4792 AUTOMOTIVE PRODUCTION

    fkm.utm.my/~jinhoe

  • IntroductionGoal of manufacturing: to create products and components that perform properly. Due to advances in materials science, there is a wide array of available materialsThe increase in the number of choices has often led to improper or poor materials selectionSometimes, a more expensive alloy is chosen when a cheaper alloy would have been sufficientDesign and material engineers have the responsibility of proper materials selection.

  • IntroductionMaterial selection processes should be constantly reevaluatedMaterials selection concerns are always changingEnvironmental pollutionRecyclingEnergy Health or safety constraintsGeopolitical issues

  • IntroductionMaterials 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 Manufacturing ProcessesMaterial and manufacturing processes are extremely interdependentChange in a material will likely cause a change in the manufacturing process neededA successful product has gone through both proper material selection and processing selectionFigure 9-4 Schematic showing the interrelation among material, properties, processing, and performance. (Material)

  • Material Selection and Manufacturing ProcessesMaterial and manufacturing processes are extremely interdependentChange in a material will likely cause a change in the manufacturing process neededA successful product has gone through both proper material selection and processing selectionFigure 9-4 Schematic showing the interrelation among material, properties, processing, and performance. (Material)

  • The Design ProcessDesign is the first stage in manufacturing processesWhat it isWhat properties must it possessWhat materialHow to make itHow many to makeWhat conditions will it see during use

  • Steps for Design1. ConceptualSeveral concepts may be considered2. FunctionalWorkable designs are developedDetailed plan for manufacturingPrototyping3. ProductionFull productionProduction speeds and quantities

  • Procedures for Material SelectionGeneral sequence of product designdesignmaterial selectionprocess selectionproductionevaluationredesignCase-history methodEvaluates what has been done in the pastModification of an existing productEvaluates the current product and manufacturing techniquesChanges or improves upon features of the existing productDevelopment of a new productFollows the full sequence of product design above

  • Geometric ConsiderationsRelative sizeShape complexitySpecified dimensionsPrecisionComponent interactionSurface-finishesTolerancesTolerances due to environmental or usage concernsMinor changes to improve manufacture or performance

  • Mechanical PropertiesStatic strengthBrittle fracturePlastic deformationAllowable bend, stretch, twist, or compressImpact loadingsVibrations or cyclic loadingsWear resistanceOperating temperatures

  • Example: Cantilever Beam Designdesign: equal strengthdesign: equal cross section

  • Physical Properties (Electrical, Magnetic, Thermal, and Optical)Electrical requirementsConductivity, resistivityMagnetic Thermal conductivityThermal expansionOptical requirementsWeightAppearance (color, texture, feel)

  • Environmental ConsiderationsOperating temperaturesCorrosionErosionLifetimeFatigueExpected level of maintenanceDisassemblyRepairabilityRecyclability

  • Manufacturing ConcernsQuantityProduction rateLevel of qualityQuality control and inspectionAssembly concernsSection thicknessStandard sizes and shapesLiability if product failure occursEnd-of-use disposal

  • Proper Materials SelectionAll factors and service conditions must be metAbsolute requirementsNo compromise possibleRelative requirementsCompromises can be madeGood, better, best are all acceptable

  • Additional 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 factorsOften, compromises between material properties and cost must be madeMaterial availabilityAre there any possible misuses on the part of the consumer?Have there been failures for similar products?Materials usage historyMaterial standardization

  • Consideration of the Manufacturing ProcessOverall attractivenessPhysical propertiesMechanical propertiesFormabilityEconomical concernsAll processes are not compatible with all materials

  • Ultimate ObjectiveDevelop a combination of material and processes that is the best solutionMaterial or manufacturing selection normally imposes restrictions or limitations on the otherEconomics, environment, energy, efficiency, recycling, inspection, and serviceability are important deciding factors

  • Decision ModelsFigure 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 ModelsFigure 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.

  • CompatibilityFigure 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 SubstitutionCare should be taken so that all requirements are still metThe total picture should be considered so that any possible compromises can be determinedAluminum sheets have replaced steel for weight reduction, but vibration problems require special design considerations

  • Material Substitutions

  • Material SubstitutionsCauses of product failureFailure to know and use the best materials informationFailure to account for all reasonable material usesUse of materials with insufficient dataInadequate quality controlMaterial selection made by unqualified people

  • Aids 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 ChartList all required material properties for a product to be designed.Screen all required properties and identify those absolute properties that must be considered for the product as Go-No-Go properties.Rate each candidate material on a scale such as 1 to 5 or 1 to 10 for each required property.Define weighted factor for each required property based on its significance. Multiply property rating by its weighted factor and sum the results for each materialsSelect the material that satisfies the Go-No-Go screen and has the highest sum of the relative rating numbers.

  • Select a Material with Rating Chart

    MaterialGo-No-Go Relative rating number - R (=rating number x weighting factor) SRSrSR/rWeldabilityStiffnessStabilityFatigueTensile145414A14B14C14

  • Select a Material with Rating ChartAdvantages:Potential materials can be compared in a uniform, unbiased mannerThe best candidate can often be selectedThere is less chance to overlook a major requirement by placing all the requirement on a single sheet.

  • Example: Selection of a Material:

  • Solution:Finding Go-No-Go property: weldability- S: satisfactory- U: unsatisfactoryCalculating: R = Relative rating number, and r = weighting factor.Relative rating number R = property rating number x weighting factorSet materials property rating number (1 5):excellent = 5, very good = 4, good = 3, fair = 2, poor = 1weighted factor for each materials property: - Stiffness :1- Stability: 4- Fatigue: 5- Tensile strength: 4

  • Solution (cont.)Rating chart for selecting material

    WeldabilityStiffnessStabilityFatigueTensile StrengthSRSrSR/SrGo-No-Goscreening(1)(4)(5)(4)XS3x13x42x53x437142.64YU3x15x43x55x458144.14ZS3x13x45x52x448143.43

  • 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.

  • SummaryProper materials selection is vital to a products successThe design engineer and materials engineer are responsible for materials selectionMaterials and process selection go hand-in-handData should be used to validate materials selection

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