7 - Mechanical Properties Many materials when in service are subjected to forces or loads the steel in automobile axle How do you select a material and

7 - Mechanical Properties Many materials when in service...

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Pravansu Mohanty: Email: [email protected]; Tel (313) 593-4254Mechanical Properties
How do you select a material and design a component such that the resulting deformation will not be excessive and fracture will not occur?The mechanical behavior of a material reflects the relationship between its response or deformation to an applied load or force.Factors that affect the mechanical properties include the nature of applied load, its duration, as well as the environmental condition
Pravansu Mohanty: Email: [email protected]; Tel (313) 593-4254Concept of Stress and StrainIf a load is static or changes relatively slowly with time and is applied uniformly over a cross section the mechanical behavior can be ascertained by simple stress-strain testType of load: tension, compression, shear, and torsionTensionCompressionShearTorsion
Pravansu Mohanty: Email: [email protected]; Tel (313) 593-4254Tensile TestCommon mechanical test is tensile testLet’s take a sample of cylindrical shape whose cross-section is A0and length is l0.Now apply a fixed amount of load ‘F’ and measure the change in the length of the sample l.The quantity is known as engineering stress (N/m2).The quantity is known as engineering strain. (What is the unit?)The output of such tensile test is recorded on a chart as stress Vs strain and is called engineering stress-strain curve0AF=σ0ll=ε
Pravansu Mohanty: Email: [email protected]; Tel (313) 593-4254Compression, Shear and Torsion TestsCompression test is done in a similar manner to the tensile test, except that the force is compressive and specimen contracts in the direction of the stressCompression test is usually conducted when the material is very brittle.For test performed using pure shear force, the tress and strain are computed asθγτtan00===ldandAFTorsion is a variation of pure shear, where in the

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