Iowa State University - ME 324Lecture12_Mechanical_Behavior_of_Materials_Pt1_Su17

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ME324: Manufacturing Engineering Summer 2017 Lecture 12 Mechanical Behavior, Properties and Testing of Materials, Part 1 Text: Kalpakjian: 2.1-2.2,2.6 2 Mechanical Behavior, Properties and T... esting of Materials Learning Objectives • What mechanical properties can you obtain from a tensile test? • Can you interpret a tensile/compression test data? • How do you convert tensile test data to show true stress and true strain? • How do you interpret hardness test data? Lecture #13 3 Mechanical Properties in Design and Manufacturing • Mechanical properties determine a material’s behavior when subjected to mechanical stresses – Properties include: • Elastic modulus • Ductility • Hardness • Measures of strength 4 Mechanical Properties in Design and Manufacturing Dilemma: • The mechanical properties that are desirable to the design engineer such as high strength, usually make manufacturing more difficult – The manufacturing engineer should appreciate the design viewpoint – And the design engineer should be aware of the manufacturing viewpoint 5 Stress-Strain Relationship • Three types of static stresses to which materials can be subjected: – Tensile - tend to stretch the material – Compressive - tend to squeeze it – Shear - tend to cause adjacent portions of material to slide against each other ? = ??/?? γ = ?/? • Stress-strain curve - basic relationship that describes mechanical properties for all three types Engineering Strain Shear Strain (2.1) Shear Strain (2.2) 6 Tensile Test • Most common test for studying stress-strain relationship, especially metals • In the test, a force pulls the material, elongating it and reducing its diameter Figure 3.1 Tensile test: (a) tensile force applied in (1) and (2) resulting elongation of material 7 Tensile Test Specimen and Setup • ASTM (American Society for Testing and Materials) specifies preparation of test specimen • Engineering stress / Nominal stress (s) • Engineering strain (e) • Young’s Modulus (E) (modulus of Elasticity) 8 Engineering Stress – Strain Curves 0 0 l l e  l  l : ins [Show More]

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