Mechanical Tests
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Mechanical tests are used to characterize materials. Tensile testing measures engineering stress and ductility through elongation and reduction of area. True stress and true strain account for changes in specimen area during loading. Toughness is the energy absorbed before fracture measured by the area under the stress-strain curve. Hardness tests like Brinell, Rockwell, and Vickers measure resistance to indentation using different indenters. Impact tests like Charpy and Izod measure energy absorption during fracture. The ductile to brittle transition temperature is important for brittle fracture behavior.
Mechanical Tests
- 2. Mechanical Tests - Materials G.Gopinath Assistant Prof - Mechanical
- 6. Engineering Stress • The engineering stress, or nominal stress, is defined as the ratio of applied load to original area of the specimen, 0A P
- 7. Ductility • 2 quantities commonly used to define ductility in a tension test are known as elongation and reduction of area. • Elongation is defined as • A second measure of ductility is known as a reduction of area, defined as 100Elongation 0 0 l llf 100areaofReduction 0 0 A AA f
- 8. True stress and true strain • Similar to stress definition, true stress is defined as where A is the actual area supporting the load (Instantaneous) • True strain is defined as A P 0 ln 0 l l l dl l l
- 9. Toughness • Energy needed to break a unit volume of material. • Area under stress strain curve.
- 13. Compressive test
- 14. Compressive test
- 15. Shear testing
- 16. Hardness • Hardness is the ability to resist plastic deformation, usually by penetration/ Indentation load. • This may also refer to resistance to scratching, abrasion or cutting.
- 21. Vickers hardness test • Vickers hardness test uses a square-base diamond pyramid as the indenter with the included angle between opposite faces of the pyramid of 136 0. • This angle approximately the most desirable ratio of indentation diameter to ball diameter in the Brinell Hardness test. • Diamond pyramid hardness Test.
- 22. VHN • It is defined as the load divided by the surface area of the Indentation. • This area is calculated from microscopic measurements of the lengths of the diagonals of the impression.
- 23. VHN
- 24. Impact testing • To measure the toughness, or energy absorption capacity of the materials. • Charpy impact test • Izod impact Test
- 25. •The Specimen is held horizontally – between two supports •The notch on the specimen faces away from the pendulum •The striking energy of the pendulum is 300 Joules Pendulum Support Specimen Charpy Impact test
- 26. •The Specimen is held vertically in a vice •The notch on the specimen faces the pendulum •The striking energy of the pendulum is 167 Joules Pendulum Vice Specimen Izod impact test
- 27. DBTT ( Ductile to Brittle Transition Temperature )
- 28. DBTT ( Ductile to Brittle Transition Temperature )