Mechanical Tests - materials

2. Mechanical Tests - Materials
G.Gopinath
Assistant Prof - Mechanical

3. (b)
Tensile testing

4. Tensile testing

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.

10. Effect of Temperature

11. Various materials

12. Various materials

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.

17. Brinell Hardness Test

18. Rockwell Hardness Test

19. Rockwell hardness test

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 )