The document discusses various mechanical properties and tests used to evaluate them. It describes the different types of strength materials can exhibit including elastic strength and plastic strength. Factors that can influence mechanical properties are then outlined such as grain size, heat treatment, and temperature. Common deformation mechanisms like slip and twinning are also defined. Different types of mechanical tests are classified as either destructive or non-destructive and specific tests are detailed including hardness, impact, fatigue, compression, and creep tests.

1. .
TESTING OF
MECHANICAL
PROPERTIES
UNIT -5

2. STRENGTH
• The ability of the material to withstand or
support an external force or load without
rupture.
• Elastic strength : It’s the value of load
corresponding to transition from elastic to
plastic range.
• Plastic strength : It’s the value of the load
corresponding to plastic range and rupture.

3. FACTORS AFFECTING
MECHANICAL PROPERTIES
.

4. FACTORS
• Grain size
• Heat treatment
• Atmospheric exposure
• Low and high temperature.

5. Plastic deformation
• It’s a deformation of a body which remains
even after removing the external load from
the body.

6. .
• The property of Palstic deformation makes
the metal suitable for various forming
processes such as rolling , forging, pressing,
drawing, spinning, extrusion and stamping

7. Mechanism of plastic
deformation
.

8. MECHANISM OF PLASTIC DEFORMATION
• Plastic deformation is defined as a process in
which the object due to applied force changes its
size or shape in a way that is not reversible.
• Plastic deformation is seen in many objects,
including:

9. Slip
• Sliding of blocks of the crystal over one another along
definite crystallographic planes called slip planes

10. Mechanism of slip
• When Shear stress applied exceeds the critical
value slip occur.

11. TWINNING
• Here the atoms in the part of a crystal
subjected to stress, rearrange themselves so
that one part of the crystal become the
mirror to the other.

12. .
• twinning differs from slip in that every plane of
atoms suffers some movement, and the
crystallographic orientations of many unit cells are
altered.

13. .

14. Fracture
.

15. Fracture - definition
• Fracture is the mechanical failure of the material
which will produce the separation or
fragmentation of a solid into 2 or more parts
under the action of stress.
Types of fracture
Brittle fracture
Ductile fracture
Fatigue fracture
Creep fracture

16. Griffith theory
• There is a difference between material
strength to theoretical value of the ideal
material.
• This is due to fine cracks in the material.
The stresses applied on the material is
concentrated more on crack portions and
lead it to fracture.

17. Mechanism of
brittle
mechanism

18. .
• Now the tensile stress is applied at the both
sides of the material.
• So the stress is maximum at the tip of the crack

19. .
The fracture which takes place by a slow propagation
of crack with appreciable plastic deformation.
DUCTILE FRACTURE

20. FATIGUE FRACTURE
• Failure occur due to repeated or
fluctuating load

21. .

22. .

23. CREEP
• It’s a slow and permanent deformation in metal under
steady load at constant temperature.

24. .

25. .

26. Mechanical tests of metals
Destructive tests

27. Classification of mechanical tests
• Destructive test
• Non – Destructive test

28. We find

29. .

30. .

31. .

32. COMPRESSION TEST
Compression load is gradually applied on the
specimen and the reduction in length is
recorded

33. Torsion test
• Rotational force given to material about longitudinal axis.
• This torsional forces produce a rotational motion about
the longitudinal axis of one end of the member relative
to the other end.

34. .

35. HARDNESS TEST
Brinell Hardness
Vickers Hardness
Rockwell Hardness

36. Brinell hardness test

37. .

38. .

39. Rockwell hardness test

40. .

41. IMPACT TEST-
TO STUDY THE BEHAVIOUR OF THE MATERIAL UNDER SUDDEN LOAD
IZOD TEST
CHARPY TEST

42. IMPACT STRENGTH
• The ability of the material withstand a blow without
fracture

43. Izod test
• Izod test uses a cantilever
specimen of size 75 mm x
10 mm x 10 mm, as
shown in Fig.
• (a). The V-notch angle is
45º and the depth of the
notch is 2 mm.
• The Izod specimen is
placed in the vise such
that it is a cantilever, as
shown in Fig..

44. Charpy Test
•The Charpy test uses a
test specimen of size 55
mm x 10 mm x 10 mm,
as shown in Fig. (a).
The V-notch angle is
45º and the depth of the
notch is 2 mm.
•The Charpy specimen
is placed in the vise as a
simply supported beam,
as shown in Fig. (b).

45. FATIGUE TESTS
• Fatigue tests determine the resistance of material to
repeated pulsating or fluctuating loads.
• Fatigue defined: The capacity of material to withstand
repeatedly applied stresses is known as fatigue.
• The resistance of a material to fatigue failure is
characterised by its fatigue or endurance limit.
• The endurance limit or endurance strength is defined as
the maximum stress which a specimen can endure
without failure when this stress is repeated for a specified
number of cycles.

46. CREEP TESTS
• The continuous deformation of a metal under a steady
load is known as creep.
• The purpose of creep tests is to determine the creep
limit. The creep limit or the limiting creep stress is
defined as the stress that will not break the specimen
when applied for an infinite period at a specific
constant temperature.
• The creep tests require the measurement of four
variables, stress, strain, temperature, and time.
• The creep tests are simply tension tests run at constant
load and constant temperature. Then the value of
strain of the test piece is noted as a function of time.

47. CREEP TEST