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21.

The tendency for brittle fracture increases with

A.	Increasing temperature	B.	Decreasing strain rate
C.	Appreciable plastic deformation before fracture	D.	Appreciable plastic deformation during propagation of the crack
E.	None of the above

22.

In general, high cohesive forces are related to

A.	Large values of elastic constants	B.	Low melting point
C.	Large coefficients of thermal expansion	D.	Small value of elastic constants
E.	None of the above

23.

The ability of material to absorb energy when deformed elastically and to return it when unloaded is called

24.

The ability of a material to absorb energy in the plastic range is known as

25.

Identify the incorrect statement

A.	The greatest error in Briuell hardness measurements occur in measuring the diameter of specimen	B.	Harder the material, greater the elastic recovery after deformation
C.	Owing to elastic recovery, the radius of curvature of the indentation will be larger than that of the spherical indentor	D.	None of the above

26.

Identify the incorrect statement

A.	Fatigue strength is seriously reduced by the introduction of a stress raiser such as a notch or hole	B.	A fatigue failure is particularly insidous, because it occurs without any warning
C.	Fatuge results in a brittle fracture with no gross deformation at the fracture	D.	As the roughness of surface increses the fatigue life of speoimen increases
E.	None of the above

27.

A surface damage which results when two surfaces in contact experience light periodic relative motion is

28.

The fatigue strength of materials increases

A.	With temperature	B.	By having scratch on the surface
C.	By having notches in specimen	D.	By under stressing the specimen
E.	By over stressing the specimen

29.

Hardness may be defined as resistance to

30.

Toughness of a material means