Question

a) Give a critical discussion on why hardness test needs to perform in engineering practice.

b) Discuss 2 possible source of errors (other than parallax error) and how it's can effect the result.

Answer 1

a)

Hardness is the property of a material which determines how it resists to deformation, scratching, penetration, indentation and other physical damages. That's why knowing hardness is important from engineering prospects because resistance to wear and tear (friction ,erosion etc ) generally increases with hardness. One more purpose it serves is If hardness of two materials are not same which otherwise appear similar then we can at once conclude that they are not same(unfortunately converse is not true).

b)

1) Many external factors such as dirt, humidity, temperature etc can cause some error, so they should be strictly monitored.

2) Indenter not being exactly perpendicular to surface is another source of error.

besides , heterogenity of micro structure , quality of samples , mistake in clamping the specimen , not properly calibrated loading system are other inevitable sources of errors.