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Chapter VIII Micro-hardness studies…
8.2 Methods of Hardness Testing
Various hardness tests can be briefly reviewed as follows on the basis of
compilations of Tabor [3] and Mott [6].
8.2.1 Dynamic Hardness
In this type of test an indenter is dropped from a given height on the surface
and the depth of the impression produced is measured. The hardness is
expressed in terms of energy of the impact and the depth and size of the
indentation.
1. Scratch hardness
This test is the oldest form of hardness measurement and was probably
developed by mineralogists. In the first test one merely observes whether the
selected material is capable of scratching another. In the second form of this
method, the hardness number is expressed in terms of width or depth of a
scratch made with a diamond or a steel indenter, under a definite load
traversing the surface at a steady rate.
2. Rebound hardness
The hardness is given by the height of rebound of diamond tipped weight falling
on the surface from a fixed height. The shore Scleroscope is an instrument of this
type.
3. Plowing hardness
In which a blunt element is moved across a surface under controlled
conditions of load and geometry and the width of the groove is the measure of
hardness. The Bierbaum test is of this type.
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