Hardness

: For the mathematical concept of the difficulty of proving a conjecture, solving an equation, etc., see computational complexity theory.

Indentation hardness

Primarily used in engineering and metallurgy, indentation hardness seeks to characterise a material's resistance to permanent, and in particular plastic, deformation. It is usually measured by loading an indenter of specified geometry onto the material and measuring the dimensions of the resulting indentation.

Related Topics:
Engineering - Metallurgy - Plastic

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There are several alternative definitions of indentation hardness, the most common of which are:

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• Brinell hardness test (HB)
• Janka hardness, used for wood
• Knoop hardness test (HK) or microhardness test, for measurement over small areas
• Meyer hardness test
• Rockwell hardness test (HR), principally used in the USA
• Shore hardness, used for polymers
• Vickers hardness test (HV), has one of the widest scales

There is, in general, no simple relationship between the results of different hardness tests. Though there are practical conversion tables for hard steels, for example, some materials show qualitatively different behaviours under the various measurement methods.

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