Hard facts

Theory of hardness testing

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Methods with static application of the test force are predominantly used for testing the hardness of metals, whereby either the penetration depth or the size of the indentation caused by an indenter is measured. A distinction is made with the static hardness testing methods between depth measurement methods and optical measurement methods.

Depth measurement methods measure the residual depth of indentation left by the indenter. The Rockwell method is the only standardised depth measurement method (see ISO 6508, ASTM E18). There are also other, non-standardised depth measurement methods: Brinell and Vickers in the depth (HBT, HVT).

Optical measurement methods measure the residual size of indentation left by the indenter. Standardised optical hardness testing methods are Brinell (ISO 6506, ASTM E10), Knoop (ISO 4545, ASTM E92, ASTM E384) and Vickers (ISO 6507, ASTM E92, ASTM E384).

Alternatively, methods involving dynamic force application, such as the Leeb rebound method, in which the height of a ball rebound is measured, can also be used for hardness testing.