Indent depth for Vickers hardness test

Description

The basic principle of the Vickers hardness test, as with all common measures of hardness, is to observe the questioned material’s ability to resist plastic deformation from a standard source. The hardness number is determined by the load over the surface area of the indentation and not the area normal to the force, and is therefore not pressure.

For thin samples indentation depth can be an issue due to substrate effects. As a rule of thumb the sample thickness should be kept greater than 2.5 times the indent diameter. Alternatively indent depth can be calculated according to the shown formula.