See the description of the Vickers Hardness test below.

The Vickers Hardness test is used to characterize hardness of various solid materials. A diamond pyramid is pressed against the solid and the hardness is calculated based on the imprint left on the surface. Schematic representation of the Vickers test is shown in Figure below. Further information regarding existing standards and procedures can be found in references [1,2].

VIckers Test
By Vickers-path.svg:

Hardness in Vickers (HV) is calculated as follows:

 HV = 0.1891*F/d^2 .

where d is the average of the two diagonals. Hardness in GPa is calculated as follows:

 H = 0.1891*9.8/1000*F/d^2 .

The yield stress can be approximated from the hardness (given in HV) as follows:

 \sigma_u = HV/0.3 .