4. Anisotropic materials

4.1 Characterization of plastic anisotropy by hardness testing

Due to the plastic anisotropy of the indented material, the residual indentation does not exhibit the symmetries of the indenter: the lengths of the diagonals of a Vickers indentation are different [56] and the indentation left by an indenter of revolution is not circular. In general, these effects remain fairly limited and, for a Vickers indentation, for example, a simple way of overcoming them is to calculate hardness from the average of the indentation diagonal lengths.

To study the effect of this plastic anisotropy, we can use a Knoop indentor (cf. ) and perform indentations for various orientations of the indenter's...