Calculation of characteristic macro-hardness from low-load indentation tests

Vickers hardness test data for several metals which exhibited a pronounced indentation size effect are re-examined by least squares regression of linear relationships derived from common descriptions of the effect. The Meyer power law is shown to be inaccurate. Three other descriptions, incorporating an indentation size or load “error” parameter, are shown to be precisely equivalent and fairly accurate down to the low-load range. The parameters are indicative of a true size effect rather than experimental error. Further analysis reveals that the size effect is itself size dependent.