Study on Methods for Measuring Vickers Indentations

 The Vickers hardness test can cover an extensive range of test loads from several gram-force (gf) to 100 kilogram-force (kgf) with a single hardness scale. It is one of the most reliable strength tests because the simplicity of the testing theory and the indenter shape minimizes variances among hardness values obtained. The most vulnerable aspect of the Vickers method is an error when measuring the diagonal length of an indentation. In particular, an inexperienced operator tends to obtain smaller measurements than the actual length of the indentation. According to research by the authors, it is also revealed that the contrast of the microscopic image of an indentation varies with the angle of aperture of the objective lens. This report presents the results of an experiment on how measurer, measuring method, and aperture of objective lens (i.e., numerical aperture: N.A.) affect measurement of a Vickers indentation