On two indentation hardness definitions

The difference between the contact area under load and the residual projected area of an indentation after complete unloading has been studied for various materials using finite element and dimensional analyses of cone indentation. The difference in the contact areas gives rise to two hardness values, one based on the contact area under load and another based upon the residual projected area. The effect of sinking-in, piling-up and elastic recovery on the residual contact area has been calculated for materials with different elastic properties and strain hardening characteristics. Based on this study, an estimation procedure is suggested for obtaining a more accurate value of the hardness under load from a measurement of the residual area of an indentation. (C) 2002 Elsevier Science B.V. All rights reserved.