Proposal for ISO 14577: Metallic materials-Instrumented Indentation test for hardness and materials parameters - Part 1: Test method (2nd. Discussion for relationships between maximum projected area and real maximum contact depth, and computing method

摘要

Due to the resolution of the dependence on indentation depth (i.e., on the test force) for computed Young's modulus by the instrumented indentation test, the relationships between the maximum projected area A_(pm) and the real maximum contact depth h_r is firstly discussed, and then the computing method for Young's modulus of specimen E_s using h_r is derived. Secondly, suitable fitting range of linear approximation on the unloading curve is investigated to determine h_r, based on both the accuracy of computed Young's modulus from each specimens and the disagreement of unloading curve among specimens. In addition, the comparison about the computed results of Young's modulus between this study's method and the prescript method in ISO 14577 is conducted. Furthermore, influence of the standard specimen for calibration on computed Young's modulus is investigated. Finally, the comparison about the dependence on the test force for Young's modulus between this study's method and the tester's method shows the obvious advantage of the former method.