A new analysis of nanoindentation load-displacement curves

Abstract

A new scheme for analysing nanoindentation load-displacement curves has been developed in previous work. The key feature of the new scheme is that Young's modulus and strain hardening can be derived from the unloading curve. This scheme uses a nonlinear curve-fitting method to fit the unloading curve. Three parameters, namely Young's modulus E, the strain-hardening parameter and the hardness parameter are directly derived from the curve fitting. A preliminary analysis shows that the strain-hardening parameter determined from the unloading curve can be correlated with the ratio of the yield stress [sgrave]_y to the ultimate stress [sgrave]_u at 29% strain. To combine current analysis with the finite-element analysis developed previously, one can derive the yield stress from the indentation loading curve. This method was applied further to various bulk materials, and the resulting Young's modulus and yield stress show good correlation with the literature values.