An improved energy method for determining Young’s modulus by instrumented indentation using a Berkovich tip

摘要

We previously proposed a method for estimating Young’s modulus from instrumented nanoindentation data based on a model assuming that the indenter had a spherical-capped Berkovich geometry to take account of the bluntness effect. The method is now further improved by releasing the constraint on the tip shape, allowing it to have a much broader arbitrariness to range from a conical-tipped shape to a flat-ended shape, whereas the spherical-capped shape is just a special case in between. This method requires two parameters to specify a tip geometry, namely, a volume bluntness ratio V[sub r] and a height bluntness ratio h[sub r]. A set of functional relationships correlating nominal hardness/reduced elastic modulus ratio (H[sub n]/E[sub r]) and elastic work/total work ratio (W[sub e]/W) were established based on dimensional analysis and finite element simulations, with each relationship specified by a set of V[sub r] and h[sub r]. Young’s modulus of an indented material can be estimated from these relationships. The method was shown to be valid when applied to S45C carbon steel and 6061 aluminum alloy.