Indentation versus uniaxial power-law creep: a numerical assessment

This study concerns the employment of instrumented indentation to characterize the power-law creep response of metallic materials. Systematic numerical finite element analyses of conical indentation, under controlled constant indentation strain rates, were conducted. The model system is pure tin (Sn) and Sn-based alloy with known uniaxial power-law creep parameters, with their stress exponents ranging from 7 to 10. It was found that the constant indentation strain rate results in a steady-state hardness which is independent of indentation depth. The indentation-derived stress exponents are almost identical to those of uniaxial creep, leading to parallel lines of strain rate versus creep stress on the logarithmic scale. A remarkably consistent ratio of uniaxial strain rate and indentation strain rate, 0.33, was obtained for all the model materials considered.