Post-Yielding Stress-Strain Determination Using Spherical Indentation

Abstract

In this research, finite element (FE) simulations were performed to verify Tabor's empirical relations that enable the use of the indentation test for determination of post-yielding uniaxial stress-strain curves of a variety of ductile metallic alloys. Both piling-up and sinking-in materials are included in this study. From the FE spherical indentation simulations, the indentation loads and projected contact radii are obtained for various elastic power-law plastic solids in both bulk and thin film substrate systems. It is found that for bulk materials, the indentation stresses and strains obtained from Tabor's empirical formula agreed well with the input uniaxial stress-strain data. This approach is then verified experimentally by spherical indentation tests on Inconel 783 alloy. In thin film substrate system, two cases, soft film on hard substrate and hard film on soft substrate were studied and the substrate effect on Tabor's relation was analyzed.