Plastic zone and pileup around large indentations

Abstract

Mechanical properties of cold-worked molybdenum, grade 4 titanium, and an α-β titanium alloy are measured with tensile tests and by indentations using conical indenters with 105, 120, and 137 deg included angles. The extent of plastic deformation and pileup around an indentation is measured using profilometry. Various models predicting the extent of plastic deformation and pileup are compared to the actual measured values. As inferred from indentation, the calculated yield strength of the material from the mean pressure does not correlate well to the yield strength measured by tensile testing. The plastic zone size surrounding an indentation can also be used to determine the yield strength of the material, and this does correlate to the yield strength measured by tensile tests. Furthermore, the extent of plastic deformation is relatively independent of the included angle of the indenter for the range of materials used in this system. Models predicting the amount of pileup at the edges of the indentation appear to approach but overestimate the actual amount of pileup in the materials tested.