A Transparent Indenter Measurement Method for Mechanical Property Evaluation

An optical Transparent Indenter Measurement (TIM) method was developed for measurement of material surface mechanical properties. During the spherical indentation test, in-situ measurements of indentation-induced surface out-of-plane displacements were obtained using an integrated phase-shifting Twyman-Green interferometer. Based on elastic recovery theory and 2D finite element analyses, a procedure was developed to determine the material Young's modulus using the measured surface out-of-plane displacements. During the spherical indentation test, contact radii were also measured and used to estimate the material post-yielding true stress-strain curve using Tabor's empirical relation. An experimental TIM apparatus was assembled to test on two engineering alloys and the results showed good agreement with known material properties.