A HYBRID METHOD FOR DETERMINING MATERIAL PROPERTIES FROM INSTRUMENTEDMICRO-INDENTATION EXPERIMENTS

The impact code EPIC was employed to study the relationship between th e applied force and the penetration depth in a micrometer-scale indent ation experiment with oxygen free high conductivity (OFHC) copper. EPI C is an elastic-plastic finite element code that uses a Lagrangian for mulation and triangular mesh, which can accommodate large deformation without the need to remesh during the computation process. By fitting the force-penetration curves for a triangular indenter with second deg ree polynomials, it was demonstrated that the fit changed with two mat erial constants in the constitutive equation. A systematic procedure f or determining the material constants is described that is based on ma tching either the slope or the curvature of the force penetration dept h curves from numerical simulation and experiments. It is concluded th at material constants can be determined from indentation data obtained using pyramidal or spherical indenters as well as a flat-ended indent er.