Method to determine the plastic properties of bulk materials by nanoindentation

The indentation of elastic-plastic strain-hardened material with a conical indenter was investigated using the finite-element method. The influence of the ratio of the elastic recovered depth h e to the maximum penetration depth h max on the deformation behaviour of the material and its relationship with the material parameters [sgrave] y/E and n were analysed. The finite-element results were compared with the results of Berkovich indentations on single-crystal aluminium, single-crystal tungsten, nickel, lead, fused silica and BK7 glass. It is found that h e/h max can be directly related to the elastic-plastic properties [sgrave] y/E and n of a material, which determine the deformation behaviour of materials. The pile-up and sinking-in behaviour of the material during indentation is controlled by both strain hardening and h e/h max. No pile-up occurs for materials with n > 0.3; for materials with n < 0.3, the critical value of h e/h ma? for pile-up and sinking-in is 0.12. The hardness of a material measured by indentation is a function of the stress at about 10% plastic strain for both soft and hard materials. Direct comparison of finite-element results with experimental indentations shows good agreement. Based on the analysis, a method that can be used to estimate the plastic properties of bulk materials is proposed.