Method to determine the plastic properties of bulk materials by nanoindentation

摘要

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(c) to the maximum penetration depth h(max) on the deformation behaviour of the material and its relationship with the material parameters sigma(y)/E and it 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 sigma(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(max) 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. [References: 17]