Journal of Materials Research

Articles

Effects of mechanical properties on the contact profile in Berkovich nanoindentation of elastoplastic materials

Jiangting Wanga1, Peter D. Hodgsona1 and Chunhui Yanga2 c1

a1 Centre for Material and Fibre Innovation, Deakin University, Geelong, Victoria 3220, Australia

a2 School of Engineering, Deakin University, Geelong, Victoria 3220, Australia

Abstract

Pile-up or sink-in is always a concern in a nanoindentation test because it gives rise to errors in the estimation of the projected contact area when it is theoretically analyzed with the classic Oliver–Pharr method. In this study, a three-dimensional finite element model is developed to simulate nanoindentation with a perfect Berkovich tip. The variation of the contact profile with respect to the work-hardening rate n and the ratio of yield stress to elastic modulus σy/E has been studied for a wide range of elastoplastic materials. The numerical results show that a low σy/E not only facilitates the pile-up for materials with little or no work-hardening but also enhances the sink-in for materials with a high work-hardening rate. It is attributed to the lateral-flow dominated plastic deformation in low work-hardening materials and the normal-flow dominated plastic deformation in high work-hardening materials, respectively. Because of the large sink-in, for the materials with high n and low σy/E, significant errors in the calculation of the projected contact area can be generated by using the classic Oliver–Pharr method.

(Received May 03 2011)

(Accepted September 16 2011)

Key Words:

  • Hardness;
  • Nanoindentation;
  • Simulation
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