A novel combined dual-conical indentation model for determining plastic properties of metallic materials

Abstract

Based on the equivalent energy principle (EEP), an explicit theoretical model between conical indentation response and uniaxial mechanical parameters is derived. In order to avoid the defect that sharp indentation technique always requires at least two indenters to penetrate different positions successively and the compatibility between the indentation points, an energy-based combined dual-conical indentation (CDI) model is created by using a novel combined indenter with dual conical surfaces. A typical piecewise load-depth curve is observed during the combined dual-conical indentation and two characteristic loading curvatures are respectively acquired from the single penetration response. Numerical verifications for the novel method are conducted by finite element analysis (FEA) within a large range of elastic–plastic materials. For six kinds of metallic materials, based on the stable load-depth curves obtained by the combined indentation tests, the uniaxial stress–strain curves as well as the yield stress, strain hardening exponent and tensile strength are predicted by CDI model. The results show that the predictions of CDI method are consistent with those from uniaxial tension. The novel method is expected to be more convenient for mechanical testing and evaluation of materials or structures.

Keywords

• Combined dual-conical indentation
• Stress–strain relation
• Tensile strength
• Finite element analysis