SPHERICAL INDENTATION METHOD TO DETERMINE STRESS-STRAIN RELATIONS AND TENSILE STRENGTH OF METALLIC MATERIALS

It is significant to obtain the uniaxial stress-strain relations and tensile strength of materials by indentation method for evaluating the integrity of structures in service. Based on energy equivalent assumptions, i.e., the Von Mises equivalence about a RVE (representative volume element) and the median energy equivalence in the effective deformation region, a semi-analytical spherical indentation(SSI) model is proposed to describe the relation among indented load, depth, the diameter of spherical indenter and Hollomon-law parameters if indented materials are uniform, continuous, isotropic and power-law hardening. The stress-strain relations and tensile strengths of the materials were obtained by the tested load-depth curves under spherical indenter loading. Considering the damage effect in the indentation process, a correction model for determining elastic modulus of the metallic materials due to the spherical indentation tests is proposed . For eleven kinds of tested ductile metallic materials with spherical indentation, the Young's modulus, stress-strain relations and tensile strength predicted by SSI model are in good agreement with the uniaxial tensile results.