Semi-analytical model for predicting mechanical properties of metals using flat truncated cone indenter and its application

Abstract

Based on the energy density equivalence method, a semi-analytical model describing the relationship between the material parameters of Hollomon’s law, load, displacement, and indenter geometry under flat truncated cone indentation (FTCI) was proposed. For a specific indenter, the model parameters were determined by presetting a small volume of material in finite element analysis (FEA). An FTCI test method to obtain the strain hardening coefficient and strain hardening exponent of the material from the load–displacement curve was proposed, and a damage factor (β) model was developed to predict the elastic modulus of the material by using multi-stage loading and unloading tests. Indentation tests were conducted on ten types of steel material using two types of flat truncated cone indenters with 15° and 30° angles. The results showed that the errors between the Young’s modulus measured via the indentation and uniaxial tensile tests were less than 5%; the relative errors between the indentation tensile strength and yield strength by the 30° flat truncated cone indenter and the uniaxial tensile test were less than 6%. For the 30° flat truncated cone indenter, the goodness-of-fit between the stress–strain relationship measured via the indentation and the uniaxial tensile tests was more than 0.95, and 80% of the goodness-of-fit was more than 0.97.