Dynamic constitutive models of Ti-6Al-4V based on isothermal ture stress–strain curves

Abstract

Ti-6Al-4V titanium alloy is a typical difficult-to-cut material used in many fields. The selection of cutting parameters exerts tremendous influences on the material removal process. Finite element numerical simulation is a low-cost method to obtain optimized cutting parameters. Finite element simulation requires the study of machining properties of machined materials. The material removal and related physical phenomena during machining are characterized by the dynamic mechanical properties of the machined material. In this paper, the dynamic mechanical properties of Ti-6Al-4V have been tested by the high temperature split Hopkinson pressure bar system to obtain true stress–strain curves under different conditions. The sensitivity of strain and temperature of Ti-6Al-4V has been analyzed. The influence of temperature-dependent specific heat capacity, which has been tested by a laser thermal conductivity tester, on adiabatic temperature rise has been considered. Adiabatic temperature rise has been calculated separately with constant specific heat capacity and temperature-dependent specific heat capacity. True stress–strain curves have been switched to true stress–strain isothermal curves to analyze separately the influence of strain rate and temperature on true stress. Based on true stress–strain isothermal curves, the constitutive models of power-law and Johnson–Cook have been introduced to fit the experimental results. The fitting results of the two constitutive models have been compared with the experiment results, which have an average error less than 6%.