Reverse identification of constitutive parameters of Inconel 718 alloy based on analytical model and thermo-mechanical loads analysis of machined surface

Abstract

Finite element simulation is able to predict cutting force, temperature, stress distribution and chip formation. Constructing a constitutive model suitable for cutting simulation can accurately describe the state of the cutting process, which plays an important role in improving surface quality as well as optimizing cutting parameters and tool geometric design. Nickel-based superalloys are widely used in aerospace due to their excellent physical and mechanical properties at high temperatures. In this study, J-C parameters reverse identification of Inconel 718 alloy was carried out in both the solution annealed state and precipitation hardened state. The average cutting force and chip thickness were obtained by conducting orthogonal cutting experiments, after which the shear angle was calculated. Through quasi-static compression experiments, the yield strength, strain hardening modulus and hardening index of the material were then obtained. Considering the influence of the cutting-edge radius on cutting force during the cutting process, the Waldorf model was introduced into the analytical model in order to describe the deformation characteristics (strain, temperature, strain rate and stress) of the primary shear zone, after which the shear force was modified. The J-C constitutive parameters of the solution annealed state and precipitation hardened state were inversely identified by the intelligent optimization algorithm. According to the given range of cutting conditions, the accuracy of the method was verified through comparison with the cutting force and chip morphology of the finite element simulation. The differences in quasi-static and cutting dynamic mechanical responses of the two states were subsequently expounded. The effects of tool wear types and cutting parameters on the material flow characteristics at the tool tip as well as the thermal-mechanical load on the machined surface of precipitation hardened state Inconel 718 alloy were analyzed via numerical simulation. Accordingly, this study may provide insight into the identification of constitutive parameters of superalloys as well as the control of machined surface quality.

Keywords

• Constitutive model
• Analytical model
• Inverse identification
• Inconel 718
• Tool wear