Study on Constitutive Model of Cyclic Elastoplastic Behavior of 6082-T6 Aluminum Alloy

Abstract

This paper aims to propose an improved constitutive model based on the classical Chaboche mixed hardening model to describe the cyclic elastoplastic behavior of 6082-T6 aluminum alloy. First, 16 specimens from 6082-T6 aluminum alloy were tested under monotonic and cyclic loads. The variation law of the backstress, yield surface size, elastic modulus, and peak stress with equivalent plastic strain was obtained and analyzed. The results show that the kinematic hardening before and after the load reversal had a significant difference. Meanwhile, the elastic modulus and yield surface radius experienced a rapid decay at the early stage of equivalent plastic strain growth and then tended to flatten out. Based on these phenomena, a modified constitutive model based on the classical Chaboche mixed hardening model was proposed. The evolutions of isotropic hardening/softening, backstress, and elastic modulus were introduced. Then, the model was introduced to the ABAQUS software by the user subroutine to define a material’s mechanical behavior (UMAT) subroutine and corresponding parameters were provided. Finally, the proposed constitutive model was proven to capture the cyclic elastoplastic properties of 6082-T6 aluminum alloy well and had a significant improvement on the classical Chaboche mixed hardening model. Among them, the constitutive model can accurately describe the initial yield surface of 6082-T6, with an accuracy improvement of 26.6% compared to the Chaboche mixed hardening model, and an accuracy improvement of 7.44% in describing changes in elastic modulus.