High Accurate Prediction of Residual Stress Considering Plasticity during Tempering Process

Abstract

During tempering process of steel materials, a plastic strain occurs along loading direction even if the macro-scopic stress is less than yield stress. The authors name this phenomenon “ tempering plasticity ”. The tempering plasticity may occur by not only external force but also residual stress. It can be expected, therefore, to improve the precision of prediction of residual stress by taking account of the tempering plasticity. In this paper the plastic strain is experimentally investigated by tempering of quenched specimen under tensile or compressive stress and a mathematical model of tempering plastic strain rate is formulated by using an analogy between transformation plasticity and tempering plasticity. The newly developed formulation of tempering plasticity is implemented in commercial FE code and is applied to evaluate the residual stress after tempering in the locally quenched steel block. It is confirmed that the new model predicts the residual stress in high precision.