A Study on the Effect of Young's Modulus Modeling on the Energy Conservation in Elastic-Plastic Material Computation

Young's modulus has a strong effect on the mechanical behavior of elastic-plastic materials, such as elastic stiffness, elastic recovery, and potential energy. Since springback prediction is important in the sheet metal forming process, many of Young's modulus studies have been focused on capturing the amount of springback. This work investigated the effect of Young's modulus modeling focusing on energy conservation point. For this study, three representative concepts of Young's modulus modeling (fixed modulus, chord modulus, and nonlinear modulus models) were employed. The three modulus models were coupled with the Chaboche kinematic hardening, and implemented into the ABAQUS User-defined material subroutine. The models were used to simulate cyclic loading, monotonic loading conditions, and 2D-draw bending process including the springback prediction. The models showed good agreement with the measured data in the numerical studies. However, in the chord modulus model, a negative potential energy phenomenon was detected during the elastic recovery path, which is unrealistic, while the fixed and nonlinear modulus models keep the energy conservation law. This work discusses the reason for the negative potential energy computation based on the energy dissipation, and presents a numerical method to compensate the negative potential energy.