Constitutive modeling and deformation analysis for the ultrasonic-assisted incremental forming process

The application of high-frequency vibration on the incremental forming process could cause changes in the plasticity of material which may contribute to the reduction of forming force, the increase of formability, and the improvement of surface finish. The present work aims to deepen the understanding of the softening effect to facilitate the accurate prediction of the ultrasonic-assisted forming process. First, a theoretical model describing the relationship between the stress and strain during the ultrasonic-assisted incremental sheet forming (UISF) was established based on the theory of crystal plasticity. In particular, the acoustic softening effect was reflected by adjusting the thermal activation process and the dislocation density evolution process. Then, the constitutive model parameters were identified through the back propagation (BP) neural network based on the experimental results. In addition, the developed model was used to simulate the UISF process by ANSYS/LS-DYNA software, and the effect of ultrasonic vibration on the deformation behavior was revealed. The results show that the FE model with the modified constitutive model considering the softening effect can improve the prediction accuracy.