On twist springback of a curved channel with pre-strain effect

In the field of automotive lightweight manufacturing, the advanced high-strength steel (AHSS) sheet gets a pivotal position owing to a good match between the plasticity and superior strength. However, in the complex multi-step loadings, the twist springback phenomenon generated by irregular and curved stampings has arisen great concerns. In this article, the material DP500 is adopted for the twist springback analysis in a two-step loading experiment. First, the large bone-shaped specimen is deformed to 4% strain along the rolling direction. Subsequently, the forming blank, cut from the large specimen at different directions, is stamped in a die to form a 3D curved channel. Meanwhile, the simulation analysis of the two-step loading procedure is built for twist springback prediction. An advanced distortional hardening model incorporated with an attenuated modulus model is applied for exactly capturing the deformation features under mutative strain path. A deep analysis with regard to the residual stress and elastic modulus distribution is conducted to evaluate the pre-strain's influence on the twist springback of this curved part. The result shows that mutative strain path induced by the change of the pre-strain axis has a significant impact on the twist springback. Keywords: Twist, DP steel, Multi-step loading, Strain path change