Abstract
In the automotive industry, advanced high strength (AHS) steel sheets are widely used for various structural and safety parts in car body. Such AHS steels exhibit complex microstructures containing different phase constituents. The yield and tensile strength of these steel sheets are significantly increased, but the formability is very restricted due to earlier occurred local damages. Their fracture behaviours are thus strongly governed by the microstructure characteristics and interplays between various phases. Besides, the forming processes of AHS parts mostly showed a non-linear strain history, for which the conventional forming limit curve (FLC) could not be properly applied. In this work, stretch-bending tests were carried out for the AHS steel sheet grade 980 after subjected to different pre-strains. FE simulations on the micro-scale of the forming experiments were performed by using 2D representative volume element (RVE) model, which was generated from the real microstructure of examined steel. Hereby, local crack occurrences in the microstructure of steel were described. Furthermore, the FE results by using isotropic and kinematic hardening law were compared. Finally, the bending limits of steel grade 980 after varying pre-strains were predicted.
Published Version
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