An application of fully coupled ductile damage model considering induced anisotropies on springback prediction of advanced high strength steel materials

Abstract

In this paper, an advanced model formulated in the framework of non-associative plasticity is used to accurately predict the springback of advanced high strength steels material. The proposed model strongly couples the isotropic ductile damage to the phenomena a combined nonlinear isotropic and kinematic hardening, initial anisotropic plastic flow and induced anisotropies due to the distortion of the yield function and the plastic potential respectively. For the application, the simulations were conducted for U-draw bending of as-received DP 780 steel sheet proposed by Numisheet’2011 Benchmark. The proposed model was able to capture adequately the Bauschinger effect, transient hardening (distortional) and ductile damage-induced softening. The results have shown that the distortion of yield function affect significantly the stress distribution especially in the sidewall curl during the forming stage thereby explaining observed variations in springback. For full coupling with isotropic ductile damage, the predicted angular springback was found in good agreement with experimental measurements and the sidewall curl was significantly improved in comparison to the simple use of hardening models. This means that isotropic ductile damage and its effect on the other physical phenomena require special attention in order to take benefit when designing newly developed advanced high strength steels (AHSS) parts for automotive and aerospace industries.