Cyclic and Biaxial Deformation Behavior for Bake-hardenable Steel Sheet

Abstract It is well known that bake hardening treatment on the bake-hardenable steel sheets leads to the increase of yield strength and appearance of yield point phenomena under uniaxial tension deformation. On the other hand, strain paths during forming process and the subsequent dent resistance are usually not monotonic nor uniaxial, so that more investigation under complex strain path and stress state are essential in order to establish its constitutive model and achieve an accurate prediction of dent resistance by numerical simulation. In the present study, the effects of bake hardening treatment on various pre-strain paths and secondary deformations after bake hardening treatment were observed. From the obtained results, the yield drop phenomena did not appear and the Bauschinger effect was observed in cyclic deformation with bake hardening treatment. On the other hand, the yield drop and the subsequent yield plateau followed by workhardening was observed in equi-biaxial tension test as similar to the result of conventional uniaxial tension test result with bake hardening treatment.