We performed measurements which show that Young's modulus of the prestrained sheet is reduced by 15%.
The aim of the paper is to demonstrate, based on the results of respective numerical simulations of a drawing process, how springback of a steel sheet drawn part is affected by stiffness degradation, which results from the material damage evolved during the forming process. For the purpose of the presented study the GTN (Gurson–Tvergaard–Needleman) damage constitutive model coupled with Mori–Tanaka approach has been implemented in ABAQUS/Explicit via VUMAT user material subroutine, while integration of the constitutive model is performed with a numerical scheme developed recently by the authors. Parameters of the constitutive model are identified, for authenticity of the study, from the measurement data obtained from classical tensile tests of cold rolled stainless steel EN 1.4301, as well as from the measured stiffness degradation, as a function of the plastic strain. From a comparative analysis of numerical results of the springback behaviour, investigated on the Demeri springback cup test under assumption of different constitutive models, it can be concluded, that stiffness degradation should be incorporated in simulations of sheet metal forming. Its influence on a predicted final shape of a steel sheet drawn part is namely too significant to be neglected.
VRH, Marko, HALILOVIČ, Miroslav, ŠTOK, Boris. Impact of Young's modulus degradation on springback calculation in steel sheet drawing = Vpliv zmanjšanja Youngovega modula na izračun elastične povračljivosti pri vleku jeklene pločevine. Stroj. vestn., 2008, letn. 54, št. 4, str. 288-296.