Numerical and experimental analysis of necking in 3D. sheet forming processes using damage variable

摘要

As fracture in metal forming is mainly due to the development of ductile damage and to represent the failure of anisotropic sheet-metals, an extension of the Gurson-Tvergaard model is presented and implemented in the context of plane-stress for shell elements. Moreover, a new necking criterion is proposed within the framework of the modified force maximum criterion which includes the determination of local necking for arbitrary strain paths as well as for anisotropic materials. The difference of orientations between the principal stresses axes and the orthotropic axes are taken account. The paper closes with a numerical and experimental study of the necking of rectangular strips in several Marciniack's experiments.