Improvement of Springback Predictability after forming and trimming

When a sheet metal forming operation, such as deep drawing, is followed by a trimming operation the numerical springback after trimming is influenced by physical parameters and loss of product stiffness due to cutting off the material. Moreover, it is affected by the finite element mesh disturbance due to numerical 3D trimming and the cutting process itself, which introduces stresses while trimming. A technique of taking into the account the stress state change due to the element mesh cutting is discussed in the present paper. This technique involves an accurate in-plane mapping of the state variables preceded by a mesh adaptivity procedure that confirms the trimline. The influence of this technique of stress state updating after trimming on the amount of the numerical springback of the whole product is the major question to be answered in this article. The appraisal of this technique with respect to the predictability of the physical springback is discussed.