Towards efficient modelling of macro and micro tool deformations in sheet metal forming

During forming, the deep drawing press and tools undergo large loads, and even though they are extremely sturdy structures, deformations occur. This causes changes in the geometry of the tool surface and the gap width between the tools. The deep drawing process can be very sensitive to these deformations. Tool and press deformations can be split into two categories. The deflection of the press bed-plate or slide and global deformation in the deep drawing tools are referred to as macro press deformation. Micro-deformation occurs directly at the surfaces of the forming tools and is one or two orders lower in magnitude. The goal is to include tool deformation in a FE forming simulation. This is not principally problematic, however, the FE meshes become very large, causing an extremely large increase in numerical effort. In this paper, various methods are discussed to include tool elasticity phenomena with acceptable cost. For macro deformation, modal methods or ’deformable rigid bodies’ provide interesting possibilities. Static condensation is also a well known method to reduce the number of DOFs, however the increasing bandwidth of the stiffness matrix limits this method severely, and decreased calculation times are not expected. At the moment, modeling Micro-deformation remains unfeasible. Theoretically, it can be taken into account, but the results may not be reliable due to the limited size of the tool meshes and due to approximations in the contact algorithms.