Finite Strain Elastoplasticity with Finite Elements Applied to Industrial Forming-Modelling and Discretization Problems

Finite strain elastoplasticity is applied to industrial forming processes — sheet metal forming by stamping and by fluid cell pressure. The objective of the work is to get an efficient code for simulation of the processes. The code should be used in the industry for design of the manufacturing tools and for steering of the process. Typical for our approach is the use of exaggerated inertia terms and an explicit integration method. The positive effects are numerical stability and shorter computer time compared to a quasistatic analysis. Another advantage with this method is that instability phenomena like wrinkling and buckling can be simulated efficiently. The method works well for displacement driven processes as stamping but can not be used directly for force driven processes such as fluid cell pressure. We show an adaptive method which seems to be promising. In order to get a realistic simulation of the springback of the sheet when the load is removed the stress history must be simulated with high accuracy. The simulation time will then be high. We suggest some remedies: A new explicit code is developed based on Kirchhoff-Love shell theory, facet triangular elements and constant strain constant curvature discretization. It is tested against experiments and compared to a well established code.