Modellierung der Belastung, des Eigenspannungsaufbaus und der Lebensdauer in Kaltmassivumformwerkzeugen

Cold forging pistons undergo high local loading which leads to cyclic plastic deformations. Because of this cyclic plastification, tensile residual stresses are built up locally. The aim of this thesis is to analyze the local loading and the build-up of residual stresses and to estimate the local lifetime. This is achieved with the help of simulations, which are performed by the Finite-Element-Package Abaqus. Because of the large mesh distortion and the resulting bad quality of the output, remeshing methods are applied. Furthermore, some variations of the piston´s penetration depth and geometry are analyzed. The effect of these variations on the lifetime is estimated by fracture mechanical methods. In a preceding step, the quality of the material model which is used to simulate the forming process is validated experimentally. The simulation of the forming process shows areas which are heavily loaded and where residual stresses develop due to cyclic plasticity. Depending on the remeshing methods which are used to model the forming process slightly different results are obtained. The different remeshing and result- mapping methods are compared critically with respect to result quality, memory usage and calculation time. The variation of penetration depth and geometry leads to important insights concerning the development of residual stresses and plasticity and their effect on tool lifetime.