Effect of Friction Modelling on Damage Prediction in Deep Drawing Simulations of Rotationally Symmetric Cups

The damage state in a formed component has a significant influence on the performance of the component in service. Controlling damage evolution during forming through specific modifications of the process parameters will therefore allow an improvement of this performance. The evolution of the stress-strain state during the forming process is the primary influencing factor of the resulting damage state. The stress-strain state is influenced by the friction between tools and workpiece. To investigate the cause-effect relationship between friction and damage evolution in the deep drawing process, Finite Element simulations of the deep drawing of rotationally symmetric cups were performed. Punch velocity and blank holder force were varied. Damage was predicted using a Lemaitre damage model. The damage states predicted using a Coulomb friction law and a model incorporating a dependence on contact normal stress and relative velocity were compared. The parameter-dependent friction model predicted a change in the damage distribution after forming when varying the process parameters, which was not found using the Coulomb friction law.