Numerical shape optimization of cold forging tools by means of FEM/BEM simulation

The procedure of a numerical shape optimization of the cold forging tool geometry allows for a reduction and a homogenization of tool load stresses. This procedure considers the workpiece-tool-machine interaction by means of the FEM/BEM coupling. The coupling requires modifications to insure accurate integration in TOSCA software for further shape optimization. The resulting distribution of the nodal displacements and changes of tool geometry are discussed and analyzed. Additionally, the numerical validation of the results by means of mechanical simulation of the optimized geometry with the extended FEM/BEM model is given. The equivalent stresses distribution at the end of lateral extrusion in the tool and in workpiece is presented. The numerical shape optimization leads to the maximum equivalent stress value reduction on the press shoulder on 856 MPa, corresponding to a percentage decrease of 24.3 % in comparison with the initial geometry. The approach for the compensation of load induced workpiece deviations, involving the described optimization procedure, is presented as well.