Numerical and experimental study of the process parameters effect on the void evolution in the cold extrusion of rods

Elimination of defects such as voids and internal cavities is required in metal forming processes to avoid premature failure of mechanical components during service. In this paper, the effect of different parameters on the void closure behavior is studied in the cold extrusion of rods. A three dimensional nonlinear dynamic finite element model is developed for this purpose. Experiments are also performed on aluminum samples to verify the accuracy of the finite element model. Results of the developed model are in good agreement with experimental findings. It is observed that voids contract in all directions during the direct extrusion which is in contrast to some other metal forming processes like forging and rolling. Effect of parameters such as die semi-angle, friction coefficient and void location on the void evolution is systematically investigated and discussed. The results of this study can help industries using metal extrusion for optimized design and control of the process to reduce voids and porosity and increase the strength of their product.