Plasticity theory of ductile fracture by void growth and coalescence

The axisymmetric cold forging is used in the automobile industry to manufacture the formed parts en masse. But, this process is often limited by the onset of surface cracking which reduces the quality of the final product. In this paper, the theoretical investigation of the initiation of the ductile fracture in axisymmetric upsetting processes is carried out using a simple method of analysis. The developed method is based on the theory of plasticity and a fracture criterion, in which the influence of the growth and coalescence of the cylindrical and spherical voids is considered. The cracking at the free surface of the cylindrical billet is modelled. Dedicated to Professor Theordor Lehmann, Bochum