Optimum shape design of die and preform for improved hardness distribution in cold forged parts

Hardness of a cold formed part increases due to plastic deformation induced during the forming process. Hardness affects forgability of the part as well as its mechanical performance in use. In this study, a method was proposed to optimize the shape of preform and die to minimize variation in hardness distribution. The method was applied to backward extrusion. A finite element model of the mechanical behavior of the material during processing was developed to predict the effective strain distribution in the part. The hardness distribution was determined using an analytical relation between effective strain and hardness. An optimization code based on the Nelder-Mead search algorithm was developed and integrated with the finite element model. The results showed the effectiveness of the proposed method.