Investigation of the morphology of internal defects in cross wedge rolling

Since internal defects in the cross wedge rolling (CWR) process can weaken the integrity of the final product and may ultimately lead to catastrophic failure, it is necessary to investigate the mechanisms of their generation and growth. Using a specially designed CWR experimental apparatus, experiments were performed at more than 50 different operating conditions. The cross-sectional profiles of the workpiece specimens were examined and compared at each condition. Based on the experiments, the influence of three primary parameters in CWR process - the forming angle α, the stretching angle β, and the area reduction ΔA were determined. From the experimental results, the morphology of void generation and growth in CWR is ascertained and discussed. Through the definition of a non-dimensional deformation coefficient ε, a method for predicting the likelihood of void formation is also established and discussed with respect to optimizing CWR tooling design.