Multi-scale Analysis of Void Closure for Heavy Ingot Hot Forging

A multi-scale model towards simulating the void closure during hot forging was introduced in the present study and the derived void evolution model was programmed into commercial code DEFORM to simulate the void closure behavior in heavy ingot during the upsetting and blocking processes. From the simulation results, it can be concluded that- (1) the cymbal-shaped die is good at closing voids not only near the die but also around the axis of the ingot when the reduction is 36% in the upsetting process, (2) the effectiveness of V-shaped die is the best for consolidating voids around the axis and near the die when the reduction is 24% in a single blocking process, however, at about 22% reduction after 90° rotate, the void-closed regions become quite large around the axis both for flat dies and FML dies and the loads are much lower than those of V-shaped dies. Upon that, void closure in multi-stroke and multi-pass forging was also discussed. The multi-scale model and simulation results provide valuable sources of reference for design and optimization of die shapes and pass schedules for heavy ingots during hot working processes.