Three-Dimensional Finite Element Analysis of Wrinkling in a Stamping Process

The three-dimensional finite element analysis was performed for the investigation of wrinkling that occurred in the stamping processes of tapered square cups and stepped rectangular cups in the present study. An interesting characteristic of these two types of wrinkling is that the wrinkles are found at the draw wall that is relatively unsupported. In the stamping process of a tapered square cup, the effect of process parameters, such as the die gap and blank-holder force, on the occurrence of wrinkling was analyzed using the finite element simulations. The simulation results show that the larger the die gap, the more serious is the wrinkling problem, and such a wrinkling cannot be suppressed by increasing the blank-holder force. In the analysis of wrinkling that occurred in the stamping process of a stepped rectangular cup, an actual production part that bears this type of geometry was examined. The wrinkles found at the draw wall are attributed to the unbalanced stretching of the sheet metal between the punch head and the step edge. An optimum die design for the purpose of eliminating the wrinkles was determined by the finite element analysis. The good agreement between the simulation results and those observed form the wrinkle-free production part validates the accuracy of the finite element analysis, and demonstrates the advantage of using the finite element analysis for the stamping die design.