Prediction of a billet shape for axisymmetric warm forming using variational analysis

When designing the warm-forming process, it is the usual practice for the preliminary shapes of billets, blanks, or preforms to be predicted by work experience, the geometry of the finished part, and the law of volume constancy. There was no guarantee that the process would be successful. Therefore, in order to verify the reliability of these traditional estimation methods in preparing the billet shapes, it was necessary to conduct a more intensive study. A set of tools in various combinations of punch and die were used both for numerical simulation and for physical modeling. This produced a number of variations in the die cavity. These variations were analyzed to evaluate the feasibility of axisymmetric warm forming with a predicted billet, made of stainless steel AISI 316L. A comparison of the results of the die fillings and load-stroke curves by simulations with experiments showed that the variational analysis is a promising method to use for predicting the critical shapes of billets in axisymmetric warm forming.