Metallurgical qualities improvement by automatic preform design of forging processes

A shape optimisation method is described for the inverse problem of dies design. It provides a very powerful tool that allows reducing the designing time and standardising the technologies. In the frame of metal forming of axisymmetrical parts under hot conditions, the basic equations for the finite element simulation and for the optimisation problem are recalled. The method consists in optimising the shape of the preform tool during a two-step forming operation for which the shape of the second operation is known. The sensitivity analysis is based on the direct differentiation of the discrete forging equations. A quasi-Newton optimisation algorithm makes it possible to find the solution in few iterations. The method is applied to several industrial problems. New designs of preforming dies are suggested in order to increase the metallurgical properties of aeronautical forged parts.