Abstract:The extrusion process of hybrid sheet metals through arbitrarily curved dies was analyzed by the method of upper bound. The material under deformation was divided into two deformation regions, bimetal and mono-metal regions, and the flow of the material in each region was assumed as plane strain state. The internal, shearing and frictional power terms were derived and they were used in the upper bound model. The extrusion forces for two types of die shapes, an optimum wedge shaped die and an optimum streamlined die shape for a hybrid sheet composed of copper as sleeve and aluminum as core were determined. The corresponding results for those two die shapes were also determined by using the finite element code, ABAQUS, and compared with the upper bound results. These comparisons show a good agreement.

Key words: extrusion; hybrid sheet metal; upper bound method