A New Deformation Model for Bimetal Tubes Extrusion Process

In this paper, bimetal tubes extrusion process through conical dies has been analyzed by upper bound method using stream functions. The bimetal tube is in un-bonded conditions initially and the proposed deformation model, investigates the bonding at the interface of two metals in the deformation zone. For this propose, the deformation region has been divided into three deformation zones where the position of the start point of bonding at the interface of two metals is determined. For each deformation zone, an admissible velocity field has been proposed and the internal power, shear and frictional powers and the total power have been calculated. The total power, which is expressed by deformation zone boundaries and the position of the start point of bonding, is optimized and the extrusion force has been calculated. Analytical results are compared with the results given by experimental data of other researchers and also by finite element method that show a good agreement. Finally the effect of various extrusion conditions such as reduction in area and semi die angle upon the extrusion force and the position of the bonding start point at the interface have been investigated.