An analytical approach for the design optimization of bearing land in the metal extrusion of shaped sections

Abstract

Bearing region plays an important role in controlling material flow and its optimal design could lead to high quality extruded products. On the other hand, too much of bearing causes the process load to increase. Thus, there must be an optimum point where the bearing lands and the extrusion pressure are just the right values. Determining the proper bearing length is often performed using trial and error methods in the extrusion industry and numerical analysis. The aim of this study is to optimize the bearing length in forward extrusion dies using upper bound method for non-axisymmetric sections. A generalized kinematically admissible velocity field is employed to obtain uniform velocity at the exit surface of the die. Dead metal zone and bearing region define the geometry of the deformation zone. The multi-objective optimization using response surface methodology was applied to optimize the relative extrusion pressure and the deviation of the mean value for the velocity at die exit. Using this method, the proper bearing length is determined. Optimization of bearing land is performed for extrusion of rectangular and L-shaped profiles. The proposed analytical method was verified by physical modelling experiments and numerical simulations. A unique answer for the bearing design could be obtained using the suggested method in a few seconds opposing to numerical method which required many timely and costly trials. This method would be useful for die designers to get the appropriate bearing land and at the same time not to increase the process load excessively.