Investigation of lubrication effect on the backward extrusion of thin-walled rectangular aluminum case with large aspect ratio

Backward extrusion processes are being increasingly considered for the manufacture of thin-walled rectangular aluminum case with large aspect ratio in lieu of multi-stage deep drawing processes. In order to design an optimized backward extrusion process, it is necessary to determine optimal frictional conditions by studying the effects of lubrication. In this study, numerical analysis based on the finite volume method is performed for investigating the effects of solid lubricants in aluminum backward extrusion processes. Various shear friction factors are used in the numerical study for investigating the friction effects. Lubrication is found to have a significant effect on the final shape. Larger friction factors are associated with increased forming heights on the wide side of the rectangular container and decreased forming heights on the narrow side. Lubrication is also found to have a significant effect on earing phenomena and a friction factor of 0.2 is found to be optimal for minimizing it. The analysis results presented herein are further validated by comparing them with experimental results. (c) 2006 Elsevier B.V. All rights reserved.