Process Parameter Investigations of Backward Extrusion for Various Aluminum Shaped Section Tubes Using FEM Analysis S. Orangi, K. Abrinia, and R. Bihamta (Submitted August 3, 2009; in revised form March 9, 2010) In this article, a FEM investigation has been carried out to analyze the backward extrusion of aluminum tubes which have internally and externally shaped sections. ABAQUS/Explicit finite element method was used to solve the problem. As a result, the distribution of stress, strain, and spatial velocity in the defor- mation region were obtained. Grid deformation patterns were also studied using the FE simulation to observe the material flow during the process. Initial billets with various cross sections such as rectangular, elliptical, hexagonal, octagonal, and square shapes were utilized in the simulations. Also various shaped punches such as circular and elliptical sections were employed for this analysis. In this article, the influence of the process parameters such as friction factor and reduction in area on the extrusion pressure was studied. The effects of reduction of area and friction factor on the configuration of free surface and velocity field have been investigated too. The results obtained from the present study were compared with analytical and experimental works and acceptable agreements were observed. Keywords backward extrusion, FEM, shaped section aluminum tubes 1. Introduction Industrial application of metal forming processes such as indirect extrusion has become increasingly popular. Detailed understanding of the material flow, stress and strain distribu- tion, the influence of the process parameters such as friction, reduction of area, shape complexity factor, and other param- eters on the extrusion pressure and the final product are very important. In one of the analytical studies carried out on the indirect extrusion of shaped sections, Bae and Yang (Ref 1) presented an upper-bound solution for the final-stage extrusion load and the deformed configuration for the three-dimensional backward extrusion of internally elliptic-shaped tubes from round billets. Later on, Bae and Yang (Ref 2) using the upper bound analysis proposed a simple kinematically admissible velocity field for the backward extrusion of internally circular-shaped tubes from arbitrarily shaped billets. A new kinematically admissible velocity field was presented by Bae and Yang (Ref 3) to determine the final-stage extrusion load and the average extruded height in the backward extrusion of internally non- axisymmetric tubes from round billets. Indirect extrusion of internally circular-shaped tubes from arbitrary shaped billets was presented by Lee and Kwan (Ref 4) in which a modified kinematically admissible velocity field was formulated. Lin and Wang (Ref 5) proposed a new upper-bound elemental method (UBET) for solving forging problems that were geometrically complex or needed a forming simulation for predicting the profile of the free boundary. Backward extrusion- forging of regular polygonal-shaped cup was analyzed by Moshksar and Ebrahimi (Ref 6) using an upper bound formulation. Finite element simulation was used to analyze axisymmetric hot backward extrusion problems by Guo et al. (Ref 7). A finite element simulation for the backward extrusion of internally hollow arbitrary shaped sections from arbitrary shaped billets was performed by Abrinia and Orangi (Ref 8-11). In this article, backward extrusion of externally various shaped sections using finite element method was simulated to study the stress, strain, and velocity distribution in the deformation zone and to investigate effect of friction, area reduction, and shape complexity on the extrusion pressure. 2. FE Simulation Simulation of backward extrusion of billets with initially shaped sections such as square, rectangle, ellipse, hexagon, and octagon, employing circular and elliptical punches were performed by ABAQUS/Explicit. AA2024-O and AA1100-O were chosen as the working materials. In this simulation, billet dimensions for the AA1100-O were 22 mm width from side-to-side and 20 mm length (Ref 4) and for the AA2024-O, 25*25*2 mm (Ref 2). In the beginning of the process the distance between the punch and the billets was S. Orangi, School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran and Aluminum Research Centre (REGAL), Laval University, Quebec City, QC, Canada; K. Abrinia, School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran; and R. Bihamta, Aluminum Research Centre (REGAL), Laval University, Quebec City, QC, Canada. Contact e-mails: Sakineh.orangi.1@ulaval.ca, cabrinia@ ut.ac.ir, and reza.bihamta.1@ulaval.ca. JMEPEG (2011) 20:40–47 ÓASM International DOI: 10.1007/s11665-010-9655-8 1059-9495/$19.00 40—Volume 20(1) February 2011 Journal of Materials Engineering and Performance