Journal of Materials Processing Technology 177 (2006) 612–616 Experimental and numerical study of energy consumption in forward and backward rod extrusion M. Saboori ∗ , M. Bakhshi-Jooybari, M. Noorani-Azad, A. Gorji Department of Mechanical Engineering, Babol Faculty of Engineering, Mazandaran University, Babol, P.O. Box 484, Mazandaran, Iran Abstract The primary concern in any metal forming operation is to produce the desired product with maximum die life and minimum die wear. These requirements are achieved when the required load and energy is minimised. In this paper, the extrusion energy is determined for the two optimal conical and curved dies, for aluminum and lead billets, in forward and backward extrusion, using FEM and by performing experiments. It is illustrated that the energy required to deform aluminum and lead billets in the optimum curved die is considerably less than that in the optimum conical die. © 2006 Elsevier B.V. All rights reserved. Keywords: Backward extrusion; Forward extrusion; Energy consumption 1. Introduction Forward and backward extrusion are the processes in which the cross-sectional area of a billet is reduced by forcing it to flow through a die with a certain shape. One of the most important fac- tors in a forming operation is the die profile that is an important parameter for optimising a process variable, such as extrusion pressure. A number of studies on plane-strain and axisymmetric extrusion using symmetric and asymmetric dies have been car- ried out by many researchers and a list of references on this topic is given by Johnson and Kudo [1]. In general, different arbitrary curved die profiles have been proposed by some researchers. Yang and Han [2] proposed an analytical method in estimating extrusion pressure for arbitrary curved dies using upper bound solution. Lee et al. [3] studied the optimisation of element sub- division in axisymetric extrusion. Many researchers, such as Ulysse [4], used the finite element method to obtain optimum die profile. Byon and Hwang [5] applied a finite element based optimal process design technique in steady-state metal forming to die profile design in forward extrusion. They predicted the die profile for the minimisation of forming energy for various process conditions and materials. The results they obtained were compared to those of theoretical solution found in the literature. Some researchers such as, Barisic et al. [6] focused on energy consumption in forward extrusion, and Jo et al. [7] investigated ∗ Corresponding author. Tel.: +98 111 3234205; fax: +98 111 3234205. E-mail address: me saboori@yahoo.ca (M. Saboori). the extrudability and energy consumption in forward extrusion for 7003 aluminum alloy. In the aforementioned research works, most focus was given to hot extrusion processes. In an earlier work by the authors [8], the optimal die profile in cold forward rod extrusion of aluminum was obtained using FE simulation and by experiments. It was illustrated that the maximum extrusion load in optimum curved die was considerably reduced compared to that in optimum conical die. In this paper, the above mentioned research by the authors is extended. The extrusion energy is obtained for the optimum curved and conical dies, both for forward and backward extru- sion of two materials: (a) aluminum billets and (b) lead billets. The investigation is performed using the finite element software, ABAQUS [9], and by doing experiments. 2. Experimental procedure Figs. 1 and 2 show the design of two die-sets used in this research for forward and backward extrusion, respectively. For each die-set, two dies are used: (a) optimum conical die and (b) optimum curved die. Fig. 3a shows the schematic of the optimum conical die with a half angle of 30 ◦ and Fig. 3b corresponds to that of the optimum curved die, in forward extrusion. Schematic illustration of the dies used in backward extrusion is shown in Fig. 4. A 600 KN DMG (Denison Mayes Group) universal testing machine was used to perform the experiments. A sodium based grease lubricant was applied manually on the contact sur- faces of billets and die-sets. Lead and aluminum billets with 30 mm in diameter and 40 mm in height were used for the experiments. The diameter of the prod- ucts is 25 mm. The chemical composition of the Billets used in experiment were made from aluminum alloy 5154 (95.61% Al, 3.93% Mg, 0.14% Fe, 0.21% Cr, 0.09% Si, 0.02% Zn) and lead alloy (66% Pb, 27% Sn, 6.5% Bi). 0924-0136/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jmatprotec.2006.04.031