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Analysis and finite element simulation of tube expansion in a rectangular cross-sectional die

Abstract The objectives of this paper are to propose a simple analytical expression, which can be used easily in a manufacturing plant to estimate the forming pressure, and to explore the plastic deformation behaviour of the tubes during the hydraulic expansion process in a rectangular cross-sectional die. At first, when considering the sticking condition, analytical expressions using the thin-walled and thick-walled theorems are proposed to determine the forming pressures needed to hydroform a circular tube into a rectangular cross-section with a desired corner radius. Then a series of finite element simulations of tube expansion are carried out to compare the simulation results of forming pressures with those from the proposed analytical expressions. The flow pattern of the tube during hydraulic expansion in a rectangular die is also examined. The effects of the friction coefficient between the die and the tube upon the thickness variations at certain positions during expansion and the thickness distributions after the expansion process are discussed.