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Free expansion of straight tubes is the simplest test to evaluate tube properties for hydroforming applications and to provide basic understanding of the mechanics of tube hydroforming. A circular cylindrical tube is sealed at both ends and fluid, usually water, is pumped into the tube to increase its internal pressure to bulge and burst the tube. Previous numerical simulations of the free expansion tube test were limited to modeling the midsection of the tube under various assumptions of deformation path. The simulation results obtained deviated from the experimental results under all simulation conditions considered. A new model is developed in this paper in which the whole tube is simulated instead of considering only its mid-section. Judged by the pressure-expansion relations, the model accurately predicted free expansion hydroforming tests results.

Tailor welded blanks (TWB) afford better utilization of sheet steel for automotive and other applications. However, forming behaviour can be complicated because of the interactions between the different sheet steels comprising the TWB and the welding processes used. At Dofasco we have studied a matrix of different steel types, sheet thicknesses, and welding processes (i.e. mash seam, laser and electron beam) in order to gain an understanding of forming behaviour of tailor welded blanks. Simulative forming tests such as hole expansion, stretch bend, stretch dome and tensile tests were used. Finite element simulations using the FTICASE code were used to determine mechanisms for part failures. In addition, weld “service” characteristics such as corrosion performance and fatigue life were evaluated. Microscopic examinations included microhardness, metallography, and tests for weld porosity and zinc entrapment.