FE simulations of the crushing of circular tubes into triangular cross-sections

The objectives of this study are to explore, using the finite element (FE) method, the plastic flow patterns of a circular tube hydraulically expanded or crushed into a regular triangular cross-section. The tubes used in the crushing process have larger diameter and smaller thickness than the tubes used in the hydraulic expansion test. The relationship of the forming pressurisation and loading pass during crushing processes is discussed. The comparisons of the simulation results such as thickness distribution of the formed product, clamping force, forming pressure, etc., between hydraulic expansion and crushing processes were made. It is known that the internal pressure and crushing force needed for the crushing process are only about 1/40 and 1/27, respectively, of those for the expansion process in a regular triangular die. The thickness distribution of the formed product obtained by crushing processes combined with hydroforming is much more uniform than that by a hydraulic expansion process only.