Numerical and experimental study of sheet metal hydroforming.

The rising hydroforming technology is taking an increasing interest in the industrial environment, particularly due to the weight reduction and uniform thickness distribution that can be achieved by this technology when compared to standard stamping process. Simple sheet and tube hydroforming have been the first studied and applied, now double sheets is a new variety of hydroforming which could offers a substantial improvement in cycle time production since two parts are formed simultaneously. In this paper we deal with the numerical simulation aspect and experimental validation on elliptical bulge tests. An implicit finite element formulation in velocity/pressure is used to solve the 3D volumic problem. Two algorithms to deal with the hydrostatic pressure are discussed. The first one is called “load control” method, consisting in solving the hydroforming equilibrium problem with an increasingly imposed pressure. Nevertheless, when a maximum of pressure is reached, the algorithm can fails. The second family of methods called “arc-length methods” have the advantage to go through the previous instability point, we have in particular developed a modified displacement control method. The Modified Maximum Force Criterion was modified by introducing the strain rate sensitivity effect and then used to predict necking. Comparison with the experiments was then made. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]