Metamodeling and optimization of the THF process with pulsating pressure

Tube hydroforming is a process used in various applications to form the tube in a desired complex shape, by combining the use of internal pressure, which provides the required stress to yield the material, and axial feeding, which helps the material to flow towards the bulging zone. In many studies it has been demonstrated how wrinkling and bursting defects can be severely reduced by means of a pulsating pressure, and how the so-called hammering hydroforming enhances the formability of the material. The definition of the optimum pressure and axial feeding profiles represent a daunting challenge in the designing phase of the hydroforming operation of a new part. The quality of the formed part is highly dependent on the amplitude and the peak value of the pulsating pressure, along with the axial stroke. In this paper, a research is reported, conducted by means of explicit finite element simulations of a hammering THF operation and metamodeling techniques aimed at optimizing the process parameters for the production of a complex part. The improved formability is explored for different factors and an optimization strategy is used to determine the most convenient pressure and axial feed profile curves for the hammering THF process of the examined part. It is shown how the pulsating pressure allows the minimization of the energy input in the process, still respecting final quality requirements.