Modelling of Tube Hydroforming Process: Identification of Best Process Parameters and Comparison Between Different FE Models

Tube hydroforming (THF) is an assessed production process for the fabrication of tubular components. Its main advantages are the enhancement of the material strength and the shortening of the production chain. Moreover, THF allows to obtain complex geometries all in one so reducing the number of production steps, assembly time and production costs. For these reasons, THF finds applications in many industrial fields. The design of the production process is typically done in two subsequent steps, using Finite Element Models (FEM) and, then, experiments. FEM allows to outline the process curves globally (punch strokes and pressures) and to estimate the loads (punch and die closing forces), while experiments validate the FEM and perform the final tuning of the process. To reduce the efforts in the experimental phase, a reliable FEM software is necessary. The available commercial software can be divided into two main groups depending on the solving algorithms: explicit and implicit. Explicit software is faster but less reliable, the opposite for implicit one. Moreover, in the case of thin-walled parts (such as tubes or sheets), also the type of mesh adopted can be grouped into two: shell and solid meshes. The main differences are the same as the solver, faster but less precise the first and the opposite for the second. Given these countertrends in computation, this paper aims at comparing two software for THF: an explicit with shell elements (PamStamp) and an implicit with solid elements (DeForm). The comparison will highlight the pro and cons of the two solutions and, finally, a trade-off will be proposed.