Sheet Metal Hydroforming Process Review Through Shape Factors Analysis and Numerical Simulation

Hydroforming is a forming technology for semi-finished goods like: tubes and sheets that aims to obtain high strength parts and to manufacture complex geometries in one step. Even the material straining caused by fluid pressure leads to a uniform rise in yield strength in the used materials, resulting in a lower need necessary for high wall thicknesses [9]. Nowadays the need of improving the quality and the reliability of products and of decreasing their cost represent general market requests in any field. In particular, in the automotive industry, the main aim is the reduction of CO2 emissions and energy consumptions through the increase of the lightness of cars. In order to satisfy such targets, the attention has been recently focused on many new methods; some of them are aimed to the forming of certain lightweight metals and alloys, while other techniques are directed to a more economic components production than conventional forming methods [10]. Hydroforming allows to overcome some of the limitations of conventional deep drawing, increasing the drawing ratio and minimizing the thickness reduction of the formed parts. Some of the advantages introduced by hydroforming are: a greater flexibility and a remarkable reduction of tooling costs [11]. The basic parts of the tool for a hydroforming process include a punch, a blank holder and a fluid chamber. The draw ratio achievable in hydroforming is quite high (values of about 3,2 are reported in literature) [12], very little thinning occurs and asymmetrical shapes can be drawn. Different studies have been conducted to design a possible classification valid for Tube Hydro Forming (THF), starting from the analysis of the shape of the formed part [13]. Though this paper only relates to Sheet metal Hydro Forming (SHF) , it refers back to the above consideration about THF. The aim of this paper is to define a “shape factors” set and to direct the designer towards a proper goal in his development of the process for metal components produced through the application of sheet hydroforming. Finite Element Analysis (FEA) has been extensively used in order to investigate and define each shape factor with a proper comparison to the macro feasibility of the chosen component geometry. In other studies, these shape factors have been also used to track the process performances through their variation thanks to the usage of the numerical simulation which has been later validated with an appropriate experimental campaign. In this paper, these parameters have been applied to a geometrical complex shape in order to investigate its own feasibility only analyzing its CAD model and to evaluate different modifications on the geometry to reach its own feasibility.