Hydroforming

About: Hydroforming is a research topic. Over the lifetime, 2796 publications have been published within this topic receiving 26293 citations. The topic is also known as: Bulge forming.

Effect of bright annealing on stainless steel 304 formability in tube hydroforming

Abstract: Effects of bright annealing (BA) on enhancing formability of stainless steel 304 tube in a tube hydroforming (THF) process were studied. The tube material was the metastable austenitic stainless steel 304 with an initial thickness of 0.5 mm and an outer diameter of 31.8 mm. Both FEA and experimental results showed that THF process of the investigated part alone failed to achieve desired tube expansion of the diameter of 50.8 mm without severe fracture. Thus, a heat treatment process, also known as bright annealing (BA), which caused little to none oxide on the surface of annealed tube, was considered. Initially, effects of different annealing parameters such as temperature and holding time on the material formability were investigated using tensile tests. Stress–strain responses of various conditions were compared. As a result, an annealing process consisted of heating at the temperature of 1,050 °C, holding for 30 min, and rapidly cooling by purging N2 gas was identified. This annealing should be applied intermediately after a pre-forming step. With the aid of the BA process, tube deformation was significantly increased and the required tube expansion could be therefore attained. In addition, strain-induced martensitic transformation occurred during the forming process was examined by X-ray diffraction (XRD) method. The amounts of martensite taking place in tubes (pre-forming, post-forming, and after annealing) were determined and discussed.

Statistical evaluation of forming limit in hydroforming process using plastic instability combined with FORM

Abstract: Deviation of raw material parameters, such as work hardening, anisotropy, yield stress, etc., leads to an uncertainty to the position of the forming limit curve (FLC). This paper presents a novel approach to statistically evaluate the forming limit in hydroforming processes when taking into account the variations in the material parameters. First, plastic instability based on the Hill’s quadratic plastic potential is employed to construct the deterministic FLC. Then, with using the assumption that all material parameters are normally distributed random variables, stochastic modeling of the FLC with a confidence level is carried out, and statistical evaluation of the FLC is performed. In this work, a first-order reliability method is adopted for the reliability assessment of the FLC, and this is verified with the Monte-Carlo simulation method.

Optimizitation of the pressure path in sheet metal hydroforming

Abstract: Fluid pressure is the most important parameter in hydroforming deep drawing process. In this manuscript, we present the results obtained from FE modelling using genetic algorithm to determine the optimum fluid pressure for the production of a two-stepped workpiece in the deep drawing hydroforming process. It is suggested that a two-stepped workpiece can be manufactured in a single step which is a significant advantage compared to conventional sheet forming processes. It is also shown that the lowest pressure point in the optimization curve occurs at the step height, which has the potential to allow for a more accurate pressure path selection procedure at shorter times while reducing the number of trials.