Abstract:Joining of lightweight frame structures in small quantities is subject to specific
conditions, which are exemplarily determined for joining by forming processes. Experimental investigations have been carried out to evaluate both feasibility and capability of joining by forming processes. Joining has been accomplished by compressing or expanding cylindrical profiles using rigid tools for rolling-in processes, fluid active medium for hydro-forming as well as active energy
for electromagnetic forming.
“…The design of the groove should be based on the forming process [2]. axial loads primarily by a mechanical resistance against deformation of an undercut section.…”
“…The design of the groove should be based on the forming process [2]. axial loads primarily by a mechanical resistance against deformation of an undercut section.…”
“…Another opportunity for formability improvement was discussed in [26] where the blank was preformed into a shape which utilized formability of the adjacent portions of the blank to fill the corners of the die shape. Authors [27] demonstrated that EHF has a better capability to form sharp corners than quasistatic hydroforming described in [28] and also requires a lower clamping force employing the inertia of the tool and the clamping press, which requires a much smaller capital investment. A reconfigurable EHF tool comprising of several small size chambers can be assembled together for the forming of various shapes, as suggested by Golovashchenko [29].…”
Electro-Hydraulic Forming (EHF) is a high rate sheet metal forming process based on the electrical discharge of high voltage capacitors in a water-filled chamber. During the discharge, the pulsed pressure wave propagates from the electrodes and forms a sheet metal blank into a die. The performed literature review shows that this technology is suitable for forming parts of a broad range of dimensions and complex shapes. One of the barriers for broader implementation of this technology is the complexity of a full-scale simulation of EHF which includes the simulation of an expanding plasma channel, the propagation of waves in a fluid filled chamber, and the high-rate forming of a blank in contact with a rigid die. The objective of the presented paper is to establish methods of designing the EHF processes using simplified methods. The paper describes a numerical approach on how to define the shape of preforming pockets. The concept includes imposing principal strains from the formed blank into the initial mesh of the flat blank. The principal strains are applied with the opposite sign creating compression in the flat blank. The corresponding principal stresses in the blank are calculated based upon Hooke’s law. The blank is then virtually placed between two rigid plates. One of the plates has windows into which the material is getting bulged driven by the in-plane compressive stresses. The prediction of the shape of the bulged sheet provides the information on the shape of the preforming pockets. It is experimentally demonstrated that using these approaches, EHF forming is feasible for forming of a fragment of a decklid panel and a deep panel with complex curvature.
“…Typical joining techniques that are used for these types of structures are laser welding, friction stir welding as well as joining by hydroforming and electromagnetic forming [14][15][16]. Certain alignment accuracy is necessary in order to apply these methods.…”
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