Modeling of electrohydraulic forming of sheet metal parts

Abstract

Electrohydraulic forming (EHF) is based upon the electro-hydraulic effect: a complex phenomenon related to the high voltage discharge inside the water filled chamber. The resulting shockwave in the liquid is propagated toward the blank, and the mass and momentum of the water in the shock wave accelerates the sheet metal blank toward the die. Methodology of numerical simulation of EHF processes was developed based upon LS-DYNA commercial code using Arbitrary Lagrange–Eulerian (ALE) Multi-Material formulation. The model incorporates energy deposition inside the plasma channel, expansion of the channel driven by high pressure inside of it, propagation of the pressure pulse through the water filled chamber in contact with the rigid walls of the chamber and with the sheet metal blank being deformed. Comparison of the numerical and experimental results was performed on maximum pressure measured on the wall of the cylindrical chamber employing the membrane method.The model was used to simulate multistage EHF of a complex geometry automotive part. Analysis of the results showed the complex nature of multistage EHF process: a clearly recognizable wave picture during the initial stage of the channel expansion which transitions to almost incompressible water flow during later stages.