Improved forming height and reduced energy consumption through an optimized hybrid quasi-static and high-speed forming strategy

Abstract

It is widely accepted that aluminum alloy-based materials exhibit improved formability and enhanced ductility under high-speed impact. However, in this study, the experimental results were not entirely similar to the traditional theoretical results. Thus, this study once again confirms the conclusion that high-rate forming can increase the forming limit of materials, and simultaneously supplements the conclusion. Herein, a hybrid process combining quasi-static hydraulic forming and electromagnetic hydraulic forming was proposed. The effects of the forming sequence and pre-deformation amount on sheet bulging and fracture morphology were analyzed via experiments and simulation. It was found that when the electromagnetic hydraulic forming is pre-deformation and the quasi-static hydraulic forming is post-deformation, the forming height of aluminum alloy does not improve significantly. Conversely, when the quasi-static hydraulic forming is pre-deformation and the electromagnetic hydraulic forming is post-deformation, the forming height of aluminum alloy improves significantly. In case of pre-deformation quasi-static liquid pressure P₀ = 2 MPa, and post-deformation electromagnetic hydraulic forming, the limit forming height is 22.4 % higher than that under quasi-static hydraulic forming. Moreover, the limiting voltage decreases with increasing pre-deformation quasi-static liquid pressure P₀, and the energy consumption reduces by 42.9 %. The deformation behavior and damage characteristics of quasi-static hydraulic forming, electromagnetic hydraulic forming, and hybrid forming were accurately predicted by multi-physics coupling analysis. Compared with quasi-static hydraulic forming, void nucleation and growth are inhibited due to high-speed impact. In particular, when the sheet is about to crack during high-speed forming, the voids that should have grown sharply are significantly inhibited. Therefore, the improved formability mainly acts at the post-deformation stage during high-speed forming, with the analytical results corroborating the experimental and simulation ones.