A novel strategy for reducing sheet springback by coupled with high strain rate and shear deformation via impact hydroforming

Springback is a critical factor in controlling the tolerance of thin-walled, curved components during manufacturing. This study proposes a strategy that utilizes impact hydroforming to eliminate springback instead of the traditional method of modifying the die for compensation. Bending tests were conducted on the 2024 aluminum alloy sheet with a bending angle of 120° and bending radius of 30 mm under three different loading modes, i.e. quasi-static rigid punch bending (QSR), high-speed rigid punch bending (HSR), and impact hydroforming (IHF) bending. Corresponding finite element simulations of these loading modes were also performed, and the simulated springback variations closely matched the experimental results. The experiments revealed that springback decreased with an increase in strain rate, and the use of a liquid medium further facilitated or even eliminated springback. The deformation sequence, strain neutral layer, principal stress, and equivalent plastic strain distribution of the sheet were analyzed under each loading mode. Two primary reasons for the reduction in springback were identified: the high strain rate induced stress relaxation and energy release, and the liquid medium altering the deformation sequence of the sheet, leading to shear deformation. These findings offer a new strategy for achieving forming precision, high efficiency, and low-cost manufacturing complex thin-walled components of made from aviation aluminum alloy.