Research on Springback Simulation in Rubber Diaphragm Forming of Aircraft U-Shaped Parts Based on Autoform

Abstract

This study investigates the springback issue of aircraft U-shaped sheet metal parts during rubber diaphragm forming. First, the principles of rubber diaphragm forming technology are elucidated. Through comparative analysis of finite element algorithms, the superiority of implicit algorithms in sheet forming and springback prediction is demonstrated. Taking a typical U-shaped fuselage beam as the research object, a finite element model was established using Autoform software, with equivalent hydraulic loading method employed to simulate rubber diaphragm pressure application. Simulation results reveal significant non-uniform springback on the upper base surface of unconstrained parts, severely compromising assembly accuracy. By analyzing stress field evolution and principal stress difference distribution during forming, the mechanism of springback caused by residual stress gradient release is uncovered. Accordingly, a springback suppression strategy incorporating pressure-constrained cover plates is proposed, establishing a multi-condition gradient pressure model. Verification simulations demonstrate that when cover plate pressure reaches 5000 kN, narrow-end springback decreases by 86.9%, wide-end springback approaches zero, and principal stress difference reduces by 79%. This research validates the significant regulatory effect of cover plate pressure on U-shaped parts springback, providing an optimized process parameter pathway for high-precision aerospace sheet metal manufacturing.