Springback inhibition of Ti-6Al-4V sheet with impact hydroforming at room temperature

Abstract

Springback is a tough issue in sheet forming, and always leads to dimensional inaccuracy of formed parts. Titanium alloy selected as desired light-weight alloy has been playing significant roles in aerospace industry because of its good comprehensive performance. Whereas, titanium alloy components manufactured always exhibit severe springback at room temperature, which greatly restrict their application. To explore the possibility of reducing springback, rectangular lath-shaped parts with Ti-6Al-4V alloy sheet were fabricated by impact hydroforming (IHF) with self-designed equipment. Consequently, much lower springback is obtained using IHF with high strain rate than that formed by conventional stretch-bending with low strain rate. Great efforts are paid to clarify the mechanism of springback restriction under IHF. Different from traditional forming methods, more complex and high-speed interaction behavior between liquid and Ti-6Al-4V alloy sheet occurs. It considerably increases the difficulty for analyzing the deformation process of sheet under IHF. Thus, a novel solid-liquid coupling numerical simulation technology for IHF was developed. To validate the simulation accuracy, experiments with different forming processes and parameters were performed. Given the combined analysis of experimental and simulation results, it is found that distinctive forming paths are introduced between stretch-bending and IHF. Specifically, the preferred deformation region of sheet transfers from middle region for conventional stretch-bending to end regions under IHF, which mainly attributes to the unique loading behavior of liquid at high strain rate.