中国有色金属学报(英文版)
Transactions of Nonferrous Metals Society of China
| Vol. 26 No. 8 August 2016 |
（1. School of Mechanical Engineering and Automation, Beihang University, Beijing 100191, China;
2. Collaborative Innovation Center of Advanced Aero-Engine, Beihang University, Beijing 100191, China;
3. Faculty of Aerospace Engineering, Shenyang Aerospace University, Shenyang 110136, China）
Abstract:A novel experimental approach was presented, namely the overlapping elliptical bulge test, which can load and research thickness normal stress. Theoretical analysis model of the overlapping elliptical bulging was described, the equivalent stress-strain curves of target sheets with different ellipticity ratios were determined experimentally, and influences of the material performance and thickness of overlapping sheets on the flow property of the target sheet were also researched. The results show that, in the overlapping hydraulic bulge test, the equivalent stress-strain curve can be determined up to larger strains before necking than in the no overlapping hydraulic bulge test. And as the die ellipticity ratio decreases, the flow stress curves tend to move away from the curve obtained by circular (b/a=1) bulging test. Meanwhile, the flow property of the target sheet can be improved by choosing higher strength coefficient K, larger work hardening exponent n and proper thickness of the overlapping sheet.
Key words: flow property; aluminum alloy; overlapping sheet; elliptical bulge; thickness normal stress
