Determination and application of stress-based forming limit diagram in aluminum tube hydroforming

• Published in: Transactions of Nonferrous Metals Society of China Vol. 17; no. A01; pp. 21 - 26
• Main Author: 周林 薛克敏 李萍
• Format: Journal Article
• Language: English
• Published: 01.11.2007
• Subjects: 加氢重整技术; 压力测试; 数字模拟技术; 破裂强度; 铝合金
• ISSN: 1003-6326

The stress-based forming limit diagram（FLSD） established with limit stress is independent of the strain paths. Compared with traditional strain-based forming limit diagram（FLD）, it is more convenient and practical to use as the criterion of forming limit under complex strain paths. The forming limit of 3A21 aluminum alloy sheet was tested and its forming limit diagram（FLD） was determined. Then the FLSD of 3A21 was constituted by transformation formulas between limit strain and limit stress. This FLSD was used in conjunction with LS-DYNA finite element simulations to predict the onset of fracture and limit forming pressure in tube hydroforming. The results indicate that the fracture often occurs in the transition region between corner and straight side of the tube, and the limit forming pressure is 46.4 MPa. The simulation result agrees with the experimental result, and the FLSD is able to predict the forming limit of tube hydroforming with remarkable accuracy.