Aiming at the problem about misjudging sheet fracture in hydroforming process, the different mechanisms between drawing and hydraulic bulging are analyzed. In this paper, a method to test the forming limit diagram (FLD) based on uniform load in thickness direction is adopted by using laminated plate hydroforming, and the quality of hydroforming process is judged more accurately. By the numerical simulation analysis, the shape of the specimen on five different linear paths is preliminarily determined, and the forming limit diagram of the sheet is obtained under the stretch-compression condition. At the same time, the influence of method of lubrication such as non-lubrication, oil, grease, and thin film on FLD is analyzed. The results show that the first principal strain and the second principal strain increase, and the bulging height decreases with the decrease of friction factor. Among them, the friction factor of thin film is reduced to the lowest. In the process of laminated sheet hydroforming, the thin film lubrication between pieces is more relatively accord with the experimental condition of stretch-compression bulging, and the FLD is more reliable to judge the quality of component formed by hydroforming.
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All the experiments were financed and supported by the pre-research project in Zhangjiagang city of China with Grant No. 599918013 and the fund was provided by Jiangsu University of Science and Technology with Grant No. 1022931803.
Gaoshen C, Wu C, Gao Z, Lang L, Sergei A (2018) Research on Al-alloy sheet forming formability during warm/hot sheet hydroforming based on elliptical warm bulging test. AIP Adv. 8(5): 55023-055023-9.doi: https://doi.org/10.1063/1.5029539