为揭示我国新一代运载火箭焊接构件在超低温环境下的力学性能与失效机理,并为提高焊接质量与贮箱的承载能力提供科学依据,本项目开展了超低温环境下非均质焊接件的力学性能研究.首先,叙述了基于数字图像相关方法(DIC)的铝合金焊接件低温力学性能试验原理并建立开放式超低温载荷环境模拟系统;其次,分别对熔焊和搅拌摩擦焊两种不同焊接工艺的焊接件进行详细的试验研究,分析了应力应变关系、沿载荷方向全场应变分布、应变集中系数等,结果表明搅拌摩擦焊试件整体的力学性能要优于熔焊试件.最后本文还对比分析了测试区域大小对测试结果的影响,表明在热影响区2~8mm范围内进行测量,其测量误差不超过8.8%.本文研究结果将为我国新一代运载火箭低温贮箱焊接工艺优化与改进提供科学依据.%In order to reveal the failure mechanism of the weld structure of the new generation launch vehicle in ultralow temperature environment and to provide scientific basis for improving the welding quality and the carrying capacity of the tank, in this project, full-field mechanical parameters inversion and failure mechanism of non uniform joints at ultralow temperature environment are studied. Firstly, the test method of ultralow temperature mechanical properties of aluminum alloy welded specimens based on DIC is described, and an open system for simulating the ultralow temperature environment is established. Secondly, two specimens based on the welding and friction stir welding were studied. In this paper, the relationship between load and stress strain curve, strain distribution along the direction of the load and the strain concentration factor of the welded specimen are analyzed in this paper, and the results show that the friction stir welding specimen is better than the fusion welding specimen in mechanical properties. Finally, this paper also compares the influence of test area effect on, and it shows that the measurement error is not more than 8.8% when heat affected zone size is between 2~8mm.This project will provide a scientific basis for the welding process optimization and improvement of the ultra temperature tank of the new generation launch vehicle in China.
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