超低温环境下非均质结构件的全场力学参数反演与失效机理研究

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.First, an open system for simulating the ultralow temperature environment is established,and study on the control method of the stable gradient temperature field,to avoid the interference of the frost on the measuring instrument in the ultra low temperature environment.Secondly, the calibration model of 3D-DIC under the condition of ultra low temperature gradient is studied,to improve and develop the calibration model and calibration method.Finally, the mechanical parameters of the non - uniform joints in the ultra low temperature environment are retrieved, and analysis the failure mechanism of non uniformly connected parts in ultra low temperature environment.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.

为揭示我国新一代运载火箭焊缝结构在超低温环境下的失效机理，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结构件的全场式力学参数反演与失效机理研究。首先，建立开放式超低温载荷环境模拟系统，研究稳定的梯度温度场控制方法，避免超低温环境下结构表面霜雾对测量仪器的干扰。其次，研究超低温梯度环境下非定常折射率对3D-DIC测量误差的影响，研究标定模型，完善并发展其标定方法。最后，研究超低温环境下非均质结构件的力学参数反演方法，获取非均质结构件的超低温力学参数，对非均质结构件在超低温环境下的失效机理进行分析，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。

本项目进行超低温载荷环境模拟系统结构设计改进，建立低温载荷环境，能够满足材料拉伸及弯曲试验光学测试要求；研究了集成数字图像相关方法（I-DIC）材料力学参数反演理论，形成低温下焊接件力学性能参数反演方法。本项目研究三维摄像测量标定理论，研制了低温标定板，建立梯度环境下的标定方法，结果显示光学测试与验证位移传感器的位移数据吻合较好，具有较高测试精度；项目实现低温环境下铝合金焊接试件的力学性能测试分析，建立精细化的力学模型，实验证明，由本项目提出的精细化仿真建模方法所得到的模拟结果，与传统模拟方法相比具有更高的计算精度。本项目研究了焊接试片常温与低温试验数据及力学性能对比，完成试片断口与失效机理分析。本项目的研究对于解决航天低温贮箱焊缝结构的力学性能评估及失效分析等问题具有重要的应用价值。