低温下2219铝合金贮箱焊接缺陷的试验与仿真分析

Experiment and Simulation Analysis for Weld Defected 2219 Aluminum Alloy Tank at Low Temperature

本文结合材料试验和断裂力学数值仿真,研究了运载火箭贮箱低温下材料及焊缝缺陷对贮箱极限承载能力的影响。通过低温光测试验获取了贮箱材料2219铝合金的弹塑性本构参数,研究了该材料从4K到300K温度环境下的断裂韧性变化,发现2219铝合金在4K下仍保持较高的断裂韧性。结合77K温度下贮箱的强度破坏试验,建立了贮箱热力耦合数值模型以及焊缝精细有限元子模型,利用子模型方法得到低温下的焊缝局部应力-应变场分布,基于断裂力学的扩展有限元数值方法揭示了焊缝处存在初始缺陷情况下的失效形式及裂纹扩展规律,使用参数化建模揭示了初始裂纹参数对裂纹扩展及贮箱极限承载能力的影响规律。

In this paper, the influence of material and weld defects on the ultimate bearing capacity of carrier rocket tank at low temperature is studied by material test and numerical simulation. The elastic-plastic constitutive parameters of 2219 aluminum alloy at low temperature are obtained by low-temperature optical test. The fracture toughness of 2219 aluminum alloy from 4K to 300K is studied by compact tensile test. It is found that 2219 aluminum alloy still maintained good fracture toughness at 4K. Combined with the strength of 77K temperature tank failure test,the tank model and weld sub-model are established and the local stress-strain field distribution under low temperature is obtained. The failure mode and the regularity of crack propagation are revealed using the extended finite element method based on fracture mechanics. The effects of initial crack parameters on crack growth and the ultimate bearing capacity are revealed through parametric modeling.