AZ31B镁合金准静态下应力三轴性对断裂行为的影响

发布时间：2018-03-03 03:17

本文选题：AZ31B镁合金　切入点：试验设计　出处：《西南科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：本文以两种形式的AZ31B镁合金材料(棒材和板材)为研究对象,通过不同应力状态下的试验设计和相应的数值模拟,分析了AZ31B镁合金不同应力状态下的断裂行为,与参考文献中的双曲线断裂准则进行了验证与对比,结果表明,棒材与该断裂准则符合度较好,而板材出现了较大的不符合度。因此本文通过试件截面长宽比分别为25:1、9:1、9:2、9:4.5、9:9的五组板材数值模型就试件几何形状对断裂准则的影响展开了研究。首先开展了AZ31B镁合金不同应力状态下的试验研究,包括低、中、高应力三轴度下的试验,在试验的基础上测量并计算不同应力状态下的断裂强度、等效断裂应变等;然后结合数值模拟分析不同试验的过程,对网格敏感度的研究表明,试件缺口半径越小,网格的敏感度越高,网格尺寸在0.001m和0.005m之间,AZ31B镁合金板材的断裂长度随网格尺寸的增加而增长;计算了各应力状态下的应力三轴度值,根据不同应力三轴度下的断裂特征选择合理的分段函数,在应力三轴度—等效断裂应变空间建立了AZ31B镁合金复杂应力状态下的断裂准则,与参考文献中的断裂准则进行了验证与对比,发现了棒材对断裂准则的高度符合以及板材对断裂准则的较大差异;最后研究了在数值模拟中试件不同几何形状对该断裂准则的符合度,结果表明随着试件截面长宽比的减小,试件表现出的断裂行为与断裂准则的符合度越高,材料的等效断裂应变逐渐增大,即材料的断裂延性逐渐增大,根据数值模拟结果拟合了等效断裂应变转折点曲线,为AZ31B镁合金材料的等效断裂应变转折点的计算提供了依据,同时对镁合金板材的应用与加工提出了建议。
[Abstract]:In this paper, two kinds of AZ31B magnesium alloy materials (bar and plate) are studied. The fracture behavior of AZ31B magnesium alloy under different stress states is analyzed through experimental design and corresponding numerical simulation under different stress states. Compared with the hyperbolic fracture criterion in reference, the results show that the bar is in good agreement with the criterion. Therefore, in this paper, the influence of geometric shape on fracture criterion of AZ31B magnesium alloy is studied by means of five sets of numerical models with the cross-section aspect ratio of 25: 1: 9: 9: 9: 9: 9: 9: 9: 9 respectively. Experimental study under different stress states, Including the tests under low, medium and high stress triaxiality, the fracture strength and equivalent fracture strain under different stress states are measured and calculated on the basis of the tests, and then the process of different tests is analyzed with numerical simulation. The research on the mesh sensitivity shows that the smaller the notch radius of the specimen, the higher the sensitivity of the mesh, and the fracture length of AZ31B magnesium alloy sheet increases with the increase of mesh size between 0.001m and 0.005m. The values of stress triaxiality under various stress states are calculated. According to the fracture characteristics of different stress triaxialities, reasonable piecewise functions are selected, and the fracture criteria of AZ31B magnesium alloys under complex stress state are established in the space of stress triaxiality and equivalent fracture strain. Compared with the fracture criterion in reference, it is found that the bar is highly consistent with the fracture criterion and the plate is different from the fracture criterion. Finally, the conformance of different geometric shapes to the fracture criterion is studied in the numerical simulation. The results show that the higher the coincidence between the fracture behavior and the fracture criterion is, the lower the ratio of length to width of the specimen is. The equivalent fracture strain of the material increases gradually, that is, the fracture ductility of the material increases gradually. According to the numerical simulation results, the equivalent fracture strain turning point curve is fitted, which provides the basis for the calculation of the equivalent fracture strain turning point of AZ31B magnesium alloy material. At the same time, some suggestions on the application and processing of magnesium alloy sheet are put forward.
【学位授予单位】：西南科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.22

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