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已有的不同类型落锤撕裂实验数据表明,高钢级管线钢的单位断裂能和裂尖张开角依赖于断裂速度。本文进一步确定了其依赖关系是由断裂韧性而非试件几何差异所引起,并且定量分析了基于断裂准则所定义的断裂韧性与断裂速度之间的关系。利用所提出的黏结本构法则分别对X80管线钢标准试件和修正试件的落锤撕裂实验进行了三维有限元模拟,并将有限元结果与实验结果进行了对比。结果表明:有限元计算的加载曲线、断裂速度、裂尖张开角与对应的实验结果吻合较好,故本文提出的黏结本构法则能较好地应用于X80管线钢的动态断裂分析;标准试件的断裂韧性高于修正试件的断裂韧性,而标准试件的断裂速度则低于修正试件的断裂速度;七次有限元计算结果都表明断裂韧性随稳态断裂速度的增大而减小,且二者的关系可以由本文提出的自然指数函数进行描述。
The existing experimental data of different types of drop weight tear show that the unit fracture energy and the crack tip angle of high grade pipeline steel depend on the fracture speed. This paper further confirms that its dependence is caused by the fracture toughness rather than the geometrical difference of the specimen, and quantitatively analyzes the relationship between the fracture toughness and the fracture velocity as defined by the fracture criterion. The proposed three-dimensional finite element simulation of the drop-weight tear test of the X80 pipeline steel standard specimen and the modified specimen was carried out by using the proposed bonding constitutive law. The finite element results were compared with the experimental results. The results show that the loading curve, the breaking speed and the crack tip opening angle of the finite element method are in good agreement with the corresponding experimental results. Therefore, the bonding constitutive law proposed in this paper can be well applied to the dynamic fracture analysis of X80 pipeline steel. The fracture toughness of the test piece is lower than that of the test piece, while the fracture speed of the standard test piece is lower than that of the test piece. The results of seven finite element analyzes show that the fracture toughness decreases with the increase of the steady state fracture speed , And the relationship between the two can be described by the natural exponential function proposed in this paper.