拉伸荷载作用下裂纹扩展过程及交汇模式试验研究及其数值模拟

Experimental study and numerical simulation of crack propagation process and intersection mode under tensile load

针对数值模拟中,张拉应力作用下多裂纹扩展及交汇模式主要采用假设的方法进行研究,为探究张拉应力作用下多裂纹扩展及交汇的真实模式,对含2条随机裂纹和平行倾斜双裂纹的PMMA试样进行拉伸试验,并借助数字散斑相关方法得到试样在拉伸荷载作用下,位移场等值线分布特征与预制裂纹之间的关系及其对裂纹扩展的影响以及试样破坏时的裂纹交汇形式。基于扩展有限元法采用2种不同交汇模式算法,对试验模型在拉伸荷载作用下的破坏过程进行模拟。研究结果表明:在拉伸荷载作用下,预制裂纹的存在对位移场等值线分布有明显的影响,在预制裂纹附近的等值线与裂纹近似垂直,对裂纹扩展路径有一定的影响;在裂纹扩展中,已存在的预制裂纹对扩展裂纹具有诱导作用,使裂纹扩展方向向其发生偏转,最后与之相交;采用裂纹尖端的坐标和传播方向的归一化方向向量得到参数形式的直线确定的交汇模式与试验观察到的裂纹交汇模式相符。

In numerical simulation,the multi-crack propagation and intersection mode under tensile stress are mainly studied by hypothesis.In order to explore the real mode of multi-crack propagation and intersection under tensile stress,the tensile tests of PMMA specimen with two random cracks and parallel inclined double cracks are carried out.The relationship between the contour distribution characteristics of the displacement field and the precast crack of the specimen under tensile load by digital speckle correlation method,the influence on the crack propagation and the crack intersection form when the specimen destroyed are obtained.Meanwhile,the failure process of the test model under tensile load is simulated with two different intersection mode algorithms based on the extended finite element method.The results show that the existence of precast cracks has a significant effect on the contour distribution of the displacement field under tensile load,and the contour line near the precast crack is approximately perpendicular to the precast,which has a certain influence on the crack propagation path.In the crack propagation process,the pre-crack existing in the front has an inducing effect on the growing crack,deflecting the crack propagation,and finally intersecting it.And it is found that the intersection mode determined in parameterized form based on the coordinates of crack-tip and the normalized direction vector of crack propagation is consistent with the crack intersection mode observed by the test.