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本文基于构型力概念提出一种可判断裂纹起裂以及裂纹扩展方向的新断裂准则。该准则假设当构型合力值达到一个临界值时裂纹开始扩展,而裂纹扩展的方向则为构型合力的矢量方向。基于此断裂准则,本文开发构型力的有限元计算方法,实现对裂纹扩展的数值模拟,并着重对工程中常见的含孔洞/夹杂结构的裂纹扩展问题展开研究。研究结果表明,基于构型力的裂纹扩展准则可以很好的预测裂纹与孔/夹杂的干涉作用,其数值模拟结果与实验结果相符,从而验证了该裂纹扩展模拟方法的有效性。通过对裂纹和夹杂(圆孔、软夹杂、硬夹杂)干涉问题的数值模拟表明,裂纹前端夹杂对裂纹的扩展具有重要影响。裂纹的扩展方向与裂纹和夹杂的相对位置、以及夹杂类型密切相关。软夹杂和圆孔会吸引裂纹向其扩展,而硬夹杂会排斥裂纹扩展,裂纹在扩展过程中会绕开硬夹杂。当裂纹与夹杂夹角较小时,夹杂对裂纹扩展的影响作用明显,当夹角较大时,夹杂对裂纹扩展的影响较小;特别当裂纹与夹杂夹角为45°时,软夹杂和圆孔可能会抑制裂纹的扩展,使裂纹扩展发生止裂。本文研究成果有助于认清含孔洞/夹杂结构中的裂纹扩展或止裂问题,对于工程中的断裂问题具有重要指导意义。
Based on the conception of configuration force, a new criterion of fracture initiation and crack propagation is proposed. The criterion assumes that the crack begins to expand when the resultant force reaches a critical value, whereas the crack propagation direction is the vector direction of the resultant force. Based on the fracture criterion, finite element method for calculating the configuration force was developed to simulate the crack propagation. The crack propagation problem with holes / inclusions in common engineering was emphasized. The results show that the crack propagation criterion based on the configuration force can well predict the interference between crack and hole / inclusion. The numerical simulation results are in good agreement with the experimental results, which verifies the validity of the crack propagation simulation method. The numerical simulation of the interference problems of cracks and inclusions (circular holes, soft inclusions and hard inclusions) shows that the inclusion of the crack tip has an important influence on the crack propagation. The direction of crack propagation is closely related to the relative position of cracks and inclusions, as well as the type of inclusions. Soft inclusions and circular holes will attract cracks to extend to them, while hard inclusions will repel crack propagation, and cracks will bypass hard inclusions during the expansion. When the included angle between crack and inclusion is small, the influence of inclusions on the crack propagation is obvious. When the included angle is large, the influence of inclusions on crack growth is small. Especially when the included angle between crack and inclusions is 45 °, Holes may inhibit the propagation of cracks and cause crack propagation to crack. The research results in this paper can help to find out the crack propagation or crack arrest in cavities / inclusions, which is of great guiding significance for the fracture in engineering.