改进的三维虚拟裂纹闭合方法

Modified Virtual Crack Closure Technique(VCCT) Applicable to Arbitrary Crack Faces of Three-Dimensional Crack Front

改进了一种基于有限元技术分析三维裂纹应力强度因子的计算方法——虚拟裂纹闭合方法,称为改进的虚拟裂纹闭合方法。应用传统的虚拟裂纹闭合方法求解三维裂纹体应力强度因子时,对有限元模型具有一定的要求,即过裂纹前缘的有限单元裂纹面必须具有相同的面积且对称。而应用文中改进的虚拟裂纹闭合方法求解三维裂纹体应力强度因子时,裂纹前缘的裂纹面可以是任意形状。文中应用改进虚拟裂纹闭合方法,建立20结点等参元有限元模型,对三维表面裂纹应力强度因子进行了验证性的分析和讨论。通过与Newman解相比较,证明该方法适用性强且计算精度高。

VCCT requires that the faces of finite elements across the crack front must have the same areas and that they must be arranged symmetrically across the crack front. We aim to make this requirement unnecessary by presenting our modified VCCT （MVCCT）. In the full paper, we explain the MVCCT in some detail; in this abstract, we just add some pertinent remarks to listing the two topics of explanation. The first topic is. a brief introduction to VCCT. The second topic is. the MVCCT. In this topic, we derive the equations numbered eq. （19） in the full paper to calculate the three energy release rates respectively for three modes of fracture. With the energy release rate, we can calculate the stress intensity factor （SIF） of the crack face of a three-dimensional crack front. Finally, to verify the MVCCT, we do the numerical calculation of the finite element model of a semi-elliptically-shaped crack. We also compare the SIFs calculated through using the MVCCT with those calculated in Ref. 3, with the comparison results given in Fig. 7. From the figure, we can see that the calculation results of the MVCCT show good agreement with those of Ref. 3, whose second author is the well known Newman, the error being at most 2. 141 7%. The calculation results of the MVCCT may well satisfy engineering requirements. We can conclude preliminarily that the MVCCT is applicable to arbitrarily-shaped finite element mesh of a crack face.