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对于已含初始裂纹平台管节点的寿命预测很大程度上依靠应力强度因子的精确值,而复杂载荷条件下的节点应力强度因子的计算尚无参数方程直接确定。本文提出了一种含表面裂纹的K节点的有限元网格产生方法,即把整个K节点划分为几个子区域,每个子区域的网格具有不同类型的单元和不同的密度。这种方法在控制网格密度,尤其是控制沿着裂纹边缘单元的边长比方面有其独特的优越性,当所有子区域的网格自动产生后,容易得到整个结构的有限元模型。同时用J积分和位移外推插值法分别计算了一个K型节点沿着裂纹前缘的应力强度因子值,发现:试验得到的应力强度因子值和提出的模型计算结果非常吻合,证明了所提有限元模型的准确性。
The prediction of the life expectancy of the pipe joints with initial crack depends greatly on the exact value of the stress intensity factor, while the calculation of the node stress intensity factor under complex load conditions is not directly determined by the parametric equation. In this paper, a finite element mesh generation method for K-joints with surface cracks is proposed. That is, the entire K-node is divided into several sub-regions. Each sub-region has different types of cells and different densities. This method has its unique advantages in controlling the density of the mesh, especially in controlling the edge length / length ratio along the edge of the crack. Finite element models of the whole structure are easily obtained when the grids of all the sub-regions are automatically generated. At the same time, the stress intensity factor of a K-type node along the crack front was calculated by J-integral and displacement extrapolation respectively. It was found that the calculated stress intensity factor was in good agreement with the proposed model. Finite element model accuracy.