海洋平台K型管节点的疲劳裂纹扩展分析 II:数值分析

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。

Fatigue crack propagation analysis of tubular K-joints II: numerical

The prediction of the damaged tubular K-joints depends very much on the accuracy of the stress intensity factors(SIFs).No parametric equations and very few results have been proposed and published in the literature for estimating the SIFs of any K-joints subjected under complex loading conditions.In this paper,a mesh generation method has been proposed for a typical K-joint containing a surface crack.This method is realized by dividing the K-joint into several sub-zones with each zone consisting of different types of elements and mesh densities.This method has a distinct advantage of controlling the mesh quality,and most importantly the aspect ratio of the elements along the crack front.When the mesh of all the sub-zones has been generated automatically and completely,they are merged to form the complete model.Two most commonly used methods,namely Jintegral and displacement extrapolation,are used to evaluate the SIF values along the crack front of a typical K-joint.To validate the accuracy of these computed SIFs,the experimental SIFs obtained in Part I were used to benchmark the numerical results.The experimental SIFs are found to be in complete agreement with the computed SIFs obtained from the generated models.Hence,the proposed finite element models are both efficient and reliable.