KK管节点中表面带裂纹应力强度因子的数值分析及参数研究

NUMERICAL ANALYSIS AND PARAMETRIC STUDY OF STRESS INTENSITY FACTORS OF A SURFACE CRACK IN TUBULAR KK-JOINTS

提出一种适用于包含表面裂纹的KK节点的有限元网格分区产生方法。这种方法是根据计算精度的需要,把整个KK节点结构划分为几个不同的子区域,其中每个子区域由不同类型的单元和网格密度组成。对KK节点中表面裂纹的模拟采用五种单元,即六面体单元、棱柱单元、四分之一结点的棱柱单元、四面体单元和棱锥单元。采用五种不同类型的单元模拟表面裂纹,可以有效避免裂纹附近单元的过度扭曲,保证计算精度。在提出的有限元模型基础上,采用J积分和位移外推插值两种方法计算KK节点中表面裂纹边缘的应力强度因子值。计算结果发现,两种方法得到的结果非常吻合,从而证明这两种方法在计算KK节点中表面裂纹应力强度因子的可行性。最后,通过对70个KK节点模型的分析计算,研究节点的几何参数以及裂纹形状对应力强度因子的影响。

A sub-zone method for producing the finite element mesh of tubular KK-joints containing a surface crack is presented in this study. In this method, the entire KK-joint structure is divided into several sub-zones according to the requirement of computation accuracy. In different zones, the element type and the mesh density are different. Five types of elements, i.e. hexahedra element, prism dement, quarter-point collapsed prism element, tetrahedml element and pyramid element, are used in modeling the surface crack in a tubular KK-joint. Using this mesh generation method can avoid badly distorted elements around the surface crack, thus the computation accuracy can be guaranteed. Based on the proposed finite element models, the stress intensity factors（SIF） along the crack front in a typical tubular KK-joint have been analyzed using both J-integral method and displacement extrapolation method. It is found from that the two sets of results agree reasonably well. Therefore, it tells that both of the two methods are suitable in the analysis of the stress intensity factor of a surface crack in tubular KK-joints. Finally, through parametric study on 70 KK-joint models, the effects of the joint geometry and the crack shape on the stress intensity factor results have been investigated.