含多裂纹对接板应力强度因子三维有限元分析

应力强度因子（SIF）分析是含多部位损伤（MSD）结构的裂纹扩展分析及寿命预测的基础，对于连接结构采用简化模型难以考虑次弯曲、铆钉变形等因素影响。本文建立了含MSD对接板的三维有限元模型，研究了不同损伤模式、设计构型和约束条件下的裂纹尖端SIF分布特性以及随裂纹长度的变化规律。结果表明，孔边裂纹Ⅰ型SIF起主导作用，Ⅱ型和Ⅲ型SIF可忽略不计；由于次弯曲效应，SIF从外表面到内表面近似呈线性关系逐渐增加；MSD裂纹之间存在较强的干涉作用，且裂纹间距离越短数量越多，干涉作用越强；SIF随拼接板厚度增加呈先增加后降低的趋势，原因是拼接板刚度和铆钉柔度对铆钉载荷传递有一定影响；采用埋头铆钉会使SIF值增加，且内外表面差异变得更大；反翘曲约束对裂纹尖端SIF均值影响很小，但能显著降低SIF沿厚度方向的变化。

Three-dimensional finite element analysis of stress intensity factors of butt-joints with multiple site damage

Stress Intensity Factor (SIF) analysis is the basis for crack propagation analysis and fatigue life prediction of structures with Multiple Site Damage (MSD). It is difficult for joint structures based on simplified models to consider factors such as secondary bending and rivet deformation. In this paper, the three-dimensional finite element models of butt-joints with MSD are established, followed by analysis of the distribution and variation of SIFs at each crack tip with different damage modes, design configurations and constraint conditions. The results show that K_I is dominant, while K_II and K_III are negligible. Due to the secondary bending, the SIF increases approximately linearly from the outer surface to the inner surface. Strong interference exists between the MSD cracks, increasing the SIF, and the shorter the distance between the cracks, the stronger the interference. With the increase of the splice plate thickness, the SIF values increase first and then decrease because of the effect of the splice plate stiffness and the rivet flexibility on the load transfer ratio of the rivet. The value of SIFs with countersunk rivets is higher than that with flat head rivets, with an increased difference between the inner and outer surfaces. While the anti-bending constraint has little effect on the average value of the SIF at the crack tip, it can significantly reduce the variation of the SIF on the thickness direction.