Some cyclically loaded components such as mooring chains can develop fatigue cracks in locations where the shape of the part is equivalent to that of a curved or bent round bar. Here we consider a semi-elliptical crack growing from the surface of a curved round bar. This geometry can for example represent a chain link segment with a crack located at its inner- or outer radius. The surface crack can be either almond shaped, sickle shaped or straight-fronted. Stress intensity factors (SIFs) over the fronts of such crack geometries are in the present work investigated for several elementary mode I stress distributions. Finite element analysis and linear elastic fracture mechanics methods are used to develop semi-analytical solutions for the SIF at any point on the crack front. Effects of relative bar curvature on numerical results are demonstrated. Relative to otherwise identical cracks in straight bars, SIFs for cracks in the curved bars considered here are found to differ by up to 8%. With an offshore mooring chain model as a case example, the estimation of SIFs for cracks in a complex residual stress field is furthermore demonstrated using a cubic polynomial stress approximation.

某些周期性加载的组件（例如系泊链）会在零件的形状与弯曲或弯曲的圆棒的形状等效的位置产生疲劳裂纹。在这里，我们考虑从弯曲的圆棒表面生长的半椭圆形裂纹。该几何形状可以例如表示在其内半径或外半径处具有裂纹的链节。表面裂纹可以是杏仁形，镰刀形或笔直的。在目前的工作中，针对几种基本的I型应力分布，研究了此类裂纹几何形状前沿的应力强度因子（SIF）。有限元分析和线性弹性断裂力学方法被用来为裂纹前沿的任意点的SIF开发半解析解。演示了相对钢筋曲率对数值结果的影响。相对于直棒上的其他相同裂纹，此处考虑的直棒上裂纹的SIF相差最多8％。以离岸系泊链模型为例，使用三次多项式应力近似法进一步证明了复杂残余应力场中裂纹的SIF估算。