Abstract A fracture mechanics (FM) based investigation on the mechanism of out-of-plane bending (OPB) between mooring chain links and its effects on fatigue lives of mooring chain links are conducted. Four types of OPB problems that mooring chain links laying on the chain wheel, chain links passing over the bending shoe, chain links constraint provided by the chain hawse, and chain links constraint provided by the chain stopper are considered. Tension ranges of mooring lines are calculated based on the combined loading process induced by the motions of wave frequency (WF) and low frequency (LF). Initial cracks are assumed to propagate from surfaces of chain links and stress intensity factors are calculated in terms of stress ranges determined by a finite element (FE) analysis. The results show that fatigue lives of mooring chain links are decreased significantly due to OPB effects. In addition, the increase of the number of pockets of chain wheel mitigates OPB effects on fatigue lives of mooring chain links laying on the chain wheel, and the increase of the track diameter would reduce OPB effects on fatigue lives of mooring chain links passing over the bending shoe as well. However, for chain links constraint provided by the chain hawse, the diameter of mooring chain hawse has no significant effect on fatigue lives of the mooring chain links subject to OPB if without the abrupt change of the contact conditions between chain links and chain hawse. For mooring links constraint provided by chain stoppers considering the effect of proof loading test, fatigue lives of mooring chain links would drop significantly with the increase of interlink angles and friction coefficient.

中文翻译：

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受平面外弯曲 (OPB) 影响的系泊链节的断裂力学分析

摘要 对系泊链节之间的平面外弯曲（OPB）机理及其对系泊链节疲劳寿命的影响进行了基于断裂力学（FM）的研究。考虑了链轮上系泊链节、链节越过弯板、链轮提供的链节约束和止链器提供的链节约束四种OPB问题。系泊缆的张力范围是基于由波浪频率（WF）和低频（LF）运动引起的联合加载过程计算的。假设初始裂纹从链节的表面传播，应力强度因子根据有限元 (FE) 分析确定的应力范围进行计算。结果表明，由于OPB效应，系泊链节的疲劳寿命显着降低。此外，增加链轮齿槽数减轻了 OPB 对铺设在链轮上的系泊链节疲劳寿命的影响，而轨道直径的增加将降低 OPB 对通过链轮的系泊链节疲劳寿命的影响。弯鞋也是如此。然而，对于链节提供的链节约束，如果链节与链节之间的接触条件没有突变，系泊链节的直径对受OPB影响的系泊链节的疲劳寿命没有显着影响。对于由链塞提供的系泊链节约束，考虑到验证加载试验的影响，