Remaining life assessment method of fatigue crack propagation in a double hull ship structure

对在役检查中可能发现疲劳裂纹的船舶结构件的适用性进行调查，以防止船舶瞬时失效以及关键舱室油密性和/或水密性等适用性的丧失。讨论了双壳船结构的疲劳裂纹扩展特征和剩余寿命评估。对船舶结构细节进行了有限元对比研究，以检验实践者计算的局部应力可能存在的变化。研究发现，壳单元模型的结果相互之间具有很高的相关性，但局部应力明显低于实验和实体单元结果。针对三维裂纹分析，提出了一种新的数值与解析权重函数相结合的方法来确定船舶结构细节中的应力强度因子，该方法被证明是一种非常有效的疲劳裂纹分析方法。还讨论了一种先进的剩余寿命评估数值模拟方法，其中精确考虑了焊接残余应力、结构冗余和弯曲裂纹扩展的影响。模拟裂纹路径和疲劳裂纹扩展寿命与实验结果吻合较好。针对双层底结构内底板关键部位检测到的裂纹，进行了疲劳剩余寿命评估，基于断裂力学方法计算剩余寿命。采用铺路法和域组合法来生成高效、鲁棒的有限元网格，这对于疲劳强度分析和疲劳裂纹扩展分析至关重要。此外，还开发了一种先进的计算方法来预测弯曲裂纹扩展。为了提高运营船舶的安全性和维护性，提出了船舶结构损伤信息系统的概念。较少的

The fitness for serviceability of structural members of ships, in which fatigue cracks could be found during in-service inspection, is investigated in order to prevent instantaneous failures of ships as well as the loss of serviceability such as oil and/or water tightness of critical compartments. The characteristics of fatigue crack propagation and the remaining life assessment of double hull ship structures are discussed.A finite element comparative study of ship structural detail has been carried out in order to examine the possible variations of calculated local stress by practitioners. It is found that the results of shell element models have high correlation with each other, but give significantly lower local stress than experimental and solid element results. With regard to the analysis of 3-D cracks, a new combined numerical and analytical weight function method is proposed for the determination of stress intensity factors in ship structural details, which is proved to be a ver … More y efficient method for fatigue crack analysis. Discussions are also made for an advanced numerical simulation method for the remaining life assessment, in which the effects of welding residual stresses, structural redundancy, and curved crack propagation are precisely taken into account. The simulated crack paths and the fatigue crack propagation lives are in fairly good agreement with the experimental results.The fatigue remaining life assessment is demonstrated for cracks detected in the critical parts of the inner bottom plate of a double bottom structure, where the remaining life is calculated based on the fracture mechanics approach. The paving method and the domain composition method are implemented for the efficient and robust finite element mesh generation which is essential for fatigue strength analysis and fatigue crack propagation analyis. Also, an advanced computational method has been developed for the prediction of curved crack growth. A concept of the information system for damages of ship structures is proposed for the improved safety and maintenance of ships in service. Less