基于谱分析LNG船典型热点疲劳可靠性分析

Fatigue reliability of LNG carrier using spectral-based analysis

研究LNG船在疲劳载荷作用下应力热点的疲劳可靠性。通过整船有限元分析得到不同浪向角规则波中各热点的应力频响函数,用谱分析法确定各热应力点在各短期海况下的应力范围模型,进而通过长期预报,用Weibull分布对各热点应力范围分布模型进行拟合并探讨热点型式和受载特性对参数变化的影响。基于线性累积损伤理论,利用S-N曲线计算各热点的疲劳累积损伤值并建立极限状态方程,评估LNG船舯部典型热点的疲劳可靠性和结构的疲劳安全性。针对不同热点讨论了应力范围长期分布函数—Weibull分布参数的取值对典型热点可靠性指标的影响,并给出典型热点目标可靠性指标和长期应力范围极值之间的关系以用于指导设计和安全性评价。

Reliability-based fatigue analysis of hot-spots of a LNG carrier under fatigue loads is made.The stress responses of the hot-spots in regular waves with different wave heading angles and wave length are evaluated by finite element method.Based on the probabilistic distribution function of hot-spots′ short-term stressrange using spectral-based analysis,Weibull distribution is adopted and discussed to fit the long-term probabilistic distribution of stressrange.Based on linear cumulative damage theory,fatigue damage is characterized by an SN relationship and the ultimate limit state function is established.The reliability index of hot-spots is calculated,and structural safety assessment of LNG middle ship section is performed.The fatigue damage behavior of typical hot spots with respect to Weibull parameters is clarified and demonstrated.It is believed that the results and conclusion can be used in calibration for design and initial fatigue safety assessment.