一种复杂载荷作用下船舶结构疲劳裂纹扩展预报方法

风暴模型是Tomita等提出的用来评估船舶结构疲劳强度的一种随机波浪载荷简化模型，它能表达波浪载荷是与时间相关的随机过程。文中介绍了风暴模型及波浪诱导应力短期分布的基本特征。将风暴模型和裂纹扩展率单一曲线模型及焊趾表面裂纹应力强度因子的计算方法结合起来，探讨了复杂载荷作用下船舶结构疲劳裂纹扩展预报方法。并用权函数法计算了给定残余应力分布的表面裂纹应力强度因子。预报了对接焊接接头焊趾处表面裂纹在风暴波浪载荷作用下的疲劳裂纹扩展行为，结果表明风暴的大小、顺序，初始裂纹尺寸及残余应力对裂纹扩展行为影响明显。合理的风暴模型参数及初始裂纹尺寸的确定对船舶结构的疲劳寿命预报是非常重要的。

A procedure to predict fatigue crack growth of ship structures under complex loading condition

Storm model proposed by Tomita and coworkers is a simplified random loading model for fatigue strength assessment of ship structures. The time dependent random wave loading can be expressed by the storm model. The basic characteristics of storm model and short-term distribution situation of wave-induced stress are described. Storm model is combined with a unique crack growth rate curve and SIF calculation e-quations for surface crack in the weld toe, and the procedure to predict the fatigue crack growth behavior of ship structures under complex loading conditions is discussed. Weight function is used to calculate SIF of surface crack under given residual stress distribution. Fatigue crack growth behavior of surface crack at weld toe of butt welded joint in ship hull under storm wave loading condition is predicted. The results show that the size and order of storms, the initial size of crack and residual stress have significant effect oncrack growth behavior. Reasonable storm model parameters and initial crack size are very important for fa-tigue life prediction of ship structures.