Ship is a kind of huge welding structure,the stress distribution around its fatigue hot spot is very complex.The key problems in predicting the crack propagation life of cracks in complex stress field are the solutions of stress intensity factor (SIF) and crack growth direction. In this paper, the crack path and crack propagation of two kinds of cracks caused by two different reasons were studied. The crack growth direction is determined by the law of first principle stress. By given different crack increasements on the crack path,effective stress intensity factors of mix-model cracks with different crack lengths were calculated,and two regression functions of SIF for bracket cracks were given by fitting these data. The fatigue life for bracket was predicted by way of the unique crack growth rate model incorporating the above SIF functions and the predicted results were in good agreement with the experiment data. The procedure proposed here can be served as a reference for building the method of fatigue life predicting of ship critical details.%船舶作为一种大型焊接结构,其疲劳热点部位的应力应变场分布很复杂,要预报这些部位的裂纹疲劳扩展寿命,必须解决复杂场中裂纹的应力强度因子计算及其裂纹扩展方向问题.该文对船舶肘板处两种不同原因产生的裂纹的扩展路径、扩展速率进行了研究.裂纹扩展方向用第一主应力准则确定,在裂纹扩展方向上给定不同的裂纹增量,得到不同长度裂纹的复合裂纹等效应力强度因子,并拟合这些计算结果得出船舶肘板的应力强度因子计算式.结合裂纹扩展率单一曲线模型对肘板裂纹扩展寿命进行了预报,预报结果与实验结果符合得较好,说明所采用的方法可行.对建立船舶典型节点的裂纹扩展寿命预报方法有参考价值.
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