基于谱分析和裂纹扩展方法的舱口角隅疲劳寿命预报方法

Fatigue Life Prediction of a Hatch Corner Based on the Spectral Analysis and Fatigue Crack Growth Approaches

以某超大型集装箱船驾驶室前椭圆形角隅为例,采用谱分析结合裂纹扩展方法预报角隅疲劳寿命.首先通过水动力和结构响应分析得到全船响应,获得角隅在不同工况下的应力分布,并依此选定可能的起裂位置.然后将全船分析结果作为ANSYS中建立的带裂纹角隅模型二次分析的边界条件,求解应力强度因子并采用最大周向应力准则(MCSC)得到角隅在不同工况下的裂纹扩展路径,在大量计算的基础上回归出相应的角隅裂纹应力强度因子经验公式.最后依据ABS船级社推荐的谱分析法构建疲劳载荷谱,采用单一曲线模型和所获得角隅裂纹应力强度因子经验公式预报角隅疲劳寿命,为角隅疲劳寿命的校核提供参考.

Hatch corner is a typical stress concentration area in a large opening ship, and is a crucial structure detail for fatigue assessment. In this paper, an elliptic hatch corner ahead of the cabin in an ultra large container ship was taken as an example to research the assessment of the fatigue life of hatch corner based on the spectral analysis and fatigue crack growth method. Firstly, the hydrodynamic and structural response analysis were performed to get the whole ship’s structural responses and the stress distribution in the hatch corner under different loading conditions, and then determine the possible crack initiation positions on the hatch corner. Secondly, the analysis results were taken as boundary conditions of FE hatch corner model with crack which is built via ANSYS, SIF(Stress Intensity Factor) was obtained. Taking the maximum circumferential stress criterion(MCSC), propagation paths of crack in the hatch corner under different load cases were gotten, then regression was used to establish a corresponding empirical formula of SIF based on a large series of analysis. Finally, the spectral analysis approach recommended by ABS was adopted to construct the fatigue load spectrum, and the Single Curve Model and the proposed empirical formula were used to predict the fatigue life of the hatch corner. The results could provide a reference for fatigue assessment of hatch corner.