大型集装箱船舱口角隅高低周复合疲劳寿命预报方法研究

Prediction method of high-and low-cycle composite fatigue of hatch corners of large container ships

大型集装箱船遭遇高海况时,舱口角隅处应力水平可能接近甚至超过材料屈服极限,因此循环极端载荷作用下的舱口角隅疲劳损伤可视为高低周复合疲劳问题。本文采用一种高低周复合疲劳寿命预报模型对某大型集装箱船的舱口角隅进行疲劳寿命预报。首先建立全船有限元模型和水动力模型,给出不同浪向角及波浪频率下舱口角隅节点的热点应力传递函数,然后采用北大西洋波浪散布图得到节点的应力范围,对其中超过80%屈服应力的海况,通过Neuber公式求出角隅节点的弹塑性循环应力应变幅,最后采用复合疲劳模型计算得到舱口角隅的高低周复合疲劳寿命。与采用谱分析方法预报的疲劳寿命进行对比后的结果显示,高海况导致舱口角隅发生的低周疲劳损伤不可忽略,应采用高低周复合疲劳评估方法对其进行寿命预报。本文工作可为船体结构疲劳寿命的准确预报提供参考。

When a large container ship encounters high sea conditions,the stress level at the hatch corners may approach or even exceed the yield limit of the material.Therefore,the fatigue damage of the hatch cor-ners under cyclic extreme load can be regarded as a high-and low-cycle composite fatigue problem.In this paper,a high-and low-cycle composite fatigue life prediction model was used to predict the fatigue life of the hatch corners of a large container ship.Firstly,the whole ship finite element model and hydrodynamic model were established,and the hot spot stress transfer function of the hatch corner node under different wave direc-tions and wave frequencies was given.Then,the North Atlantic wave scatter diagram was used to obtain the stress range of the node.For sea conditions with 80%yield stress,the elastoplastic cyclic stress-strain ampli-tude of the corner joints was calculated by the Neuber formula.Finally,the composite fatigue model was used to calculate the high-and low-cycle composite fatigue life of the hatch corners.By comparing with the fa-tigue life predicted by the spectral analysis method,the results show that the low-cycle fatigue damage of the hatch corners caused by high sea conditions cannot be ignored,and that the high-and low-cycle composite fatigue assessment method should be used to predict the hatch lives.The work in this paper can serve as a ref-erence for the accurate prediction of the fatigue life of a hull structure.