在非线性波浪载荷作用下计及多种应力组合时船体总纵弯曲累积损伤计算

Accumulated damage calculation for ship hull of overalllongitudinal bending including combined stress andnonlinear wave loads

在时域内计算计及非线性时的船体总纵弯曲应力,与船体局部弯曲应力迭加后,可得纵向构件中合成应力的时历。对该应力时历进行雨流计数,经统计分析获得应力范围的长期分布,进而算出船体总纵弯曲时纵向构件在多种应力成份组合下的疲劳损伤。为方便此时的计算,本文提出了基于等效规则波概念的简化方法。数例表明按严格方法与按简化方法所得的结果比较接近。

The overall longitudinal bending stress of ship hull, subjected to nonlinear wave loads, is calculated in time domain. The combined stress time history of ship hull's longitudinal component is obtained from combining the overall longitudinal bending stress with local bending stress. A long-term distribution of combined stress range is gained by applying the means of rain-flow cycle counting to the combined stress time history and using the approach of probability and mathematical statistics. Then the combined stress-induced fatigue damage to longitudinal component is calculated during overall longitudinal bending of ship. A simplified way of calculation based on the concept of equivalent regular wave is presented in this paper for the purpose of simplifying the calculation of fatigue damage. As an example, the results obtained by the simple method are compared with the one by rigorous method and they are shown reasonable agreement.