船舶典型节点疲劳强度试验及S-N曲线拟合方法研究

Fatigue Strength Experiment and S-N Curve Fitting Method of Ship Typical Joints

疲劳评估的关键问题是S-N曲线的选取,对于某些结构复杂的大型船舶特有的结构形式,现有规范没有合适的SN曲线。为了更合理准确地进行结构疲劳强度研究,本文选取某型具有复杂结构的船舶,用实尺度模型试验的方法研究几种典型节点的S-N曲线特性。通过全船有限元谱分析疲劳强度计算,筛选出疲劳问题重点关注区域,确定模型试验部位;根据疲劳问题严重区域的实船结构,设计加工典型节点实尺度疲劳试验模型;确定多个加载工况,进行典型节点疲劳强度试验,获取典型节点多种载荷工况下的疲劳寿命值,在此基础上,研究得到各节点S-N曲线及P-S-N曲线;应用试验所得P-S-N曲线,对船体典型节点部位进行疲劳强度评估,并与规范S-N曲线结果进行了对比,指出了它们的差异。

The selection of S-N curves has always been a key issue in fatigue assessment for ship structures.For some specific structural forms of large ships,no suitable S-N curves in the existing classification society rules can be applied to structural fatigue assessment.In this paper,a large ship with a complex structure was selected as an example.The S-N curve characteristics of typical joints were studied through real scale model fatigue experiments.Through finite element calculation of the fatigue strength of the whole ship based on spectrum analysis,the key areas with serious fatigue problems were identified for determination of the test locations in the model.The real scale fatigue experiment models were designed and built according to the real ship structure of the selected typical joints.Fatigue strength experiments of each typical joint under multiple load conditions were conducted to obtain fatigue life values of typical joints under each load condition.S-N and P-S-N curves for each typical joint were fitted on the basis of the experimental results.The fitted P-S-N curves obtained by the experimental results were applied to the fatigue strength assessment of typical joints,the results were compared with those obtained by the S-N curves of existing classification society rules,and the differences were presented.