深水半潜式平台结构关键节点疲劳破坏机理试验研究

Experimental study on the fatigue failure mechanism of key joints in deepwater semi-submersible platform structures

深水半潜式平台结构在深海环境荷载及作业动荷载的作用下容易产生疲劳损伤累积,加速疲劳裂纹扩展,导致结构发生疲劳破坏。对深水半潜式平台横撑部位的两类关键节点进行了疲劳试验研究,分析了关键节点的疲劳破坏现象、疲劳破坏过程以及疲劳裂纹扩展规律。试验结果表明:应用规范给出的裂纹扩展模型和参数估算关键节点的疲劳寿命低于试验所得的疲劳寿命,说明应用规范给出的裂纹扩展模型和参数估算节点的疲劳寿命比较安全;根据疲劳试验结果建立的关键节点的S-N曲线参数与DNV规范给出的较为吻合;关键节点焊趾处的ε-N关系曲线可以反映出关键节点疲劳破坏的三个阶段破坏规律。研究结果为有效地预测平台结构关键节点的疲劳损伤程度,及时进行维修加固延长结构的使用寿命提供参考。

Deepwater semi-submersible platform structures under the loads of deep-sea environment and operation will generate fatigue damage accumulation,which accelerates the expansion of fatigue crack and causes the fatigue failure of the platform structures. The fatigue tests of two-type key joints in the brace of platform were investigated,and the analyses of fatigue failure phenomenon,fatigue failure procedures and fatigue crack growth law were carried out. The test results show that fatigue lives estimated by using the crack propagation model and parameters given in the specification are lower than the fatigue lives obtained in the test,which illustrates that it is safe to estimate the fatigue lives of key joints by using the crack propagation model and parameters given in the specification; the parameters of S-N curves of key joints established by the test results agree well with the parameters of S-N curves given in the DNV specification; the ε-N relation curves of weld toe can reflect the three-stage fatigue damage rule of the key joints. It will provide a reference for the effective prediction of fatigue damage degree,maintenance and reinforcement of the structures in time,the service life extension of the platform＇s crucial structures.