基于结构应力的海底管道悬跨段涡激振动的焊缝疲劳研究

Research on weld fatigue under the vortex induced vibration of submarine pipeline span based on structural stress

针对涡激响应条件下海底悬跨管道传统焊接疲劳的局限性,本文根据实际海洋工况条件,建立全尺寸海底悬跨管道含焊缝的“Beam-shell”有限元耦合模型,并将网格不敏感的结构应力法与涡激振动理论模型相结合,对相关的疲劳寿命公式拓展,提出适用于含焊缝的悬跨管道涡激振动的疲劳评价模型,使其具有海洋工程特色。结果表明:涡激振动导致的焊缝疲劳不仅取决于流速引起的涡激振动主导区间,而且还与海流流速的分布概率密切相关。在该小流速主导的海域中,由于顺流向涡激振动启动流速较低,更易被激发多模态的涡激振动,反而较横流向涡激振动更危险;横流向涡激振动虽然更剧烈,但启动流速较高,小流速的海况很难激发其响应。另外,该涡激响应的焊接疲劳评价模型具有很好的网格不敏感性,且主S-N曲线不存在选取的主观性,其评价结果可靠。因此,在工程上,可结合该网格不敏感的疲劳评价模型,提高海底管道设计的安全性和可靠性。

Aiming at the traditional weld fatigue limitation about pipeline span under vortex induced vibration(VIV),it established a full-size"Beam-Shell with girth weld"coupled FE model for submarine pipeline span based on the working condition.Combined with mesh-insensitive structural stress,it proposed a VIV weld fatigue evaluation model for pipeline span,and to extend the fatigue formula,which made it characteristic of ocean engineering.The results show that the weld fatigue on vortex induced vibration response not only depends on the VIV zone caused by flow velocity,but also is closely related to the current distribution probability.In the sea with lower current velocity,the multi-mode vortex induced vibration response is more likely to be excited along the inline direction,which is more dangerous.Although the cross-flow VIV response is more intense,the starting velocity is higher,and it is difficult to stimulate the response with lower current velocity.Therefore,it can combine the mesh-insensitive fatigue model to improve the safety and reliability of submarine pipeline design in engineering.