Buckle propagation in offshore pipelines is a catastrophic mode of failure critical to the design and operation of such structures. The collapse of a locally weakened section in the pipeline can initiate a buckle that travels at high velocity, flattening long sections of the structure. The propagating buckle velocity increases with the ambient pressure and, as the collapse pressure of the pipe is approached, propagation switches to the flip-flop mode — first reported in Kyriakides and Babcock [1979]. In this letter, the problem is revisited; new experiments that capture the dynamic buckle propagation and the formation of a flip-flop are first presented, followed by numerical simulations. The combined results further elucidate the dynamics of buckle propagation and the unique flip-flop mode.

海上管道中的扣环传播是一种灾难性的故障模式，对此类结构的设计和操作至关重要。管道中局部弱化部分的坍塌会引发高速弯曲，从而压平结构的长部分。传播的屈曲速度随着环境压力的增加而增加，并且随着接近管道的坍塌压力，传播切换到触发器模式——首先在 Kyriakides 和 Babcock [1979] 中报道。在这封信中，重新审视了这个问题；首先介绍了捕捉动态弯曲传播和触发器形成的新实验，然后是数值模拟。综合结果进一步阐明了弯曲传播的动力学和独特的触发器模式。