The flexible pipe industry has been confronted with the potential threat of armour wires lateral buckling for over two decades. Cyclic bending is recognized to play a significant role in the lateral buckling mechanism since it facilitates the armour wire sliding against the frictional resistance. If a flexible pipe is exposed to axial compression larger than the critical load for a certain period, the risk of lateral buckling may be controlled by limiting the number of bending cycles. Thus, the estimation of the bending cycles number to initiate buckling is favorable to prevent buckling failure and enlarge the potential application scope of flexible pipes. The present paper presents an analytical model for an approximate estimation of the number of bending cycles required to initiate the lateral buckling in wet annulus conditions. The analytical results are compared with the available test data in the literature and relatively good correlations are observed on the cycle numbers to buckle. Based on this analytical model, parameter studies are performed and the effects of axial compression, bending curvatures, and friction coefficient on the number of bending cycles to initiate buckling, as well as the stress states at the onset of buckling, are discussed.

在过去的二十多年中，挠性管行业一直面临着铠装线横向屈曲的潜在威胁。周期性弯曲在横向屈曲机构中起着重要作用，因为它有助于铠装线抵抗摩擦阻力滑动。如果挠性管在一定时期内承受的轴向压缩力大于临界载荷，则可以通过限制弯曲次数来控制横向屈曲的风险。因此，估计弯曲周期数以引发屈曲有利于防止屈曲失败并扩大挠性管的潜在应用范围。本文提出了一种分析模型，用于近似估计在湿环空条件下引发侧向屈曲所需的弯曲循环数。将分析结果与文献中的可用测试数据进行比较，并且在扣紧的循环次数上观察到相对较好的相关性。基于该分析模型，进行了参数研究，并讨论了轴向压缩，弯曲曲率和摩擦系数对引发屈曲的弯曲循环次数以及屈曲开始时的应力状态的影响。