The carcass layer of flexible pipe adopts the structural form of interlocking wrap, which leads to its inner surface not being smooth and having gaps. The fluid transported at high speed in the pipe may contain sand or solid impurities. These impurities will impact the gap between close parts of the carcass layer causing erosion, leading to thinning of the steel strip of the carcass layer and reducing the pressure collapse resistance of the carcass layer. The carcass layer will have serious consequences in the event of a collapse failure. The collapse pressure of flexible pipes is investigated by modeling the carcass layer of flexible pipes containing erosion defects. The proposed solution proved to be able to predict the collapse pressure of flexible pipe carcass layers containing erosion defects.
Non-bonded flexible pipes better adapt to the ocean's complex environment. Local steel layers in the carcass layer get thinner when the carcass layer erodes. Furthermore, with the action of external load, the erosion position of the carcass layer may have stress concentration. The pipeline will collapse and fail as a result of the external pressure. Paumier et al. (2009) completed over 200 experimental verifications on the pipeline structure and determined the flexible pipeline collapse pressure. Malta et al. (2012) did a study on pipe collapse modes, proposing that when a three-layer pipe is destroyed, it will emerge in two collapse modes. Souza et al. (2002) conducted experimental testing with flexible pipes to illustrate the structural behavior of the pipe until it collapses under the action of radial compression and external pressure. Clevelario et al. (2010) did a similar investigation and discovered that the collapse pressure of curved pipes was lowered by more than 10% when compared to straight pipes. Zhang et al. (2013) estimated the equivalent thickness of the complicated cross-section to anticipate the collapse pressure of the carcass layer, using the cross-sectional area equivalent technique to equate the complex cross-section carcass layer to a steel ring of uniform thickness.
