Abstract Sandwich pipes have been studied as one option to overcome the high pressure problems in deep and ultra-deep waters. They have become a possible alternative solution for submarine infrastructure due to its thermal insulation capacity. This contribute to preventing the pipeline from clogging due to the difference in temperature between reservoir fluids and water at the bottom of the sea. The pipelines in ultra-deepwater are continually exposed to severe operating conditions, such as the effect of high levels of external pressure that can cause local deformation or even collapse of the pipe. Thus, a greater understanding of the mechanical behavior of sandwich pipes is required. This paper presents a FEM-based evaluation of friction and initial imperfection effects on sandwich pipes local buckling. The non-linear evaluation was carried out in FEM of local buckling of two sandwich pipes, with polypropylene and cement as filled annular material. The influence of initial imperfections and the degree of friction, between the annular material and the steel pipes, as well as geometric variations of the pipe were considered. The numerical simulations results indicate a capacity to withstand ultra-deep waters collapsing pressures, around 3000 m, either for polypropylene or cement filled annular material model. In addition, the results indicate that the collapse pressure is inversely proportional to the increase in annular thickness and directly proportional to the decrease in friction which have an impact and contribution on the carrying capacity of the sandwich pipe. Further research will consider a design of experiments analysis of reported effects for different diameter-to-thickness ratios.

中文翻译：

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基于有限元法的摩擦和初始缺陷对夹层管局部屈曲的影响评估

摘要 夹心管已被研究作为克服深水和超深水高压问题的一种选择。由于其隔热能力，它们已成为潜艇基础设施的可能替代解决方案。这有助于防止管道因油藏流体和海底水之间的温差而堵塞。超深水中的管道持续暴露在严酷的操作条件下，例如会导致管道局部变形甚至坍塌的高水平外部压力的影响。因此，需要更深入地了解夹层管的机械性能。本文提出了基于 FEM 的摩擦和初始缺陷对夹层管局部屈曲的影响的评估。以聚丙烯和水泥为填充环形材料的两根夹层管局部屈曲的有限元法进行非线性评估。考虑了环形材料和钢管之间的初始缺陷和摩擦程度的影响，以及管道的几何变化。数值模拟结果表明，聚丙烯或水泥填充环形材料模型能够承受约 3000 m 的超深水坍塌压力。此外，结果表明，坍塌压力与环形厚度的增加成反比，与摩擦的减少成正比，这对夹层管的承载能力有影响和贡献。