Abstract Flexible pipes are key equipment for offshore oil and gas production systems, conveying fluids between the platform and subsea wells. The structural arrangement of unbonded flexible pipes is quite complex, encompassing several layers with polymeric, metallic and textile materials. Different topologies and a large amount of intricate nonlinear contact interactions between and within their components, especially because of the relative stick-slip mechanism during bending, makes numerical analysis challenging. This paper presents an alternative three-dimensional nonlinear finite element model that describes the response of flexible pipes subjected to combined axisymmetric and bending loads. To simulate the response of a flexible pipe under axial tension or compression combined with uniform curvature, an equivalent thermal loading is employed on the external sheath, which is modelled as an orthotropic thermal expansion material with temperature-independent mechanical properties. To assess the feasibility of the proposed model, the bending moment versus curvature of the finite element solution is compared with experimental results obtained in literature and good agreements are found between them. Detailed finite element results such as contact pressures, armour wire slip displacements and friction, normal and transverse bending stresses are also shown and compared with available analytical models.

中文翻译：

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轴对称和弯曲复合荷载作用下无粘结柔性管的有限元模型

摘要 柔性管是海上油气生产系统的关键设备，在平台和海底井之间输送流体。无粘结软管的结构布置非常复杂，包括多层聚合物、金属和纺织材料。不同的拓扑结构以及组件之间和组件内部的大量复杂非线性接触相互作用，尤其是由于弯曲过程中的相对粘滑机制，使得数值分析具有挑战性。本文提出了一种替代的三维非线性有限元模型，该模型描述了柔性管在轴对称和弯曲载荷组合下的响应。为了模拟软管在轴向拉伸或压缩以及均匀曲率下的响应，在外部护套上采用等效热载荷，将其建模为具有与温度无关的机械性能的正交各向异性热膨胀材料。为了评估所提出模型的可行性，将有限元解的弯矩与曲率与文献中获得的实验结果进行比较，发现它们之间具有良好的一致性。还显示了详细的有限元结果，例如接触压力、铠装线滑动位移和摩擦、法向和横向弯曲应力，并与可用的分析模型进行了比较。将有限元解的弯矩与曲率与文献中获得的实验结果进行比较，发现它们之间具有良好的一致性。还显示了详细的有限元结果，例如接触压力、铠装线滑动位移和摩擦、法向和横向弯曲应力，并与可用的分析模型进行了比较。将有限元解的弯矩与曲率与文献中获得的实验结果进行比较，发现它们之间具有良好的一致性。还显示了详细的有限元结果，例如接触压力、铠装线滑动位移和摩擦、法向和横向弯曲应力，并与可用的分析模型进行了比较。