Torsional Response Analysis of Flexible Pipe Based on Theory and Finite Element Method

As key components connecting offshore floating production platforms and subsea imports, offshore flexible pipes play significant roles in oil, natural gas, and water injection. It is found that torsional failure is one of the failure modes of flexible pipes during transportation and laying. In this paper, a theoretical model(TM) of a flexible pipe section mechanics is established, in which the carcass layer and the pressure armor layer are equivalent to the orthogonal anisotropic layers due to its complex cross-section structure. The calculation results of the TM are consistent with those of a finite element model(FEM), which can accurately describe the torsional response of the flexible pipe.Subsequently, the TM and FEM are used to discuss the influence of boundary conditions on the torsional response.The structure of the flexible pipe is stable when twisted counterclockwise. However, limiting the top axial displacement can improve the axial and radial instability of the tensile armor layer when twisted clockwise. Finally, it is recommended that the flexible pipe can be kept under top fixation during service or installation to avoid torsional failure.

Prediction of Load-Displacement Curve of Flexible Pipe Carcass Under Radial Compression Based on Residual Neural Network

The carcass layer of flexible pipe comprises a large-angle spiral structure with a complex interlocked stainless steel cross-section profile, which is mainly used to resist radial load. With the complex structure of the carcass layer, an equivalent simplified model is used to study the mechanical properties of the carcass layer. However, the current equivalent carcass model only considers the elastic deformation, and this simplification leads to huge errors in the calculation results. In this study, radial compression experiments were carried out to make the carcasses to undergo plastic deformation. Subsequently, a residual neural network based on the experimental data was established to predict the load-displacement curves of carcasses with different inner diameter in plastic states under radial compression.The established neural network model’s high precision was verified by experimental data, and the influence of the number of input variables on the accuracy of the neural network was discussed. The conclusion shows that the residual neural network model established based on the experimental data of the small-diameter carcass layer can predict the load-displacement curve of the large-diameter carcass layer in the plastic stage. With the decrease of input data, the prediction accuracy of residual network model in plasticity stage will decrease.

Analytical and Numerical Modeling for Flexible Pipes

The unbonded flexible pipe of eight layers, in which all the layers except the carcass layer are assumed to have isotropic properties, has been analyzed. Specifically, the carcass layer shows the orthotropic characteristics. The effective elastic moduli of the carcass layer have been developed in terms of the influence of deformation to stiffness. With consideration of the effective elastic moduli, the structure can be properly analyzed. Also the relative movements of tendons and relative displacements of wires in helical armour layer have been investigated. A three-dimensional nonlinear finite element model has been presented to predict the response of flexible pipes under axial force and torque. Further, the friction and contact of interlayer have been considered. Comparison between the finite element model and experimental results obtained in literature has been given and discussed, which might provide practical and technical support for the application of unbonded flexible pipes.

Axial mechanical experiments of unbonded flexible pipes

Axial structural damping behavior induced by internal friction and viscoelastic properties of polymeric layers may have an inevitable influence on the global analysis of flexible pipes.In order to characterize this phenomenon and axial mechanical responses,a full-scale axial tensile experiment on a complex flexible pipe is conducted at room temperature,in which oscillation forces at different frequencies are applied on the sample.The parameters to be identified are axial strains which are measured by three kinds of instrumentations:linear variable differential transformer,strain gauge and camera united particle-tracking technology.The corresponding plots of axial force versus axial elongation exhibit obvious nonlinear hysteretic relationship.Consequently,the loss factor related to the axial structural damping behavior is found,which increases as the oscillation loading frequency grows.The axial strains from the three measurement systems in the mechanical experiment indicate good agreement,as well as the values of the equivalent axial stiffness.The damping generated by polymeric layers is relatively smaller than that caused by friction forces.Therefore,it can be concluded that friction forces maybe dominate the axial structural damping,especially on the conditions of high frequency.

The development of studying flexible pipe bend reinforced by Kevlar fibers

The flexible pipe bend can not only reduce the structural vibration and fluid noise in pipeline, but also realize the flexible connection of a horizontal line and a vertical line and compensate the displacement of three dimensions produced by the shock or vibration of pipeline in the special situations. Up to now, little attention has been paid to study the flexible pipe bend applied in the pipeline of medium or high pressure, because no appropriate framework materials can be used to reinforce it which must endure the burst pressure higher than 10 MPa. The investigation shows that it is possible to produce the flexible pipe bend of medium or high pressure if such fibers with high performance as Kevlar fibers are used to be its reinforced materials. However, its structural designing theory, manufacturing technology and measuring techniques aren't yet perfect and systematic, which leads to the instability of the performance of products. Furthermore, few references about its research can be seen. Therefore, it is necessary to systematically and thoroughly develop the structural designing theory, manufacture technology and measuring techniques of flexible pipe bend.

An Analytical Approach for Assessing the Collapse Strength of an Unbonded Flexible Pipe

这篇论文为预言一根灵活管子的倒塌力量论述一个分析计划，它考虑在相关的层之间的结构的相互作用。分析结果与一个 FEA 模型和很多个测试数据相比，并且显示出相当好的同意。理论分析证明压力盔甲层对弄弯提高了尸体的力量，尽管障碍削弱了这效果。管子的倒塌力量被象管子，层的厚度和材料的机械性质的内部半径那样的许多因素影响。例如，障碍的厚度的增加将增加接触压力并且接着减少批评压力。

Mode Transitions in Vortex-induced Vibrations of a Flexible Pipe near Plane Boundary

有 4.30 的集体比率(集中 / 代替的团) 的一个管子模型被测试在海床附近调查海底的管道跨度的导致旋涡的颤动。管子模型作为弯曲被设计僵硬主导的横梁。在管子结束的差距比率(到直径比率的差距) 是 4.0， 6.0，和 8.0。流动速度系统地基于第一自然频率在 016.71 nondimensional 速度范围被改变。模式转变在之间第一并且流动速度增加的第二个模式被调查。在各种各样的转变流动速度，研究显示关于排水量的山峰频率不沿着也为开始的四个模式与振幅系列的山峰联系的管子，也不频率是相同的。模式转变在振幅，而是 theres 与一个连续变化被联系一在频率的 jump，和沿着管子长度的一个渐渐的过程。

Fiber-Reinforced Polymer Bridge Design in the Netherlands： Architectural Challenges toward Innovative, Sustainable, and Durable Bridges

本文综述了纤维增强复合材料(FRP)在荷兰桥梁的建筑性与结构性设计方面的应用,讨论了这种相对较新的材料给建筑师和工程师带来的挑战和机遇。本文涵盖了纤维增强复合材料的最新结构处理方案,以及对于纤维增强复合材料在建筑方面应用的讨论,这些应用来源于笔者与其他科研人员在建筑上的实践。

深海采矿柔性管力学性能及加工工艺研究综述

海洋蕴藏着储量丰富的矿产资源,深海矿产资源开发逐渐成为学术界和工程界的研究热点。管道提升式开采方案是目前公认的最具商业前景的海洋矿产开发方案。矿产输运管道作为连接海底中继舱和海上采矿平台的纽带,需要承受恶劣的风、浪、流环境载荷和复杂作业工况的工作载荷,其设计制造和力学性能分析一直备受关注。相比于刚性管道,柔性管道的弯曲刚度小、便于安装与回收、使用寿命较长。然而,柔性管道的结构复杂,各层之间相互影响,金属柔性管道由于自身结构的限制,在深海采矿行业中难以广泛应用,人们开始把目光放在非金属柔性管的设计与应用上。本文回顾了柔性管的发展历程,总结阐述了柔性管设计及加工制造中的力学性能分析方法和力学特性,并对柔性管设计制造的未来发展提供力所能及的展望。

层间摩擦系数对非黏结柔性管抗拉铠装层轴压屈曲失效模式的影响研究

在柔性管运输、铺设安装和服役过程中,由于其抗拉铠装层钢带为柔性细长螺旋结构,当外部载荷超过临界值时,抗拉铠装层钢带容易发生屈曲失效。考虑非线性材料、几何大变形、层间接触和摩擦等非线性效应的影响,运用ABAQUS有限元软件建立了63.5mm典型非黏结柔性管8层完整结构模型,研究了在抗拉铠装层不同层间摩擦系数的情况下,非黏结柔性管在轴向压缩载荷作用下的力学性能和屈曲失效模式。研究结果表明,层间摩擦系数对非黏结柔性管的抗压刚度和抗拉铠装层屈曲失效模式有较大影响,层间摩擦系数以0.1和0.2为分界点,抗压刚度和屈曲失效模式均呈现出“三段式”变化规律。研究成果可为海洋非黏结柔性管的结构设计和屈曲失效评估提供技术参考。

LNG螺旋骨架复合耐超低温柔性管道拉伸性能分析研究

LNG螺旋骨架复合耐超低温柔性管道采用了以螺旋骨架支撑,多层复合材料缠绕的非粘接结构形式,这类结构的力学性能分析中涉及到几何大变形、超低温环境、复杂层间接触等难题。传统的柔性管道拉伸理论模型不再适用于这类结构形式。本文针对12英寸(1英寸=0.025 4 m)口径的低温柔性管道开展了常、低温拉伸性能实验研究,建立了低温柔性管道的精细数值模型,并通过实验进行了模型修正。基于所建立的数值模型开展了温度、支撑层参数对管道拉伸性能的敏感性分析。结果表明,低温环境下管道的抗拉伸性能提高了12.69%,支撑层螺距增大50%将导致管道的抗拉伸性能降低52.36%。本文的研究为LNG螺旋骨架复合耐超低温柔性管道的设计和优化提供了一定的参考和指导。

弯管内可控万向铰接柔性管动力学特性研究

针对弯管内可控万向铰接柔性管随机动态接触问题,以弯管和可控铰接柔性管为研究对象,采用哈密顿原理结合多体系统动力学理论,引入刚体运动坐标系描述可控铰的运动约束,以管-管接触模型描述可控万向铰接管和弯管的动态接触,建立了弯管内可控万向铰接柔性管多体系统接触非线性动力学的数值计算方法。以超短半径水平井造斜段柔性钻具为例,根据贝克休斯公司的钻具动力学特性标准,对柔性钻杆的振动特性进行了评价,研究了不同转速和不同钻压对柔性钻杆动力学特性的影响。研究结果表明:横向振动是导致柔性钻具可能失效的主要因素;柔性钻杆的横向振动剧烈程度随着转速的增加而减小,随着钻压的增加而增大。

内压载荷下输氢复合柔性管力学性能研究

中国氢能产业正随着碳中和愿景的不断推进而快速发展,由于氢气在钢管中容易引发“氢脆”现象,使用钢管输送氢气存在较大挑战,纤维增强复合柔性管作为一种非金属管道在氢气输送领域备受关注,其结构设计及强度分析是产业化应用的瓶颈。为探讨内压工况下输氢复合柔性管的结构响应,考虑不同层材料的各向同性及各向异性,基于三维各向异性弹性力学,建立了纤维增强输氢复合管道在内压作用下的力学理论模型,并采用数学方法求解管道位移微分方程,进而获得了N层缠绕增强层输氢复合管道在内压作用下的应力应变解析解,计算结果与内压作用下13层输氢复合柔性管的数值计算结果相符。管道的环向应力最大值出现在防渗透层,输氢软管的增强层承担约70%的载荷作用,径向应力绝对值大小随距离管道截面中心点的距离增大而减小。提出的力学行为分析模型及求解方法为设计输氢复合柔性管提供了重要的理论支撑。

基于自整定模糊PID的柔性管道加热控制系统研究

针对传统温度控制器调节控制精度低、超调量大的缺点,设计了一套模糊控制策略+比例积分微分(PID)控制方法+物联网云平台技术的柔性管道加热控制系统。该系统可实现过程实时监控、温度检测和闭环控制功能,使输气管道在加热过程中的温度控制稳定、温度调节响应速度快、超调量小。通过对控制过程的可视化,可实时分析系统运行状况,从而实现对加热过程和气体输送过程的动态监控。该系统具有加热及温度控制、运行状态实时监测功能。适用于管道加热系统的柔性管道加热控制系统对半导体企业降低生产能耗、提高生产效率、过程监控、保证输送系统安全和平稳运行有重要意义。

柔性复合管在油田服役后的性能

为评价柔性复合管在油气田地面集输系统中的应用效果,采用宏观观察、微观分析、水压爆破试验、气密封性能测试、结构组成分析、热分析、红外光谱分析、力学性能测试等方法对两条柔性复合管进行分析,以确定其在不同工况下的适用性。结果表明:在经过一段时间的服役后,两条柔性复合管结构层保持完整,未发现明显缺陷,内衬层颜色加深;两条管道的失效形式均为管体爆破,其中1号试样因长期高温运行,其爆破压力不满足标准要求;两条管道的内衬层分别为交联聚乙烯和普通聚乙烯,增强层分别为芳纶纤维和涤纶纤维,热分解温度分别为580℃和440℃,但芳纶纤维的抗拉强度明显小于涤纶纤维。

海洋纤维增强柔性管压溃失效特性研究及参数敏感性分析

以一种黏结型的纤维增强柔性管作为研究对象,基于ABAQUS建立纤维增强柔性管的实体单元模型。根据二维Hashin失效判据判断柔性管失效情况,充分考虑管道内外护套层塑性及纤维增强层复合材料渐进失效,建立纤维增强柔性管的压溃数值模型。将特征值法与弧长法相结合,计算得到了较为精准的纤维增强柔性管临界压溃压力及对应的外压—椭圆度曲线;并对影响柔性管临界压溃压力的几个敏感性参数如椭圆度、纤维缠绕角度、直线度进行分析。研究结果表明椭圆度和直线度偏差的增大及纤维缠绕角度的降低均会使柔性管的临界压溃压力下降,该结果对纤维增强柔性管的设计与使用均具有一定的参考意义。

深水油气输送软管内部流体渗透规律研究进展

海洋柔性管道作为我国实现海上油气自主开发急需的关键技术装备,由于其结构及材料特点,无法避免内部流体的渗透,国内相关研究仍处于起步阶段,渗透带来的后果尚不明确,研究方法尚不成熟。从输送软管内部气体的渗透行为出发,阐明渗透可能引起的危害;对目前国内外软管渗透的数学模型、实验方法、现场测试手段三种研究方法进行详细分析,并对比评价输送软管流体渗透量的预测模型,阐述未来模型构建应当囊括的因素;材料实验应侧重不同工况下的材料渗透性质,样管及原型实验应侧重模拟屏蔽效应等影响渗透的因素;系统梳理现有的现场测试手段,认为测试应重点向环空剩余体积连续监测、环空流体组分检测和外包覆层破损检测方向发展。

AutoPIPE软件在氧化铝工厂管道设计中的应用

随着我国氧化铝工业进入百万吨级时代,大型化将成为今后的发展趋势。大型化设计不是简单的放大,已有的设计经验不一定适用。管道设计是氧化铝工厂设计过程中不可缺少的组成部分,涉及各种工况、介质的压力管道,工厂大型化后管道直径必然加大,这样管道布置走向、支架型式都会发生改变。为了确保压力管道设计安全、可靠,设计人员常借助应力分析软件来进行柔性设计。AutoPIPE作为国内外应用广泛的应力分析软件,其应用涵盖了许多领域。本文以某氧化铝厂母液蒸发工序的铝酸钠溶液压力管道为例,利用AutoPIPE应力分析软件进行了柔性设计、弹簧选型设计、泵设备分析,探究了该软件在氧化铝工厂管道设计中的应用情况,为管道设计的安全提供保障。

船舶管子柔性产线控制系统设计与实现

随着先进制造技术不断提升迭代以及产品质量追溯管控要求,船舶管子制造也由传统粗放的生产模式不断向自动化生产模式演变,众多船厂逐步实现并推广,以便消除制造效率与焊接质量等方面的瓶颈。为了提高产线自动化水平,应不断优化和改进相应产线控制系统。结合现场实际调研需求,梳理管子自动化产线制造工艺,并从系统功能、数据库设计、系统集成等方面进行研究与实现,以满足管子自动化产线任务接收,对具有限定条件的柔性管加工生产线精细化管理。通过任务的合并标序,完成无序上料到有序生产的能力建设。通过全周期的监控并控制自动化产线,实现安全、有序、高效的无人化生产。