Local structural analysis of flexible pipes subjected to traction,torsion and pressure loads

Helically armored cables or pipes find a wide range of applications as structural members in engineering. An example of this is the increasing use of flexible pipes in the oil offshore production. Although keeping a geometrical similarity with other helically armored structures such as wire ropes and ACSR conductors, and borrowing from them a useful methodology for the structural analysis, some care must be taken in order not to indiscriminately use an approach which was not thought for a flexible pipe: internal and external pressures, for instance, are a great concern in the analysis of flexible pipes, but obviously not for wire ropes. This work aims at giving some additional contribution to the structural response of flexible pipes when subjected to axisymmetric loads, including the effect of both internal and external pressure in pipe displacements. Derivation of linear operators, relating the stress-resultants to their related displacements or deformations in each of the layers of the pipe, as well as the process of deriving an analogous linear operator to represent the behavior of the pipe as a whole, are clearly presented, highlighting interesting mathematical aspects and their associated physical meaning. A numerical case study of a 2.5″ flexible pipe subjected to traction and internal pressure is also presented and discussed.     

非粘结柔性立管静态分析

海洋柔性立管因材料和结构上的复杂性在设计分析中存在许多技术难题。本文在变形能原理和能量守恒的基础上,推导出了柔性立管各层的刚度矩阵。将各层刚度矩阵进行叠加,得到柔性立管总体刚度矩阵,并用总体刚度矩阵求解静载荷作用下立管变形响应。同时基于ABAQUS软件建立八层非粘结柔性立管有限元模型,并将有限元计算结果和刚度矩阵计算结果进行比较。结果分析表明：运用推导得到的刚度矩阵求解静态载荷下立管的变形是一种简便且准确的方法。     

A finite element model for flexible pipe armor wire instability

The constructive disposition of metallic and plastic layers confers flexible pipes with high and low axial stiffness respectively when tensile and compressive loads are applied. Under certain conditions typically found during deepwater installation or operation, flexible pipes may be subjected to high axial compression, sometimes accompanied by bending. If not properly designed, the structure may not be able to withstand this loading and fails. From practical experience observed offshore and in laboratory tests two principal mechanisms, which will be discussed in this paper, have been identified regarding the configuration of the armor wires. When the pipe fails by compression the armor wires may exhibit localized lateral or radial deflections, consequently permanent damage is observed in the armor wires with a sudden reduction of the structure’s axial stiffness. The pressure armor may also unlock, thus causing potential fluid leakage.In this work a finite element model is developed to estimate the critical instability load and failure modes. An axi-symmetric model is constructed employing a complex combination of beam and spring elements. For each armor layer only one wire needs to be modeled, hence the computational cost is minimized without compromising the phenomenon characterization. A parametric case study is performed for a typical flexible pipe structure, where the friction coefficient between the wire armors and the external pressure are varied, and the critical instability loads and failure modes are obtained and results are discussed.     

ABAQUS二次开发在海洋柔性立管设计分析中的应用

基于ABAQUS软件利用Python脚本语言和GUI功能开发了针对柔性立管的建模界面和求解模块.借此设计分析人员可以快速地建立柔性立管的有限元模型并进行计算分析,有效地解决了柔性立管在研制阶段的设计-分析-校核的重复繁琐问题,缩短了研发周期.     

柔性技术在汽车制造行业的应用

柔性技术在汽车行业的应用可以减少新设备的投入和生产线改造,确保新产品切换时改动量最小,以投入较少的设备费用来实现共线生产。文章详细地阐述了几种典型柔性技术的特点及其在实际生产中的应用,指出柔性技术在检测设备、工艺装备及整车开发的广泛使用,可在有限的规划区域内满足多方面的制造需求,并且降低生产成本。     

ATB-25柔性基层配合比设计

介绍了ATB-25柔性基层的配合比设计方法及过程.     

浅谈基层就地冷再生技术在辽宁省的应用

在道路养护施工方案中,道路基层就地冷再生以其适用范围广、对公共交通影响小、节约工期、再生层质量高、节省成本和国家土地资源、环保等诸多优势正在成为现有道路养护施工中的热门方案,它的发展必将代替传统的旧路面基层施工.     

被动柔性防护网结构足尺冲击试验研究

为研究被动柔性防护网结构的落石防护性能,设计2组防护能级为750 k J的柔性被动防护网结构,进行足尺冲击试验研究。模型1为按照现有标准所选型得到的系统配置;模型2为改进后的柔性被动防护网结构。试验结果表明:模型1无法拦截750 k J落石的冲击,系统崩溃;模型2成功地拦截了落石,且冲击后模型2的各主要组成构件等均未发生破坏,仅需要对耗能元件进行更换,即可继续投入使用。通过对高速视频的解构,对各部分组成构件的运动和受力特征进行详细分析,明确系统的三阶段工作历程,并分析系统失效的关键因素,同时,对实测的钢丝绳拉力时程进行对比分析。研究结果为今后柔性被动防护网结构的设计提供了理论基础。     

汽车柔性多体系统动力学建模综述

对汽车柔性多体系统动力学的建模理论、方法、作用以及国内外发展状况和目前我国在这方面的差距，作了简要的综述。应用汽车柔性多体系统动力学的建模理论和方法，可以较精确地建立整车或总成的分析模型，进而实现虚拟样车的设计和动力学仿真分析及优化。