【作者】 卢青针；

【导师】 岳前进； 阎军；

【作者基本信息】 大连理工大学 ， 工程力学， 2013， 博士

【摘要】 水下生产系统是深水石油开发中的一种经济有效的开发模式,随着我国南海石油开发的快速发展,有广泛的应用前景。连接海上浮体和海底设备的动态脐带缆是水下生产系统的关键装备之一,为海底设备提供电力、液压和化学药剂注入以及数据传输。目前只有少数国外公司具备设计及制造能力,国内所用的脐带缆均从国外公司购买,价格昂贵且采购周期长,严重制约我国水下生产系统的应用和发展。深水动态脐带缆设计对结构性能的要求比较高。由于自重原因,要求脐带缆能够承受较大的拉伸荷载；由于卷管安装、海洋环境以及浮体运动作用,要求脐带缆有较小的弯曲半径；同时还要求在恶劣的环境荷载下,脐带缆满足长期的使用寿命。因此脐带缆结构性能设计应具有较好的抗拉性、柔顺性、高疲劳寿命以及优化的单元布局。由于脐带缆为复杂的多单元、非粘结、多层螺旋缠绕结构,结构性能设计的预测模型比较复杂,理论与数值模型预测存在较多的不准确性,脐带缆设计需要通过室内原型实验验证。本文依托“十一五”国家高技术研究发展863计划,海洋技术领域“水下生产系统脐带缆关键技术研究”专题(2009AA092301),开展面向提高脐带缆结构性能设计的分析方法与实验方法研究。分别建立了脐带缆的拉伸性能、弯曲性能以及疲劳性能的预测模型,并提出原型实验方法进行验证；提出了单元布局优化设计的量化方法。本文所开展的主要工作及研究成果归纳如下：(1)脐带缆拉伸性能的设计与验证深水动态应用的脐带缆在安装及在位过程中受到较大拉伸荷载作用,如果结构的拉伸刚度过低则将导致结构变形过大,进而引起结构的变形失效。脐带缆的拉伸刚度是衡量结构拉伸性能设计的一个重要指标。针对脐带缆缆芯结构的径向可收缩特点,结合解析分析与数值分析方法,建立拉伸刚度的半解析分析模型。通过二维有限元模型,分析缆芯的等效径向刚度并作为解析分析模型的输入参数,进而快速计算脐带缆结构的拉伸刚度。在实验室搭建原型拉伸实验测试系统,验证了上述半解析分析模型的适用性。研究了脐带缆结构参数包括缆芯的径向刚度、铠装钢丝的缠绕角度及钢丝直径对拉伸刚度设计的影响。(2)脐带缆弯曲性能的设计与验证深水动态应用的脐带缆在位过程中,其顶部与底部受到较大弯曲荷载作用,因此减小顶部或者底部的曲率可以避免弯曲失效。脐带缆的弯曲刚度是动态荷载分析的重要输入参数,对曲率响应有较大影响,因此弯曲刚度是衡量结构弯曲性能设计的一个重要指标。考虑截面各单元间之间的摩擦作用,建立脐带缆全三维有限元分析模型,对非线性弯曲行为进行了数值模拟。该有限元模型能够准确预测脐带缆从无滑动、部分滑动到全滑动的过程。在实验室搭建了原型弯曲实验测试系统,验证了有限元分析模型的正确性。研究了脐带缆结构参数包括单元间的摩擦系数、单元的缠绕角度以及护套材料对弯曲刚度设计的影响。(3)脐带缆疲劳性能的设计与验证周期性波浪荷载以及平台运动使得深水动态脐带缆顶部受到较大的拉伸荷载与循环弯曲荷载的组合作用,导致内部单元受到交变应力而产生累积损伤进一步引起疲劳破坏。截面单元间相互摩擦作用对疲劳寿命有显著的影响,在疲劳寿命分析过程中,整体荷载分析模型中采用非线性弯曲刚度作为输入,同时局部应力分析中考虑单元间接触引起的摩擦应力影响。基于上述整体荷载及局部应力分析模型可得到更准确的脐带缆疲劳寿命预测。提出四点纯弯曲疲劳实验方法并建立相应室内原型疲劳实验系统,对上述脐带缆疲劳性能的分析模型与方法进行检验。(4)脐带缆单元布局的优化设计脐带缆规范ISO13628-5中关于截面的布局要求仅给出了对称性等一般性原则,并未给出可操作的具体方法及工具。基于对称性及结构力学性能要求,提出脐带缆单元的最优布局设计方法。首先为保证截面每层单元的对称排布,提出旋转对称及最大对称轴的数学描述模型,并开发相应设计软件进行求解。然后建立不同布局方式的截面精细分析有限元模型,定量分析结构力学性能,筛选确定最优的截面布局,保证脐带缆具有更优的抗拉性能及抗疲劳性能。更多还原

【Abstract】 The subsea production system is an effective and economic development mode for the deepwater offshore oil exploitation. With the rapid progress of the oil development in the South China Sea, it has a good application prospect. Dynamic umbilical that connect the top floating platform and the subsea device is one of the key equipments of the subsea production system. It provides power, data transmission, hydraulic and chemical injection for the subsea device. Only a small number of foreign companies have the ability to design and manufacture umbilicals. All the umbilicals that used in China were bought from foreign companies. The application and development of the subsea production system are seriously restricted by the expensive price and long cycle of umbilical.The design of deepwater dynamic umbilicals has a higher requirement of the structure performance. It needs to meet big tension due to self-weight, bending and high fatigue life due to rugged ocean environment and floating movement. Therefore, in order to prevent the tension, bending and fatigue failure, the umbilical structure should be designed with better tension performance, bending performance, fatigue performance and optimal layout. Due to the umbilical characteristics of multi-unit, multi-material and helical wound structure, the predicting model of the structural performance is complex. The theoretical and numerical models are imprecise. So the design needs to be verified by experiment.The support for the research is provided by the subject "The Key Technology of Umbilical of Subsea Production System"(No.2009AA09Z301) of the marine technology field of the "863" High Technology Research and Development Program of China. The analysis method and experimental research, which aimed to improve the structure performance of deepwater umbilicals, are developed. The predicting models and experimental verification platform of tension performance, bending performance, and fatigue performance are studied in the dissertation. Quantitative method of the optimal layout design is proposed. The main works and research results are summarized as follows:(1) Tension stiffness design and analysis of umbilicalThe top of deepwater dynamical umbilicals will be subjected to large tension loads during installation and operation. If the tension stiffness of the structure is too low, it will lead to a large deformation, which may lead to structural deformation failure. Umbilicals tension stiffness is an important design indicator to measure the performance of the structure tension. Due to the radial contraction characteristics of the umbilical core, a semi-analytic model of the tension stiffness that considered the radial stiffness of the core is proposed. The model combined with theory analysis model and numerical analysis model. The radial stiffness of the umbilical core which can be got from the two-dimension finite element analysis model of the cross-section is the input parameter of the theory analysis model. The tension stiffness of the umbilical can be rapidly and accurately calculated by the semi-analytic model. To verify the applicability of the proposed model, the analysis results were compared with results of the tension test in the lab. Parametric studies are conducted to investigate the effect of the umbilical design parameters that consist the radial stiffness, diameter and laying angle of armored wires on the results of tension stiffness.(2) Bending stiffness design and analysis of umbilicalThe top and bottom of dynamic umbilicals will be subjected to large bending loads. Thus reducing the curvature load can avoid bending failure. The bending stiffness of the umbilical is an important input parameter of dynamic load analysis. It has a great effect on the curvature load response. So the bending stiffness is an important design indicator to measure the performance of structural bending. The full three-dimension finite element analysis model of umbilical that considers the friction effect between components is established. The nonlinear bending behavior from no-slip stage, part-slip stage to full-slip stage can be accurately simulated by the model. The analysis results were compared with results of the bending test in the lab to verify the correctness of the finite element model. Parametric studies are conducted to investigate the effect of the umbilical design parameters that consist of the frictional coefficient, laying angle of components and the material of sheaths on the results of bending stiffness.(3) Fatigue life design and analysis of umbilicalAt the top of dynamic deepwater umbilicals, it is subjected to big tension load and cyclic bending load due to the periodic wave loads and platform motion. Alternating stress of components are produced, which can lead to cumulative damage and fatigue failure of the umbilical. The fatigue life analysis method of dynamic umbilical is presented. One of the important structural characteristic of the umbilical is the contact and friction between components. During the process of the fatigue life analysis, nonlinear bending stiffness is considered in the fatigue load analysis and friction stress are considered in the fatigue stress analysis. Based on the fatigue load analysis model and the fatigue stress analysis model, more accurate fatigue life can be predicted. Four-point bending fatigue test is proposed to verify the fatigue performance of the umbilical.(4) Cross-sectional layout design of umbilical Only general principles of such as symmetry of the layout requirements are given in the umbilical specification ISO13628-5. But methods and tools which can be specifically operated did not give. The optimal layout design method of umbilical cross-section is proposed based on component symmetry and structural mechanical properties. Firstly, in order to make sure the symmetrical arrangement of components in each layer, mathematical description model and the appropriate design software of symmetry is developed based on the rotational symmetry and the maximum number of the axis. Then after the symmetry arrangement of each layer of different layout design concepts, the quantitative analysis results based on finite element analysis of mechanical properties to determine the final optimal layout design is presented.更多还原