深海柔性立管动力及力学性能实验分析

发布时间：2018-09-07 11:29

【摘要】：随着海洋资源的开发逐渐向深海迈进，，深海装备的研发已成为近几年的热点。非粘结柔性立管由于其弯曲刚度小、质量轻、耐腐蚀以及抗疲劳性能强等特点，适用于深海恶劣的海况。然而，由于非粘结柔性立管结构的复杂性和深海环境载荷的复杂性，使得非粘结柔性立管在设计和服役过程中的结构失效分析面临很大的挑战。首先，非粘结柔性立管的局部结构由多层互相非粘结的功能层以及高分子层组成，层间可相互滑移、摩擦，造成了立管非线性的力学性能和特殊的本构关系；其次，其复杂的结构导致其拉伸刚度远远强于其弯曲刚度，致使其在求解动力响应问题过程中容易造成计算的不收敛，使得其动力响应难以准确求解；最后，由于柔性立管的疲劳破坏往往不是所有结构层同时发生，传统的疲劳寿命分析方法无法分析柔性立管结构多层的疲劳性能。本文针对非粘结柔性立管设计和运行中所遇到的挑战进行了详细的研究，主要的工作如下： 1、运用新型简化模型对柔性立管的局部力学性能进行分析。非粘结柔性立管结构复杂，采用传统的实体建模的方法虽然能较为准确地对其力学性能进行评估，但是由于模型节点自由度数量巨大，此外还需考虑层间的接触和摩擦等非线性因素使得其计算成本十分高昂，而传统的简化模型忽略了立管层间的摩擦又无法反映非粘结柔性立管特殊的非线性本构关系。运用改进后的梁壳组合新型简化模型对非粘结柔性立管进行局部力学分析可以在保证计算精度的前提下大大减少计算成本，并能够准确反映其非线性的力学特性。 2、提出运用多层应力分配法对非粘结柔性立管的本构关系进行分析。多层非粘结柔性结构物的本构关系一直是力学分析的难点，本文提出运用多层应力分配法，结合层间的接触关系和摩擦关系，引进滑移/粘滞模型，对立管的各层结构分别建立本构方程，并用之前建立的数值分析模型来进行验证。本构关系的建立是解决非粘结柔性立管力学问题的关键，也是后续疲劳分析的基础。 3、提出了耦合单元法求解非粘结柔性立管的动力响应。针对非粘结柔性立管动力分析遇到的计算不收敛问题，推导并建立了适用于柔性结构物的总体动力分析方法。考虑到复杂的海洋环境载荷，采用时域动力分析的方法使结果更加准确。分别运用经典的静力算例和动力分析算例来验证提出方法的可靠性。并运用该方法求解了自由悬挂式立管的动力响应。 4、采用多层疲劳寿命分析法求解非粘结柔性立管的疲劳寿命。针对传统方法无法求解非粘结柔性立管多层的疲劳寿命分析问题，结合前文的多层应力分配法，将总体的动力响应分配到各层中，再对立管所有的结构功能层进行疲劳寿命分析。并讨论了设计变量对非粘结柔性立管疲劳寿命计算的影响。
[Abstract]:With the development of marine resources, the research and development of deep-sea equipment has become a hot spot in recent years. The unbonded flexible riser is suitable for the bad sea conditions in the deep sea due to its small bending stiffness, light weight, corrosion resistance and fatigue resistance. However, due to the complexity of the non-bonded flexible riser structure and the complexity of the deep-sea environment load, the failure analysis of the non-bonded flexible riser structure in the design and service process faces a great challenge. Firstly, the local structure of the unbonded flexible riser is composed of multi-layer non-bonded functional layer and polymer layer. The sliding and friction between layers lead to the nonlinear mechanical properties and special constitutive relationship of the riser. Because of its complex structure, its tensile stiffness is much stronger than its bending stiffness, which makes it easy to solve the dynamic response problem without convergence, which makes the dynamic response difficult to solve accurately. Because the fatigue failure of flexible riser does not occur at the same time, the traditional fatigue life analysis method can not analyze the fatigue performance of flexible riser structure. In this paper, the challenges in the design and operation of unbonded flexible risers are studied in detail. The main work is as follows: 1. The local mechanical properties of flexible risers are analyzed by using a new simplified model. The structure of unbonded flexible riser is complex. Although the traditional solid modeling method can accurately evaluate its mechanical properties, the number of degrees of freedom of the model nodes is huge. In addition, nonlinear factors such as interlayer contact and friction should be taken into account, which makes the calculation cost very high. However, the traditional simplified model ignores the friction between the riser layers and can not reflect the special nonlinear constitutive relationship of the non-bonded flexible riser. The local mechanical analysis of the unbonded flexible riser by using the new simplified model of beam-shell combination can greatly reduce the calculation cost on the premise of ensuring the calculation accuracy. It can accurately reflect its nonlinear mechanical properties. 2. A multi-layer stress distribution method is proposed to analyze the constitutive relationship of unbonded flexible risers. The constitutive relationship of multilayer unbonded flexible structures is always a difficult point in mechanical analysis. In this paper, a sliding / viscous model is introduced by using the multilayer stress distribution method and the contact and friction relations between layers. The constitutive equations of each layer of the opposing tube are established and verified by the previous numerical analysis model. The establishment of constitutive relationship is the key to solve the mechanical problems of unbonded flexible risers and the basis of subsequent fatigue analysis. 3. A coupled element method is proposed to solve the dynamic response of unbonded flexible risers. In order to solve the problem of unconvergent calculation in dynamic analysis of unbonded flexible risers, a general dynamic analysis method for flexible structures is derived and established. Considering the complex marine environment load, the time domain dynamic analysis method is used to make the results more accurate. The reliability of the proposed method is verified by classical static examples and dynamic analysis examples respectively. The dynamic response of free hanging riser is solved by this method. 4. The fatigue life of unbonded flexible riser is solved by multilayer fatigue life analysis. In view of the traditional method can not solve the fatigue life analysis problem of non-bonded flexible riser, combined with the multi-layer stress distribution method, the dynamic response of the whole is distributed to each layer. Then the fatigue life of all the structural functional layers of the opposite tube is analyzed. The influence of design variables on fatigue life calculation of unbonded flexible riser is discussed.
【学位授予单位】：上海交通大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P751

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