深海脐带缆耦合等效模型及随机性优化设计研究

A coupled element method for the umbilical global dynamic analysis and a metamodel methodology for fatigue reliability based design optimization is proposed for the design of deepwater umbilical bending stiffener. Umbilicals are “life lines” for oil production subsea system. Bending stiffener is a key components of umbilical to protect the upper connection against damage from overbending. It is prone to cause fatigue failure due to the wave and vessel motions. So its fatigue character has a great impact on the safety of oil and gas production and we should pay more attention on it. In addition the timedomain fatigue analysis involve material, geometric and loading uncertainties, hence the reliability analysis is performed for considering the influence of uncertain factors. Furthermore the smaller bending stiffener is not only economical but also advantageous to install and interface with other equipment.Therefore, it is significant to perform the optimization design of bending stiffener and take fatigue requirement into account considering the safety. But some uncertainties are unavoidable and inherent in the design and analysis of bending stiffener due to the variations in ocean environmental loads, material properties, manufacturing tolerances, etc. In contrast with the traditional optimization strategy, the fatigue reliability based design optimization (FRBDO) for bending stiffener is more meaningful which concerns the probabilistic constraints evaluated through the fatigue reliability analysis. The fatigue life prediction is a complex and time-consuming process, especially in the timedomain. Before the stress or strain response are obtained from local dynamic analysis, the highly nonlinear global dynamic analysis was performed firstly. In addition FRBDO including the iterative cycle process is also computationally expensive. Metamodel technique can be applied to optimize for reducing the computational cost, which instead of the actual analysis codes and keep without sacrificing accuracy. In this project, a practical methodology for fatigue relibility based design optimization with metamodel is applied for design bending stiffener. Firstly, a coupled element modeling scheme for the global dynamic analysis of umbilical was developed. The fatigue behaviour of polyurethane material is obtained by experiment tests. Secondly, the method of time domain fatigue analysis is proposed for bending stiffener of deepwater umbilical. Thirdly, reliability based design optimization considering fatigue constraint is proposed for the design of bending stiffener. Finally, the optimum design solution will be checked by full scale fatigue tests. The overall objective of the study is the continued development of new design methodolgy of umbilical for ultra-deepwater applications. The project will also proved strong technical support and science fundation for our country subsea system umbilical design.

研究深海脐带缆耦合等效模型和基于超模型的可靠度优化设计方法。弯曲加强器是安装在油气开采“生命线”的脐带缆顶部与平台连接的关键设施，由于受到波浪、流以及平台运动而易产生疲劳破坏，危及油气安全生产。同时时域疲劳分析中存在诸多不确定因素，且减小其体积不仅降低制造成本也利于安装。此外，弯曲加强器的结构动力非线性以及随机性特性，使得疲劳可靠度优化设计运算量极大，研究提出基于超模型的疲劳可靠度优化设计方法意义较大。首先建立脐带缆耦合等效整体模型，接着对弯曲加强器材料疲劳性能试验得到疲劳曲线；然后对弯曲加强器进行疲劳分析；考虑疲劳概率性约束，进行基于超模型的疲劳可靠度优化设计分析，最终实现满足一定安全可靠度的、成本最低的弯曲加强器设计，并且进行相应的疲劳测试实验验证优化方案。本项目的研究将为深海脐带缆设计提供新的途径和方法，为我国深海资源开发的水下脐带缆系统提供科学依据和技术保障。

在国家自然科学面上项目基金（51379005）资助下，本项目课题组在国内外学术刊物上研究中分别标注论文27篇，其中国际杂志文章12篇，国内核心期刊文章15篇，SCI收录13次，EI收录7次。已培养研究生11名，取得可喜成绩。本项目研究工作的创新内容如下：.1) 建立深海脐带缆新型数值分析模型，并且与实验分析结果相对比。深海脐带缆是深水资源开发的关键设备，安装成本低，适用于恶劣的深海环境，由于脐带缆结构型式复杂，层与层之间摩擦、接触等诸多强非线性特性，提出一个高效的数值分析模型，对其刚度进行求解，与实验对比，探讨了内压和拉伸、扭转、弯曲等组合载荷对脐带缆刚度的影响。所提简化数值分析模型与实验结果吻合较好。.2) 提出不规则波浪条件针对深海立管参量共振与涡激振动耦合的分析计算方法。在实际的海洋环境条件下，立管同时遭受到海洋波浪和海流的作用，传统的立管的参量共振分析仅仅考虑平台运动导致的参量共振，或者仅仅考虑流导致的涡激振动。然而，实际的海洋环境下，参量共振与涡激振动会同时作用于立管，这样将导致立管疲劳破坏。研究提出新的涡激振动和多频激励下的参量共振耦合作用方法，分析给出了抑制不规则波浪条件下涡激振动与参量共振发生的深海立管设计建议。.3) 提出深海复合材料立管基于可靠度的优化设计方法。对于正交各向异性层合复合材料结构而言，叠层顺序不同、各层铺角变化以及层间厚度差异等都会影响到结构的承载能力，因此，有必要引进可靠度作为优化设计指标。首先，根据经典层合板理论计算等效模型，建立悬链线复合立管整体模型，运用实验设计方法构建近似模型，最后利用蒙特卡罗法对比分析确定性优化与可靠度优化计算的结果，研究表明，优化后的深海复合材料立管在满足设计要求下，可以有效降低设计成本，所提出的基于可靠度优化设计的复合材料悬链线立管具有可行性。所提的方法和研究结论可为深海脐带缆设计提供参考。所有预期的项目指标都圆满完成。