深水柔性立管抗疲劳设计关键力学问题研究

发布时间：2018-02-23 06:46

本文关键词： 海洋柔性立管抗疲劳设计疲劳寿命非线性弯曲响应有限元　出处：《大连理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：海洋柔性管道是连接浮式平台与海底井口进行深海油气开发的关键装备。在周期性交变载荷作用下,柔性立管的金属铠装层容易发生疲劳破坏,导致灾难性后果。由于金属铠装层间的接触摩擦,其弯曲响应往往呈现明显的非线性特征,使得其疲劳寿命设计与分析存在问题。柔性立管的疲劳寿命是其抗疲劳性能的核心衡量指标,直接决定了深水柔性立管在位运行的安全可靠性。柔性立管的抗疲劳设计是以其疲劳寿命分析为基础,提出以安全寿命设计准则和S-N曲线法为基础的柔性立管疲劳寿命预测模型与流程。为了更好的设计立管结构,使其具有更长的服役寿命,其中关键力学问题研究包括：由于柔性立管复杂的结构和环境,其非线性弯曲刚度无法应用经典的梁理论模型予以刻画。分别建立预测柔性立管非线性弯曲刚度的数值模型和解析模型,通过与弯曲刚度测试值对比验证数值模拟模型的准确性。基于数值模型预测结果,考虑弯矩与曲率的非线性关系,建立疲劳载荷分析模型。针对当前关于弯曲应力解析模型的局限性,建立单根螺旋钢丝缠绕圆柱内核的力学模型,计算特定曲率下钢丝局部应力；对比公开发表的三大类7种解析模型,将解析模型预测结果与数值预测结果比较,确定解析模型的适用性。同时,讨论了钢丝的宽高比和螺旋角对解析模型适用性的影响。本文依托国家“十二五”863项目“柔性海底管道关键技术,究”专题,以1500米水深的8寸内径柔性立管为例,对其疲劳寿命进行计算。考虑影响海洋柔性管道疲劳强度的主要因素,提出了进行疲劳校核时依据的S-N曲线模型；着重考虑了各种非线性因素和平均应力对疲劳寿命预测的影响。以上研究工作对我国深海立管的设计提供一定的理论基础和数值分析方法。
[Abstract]:The offshore flexible pipeline is the key equipment to connect the floating platform with the submarine wellhead for deep-sea oil and gas development. Under the cyclic alternating load, the metal armour layer of the flexible riser is prone to fatigue damage. Because of the contact friction between the metal armour layers, the bending response of the metal sheathed layer often shows obvious nonlinear characteristics, The fatigue life of flexible riser is the key index of fatigue resistance. The safety and reliability of deep water flexible riser are directly determined. The fatigue resistance design of the flexible riser is based on the analysis of its fatigue life. Based on the safety life design criterion and S-N curve method, the fatigue life prediction model and flow chart of flexible riser are proposed. In order to better design riser structure and make it have longer service life, The key mechanical problems include: because of the complicated structure and environment of flexible riser, The nonlinear bending stiffness can not be described by the classical beam theory model. The numerical model and the analytical model for predicting the nonlinear bending stiffness of flexible riser are established. The accuracy of the numerical simulation model is verified by comparing with the measured results of bending stiffness. Based on the prediction results of the numerical model, the nonlinear relationship between bending moment and curvature is considered. Aiming at the limitation of the present analytical model of bending stress, the mechanical model of single spiral steel wire winding cylindrical core is established to calculate the local stress of steel wire with specific curvature. The applicability of the analytical model is determined by comparing the prediction results of the analytical model with the numerical prediction results of the three categories and seven analytical models published in the paper. The influence of the ratio of width to height and the helix angle of steel wire on the applicability of the analytical model is discussed. Based on the national "12th Five-Year" 863 project "key technology of flexible submarine pipeline, research", the paper takes the 8 inch flexible riser with 1500m water depth as an example. The fatigue life of the pipeline is calculated. Considering the main factors affecting the fatigue strength of marine flexible pipeline, the S-N curve model based on which the fatigue checking is carried out is put forward. The effects of various nonlinear factors and average stresses on fatigue life prediction are emphatically considered. The above work provides a theoretical basis and numerical analysis method for the design of deep-sea risers in China.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE95

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