无限长夹层圆柱壳受均布外压作用的后屈曲失稳研究

发布时间：2018-02-27 07:00

本文关键词： 夹层管 Ritz法后屈曲后屈曲压力有限元　出处：《暨南大学》2015年硕士论文　论文类型：学位论文

【摘要】：深海管道在制作或加工过程中,由于加工工艺和技术的限制,管道必定存在某种程度的初始缺陷。含有初始缺陷的海底管道在深水压力作用下会发生沿径向的屈曲现象,从而引起管道的结构失效。当管道上下内壁相互接触后,形成狗骨形状的后屈曲模态。此时如果海水的压力达到某个临界值,即屈曲传播压力,狗骨形后屈曲模态开始沿着管道轴向进行传播。近年来由于石油开采由近海区域向海洋深处延伸,在深海海底油井和海底表面存在的一定的温差,石油从油井开采出来到海底岩层表面会因为温度骤降而使石油冷凝固结进而堵塞管道,这无疑对海底管道的设计提出了更高的要求。目前海底保温管道普遍应用于深海油田开发。本文运用弹性力学、非线性稳定理论、一阶剪切夹层壳理论及有限元分析的体系,研究深海无限长夹层保温管道受海底水压力作用下管道后屈曲失稳。主要研究内容有:建立深海夹层圆柱壳受外压作用局部失效的非线性屈曲控制方程。运用一阶剪切夹层壳理论,分析夹层结构的内力状态,考虑中面转角,建立圆柱壳的弯曲平衡方程及夹层结构径向的平衡方程;考虑中面的面内薄膜力影响,借助非线性大挠度薄壳的理论,分析应变位移关系,建立相容方程。引入转角函数,面外挠度函数和应力函数,建立适用于长夹层圆柱壳的非线性屈曲方程。采用Ritz法求解控制方程。依据分析模型,考虑夹层圆柱壳在面板和夹芯连接处位移和力的连续性、无限长夹层管道的边界条件,建立定解条件。引入局部的屈曲失稳模态,结合经典平面应变解,假定夹层圆柱壳横截面的后屈曲失稳模态为椭圆形,求解应力函数与转角函数,建立能量方程。运用最小势能原理求解能量方程,得到夹层圆柱壳在均布外压作用下沿着管道轴向传播的传递区的传播长度的计算公式、夹层管后屈曲失稳传播时的后屈曲传播压力表达式。参数分析。分析不同夹层管的径厚比、面板厚度与夹芯厚度之比对后屈曲压力和传递区长度的影响。同时改变夹芯和面板材料参数,分析材料的影响。最后把夹层管道夹芯退化为零与经典单管屈曲压力进行比较。通过以上对比分析夹层管道在承载能力方面的特性。有限元仿真模拟。应用Abaqus软件模拟有限长夹层管道在两端固支下的后屈曲失稳。在有限元分析中采用弧长法模拟夹层管道屈曲分析,通过在前屈曲中的分析,得到夹层管道在外压作用下的屈曲特征值和屈曲模态,然后采用一致模态缺陷法即用最低阶的屈曲模态来模拟结构的初始缺陷分布。引入前屈曲初始缺陷并考虑面板的塑性对夹层管进行后屈曲分析,获得夹层管后屈曲失稳模态。所得的屈曲压力与传递区长度的有限元分析结果与理论解进行比较,二者的结果具有较好的吻合度。
[Abstract]:In the process of making or processing deep-sea pipeline, due to the limitation of processing technology and technology, the pipeline must have some initial defects, and the submarine pipeline with the initial defect will buckle along the radial direction under the action of deep-water pressure. When the upper and lower walls of the pipe contact with each other, the post-buckling mode of dog bone is formed. If the pressure of seawater reaches a certain critical value, that is, the buckling propagation pressure, The post-buckling mode of the dog bone began to propagate along the axial direction of the pipeline. In recent years, due to the extension of oil production from offshore areas to the depths of the ocean, there has been a certain temperature difference between the oil wells and the surface of the deep seabed. Oil extracted from oil wells to the surface of undersea rock layers will be condensed and consolidated because of the sudden drop in temperature, and the pipeline will be blocked. This undoubtedly puts forward higher requirements for the design of submarine pipelines. At present, submarine thermal insulation pipelines are widely used in the development of deep-sea oil fields. In this paper, elastic mechanics, nonlinear stability theory, first-order shear intercalation theory and finite element analysis system are used. In this paper, the post-buckling instability of deep sea infinite sandwich insulation pipeline under the action of submarine water pressure is studied. The main research contents are as follows: the nonlinear buckling governing equation of local failure of deep sea sandwich cylindrical shell subjected to external pressure is established. Order shear sandwich shell theory, By analyzing the state of internal force of sandwich structure, considering the angle of middle plane, the bending equilibrium equation and radial equilibrium equation of sandwich structure are established, and the theory of nonlinear thin shell with large deflection is taken into account. The nonlinear buckling equation for long sandwich cylindrical shells is established by introducing rotation angle function, out-of-plane deflection function and stress function. The control equation is solved by Ritz method. According to the analytical model, the nonlinear buckling equation is obtained. Considering the continuity of displacement and force of sandwich cylindrical shell at the connection of panel and sandwich core, the boundary conditions of infinite sandwich pipe are considered, and the fixed solution condition is established. The local buckling instability mode is introduced, and the classical plane strain solution is combined with the classical plane strain solution. Assuming that the post-buckling instability mode of sandwich cylindrical shell cross section is elliptical, the energy equation is established by solving the stress function and the rotation function, and the energy equation is solved by using the principle of minimum potential energy. A formula for calculating the propagation length of a sandwich cylindrical shell propagating along the axial transmission zone of a pipe under uniform external pressure is obtained. Expression of post-buckling propagation pressure during post-buckling instability propagation of sandwich tubes; parameter analysis; analysis of diameter to thickness ratio of different sandwich tubes, The influence of the thickness of the panel to the thickness of the sandwich core on the post-buckling pressure and the length of the transfer zone. Finally, the buckling pressure of sandwich pipe to zero is compared with that of classical single pipe. Through the above comparison, the characteristics of sandwich pipe in bearing capacity are analyzed. The finite element simulation is used to simulate and apply Abaqus soft. The post buckling instability of finite length sandwich pipeline is simulated by finite element method, and the finite element method is used to simulate the buckling of sandwich pipe. The buckling eigenvalues and buckling modes of sandwich pipes under external pressure are obtained by the analysis of pre-buckling. Then the uniform modal defect method is used to simulate the initial defect distribution of the structure with the lowest buckling mode. The post-buckling analysis of the sandwich tube is carried out by introducing the pre-buckling initial defect and considering the plasticity of the panel. The post-buckling instability mode of sandwich tube is obtained. The results of finite element analysis of buckling pressure and the length of transfer zone are compared with the theoretical solution, and the results are in good agreement with each other.
【学位授予单位】：暨南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P756.2

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