本文關鍵詞： 夾層管 Ritz法 后屈曲 后屈曲壓力 有限元　出處：《暨南大學》2015年碩士論文　論文類型：學位論文

【摘要】：深海管道在制作或加工過程中,由于加工工藝和技術的限制,管道必定存在某種程度的初始缺陷。含有初始缺陷的海底管道在深水壓力作用下會發(fā)生沿徑向的屈曲現(xiàn)象,從而引起管道的結構失效。當管道上下內壁相互接觸后,形成狗骨形狀的后屈曲模態(tài)。此時如果海水的壓力達到某個臨界值,即屈曲傳播壓力,狗骨形后屈曲模態(tài)開始沿著管道軸向進行傳播。近年來由于石油開采由近海區(qū)域向海洋深處延伸,在深海海底油井和海底表面存在的一定的溫差,石油從油井開采出來到海底巖層表面會因為溫度驟降而使石油冷凝固結進而堵塞管道,這無疑對海底管道的設計提出了更高的要求。目前海底保溫管道普遍應用于深海油田開發(fā)。本文運用彈性力學、非線性穩(wěn)定理論、一階剪切夾層殼理論及有限元分析的體系,研究深海無限長夾層保溫管道受海底水壓力作用下管道后屈曲失穩(wěn)。主要研究內容有:建立深海夾層圓柱殼受外壓作用局部失效的非線性屈曲控制方程。運用一階剪切夾層殼理論,分析夾層結構的內力狀態(tài),考慮中面轉角,建立圓柱殼的彎曲平衡方程及夾層結構徑向的平衡方程;考慮中面的面內薄膜力影響,借助非線性大撓度薄殼的理論,分析應變位移關系,建立相容方程。引入轉角函數(shù),面外撓度函數(shù)和應力函數(shù),建立適用于長夾層圓柱殼的非線性屈曲方程。采用Ritz法求解控制方程。依據(jù)分析模型,考慮夾層圓柱殼在面板和夾芯連接處位移和力的連續(xù)性、無限長夾層管道的邊界條件,建立定解條件。引入局部的屈曲失穩(wěn)模態(tài),結合經典平面應變解,假定夾層圓柱殼橫截面的后屈曲失穩(wěn)模態(tài)為橢圓形,求解應力函數(shù)與轉角函數(shù),建立能量方程。運用最小勢能原理求解能量方程,得到夾層圓柱殼在均布外壓作用下沿著管道軸向傳播的傳遞區(qū)的傳播長度的計算公式、夾層管后屈曲失穩(wěn)傳播時的后屈曲傳播壓力表達式。參數(shù)分析。分析不同夾層管的徑厚比、面板厚度與夾芯厚度之比對后屈曲壓力和傳遞區(qū)長度的影響。同時改變夾芯和面板材料參數(shù),分析材料的影響。最后把夾層管道夾芯退化為零與經典單管屈曲壓力進行比較。通過以上對比分析夾層管道在承載能力方面的特性。有限元仿真模擬。應用Abaqus軟件模擬有限長夾層管道在兩端固支下的后屈曲失穩(wěn)。在有限元分析中采用弧長法模擬夾層管道屈曲分析,通過在前屈曲中的分析,得到夾層管道在外壓作用下的屈曲特征值和屈曲模態(tài),然后采用一致模態(tài)缺陷法即用最低階的屈曲模態(tài)來模擬結構的初始缺陷分布。引入前屈曲初始缺陷并考慮面板的塑性對夾層管進行后屈曲分析,獲得夾層管后屈曲失穩(wěn)模態(tài)。所得的屈曲壓力與傳遞區(qū)長度的有限元分析結果與理論解進行比較,二者的結果具有較好的吻合度。
[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.
【學位授予單位】：暨南大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：P756.2

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