轴压复合材料柱形壳屈曲特性及工程应用

发布时间：2019-01-10 11:27

【摘要】：复合材料具有比强度高、比模量大、可设计性强、耐腐蚀性好等特点,柱形壳具有很好的承载能力与空间利用率,常被用于海洋平台桩腿、潜水器耐压壳等结构的制造。本文研究了轴压复合材料柱形壳的屈曲特性与优化设计方法,以提高其轴向承载能力。从生产制造与工程实际出发,系统地建立复合材料柱形壳设计计算流程、失稳分析方法,对于复合材料柱形壳的设计、校核、优化具有指导性作用。(1)由碳纤维复合材料单轴拉伸试验得到试验材料的力学属性,用于柱形壳的计算与分析。对轴压复合材料柱形壳进行线弹性屈曲分析,得出前50阶屈曲失稳模式,即模态缺陷。基于复合材料薄壳理论、NASA SP-8007规范,分别得到轴压复合材料柱形壳屈曲临界载荷解析解、经验值,验证线弹性数值模型正确性。基于弧长法研究不同模态缺陷条件下轴压复合材料柱形壳的非线性屈曲特性。由复合材料柱形壳三维扫描试验得到其初始几何缺陷,由轴向压缩试验得到其轴压屈曲特性。(2)将数值分析结果、理论计算结果与轴压试验结果作对比分析,结果表明:对于轴压复合材料柱形壳屈曲问题,第1阶模态缺陷不一定是最差缺陷,高阶模态缺陷条件下的非线性屈曲临界载荷与试验值较为吻合;屈曲载荷下降受缺陷形状、幅值双重影响,复合材料柱形壳屈曲计算需考虑多模态问题;NASA规范求出的复合材料柱形壳屈曲载荷低于试验值较多,往往会造成结构笨重、材料浪费、性能降低。(3)综合运用线弹性屈曲与非线性屈曲分析方法,研究材料铺层、壳体尺寸对轴压复合材料柱形壳屈曲特性的影响,得到较为合理的铺层方式与壳体尺寸。结合仿生学原理对柱形壳进行形状优化,运用等质量、等容积两种方法,设计与柱形壳开口直径相同的蛋形壳,并进行线弹性与非线性屈曲分析。结果表明:相对复合材料柱形壳,蛋形壳具有更好的轴向承载能力与更低的缺陷敏感度。(4)从工程实例出发,以单立柱固定式海洋平台的柱形壳桩腿为背景,采用分段式模块化设计的方法,在5%多模态缺陷条件下,研究一般钢结构柱形壳桩腿、碳纤维复合材料柱形壳桩腿、碳纤维复合材料多蛋交接形桩腿的轴压屈曲特性。由DH-300电子比重计测量复合材料密度。结果表明:在相同的承载能力下,复合材料多蛋交接形桩腿具有更小的质量、更低的缺陷敏感度与更好的稳定性。
[Abstract]:The composite material has the characteristics of high specific strength, high specific modulus, strong designability, good corrosion resistance and so on. The cylindrical shell has good bearing capacity and space utilization ratio. It is often used in the manufacture of offshore platform pile leg and pressure shell of submersible. In this paper, the buckling characteristics and optimum design method of composite cylindrical shells under axial compression are studied in order to improve their axial bearing capacity. Based on the production and engineering practice, the design and calculation flow of composite cylindrical shell, the method of instability analysis, and the design and verification of composite cylindrical shell are systematically established. The optimization is instructive. (1) the mechanical properties of the tested materials are obtained from uniaxial tensile tests of carbon fiber composites and used in the calculation and analysis of cylindrical shells. Based on the linear elastic buckling analysis of axially compressed composite cylindrical shells, the first 50 order buckling modes, i.e. modal defects, are obtained. Based on the theory of thin composite shell and NASA SP-8007 code, the analytical solution of buckling critical load of composite cylindrical shell under axial compression is obtained, and the empirical values are obtained to verify the correctness of the linear elastic numerical model. The nonlinear buckling behavior of composite cylindrical shells subjected to axial compression under different modal defects is studied based on arc length method. The initial geometric defects of composite cylindrical shell were obtained by three-dimensional scanning test, and the axial compression buckling characteristics were obtained by axial compression test. (2) the results of numerical analysis, theoretical calculation and axial compression test were compared with those of axial compression test. The results show that the first order modal defect is not necessarily the worst for the buckling of composite cylindrical shells under axial compression, and the nonlinear buckling critical load under the condition of high order modal defects is in good agreement with the experimental values. The reduction of buckling load is affected by the shape and amplitude of the defect, so the multimodal problem should be considered in the buckling calculation of composite cylindrical shells. The buckling loads of composite cylindrical shells calculated by NASA Code are much lower than the experimental values, which often result in bulky structure, material waste and poor performance. (3) the linear elastic buckling and nonlinear buckling analysis methods are comprehensively used to study the material layering. The effect of shell size on the buckling characteristics of composite cylindrical shells under axial compression was investigated, and a more reasonable lamination method and shell size were obtained. Based on the bionic principle, the shape of cylindrical shell is optimized. Using equal mass and equal volume, the eggshell with the same opening diameter as cylindrical shell is designed, and the linear elasticity and nonlinear buckling analysis are carried out. The results show that the eggshell has better axial bearing capacity and lower defect sensitivity than the composite cylindrical shell. (4) based on the engineering example, the pile leg of the single column fixed offshore platform is taken as the background. In this paper, the axial buckling characteristics of the common steel structure pile-leg with cylindrical shell and carbon fiber composite with multi-egg junction are studied under the condition of 5% multi-mode defect by using the segmented modular design method. The density of composites was measured by DH-300 electronic hydrometer. The results show that under the same bearing capacity, the composite multi-egg joint pile leg has lower mass, lower defect sensitivity and better stability.
【学位授予单位】：江苏科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB33

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