夹层板的屈曲及相关动态特性的数值与实验研究

发布时间：2018-04-23 18:20

本文选题：夹层板 + 有限元　；参考：《燕山大学》2015年博士论文

【摘要】：本文针对夹层板结构组成单元的材料搭配设计,通过有限元三维实体建模,采用有限元非线性屈曲分析与动态应变试验相结合的方法,研究蜂窝夹层板组元材料几何与物理参数改变对屈曲载荷与动态响应的影响。首先由弹性力学板壳理论,结合边界条件、几何变形与协调方程,推导出夹层板静力广义平衡方程;再通过临界平衡条件得到板的屈曲平衡方程,并以单向受压两端简支狭长矩形板为例,得出屈曲应力表达式。然后改变表板厚度、夹芯网格高度、夹芯网格疏密程度、夹芯胞壁厚度以及表板和夹芯材料进行有限元建模,通过有限元非线性屈曲分析,分别研究在单向压缩载荷与弯曲载荷作用条件下,各参数对夹层板临界屈曲载荷的影响规律与敏感度。发现夹芯高度、表板厚度和夹芯密度是影响压缩临界载荷的敏感因素;胞壁间距与夹芯高度是影响弯曲临界载荷的敏感因素;厚夹芯夹层板各参数的敏感性受夹芯网格疏密影响较大,呈非线性变化。通过动态应变实验分析,验证了有限元计算得到的大部分规律,通过各测点应变变化与加载曲线结合实验现象分析了蜂窝夹层板受压局部与整体屈曲的破坏形式。利用微力试验机以分阶段加载的方式,对六边形蜂窝夹层板进行压缩屈曲实验,研究了夹芯的压屈破坏过程。等效理论对优化复杂夹层结构的建模分析至关重要,文中结合微小试样的动态热性能试验(DMA)与夹层板结构的实验模态分析和有限元调参方法,讨论了夹层结构的实验等效模量的测试与研究方法。研究了夹层板表板对软硬夹心复合材料的储能模量与损耗因子等本构参数随着环境温度与工作振动频率的影响趋势。发现表板对软夹芯提高整体复合材料的动态模量效果显著,对于硬夹芯材料基本没有显著的改善作用。金属表板对提高粘弹性材料弯曲模量具有显著地效果;表板对抑制树脂夹芯随温度升高过程中发生较大变形有显著效果。本文以模态分析方法,通过改变表板厚度、夹芯网格高度、夹芯网格疏密程度、夹芯胞壁厚度以及表板和夹芯材料属性,研究各参数对夹层板固有频率的影响规律;研究发现夹层板固有频率对夹芯高度变化敏感,对夹芯疏密不敏感,表板厚度的影响随不同夹芯高度变化。通过不同表板厚度与夹芯高度的矩形夹层板与大尺寸夹层圆板的实验模态分析验证了上述研究规律,为夹层板的优化设计提供了有价值的参考数据。
[Abstract]:In this paper, according to the material collocation design of sandwich plate structure elements, the finite element three-dimensional solid model is established, and the nonlinear buckling analysis of finite element method and dynamic strain test are adopted. The effects of geometric and physical parameters on the buckling load and dynamic response of honeycomb sandwich plates are studied. Based on the theory of plate and shell in elastic mechanics, combined with boundary condition, geometric deformation and coordination equation, the static generalized equilibrium equation of sandwich plate is derived, and then the buckling equilibrium equation of sandwich plate is obtained by critical equilibrium condition. The buckling stress expression is obtained by taking the simple supported rectangular plate with simple support at both ends of unidirectional compression as an example. Then the thickness of the plate, the height of the sandwich mesh, the density degree of the sandwich mesh, the thickness of the sandwich cell wall, the surface plate and the sandwich material are modeled by finite element method, and the nonlinear buckling analysis is carried out by the finite element method. The effects of different parameters on the critical buckling load of laminated plates under uniaxial compression and bending loads are studied. It is found that the height of the core, the thickness of the surface plate and the density of the core are the sensitive factors affecting the critical load of compression, and the cell wall spacing and the height of the sandwich are the sensitive factors affecting the critical load of bending. The sensitivity of each parameter of thick sandwich plate is greatly influenced by the mesh density of sandwich core, which shows nonlinear variation. Most of the laws obtained by finite element method are verified by dynamic strain experimental analysis. The failure modes of local and global buckling of honeycomb sandwich plates under compression are analyzed by means of the strain variation and loading curves of various measuring points combined with experimental phenomena. The compression buckling experiments of hexagonal honeycomb sandwich plates were carried out by means of a micro-force testing machine, and the buckling failure process of the sandwich cores was studied. The equivalent theory is very important to optimize the modeling and analysis of complex sandwich structures. In this paper, the dynamic thermal performance test of small specimens is combined with the experimental modal analysis of sandwich plate structures and the finite element parameter adjustment method. The test and research method of the experimental equivalent modulus of sandwich structure is discussed. The influence trend of constitutive parameters such as storage modulus and loss factor of sandwich panels on soft and hard sandwich composites with ambient temperature and working vibration frequency was studied. It is found that the table plate can improve the dynamic modulus of the whole composite material significantly, but it has no significant effect on the hard core material. The metal sheet has a significant effect on increasing the flexural modulus of viscoelastic materials, and it has a remarkable effect on restraining the larger deformation of the resin sandwich core with the increase of temperature. In this paper, by changing the thickness of the plate, the height of the sandwich mesh, the density of the sandwich mesh, the thickness of the sandwich cell wall and the properties of the plate and the sandwich material, the influence of various parameters on the natural frequency of the sandwich plate is studied by modal analysis method. It is found that the natural frequency of sandwich plate is sensitive to the height of sandwich core, but not sensitive to the density of sandwich core, and the influence of plate thickness varies with the height of sandwich core. The experimental modal analysis of rectangular sandwich plate and large scale sandwich circular plate with different thickness and height of sandwich plate verifies the above research rule and provides valuable reference data for the optimization design of sandwich plate.
【学位授予单位】：燕山大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：O344.1

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