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基于改进Reddy型TSDT的弹性地基上FG-CNTRC板线性弯曲与自由振动无网格分析

MESHLESS ANALYSIS OF LINEAR BENDING AND FREE VIBRATION OF FUNCTIONALLY GRADED CARBON NANOTUBE-REINFORCED COMPOSITE PLATE ON ELASTIC FOUNDATION BASED ON IMPROVED REDDY TYPE THIRD-ORDER SHEAR DEFORMATION THEORY

  • 摘要: 基于改进Reddy型3阶剪切变形理论(third-order shear deformation theory, TSDT)假设, 考虑碳纳米管(carbon nanotubes, CNTs)转向及功能梯度材料的不均匀性, 建立弹性地基上功能梯度碳纳米管增强复合材料(functionally graded carbon nanotube-reinforced composite, FG-CNTRC)板的线性弯曲和自由振动无网格分析模型. 利用改进Reddy型TSDT推导FG-CNTRC板的势能和动能, 给出弹性地基势能的表达式, 再将其分别进行叠加, 通过最小势能原理及Hamilton原理推导出弹性地基上FG-CNTRC板的线性弯曲和自由振动控制方程. 采用稳定移动克里金插值(stabilized moving Kriging interpolation, SMKI)对问题域内的节点进行离散, 该近似形函数的构造方法满足克罗内克条件, 可以直接施加边界条件. 文中首先给出基于三阶剪切变形理论的弹性地基FG-CNTRC板线性弯曲与自由振动无网格离散模型. 随后通过基准算例, 研究本文方法的有效性及精度问题. 最后数值分析了CNTs的分布形式、转向角、体积分数、地基系数、宽厚比和边界条件等对FG-CNTRC板的线性弯曲及自振频率的影响. 研究表明: 采用本文方法计算FG-CNTRC薄板、中厚板、甚至厚板的线性弯曲和自振频率均具有较高的计算精度; 随着CNTs体积分数和地基系数的增加, FG-CNTRC板结构刚度逐渐增大; FG-CTRC板结构刚度与宽厚比成正相关, 厚度增加的剪切效应会让CNTs转向角对结构刚度的影响逐渐降低.

     

    Abstract: Based on the improved Reddy type third-order shear deformation theory (TSDT), and considering the orientation of carbon nanotubes (CNTs) and the inhomogeneity of functionally gradient materials, a meshless analysis model for the linear bending and free vibration of functionally graded carbon nanotube reinforced composite (FG-CNTRC) plates on elastic foundation is established. The potential energy and kinetic energy of FG-CNTRC plate are derived by the improved Reddy type TSDT, and then the expression of the potential energy of elastic foundation is given, and then they are respectively superposed. The linear bending and free vibration control equations of FG-CNTRC plate on elastic foundation are derived by the principle of minimum potential energy and Hamilton principle. Stable moving Kriging interpolation (SMKI) is used to discretize the nodes in the problem domain. The construction method of the approximate shape function satisfies the Kronecker condition and can directly apply the boundary conditions. In this paper, a meshless discrete model of linear bending and free vibration of FG-CNTRC plate on elastic foundation based on the third-order shear deformation theory is presented. Then, the effectiveness and accuracy of the proposed method are studied by a benchmark example. Finally, the effects of CNTs distribution, orientation angle, volume fraction, foundation coefficient, width thickness ratio and boundary conditions on the linear bending and natural frequency of FG-CNTRC plate are numerically analyzed. The results show that the proposed method has a good accuracy in calculating the linear bending and natural frequencies of FG-CNTRC thin, medium-thick, and even thick plates. As the volume fraction of CNTs and the foundation coefficient increase, the stiffness of the FG-CNTRC plate structure gradually increases. The stiffness of the FG-CTRC plate structure is positively correlated with the width-thickness ratio, and the shear effect of increasing thickness gradually reduces the influence of the CNTs orientation angle on the plate stiffness.

     

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