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首页> 外文期刊>Aerospace science and technology >Effects of porosity and thermomechanical loading on free vibration and nonlinear dynamic response of functionally graded sandwich shells with double curvature
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Effects of porosity and thermomechanical loading on free vibration and nonlinear dynamic response of functionally graded sandwich shells with double curvature

机译：孔隙率和热机械负荷对双曲率功能渐变夹心壳自由振动和非线性动力响应的影响

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摘要

The fundamental frequencies and nonlinear dynamic responses of functionally graded sandwich shells with double curvature under the influence of thermomechanical loadings and porosities are investigated in this study. Two material models are considered. The continuity requirement of material properties throughout layers are fulfilled by newly introducing refined effects of two porosity types regarding the average of constituent properties weighted by the porosity volume fraction. The first-order shear deformation theory taking the out-of-plane shear deformation into account is employed to obtain the Lagrange equation of motions. The number of primary variables reduces from five to three after introducing the Airy stress function. The system of dynamic governing equations is obtained by utilizing the Bubnov-Galerkin procedure. The natural frequencies are analytically computed by solving eigenvalue problems, and the fundamental frequencies are acquired by further assumptions about the inertial force caused by the shell rotation variables. The nonlinear dynamic responses of the functionally graded spherical, cylindrical, and hyperbolic paraboloid shells under the influence of different geometry configurations, loading conditions, and porosity types and degrees are obtained by applying the fourth-order Runge-Kutta method. The numerical results are presented and verified with available studies in the literature. Although porosities are usually considered material defects weakening the structure performance, this study has proved clearly that porosities stiffen the shell structures to some extent. (C) 2019 Elsevier Masson SAS. All rights reserved.
机译：本研究研究了在热机械载荷和孔隙率影响下具有双曲率的功能分级夹心壳的基本频率和非线性动力响应。考虑了两种材料模型。通过新引入两种孔隙率类型的细化作用，满足了整个层的连续性要求，其关于通过孔隙体积分数加权的成分特性的平均值。考虑到外平面外剪切变形的一阶剪切变形理论用于获得运动的拉格朗日方程。在引入通气应力功能后，初级变量的数量从五到三个减少。通过利用Bubnov-Galerkin程序获得动态控制方程系统。通过解决特征值问题来分析自然频率，通过围绕由壳旋转变量引起的惯性力的进一步假设来获得基本频率。通过施加四阶径 - 库特塔方法，获得了在不同几何构造，装载条件和孔隙率类型和度的影响下的功能梯度球形，圆柱形和双曲抛物面壳的非线性动力响应。呈现了数值结果，并在文献中提供了可用研究。虽然孔隙率通常被认为是材料缺陷削弱了结构性能，但这项研究明显证明了孔隙座在一定程度上加强了壳体结构。 （c）2019年Elsevier Masson SAS。版权所有。

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