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1.
弹性一粘弹性复合结构模态理论 总被引:10,自引:0,他引:10
本文研究弹性一粘弹性复合结构动力学基本问题复合结构动力学方程是一组微分积分方程,引入增广状态变量,将其变换为常规的状态方程,研究了状态方程特征解的性质,提出了“振荡模态”和“蠕变模态”概念给出了脉冲响应矩阵和传递函数矩阵,讨论了它们的特性,复合结构模态理论为其动特性和动响应分析提供理论依据。 相似文献
2.
粘弹复合结构特征问题的迭代算法 总被引:12,自引:1,他引:12
本文研究由弹性材料和粘弹性材料构成复合结构的动力学问题。引入耗散位移概述,将复合材料的动力学方程变换为状态方程,进一步研究了状态方程特征解的性质。为了求复合结构的模态参数,定义了复合结构的保守粘性结构的概念,提出了计算复合结构特值问题的一个实用算法。最后讨论了复合结构的动力响应。 相似文献
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对基于结构网格的Euler方程及N-S方程求解器和基于非结构网格的Euler方程求解
器,采用结构模态分析方法和柔度矩阵方法,对无人机大展弦比机翼在Ma=0.6,
α=2?, 飞行高度20km的巡航状态下的静气动弹性特性进行了数值模
拟. 验证了两种求解器对静气动弹性模拟的准确性. 同时,对模态分析方法和柔度
矩阵方法进行了对比研究,发现柔度矩阵方法更适用于静气动弹性数值模拟. 另外,
对应用物面法向偏转方法替代网格变形技术模拟静气动弹性进行了研究,计算表明
物面法向偏转方法可以大大提高静气动弹性计算效
率和克服机翼结构变形过大时动网格技术无法处理的不足. 相似文献
4.
静气动弹性计算方法研究 总被引:7,自引:0,他引:7
对基于结构网格的Euler方程及N-S方程求解器和基于非结构网格的Euler方程求解器,采用结构模态分析方法和柔度矩阵方法,对无人机大展弦比机翼在Ma=0.6,α=2?, 飞行高度20km的巡航状态下的静气动弹性特性进行了数值模拟. 验证了两种求解器对静气动弹性模拟的准确性. 同时,对模态分析方法和柔度矩阵方法进行了对比研究,发现柔度矩阵方法更适用于静气动弹性数值模拟. 另外,对应用物面法向偏转方法替代网格变形技术模拟静气动弹性进行了研究,计算表明物面法向偏转方法可以大大提高静气动弹性计算效率和克服机翼结构变形过大时动网格技术无法处理的不足. 相似文献
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随着航空航天等领域中实际工程结构的大型化和柔性化,结构的非线性振动和主动振动控制问题越来越凸显.分析和处理此类结构出现的复杂振动问题的关键在于建立系统的非线性动力学模型与状态空间模型.对于由柔性部件、刚体、连接部件构成的复合柔性结构,由于各部件之间的振动耦合效应,单个柔性部件在悬臂、简支和自由等静定边界下的模态与结构的真实模态有较大差异.为此,本文提出复合柔性结构全局模态的解析提取方法,通过全局模态离散得到系统非线性动力学模型,从而构建状态空间模型.该方法采用笛卡尔坐标描述系统的运动,建立系统的运动方程;结合描述柔性部件的偏微分方程、刚体的常微分运动方程、连接界面处力、力矩、位移和转角的匹配条件以及系统的边界条件,利用分离变量法给出统一形式的频率方程,获取系统的固有频率和解析函数表征的全局模态.这里提出的全局模态提取方法不仅便于复合柔性结构固有频率和全局模态的参数化分析,而且为建立复合柔性结构低维非线性动力学模型和状态空间模型提供了有效的途径,对于推进这类结构的非线性动力学分析与主动振动控制研究具有重要意义. 相似文献
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随着航空航天等领域中实际工程结构的大型化和柔性化,结构的非线性振动和主动振动控制问题越来越凸显.分析和处理此类结构出现的复杂振动问题的关键在于建立系统的非线性动力学模型与状态空间模型.对于由柔性部件、刚体、连接部件构成的复合柔性结构,由于各部件之间的振动耦合效应,单个柔性部件在悬臂、简支和自由等静定边界下的模态与结构的真实模态有较大差异.为此,本文提出复合柔性结构全局模态的解析提取方法,通过全局模态离散得到系统非线性动力学模型,从而构建状态空间模型.该方法采用笛卡尔坐标描述系统的运动,建立系统的运动方程;结合描述柔性部件的偏微分方程、刚体的常微分运动方程、连接界面处力、力矩、位移和转角的匹配条件以及系统的边界条件,利用分离变量法给出统一形式的频率方程,获取系统的固有频率和解析函数表征的全局模态.这里提出的全局模态提取方法不仅便于复合柔性结构固有频率和全局模态的参数化分析,而且为建立复合柔性结构低维非线性动力学模型和状态空间模型提供了有效的途径,对于推进这类结构的非线性动力学分析与主动振动控制研究具有重要意义. 相似文献
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连接部件动态特性的准确辨识对预测装配式机械结构的动力学行为有重要意义. 针对传统基于子结构解耦的连接结构动力学特性识别方法难以直接利用可测量数据进行辨识及辨识结果受噪声影响显著等问题, 本文提出了一种新方法. 首先, 提取子结构解耦基本方程在测试自由度上的分量, 并经矩阵变换得到显含连接动刚度矩阵的形式, 而后由真实连接动刚度矩阵分解为已知的初始矩阵与待求的增量矩阵, 推导了具有收敛性质的增量型方程以增强界面自由度较多时辨识的数值稳定性, 并采用多项式拟合动刚度将其转化为了拟合系数的频域估计方程, 按给定准则选取合适的频率点联立方程后, 得到了只需装配体测试自由度上的频响函数来辨识连接特性的迭代公式. 最后, 以若干算例说明了算法的具体流程. 对10自由度弹簧?质量块系统进行了数值仿真, 验证了所提方法的正确性及抗噪性; 对包含一处胶接连接的T形梁结构和包含两处螺栓连接的L形梁结构进行了试验, 所辨识连接结构与残余结构重组的装配体有限元模型计算的频响函数与测量值在较宽频带内吻合较好, 表明了该方法能有效识别实际装配体结构中的连接特性. 相似文献
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中心刚体-柔性梁耦合系统离散模型的研究 总被引:1,自引:1,他引:0
采用数值仿真对由中心刚体、柔性梁组成的刚-柔耦合系统的动力学离散模型进行了研究.考虑到刚柔-耦合系统的控制方程没有精确解析解,只能寻求数值解,最广泛使用的离散方法是有限元,但其广义坐标数目过于庞大,因此本文探讨了采用经典结构动力学中不同边界的模态函数离散动边界下刚柔耦合动力学方程的可行性及各自的优劣,得到刚柔耦合系统的模态缩减规律. 相似文献
11.
The present paper investigates the vibration modal theory of composite structures constructed with elastic and viscoelastic materials. The equation of motion that comes in the form of integrodifferential equations is transformed into the first order differential equation in state space. Then modal analysis is carried out. The concepts of vibrating modal set and creeping modal set are proposed. And impulsive response matrix and transfer function matrix are defined and discussed in detail. Finally sample problems are given to support the theory developed in this paper. 相似文献
12.
Proper orthogonal modes (POMs) are used for order reduction ina beam with frictional excitation. The distributed model is based on anEuler–Bernoulli beam with frictional excitation. The friction ismodeled with Coulomb's law and contact compliance, and the contactsurface undergoes an imposed oscillation. The POMs are selected from achaotic response to build the reduced system model. These POMs areextrapolated into proper orthogonal modal functions (POMFs) by using thelinear normal modes as basis functions. The POMFs are used as the basisfor projection the partial differential equation of motion to alow-order set of ordinary differential equations. Simulated responsesbased on the POMFs and linear normal modes are compared to that of a'truth set' simulation, which is based on ten linear normal modes. 相似文献
13.
EIGEN THEORY OF VISCOELASTIC MECHANICS FOR ANISOTROPIC SOLIDS 总被引:4,自引:0,他引:4
Guo Shaohua 《Acta Mechanica Solida Sinica》2001,14(1):74-80
Anisotropic viscoelastic mechanics is studied under anisotropic subspace. It is proved that there also exist the eigen properties
for viscoelastic medium. The modal Maxwell's equation, modal dynamical equation (or modal equilibrium equation) and modal
compatibility equation are obtained. Based on them, a new theory of anisotropic viscoelastic mechanics is presented. The advantages
of the theory are as follows: 1) the equations are all scalar, and independent of each other. The number of equations is equal
to that of anisotropic subspaces, 2) no matter how complicated the anisotropy of solids may be, the form of the definite equation
and the boundary condition are in common and explicit, 3) there is no distinction between the force method and the displacement
method for statics, that is, the equilibrium equation and the compatibility equation are indistinguishable under the mechanical
space, 4) each model equation has a definite physical meaning, for example, the modal equations of order one and order two
express the volume change and shear deformation respectively for isotropic solids, 5) there also exist the potential functions
which are similar to the stress functions of elastic mechanics for viscoelastic mechanics, but they are not man-made, 6) the
final solution of stress or strain is given in the form of modal superimposition, which is suitable to the proximate calculation
in engineering. 相似文献
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In this paper, the on-orbit identification of modal parameters for a spacecraft is investigated. Firstly, the cou-pled dynamic equation of the system is established with the Lagrange method and the stochastic state-space model of the system is obtained. Then, the covariance-driven stochas-tic subspace identification (SSI-COV) algorithm is adopted to identify the modal parameters of the system. In this algo-rithm, it just needs the covariance of output data of the system under ambient excitation to construct a Toeplitz matrix, thus the system matrices are obtained by the singular value decom-position on the Toeplitz matrix and the modal parameters of the system can be found from the system matrices. Finally, numerical simulations are carried out to demonstrate the validity of the SSI-COV algorithm. Simulation results indi-cate that the SSI-COV algorithm is effective in identifying the modal parameters of the spacecraft only using the output data of the system under ambient excitation. 相似文献
16.
《应用数学和力学(英文版)》2017,(2)
In this paper, transverse vibration of an axially moving beam supported by a viscoelastic foundation is analyzed by a complex modal analysis method. The equation of motion is developed based on the generalized Hamilton's principle. Eigenvalues and eigenfunctions are semi-analytically obtained. The governing equation is represented in a canonical state space form, which is defined by two matrix differential operators. The orthogonality of the eigenfunctions and the adjoint eigenfunctions is used to decouple the system in the state space. The responses of the system to arbitrary external excitation and initial conditions are expressed in the modal expansion. Numerical examples are presented to illustrate the proposed approach. The effects of the foundation parameters on free and forced vibration are examined. 相似文献
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智能结构以主动元件为传感器和驱动器,根据结构的动态响应和控制要求,自适应地改变结构的动态性能,实现结构特性的自调节功能,以增强结构适应于外界环境变化的能力.结构振动主动控制方法中常用的模态空间控制方法,就是将系统方程转化到模态坐标下,从而得到内部解耦的以模态坐标表示的方程组,然后根据一定的控制方法,计算出模态控制力,实现实时控制.该方法计算简单,效率高,能满足实时控制的需要.本文根据一个三层智能结构主动控制实验,介绍了耦合模态控制理论及实现方法,设计并阐述了压电主元杆件的工作原理,根据Riccati方程得到了主元杆件的最优布置.通过对实验数据运用五点滑动平均平滑法进行处理分析及频谱分析可以看到,智能结构通过主动控制,对相应的控制模态位移及加速度有很大的抑制作用,对应的模态阻尼系数得到了不同程度的提高. 相似文献
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This paper investigates large amplitude multi-mode free vibration andrandom response of thin cylindrical panels of rectangular planform usinga finite element modal formulation. A thin laminated composite doublycurved element is developed. The system equation in structural nodal DOFis transformed into the modal coordinates by the using the modes of theunderlying linear system. The nonlinear stiffness matrices are alsotransformed into nonlinear modal stiffness matrices. Numericalintegration is employed to determine free vibration and random response.Single-mode free vibration results are compared with existing classicalanalytical solutions to validate the nonlinear modal formulation.Nonlinear random analysis results for cylindrical panels have shown thatthe root mean square of panel deflections could be larger than thoseobtained using the linear structure theory. Time histories, probabilitydistribution functions, power spectral densities, and phase plane plotsare also presented. 相似文献
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