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分离变量法与哈密尔顿体系 总被引:4,自引:0,他引:4
数学物理与力学中用分离变量法求解偏微分方程经常导致自共轭算子的sturmLiouville问题,在此基础上而得以展开求解。然而在应用中有大量问题并不能导致自共轭算子。本文通过最小势能变分原理,选用状态变量及其对偶变量,导向一般变分原理。利用结构力学与最优控制的模拟理论,导向哈密尔顿体系。将有限维的理论推广到相应的哈密尔顿算子矩阵及共轭辛矩阵代数的理论。拓广了经典的分离变量法,证明了全状态本征函数向量的共轭辛正交归一性质及按本征函数向量展开的理论。以条形板为例,说明了应用。 相似文献
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基于弱形式的力学方程,阐述了弱形式广义方程是拟协调有限元的内在本质,用弱形式给出的微分方程和边界条件根本上是降低了函数光滑性,不过对工程问题而言,给出的有限元解比原始方程更接近真实解,其数值解就是广义协调方程的直接解,同时满足平衡和几何方程弱连续条件。进而就导出的对偶体系弱形式哈密尔顿方程,采用辛相似变换,利用平方约化法求解哈密尔顿矩阵特征值问题,使其哈密尔顿结构得到了保证。辛算法具有较强的有效性,可以解决常规有限元难以适应的领域,对计算力学发展有着重要的作用。 相似文献
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基于Reissner板理论,通过对混合能变分的修正,建立了更一般的哈密尔顿型广义变分原理,并给出了Reissner板问题的哈密尔顿正则方程及其共轭辛正交解析法。 相似文献
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基于Reisner板理论,通过对混合能变分原理的修正,建立了更一般的哈密尔顿型广义变分原理,并给出了Reisner板问题的哈密尔顿正则方程及其共轭辛正交解析法 相似文献
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对弹性平面扇形域问题,将径向坐标模拟成时间坐标,通过适当的变换,将扇形域问题导向哈密尔顿体系,利用分离变量法及本征函数向量展开等方法,推导出裂纹尖端的应力奇性解的计算公式,结合变分原理,提出一种解决应力奇性计算的断裂分析元,将此分析元与有限元法相结合,可以进行某些断裂力学或复合材料等应力奇性问题的计算及分析,数值计算结果表明,该方法具有精度高,使用十分方便,灵活等优点,是哈密尔顿体系和辛数学优越性的一次具体体现。 相似文献
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弹性力学的一种正交关系 总被引:8,自引:2,他引:8
在弹性力学求解新体系中,将对偶向量进行重新排序后,提出了一种新的对偶微分矩阵,对于有一个方向正交的各向异性材料的三维弹性力学问题发现了一种新的正交关系.将材料的正交方向取为z轴,证明了这种正交关系的成立.对于z方向材料正交的各向异性弹性力学问题,新的正交关系包含弹性力学求解新体系提出的正交关系。 相似文献
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互等定理与共轭辛正交关系 总被引:12,自引:2,他引:12
本文指出,哈密尔顿矩阵的本征向量间的辛正交关系可以由结构力学的互等性定理导出。尤其当哈密尔顿矩阵出现多重本征根以及约当(Jordan)型时,本文指出了使约当型保持哈密尔顿矩阵结构形式不变的变换;并且证明了对于次本征向量的恰当选择可以使各个(次)本征向量之间仍保持共轭辛正交归一关系。 相似文献
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电磁波导的半解析辛分析 总被引:18,自引:1,他引:18
根据电磁波导的Hamilton体系,辛几何可用于任意各向异性材料,而且便于处理不同区段的界面条件,横向的电场和磁场构成了对偶向量.基于Hamilton变分原理用半解析法进行横向离散应当保持体系的辛结构.离散后可以运用应用力学的有效算法,求解其辛本征值问题.每段波导可以引入两端Riccati矩阵,用精细积分法求解其方程组. 相似文献
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Appling Mindlin's theory of thick plates and Hamilton system to propagation of elastic waves under free boundary condition, a solution of the problem was given. Dispersion equations of propagation mode of strip plates were deduced from eigenfunction expansion method. It was compared with the dispersion relation that was gained through solution of thick plate theory proposed by Mindlin. Based on the two kinds of theories, the dispersion curves show great difference in the region of short waves, and the cutoff frequencies are higher in Hamiltonian systems. However, the dispersion curves are almost the same in the region of long waves. 相似文献
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Applying Lagrange–Germain’s theory of elastic thin plates and Hamiltonian formulation, the dynamics of cantilever plates and the problem of its vibration control are studied, and a general solution is finally given. Based on Hamiltonian and Lagrangian density function, we can obtain the flexural wave equation of the plate and the relationship between the transverse and the longitudinal eigenvalues.Based on eigenfunction expansion, dispersion equations of propagation mode of cantilever plates are deduced. By satisfying the boundary conditions of cantilever plates, the natural frequencies of the cantilever plate structure can be given.Then, analytic solution of the problem in plate structure is obtained. An hybrid wave/mode control approach, which is based on both independent modal space control and wave control methods, is described and adopted to analyze the active vibration control of cantilever plates. The low-order(controlled by modal control) and the high-order(controlled by wave control) frequency response of plates are both improved. The control spillover is avoided and the robustness of the system is also improved. Finally, simulation results are analyzed and discussed. 相似文献
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A method to study dynamical instability and non-linear parametric vibrations of symmetrically laminated plates of complex shapes and having different cutouts is proposed. The first-order shear deformation theory (FSDT) and the classical plate theory (CPT) are used to formulate a mathematical statement of the given problem. The presence of cutouts essentially complicates the solution of buckling problem, since the stress field is non-uniform. At first, a plane stress analysis is carried out using the variational Ritz method and the R-functions theory. The obtained results are applied to investigate buckling and parametric vibrations of laminated plates. The developed method uses the R-functions theory, and it may be directly employed to study laminated plates of arbitrary forms and different boundary conditions. Besides, the proposed method is numerical-analytical, what greatly facilitates a solution of similar-like non-linear problems. In order to show the advantage of the developed approach, instability zones and response curves for the layered cross- and angle-ply plates with external cutouts are constructed and discussed. 相似文献
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Appling Mindlin's theory of thick plates and Hamilton system to propagation of elastic waves under free boundary condition, a solution of the problem was given. Dispersion equations of propagation mode of strip plates were deduced from eigenfunction expansion method. It was compared with the dispersion relation that was gained through solution of thick plate theory proposed by Mindlin. Based on the two kinds of theories, the dispersion curves show great difference in the region of short waves, and the cutoff frequencies are higher in Hamiltonian systems. However, the dispersion curves are almost the same in the region of long waves. 相似文献
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A hybrid method is presented for the analysis of layers, plates, and multilayered systems consisting of isotropic and linear elastic materials. The problem is formulated for the general case of a multilayered system using a total potential energy formulation. The layerwise laminate theory of Reddy is employed to develop a layerwise, two-dimensional, displacement-based, hybrid boundary element model that assumes piecewise continuous distribution of the displacement components through the system's thickness. A one-dimensional finite element model is used for the analysis of the multilayered system through its thickness, and integral Fourier transforms are used to obtain the exact solution for the in-plane problem. Explicit expressions are obtained for the fundamental solution of a typical infinite layer (element) assuming linear displacement distribution through its thickness. This fundamental solution is given in a closed form in the cartesian space, and it can be applied in the two-dimensional boundary integral equation model to analyze layered structures with finite dimensions. The proposed method provides a simple, efficient, and versatile model for a three-dimensional analysis of thick plates or multilayered systems. 相似文献
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《International Journal of Solids and Structures》2006,43(21):6568-6573
In this paper, based on Lagrange–Germanian theory of elastic thin plates, applying the method in Hamiltonian state space, the elastic waves and vibrations when the boundary of the two lateral sides of the strip plate are free of traction are investigated, and the process of analysis and solution are proposed. The existence of all kinds of vibration modes and wave propagation modes is also analyzed. By using eigenfunction expansion method, the dispersion relations of waveguide modes in the strip plate are derived, and the comparisons with the dispersion relations directly obtained by the classical theory of thin plates are also presented. At last, the results are analyzed and discussed. 相似文献
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Gyroscopic dynamic system can be introduced to Hamiltonian system.Based on an adjoint symplectic subspace iteration method of Hamiltonian gyroscopic system, an adjoint symplectic subspace iteration method of indefinite Hamiltonian function gy- roscopic system was proposed to solve the eigenvalue problem of indefinite Hamiltonian function gyroscopic system.The character that the eigenvalues of Hamiltonian gyroscopic system are only pure imaginary or zero was used.The eigenvalues that Hamiltonian function is negative can be separated so that the eigenvalue problem of positive definite Hamiltonian function system was presented,and an adjoint symplectic subspace iteration method of positive definite Hamiltonian function system was used to solve the separated eigenvalue problem.Therefore,the eigenvalue problem of indefinite Hamiltonian function gyroscopic system was solved,and two numerical examples were given to demonstrate that the eigensolutions converge exactly. 相似文献
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