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1.
基于对偶变量变分原理,选择积分区间两端位移为独立变量,构造了求解完整约束哈密顿动力系统的高阶保辛算法。首先,利用拉格朗日多项式对作用量中的位移、动量及拉格朗日乘子进行近似;然后,对作用量中不包含约束的积分项采用Gauss积分近似,对作用量中包含约束的积分项采用Lobatto积分近似,从而得到近似作用量;最后,在此近似作用量的基础上,利用对偶变量变分原理,将求解完整约束哈密顿动力系统问题转化为一组非线性方程组的求解。算法具有保辛性和高阶收敛性,能够在位移的插值点处高精度地满足完整约束。算法的收敛阶数及数值性质通过数值算例验证。  相似文献   

2.
将广义位移和动量同时用拉格朗日多项式近似,并选择积分区间两端位移为独立变量,然后基于对偶变量变分原理导出了哈密顿系统的离散正则变换和对应的数值积分保辛算法。当位移和动量的拉格朗日多项式近似阶数满足一定条件时,可以自然导出保辛算法的不动点格式。通过数值算例分析了位移和动量采用不同阶次插值所需最少Gauss积分点个数,并讨论了位移插值阶数、动量插值阶数以及Gauss积分点个数对保辛算法精度的影响,说明了上述不动点格式恰好是一种最优格式。  相似文献   

3.
给出了非传统哈密顿变分原理的一种简化形式,并在此基础上利用拉格朗日多项式近似位移和动量,采用高斯积分法对时间积分,建立了针对动力学初值问题的一类高阶辛算法。在建立高阶辛算法的过程中,本文方法与基于传统哈密顿变分原理的辛算法不同,无需由端值问题向初值问题转换,因此更加简捷有效。此外,给出了线性动力问题中本文算法保辛性的证明。当位移、动量的插值次数和高斯积分点个数均为m时,本文算法是具有2m阶精度的辛算法,且是线性无条件稳定的。通过数值算例结果表明,本文算法与辛算法性质吻合,并且计算效率比同阶辛龙格库塔法提高了约50%。  相似文献   

4.
文献[1]给出了哈密顿系统的一个新的变分原理,并基于此变分原理,通过选择一个时间步长两端不同广义位移或广义动量为独立变量,给出了四种不同类型的求解哈密顿动力系统的数值方法。本文将分别证明这四类数值方法都是保辛的数值方法。  相似文献   

5.
马立明  付冰梅 《力学季刊》1995,16(2):152-157
本文通过对具有单重卷积积分的二类变量的Gurtin型混合变分原理进行修正,采用“部分应力杂交”的概念,建立了线弹性动力分析 部分应力杂交变分格式,并在此基础上构造出时间有限元模型,这种模型对于分层复合板的动力分析尤其适用。  相似文献   

6.
吴俊超  吴新瑜  赵珧冰  王东东 《力学学报》2022,54(12):3283-3296
无网格法具有高阶连续光滑的形函数, 在结构分析中呈现出显著的精度优势. 但无网格形函数在节点处一般没有插值性, 导致伽辽金无网格法难以直接施加本质边界条件. 采用变分一致尼兹法施加边界条件的数值解具有良好的收敛性和稳定性, 因而得到了非常广泛的应用, 然而该方法仍然需要引入人工参数来保证算法的稳定性. 本文以赫林格?赖斯纳变分原理为基础, 建立了一种变分一致的本质边界条件施加方法. 该方法采用混合离散近似赫林格?赖斯纳变分原理弱形式中的位移和应力, 其中位移采用传统无网格形函数进行离散, 而应力则在背景积分单元中近似为相应阶次的多项式. 此时的无网格离散方程可视为一种新型的尼兹法施加本质边界条件, 其中修正变分项采用再生光滑梯度和无网格形函数进行混合离散, 稳定项则内嵌于赫林格?赖斯纳变分原理弱形式中, 无需额外增加稳定项, 消除了对人工参数的依赖性. 该方法无需计算复杂耗时的形函数导数, 并满足积分约束条件, 保证了数值求解的精度. 数值结果表明, 所提方法能够保证伽辽金无网格法的计算精度最优误差收敛率, 与传统的尼兹法相比明显提高了计算效率.   相似文献   

7.
文献[1,2]给出了四种不同类型的求解哈密顿动力系统的数值方法,并证明了它们的保辛特性。本文将讨论这四类算法的具体数值性能,包括算法的线性稳定性,精度和效率等。  相似文献   

8.
基于位移型Gurtin变分原理计算动力响应的逐步积分法   总被引:8,自引:0,他引:8  
本文利用位移型Gurtin变分原理,在时间域上采用三次Hermite插值函数进行离散,给出了一种计算结构动力响应的逐步积分方法。通过稳定性分析研究了该方法的稳定区情况表明,当1.64≤θ≤2.08时,该方法的数值计算精度很高,但是条件稳定积分格式。当θ≥4.1时,该方法是无条件稳定的积分格式,精度较高。  相似文献   

9.
Gurtin变分原理及其应用的时间有限元法   总被引:1,自引:0,他引:1  
动力学Gurtin变分原理完整地表征了动力学的全部特征。由于在Gurtin变分原理的泛函中含有双重卷积,给时间域的离散带来很大困难。本文通过在Laplace空间构造泛函,获得了几个具有单重卷积的Gurtin原理。由于卷积降阶,所给出的泛函更加便于应用。本文还通过在时间域采用适当的插值多项式逼近广义节点坐标,进一步讨论了时间有限元法实施的基本原理和步骤。  相似文献   

10.
针对三维共振腔的电磁场分析,利用Maxwell方程的对偶方程体系形式,从其相应的对偶变量变分原理出发,导出了三维电磁场辛有限单元的详细列式。为了有限元列式的保辛,变分原理被积函数可导向对于对偶变量为对称的形式。变分原理的边界积分项对于相邻单元相互抵消。由于采用了对偶变量的插值函数,使得电磁场单元构造可以在层面上进行,从而避免了所谓的连续性问题。无物理意义的零本征解可采用奇异值分解加以排除。文末分别对矩形及圆柱形的共振腔做了数值计算并与解析解和棱边元计算结果进行对比,算例表明了列式及算法的有效性。  相似文献   

11.
The Chebyshev spectral variational integrator(CSVI) is presented in this paper. Spectral methods have aroused great interest in approximating numerically a smooth problem for their attractive geometric convergence rates. The geometric numerical methods are praised for their excellent long-time geometric structure-preserving properties.According to the generalized Galerkin framework, we combine two methods together to construct a variational integrator, which captures the merits of both methods. Since the interpolating points of the variational integrator are chosen as the Chebyshev points,the integration of Lagrangian can be approximated by the Clenshaw-Curtis quadrature rule, and the barycentric Lagrange interpolation is presented to substitute for the classic Lagrange interpolation in the approximation of configuration variables and the corresponding derivatives. The numerical float errors of the first-order spectral differentiation matrix can be alleviated by using a trigonometric identity especially when the number of Chebyshev points is large. Furthermore, the spectral variational integrator(SVI) constructed by the Gauss-Legendre quadrature rule and the multi-interval spectral method are carried out to compare with the CSVI, and the interesting kink phenomena for the Clenshaw-Curtis quadrature rule are discovered. The numerical results reveal that the CSVI has an advantage on the computing time over the whole progress and a higher accuracy than the SVI before the kink position. The effectiveness of the proposed method is demonstrated and verified perfectly through the numerical simulations for several classical mechanics examples and the orbital propagation for the planet systems and the Solar system.  相似文献   

12.
参变量变分原理及其参数二次规划算法是由钟万勰院士1985年针对弹性接触边界非线性问题首次提出来的,经过将近40年的不断发展,目前参变量变分原理已经成功应用于各个领域,其中包括弹塑性分析、接触问题、润滑力学、岩土力学、变刚度杆系结构、先进材料性能分析、材料的蠕变与损伤、柔性结构力学和LQ最优控制等各个工程领域。本文首先回顾了参变量变分原理的起源,介绍了参变量变分原理的基本概念,然后以弹塑性分析问题为例,阐明建立参变量变分原理的理论模型以及实现数值参数二次规划求解原理,最后详细回顾了参变量变分原理的基本理论与相应数值算法在各个领域的发展及其工程应用,展示了参变量变分原理在求解各类非线性问题的特色与优势。  相似文献   

13.
In this paper, the shallow water problem is discussed. By treating the incompressible condition as the constraint, a constrained Hamilton variational principle is presented for the shallow water problem. Based on the constrained Hamilton variational principle, a shallow water equation based on displacement and pressure (SWE-DP) is developed. A hybrid numerical method combining the finite element method for spatial discretization and the Zu-class method for time integration is created for the SWEDP. The correctness of the proposed SWE-DP is verified by numerical comparisons with two existing shallow water equations (SWEs). The effectiveness of the hybrid numerical method proposed for the SWE-DP is also verified by numerical experiments. Moreover, the numerical experiments demonstrate that the Zu-class method shows excellent performance with respect to simulating the long time evolution of the shallow water.  相似文献   

14.
Based on the Gurtin variational principle and the finite element method two recurrence formulae of solving dynamic response are derived in this paper. The first recurrence formula which is conditionally stable is obtained by adopting “dual temporal finite element” to discretize the Gurtin variational principle and then making use of convolution, while the second, an unconditionally stable one derived by discritizing the variational principle in each time step and taking approprlate integration parameter θ. The paper had been accepted by the XVIth International Congress of IUTAM, Lyngby, Denmark, August, 1984.  相似文献   

15.
Linear and non-linear peaky fuzzy numbers and their arithmetic operations are constructed for the analysis of engineering structures with fuzzy characteristic quantities. Fuzziness of the corresponding quantities is consistently incorporated into the functional of the total potential energy. A set of deterministic recursive equations is obtained as the alternative expressions of the fuzzy variational principle by means of the second-order perturbation technique. The fuzzy Ritz method and the fuzzy finite element method are presented as the applications of the fuzzy variational principle. Accordingly, the roundabout procedures frequently used in the formulations of the fuzzy finite element method are avoided. A benchmark problem of a bending beam with fuzzy Young's modulus under fuzzy external loading is solved by the developed fuzzy numerical methods. Numerical examples show that results determined by these two fuzzy methods are both little conservative, and are in good agreement with those obtained by the analytical method. Moreover, the fuzzy Ritz method or the fuzzy finite element method can provide more valuable information than the conventional deterministic methods.  相似文献   

16.
This paper develops a new approach to construct variational integrators. A simplified unconventional Hamilton’s variational principle corresponding to initial value problems is proposed, which is convenient for applications. The displacement and momentum are approximated with the same Lagrange interpolation. After the numerical integration and variational operation, the original problems are expressed as algebraic equations with the displacement and momentum at the interpolation points as unknown variables. Some particular variational integrators are derived. An optimal scheme of choosing initial values for the Newton-Raphson method is presented for the nonlinear dynamic system. In addition, specific examples show that the proposed integrators are symplectic when the interpolation point coincides with the numerical integration point, and both are Gaussian quadrature points. Meanwhile, compared with the same order symplectic Runge-Kutta methods, although the accuracy of the two methods is almost the same, the proposed integrators are much simpler and less computationally expensive.  相似文献   

17.
In this paper a simple derivation of a new version of the variational principle of Hashin and Shtrikman is given. It appears possible to dispense with some subsidiary conditions which in the original principle had to be imposed on the class of functions considered in the variational process. However, through the use of the new principle the possibility of obtaining a pair of two sided bounds is lost and this has to be compensated by invoking one of the complementary principles which are formulated in the sequel.  相似文献   

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