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91.
根据修正的余能原理,推导出一种求解复合材料层合圆柱壳的杂交应力单元。取用六面体等参单元,此单元反映了各层材料性质不同及应力分布沿整个厚度不连续现象,同时计入横向剪切变形和法向挤压变形,适用于厚层壳体。文章通过实例说明此单元能准确求出各层内的应力值,实用价值高。 相似文献
92.
For the N-degree-of-freedom of linear conservative vibratory systems, the corresponding potential functions can be viewed as N-hypersurfaces in (N + 1)-dimensional space. In this paper, a connection between the geometrical properties (principal curvatures, curvature lines) of potential surfaces and the vibratory characteristics (natural frequencies, linear modes) of the system is built. It is proved that the linear normal modes are exactly the projections of the lines of curvature on the potential surface onto the configuration space with metric mij (the mass-matrix); and that the squared natural frequencies are exactly the principal curvatures, at the origin of the configuration space, of the potential surface. 相似文献
93.
This paper presents stability and convergence results on a novel approach for imposing holonomic constraints for a class of multibody system dynamics. As opposed to some recent techniques that employ a penalty functional to approximate the Lagrange multipliers, the method herein defines a penalized dynamical system using penalty-augmented kinetic and potential energies, as well as a penalty dependent constraint violation dissipation function. In as much as the governing equations are not typically cocreive, the usual convergence criteria for linear variational boundary value problems are not directly applicable. Still numerical simulations by various researchers suggest that the method is convergent and stable. Despite the fact that the governing equations are nonlinear, the theoretical convergence of the formulation is guaranteed if the multibody system is natural and conservative. Likewise, stability and asymptotic stability results for the penalty formulation are derived from well-known stability results available from classical mechanics. Unfortunately, the convergence theorem is not directly applicable to dissipative multibody systems, such as those encountered in control applications. However, it is shown that the approximate solutions of a typical dissipative system converge to a nearby collection of trajectories that can be characterized precisely using a Lyapunov/Invariance Principle analysis. In short, the approach has many advantages as an alternative to other computational techniques:
Just as importantly, these results for nonlinear systems can be sharpened considerably for linear systems:
相似文献
(1) | Explicit constraint violation bounds can be derived for a large class of nonlinear multibody dynamics problems |
(2) | Sufficient conditions for the Lyapunov stability, and asymptotic stability, of the penalty formulation are derived for a large class of multibody systems |
(3) | The method can be shown to be relatively insensitive to singular configurations by selecting the penalty parameters to dissipate constraint violation energy |
(4) | The Invariance Principle can be employed in the method, in certain cases, to derive the asymptotic behavior of the constraint violation for dissipative multibody systems by identifying constraint violation limit cycles |
(5) | Explicit spectral error estimates can be obtained for substructure synthesis |
(6) | The penalty equations can be shown to be optimal in the sense that the terms represent feedback that minimizes a measure of the constraint violation |
94.
We prove the existence of a unique weak solution to the quasistatic problem of frictional contact between a deformable body
and a rigid foundation. The material is assumed to have nonlinear viscoelastic behavior. The contact is modeled with normal
compliance and the associated version of Coulomb's law of dry friction. We establish the continuous dependence of the solution
on the normal compliance function. Moreover, we prove the existence of a unique solution to the problem of sliding contact
with wear.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
95.
<正> 1、引言 流体运动总是同时受动力学和热力学规律的约制,通常处理流动问题时这两方面的考虑也总是交织在一起,例如,为了定义描述流动现象的诸流动变量,首先要假定每个流体质点微团是处于热力学平衡态,即假定流动系统满足“局域热平衡”条件。这样才可以定义各“点”的压力、密度、熵等变量。由于流动系统同时又是一个热力学系统,因此它的 相似文献
96.
Stability of a geothermal system is considered in a case when the water layer lies over the layer of superheated vapor in a stratum having relatively low permeability. This stratum locates between two parallel high permeable layers. Under the assumption of smallness of advective energy transfer as compared with the conductive one, the stationary distribution of the characteristics in the stratum with an interface of phase transition is obtained. The interface separates the domains occupied by water and vapor. Investigation of normal stability of the interface shows, that stable configurations in the geothermal system under consideration exist within the range of permeability values bounded by k 0.6 × 10–15 m2 from above. The most unstable configurations occur to be the quiescent states when the permeability exceeds a certain threshold. A sufficiently high value of permeability, satisfying the criterion of smallness of the advective energy transfer as compared with the conductive one makes it possible to explain the existence of a wide class of stable natural geothermal reservoirs, where the vapor layer underlies the water one. 相似文献
97.
98.
Contribution to efficiency of irreversible passive energy pumping with a strong nonlinear attachment 总被引:1,自引:0,他引:1
The present study deals with nonlinear energy pumping which consists in passive irreversible transfer of energy from a linear
structure to a nonlinear one. Various results (theoretical, numerical, and experimental) about energy pumping based on recent
works are given. Thus, the phenomenon is studied for different excitations: transient and periodical. Moreover, advantages
of such a system are carried out in particular efficiency of this phenomenon. That is why the robustness and comparison with
classical tuned mass damper are analyzed. An application is considered with physical experiment using a reduced scale building. 相似文献
99.
A UNIFORMLY CONVERGENT DIFFERENCE SCHEME FOR THE SINGULAR PERTURBATION PROBLEM OF A HIGH ORDER ELLIPTIC DIFFERENTIAL EQUATION 总被引:1,自引:0,他引:1
AUNIFORMLYCONVERGENTDIFFERENCESCHEMEFORTHESINGULARPERTURBATIONPROBLEMOFAHIGHORDERELLIPTICDIFFERENTIALEQUATION(刘国庆)(苏煜城)AUNIFO... 相似文献
100.