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81.
In the rational fraction polynomial method [1] the identification of modal parameters is obtained through a direct linear least-square optimization technique but a particular form of fitting error is minimized. An iterative algorithm has been recently developed which uses the true fitting error [2]. In this paper a statistical analysis is developed to estimate the bias effects on the identified parameters when the data are polluted with noise. Both the direct and iterative procedures are considered. Numerical simulations are used to validate the results predicted by the theoretical analysis, which shows that the iterative approach is by far more efficient than the direct method.A first version of this paper was presented at 17th Int. Seminar on Modal Analysis, Leuven (Belgium), 23–25 September 1992, and preprinted in the Proceedings. 相似文献
82.
V. Z. Stankevich B. M. Stasyuk O. M. Khai 《Journal of Applied Mechanics and Technical Physics》2005,46(1):124-128
The three-dimensional dynamic problem of coplanar circular cracks in an elastic half-space with a clamped boundary condition is considered. The crack faces are subjected to harmonic loads. The problem is reduced to a system of two-dimensional boundary integral equations of the type of the Helmholtz potential for unknown discontinuities in the displacements of the opposite faces of the cracks. The stress intensity factors at the crack contours are obtained and discussed.Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 46, No. 1, pp. 153–159, January–February, 2005 相似文献
83.
The purpose of the present paper is to solve an active control problem of nonlinear continuous system parametric vibrations excited by the fluctuating force. The problem is solved using the concept of distributed piezoelectric sensors and actuators with a sufficiently large value of velocity feedback. The direct Liapunov method is proposed to establish criteria for the almost sure stochastic stability of the unperturbed (trivial) solution of the shell with closed-loop control. The distributed control is realized by the piezoelectric sensor and actuator, with the changing widths, glued to the upper and lower shell surface. The relation between the stabilization of nonlinear problem and a linearized one is examined. The fluctuating axial force is modeled by the physically realizable ergodic process. The rate velocity feedback is applied to stabilize the shell parametric vibrations. 相似文献
84.
The nonlinear dynamics of the same experimental model of an internally resonant hanging elastic cable considered in Part I [1] are addressed here from the point of view of the global system behaviour in the control parameter space. Synthetic results of systematic response measurements, made at different amplitudes of the support motion in frequency ranges including meaningful external resonance conditions, are reported and discussed. Attention is devoted to the detection of the most robust classes of motion. Quite complicated overall pictures of regular response regions with variable contributions from different planar and nonplanar cable modes are observed, as well as several regions of quasiperiodic and chaotic responses. Sample quantitative characterizations of nonregular motions are presented. Some experimental results are also observed against the background of the nonlinear dynamic phenomena exhibited by a theoretical model of a continuous cable with four-degrees-of-freedom. 相似文献
85.
86.
The paper proposes a numerical-analytic approach to studying the free vibrations of orthotropic shallow shells with double
curvature and rectangular planform. The approach is based on the spline-approximation of unknown functions. Calculations are
carried out for different types of boundary conditions. The influence of the mid-surface curvature and variable thickness
on the behavior of dynamic characteristics is studied
__________
Translated from Prikladnaya Mekhanika, Vol. 43, No. 6, pp. 102–115, June 2007. 相似文献
87.
Wavelet-based methods are reviewed, and their advantages in comparison to standard approaches are outlined. Then, a wavelet analysis is performed to investigate parametric vibrations of flexible plates under a sinusoidal load. In particular, a scenario leading from regular motion to chaos is analyzed 相似文献
88.
V. F. Sivak 《International Applied Mechanics》2004,40(12):1419-1421
The resonance synchronization of the vibrations of a system of shells is studied. It is established that the vibrations of isolated components excite the vibrations of the whole system, consisting of three cylindrical shells on a common elastic base.__________Translated from Prikladnaya Mekhanika, Vol. 40, No. 12, pp. 134–137, December 2004. 相似文献
89.
A self-excited three-mass chain system is considered here. For a self-excitation of van der Pol type, the possibility of multi-frequency
oscillations is investigated. Both analytical approximate solutions and numerical simulation are used. The averaging method
is used to establish existence and stability of the normal modes, the two-frequency modes as well as the three-frequency oscillations
solutions. We found at first that the single mode seems to prevail. However a three-frequency solution can be stabilised by
adapting the system slightly. A generic bifurcation diagram is given where all the possible phase portraits are sketched.
The flow turns out to be quite predictable. There is no “room” for chaos or strange attractors. This behaviour is not typical
for systems of coupled oscillators but turns out to be partly related to the involved symmetries as well as the particular
choice of the system parameters. 相似文献
90.
On Free Nonlinear Vibrations of Fluid-Filled Cylindrical Shells with Multiple Natural Frequencies 总被引:1,自引:0,他引:1
Nonlinear free vibrations of a cylindrical shell fully filled with a perfect incompressible fluid are studied. The case is
examined where two natural frequencies of the shell are close
__________
Published in Prikladnaya Mekhanika, Vol. 41, No. 10, pp. 127–138, October 2005 相似文献