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191.
In this study, a new periodic beam model is introduced. This beam consists of the concentrated rigid masses and tapered beam elements with linearly variable width. The theoretical equations are derived by employing the Euler-Bernoulli beam and the Bloch–Floquet theorem and then solved using the generalized differential quadrature rule method to calculate the first two band gaps. The effects of the mass, mass moment of inertia and taper ratio on the widths and central frequencies of the first two band gaps are investigated. Results show that the wide band gaps at low frequency ranges can be obtained by changing the geometrical parameters. This is of interest for different applications of the band gap phenomenon such as broadband piezoelectric energy harvesting. Finally, the finite element simulation (ANSYS software) is used to validate the analytical method and good agreement is found. 相似文献
192.
Anupam Chakrabarti Pijush Topdar Abdul Hamid Sheikh 《European Journal of Mechanics - A/Solids》2006,25(6):981-995
The vibration and buckling characteristics of sandwich plates having laminated stiff layers are studied for different degrees of imperfections at the layer interfaces using a refined plate theory. With this plate theory, the through thickness variation of transverse shear stresses is represented by piece-wise parabolic functions where the continuity of these stresses is satisfied at the layer interfaces by taking jumps in the transverse shear strains at the interfaces. The transverse shear stresses free condition at the plate top and bottom surfaces is also satisfied. The inter-laminar imperfections are represented by in-plane displacement jumps at the layer interfaces and characterized by a linear spring layer model. It is quite interesting to note that this plate model having all these refined features requires unknowns only at the reference plane. To have generality in the analysis, finite element technique is adopted and it is carried out with a new triangular element developed for this purpose, as any existing element cannot model this plate model. As there is no published result on imperfect sandwich plates, the problems of perfect sandwich plates and imperfect ordinary laminates are used for validation. 相似文献
193.
194.
G. Komandi 《Journal of Terramechanics》2006,43(2):213-223
During the past decades the author has continually worked on and perfected his conception of the interaction between the soil and the wheel. First, this work is summarized in this paper. The author then describes his conception of the mechanical interaction between them and clarifies the connection between the kinematic and dynamic processes that take place when a tractor is exerting pull. He shows by means of his kinematic model how the peripheral force is developed. Finally, he derives the appropriate equations for the computation of the peripheral force and the drawbar pull for both two-wheel-drive and four-wheel-drive tractors. Practical experience has proven that the concept is correct and the method is practical. 相似文献
195.
Analysis of strongly nonlinear (vibro-impact) systems revealed an existence of nonlinear modes of vibration with spatial and
temporal concentration of energy. The modes can be realised, for example, through intensification of the vibration process
by condensing the vibration into a sequence of collisions for impulsive action of the tools to the media being treated or
can be as a result of some discontinuity (slackening of a contact, arrival of crack, etc.) in the structure. The use of the
nonlinear modes to develop useful mechanical work leads to necessity of excitation and control of resonance in ill-defined dynamical systems. This is due to the poorly predictable response of the media being treated. Excitation, stabilisation and
control of a nonlinear mode at the top intensity in such systems is an engineering challenge and needs a new method of adaptive
control for its realisation.
Such a control technique was developed with the use of self-exciting mechatronic systems. The excitation of the nonlinear
mode in such systems is a result of artificial instability of mechanical system conducted by positive electronic feedback.
The instability is controlled by intelligent identification of the mode and active tracing of the optimal relationship between
phase shifting and limitation in the feedback circuitry. This method of control is known as autoresonance. Applications of autoresonant control for development of the new machines are described.
The paper is a revised and extended version of authors’ presentation at ASME 2004 International Mechanical Engineering Congress,
Anaheim, CA, USA.
An erratum to this article can be found at 相似文献
196.
The study sets up a simple model for predicting vibration induced sliding of mass, and provides quantitative experimental evidence for the validity of the model. The results lend confidence to recent theoretical developments on using vibration induced sliding for passive vibration damping, and contributes to a further understanding of this nonlinear phenomenon. A mathematical model is set up to describe vibration induced sliding for a base-excited cantilever beam with a spring-loaded pointmass. Approximations simplify the model into two nonlinear ordinary differential equations, describing motions of the system at near-resonant excitation of a single beam mode. This simplified model is studied numerically and analytically, and tested against laboratory experiments. The experiments provide evidence that the simplified mathematical model retains those features of the real system that are necessary for making useful predictions of transient and stationary first-mode response. 相似文献
197.
在文献(5)讨论移动荷载作用于箱梁的基础上,进一步考虑了移动质量对梁的动力作用;推导,建立了与前者性质,形式完全不同的变系数振动方程,并用数值方法救是解答,算例验证了本文建立了振动方程是正确的。 相似文献
198.
Samer Hassan Tatyana P. Lyubimova Dmitry V. Lyubimov Masahiro Kawaji 《International Journal of Multiphase Flow》2006
The effects of small vibrations on a particle oscillating near a solid wall in a fluid cell, relevant to material processing such as crystal growth in space, have been investigated experimentally and theoretically. Assuming the boundary layer around the particle to be thin compared to the particle radius at high vibration frequencies, an inviscid fluid model was developed to predict the motion of a spherical particle placed near a wall of a rectangular liquid-filled cell subjected to a sinusoidal vibration. Under these conditions, a non-uniform pressure distribution around the particle results in an average pressure that gives rise to an attraction force. Theoretical expressions for the attraction force are derived for the particle vibrating normal to and parallel with the nearest cell wall. The magnitude of this attractive force has been verified experimentally by measuring the motion of a steel particle suspended in the fluid cell by a thin wire. Experiments performed at high frequencies showed that the mean particle position, when the particle is brought near a cell wall, shifts towards the same wall, and is dependent on the cell amplitude and frequency, particle and fluid densities. 相似文献
199.
Nonlinear forced oscillations of a vertical continuous rotor with distributed mass are discussed. The restoring force of the rotor has geometric stiffening nonlinearity due to the extension of the rotor center line. The possibility of the occurrence of nonlinear forced oscillations at various subcritical speeds and the shapes of resonance curves at the major critical speeds and at some subcritical speeds are investigated theoretically. Consequently, the following is clarified: (a) the shape of resonance curves at the major critical speed becomes a hard spring type, and (b) among various kinds of nonlinear forced oscillations, only some special kinds of combination resonances have possibility of occurrence. 相似文献
200.
D. I. Bardzokas M.L. Filshtinsky 《Archive of Applied Mechanics (Ingenieur Archiv)》2004,74(3-4):165-178
Summary The anti-plane mixed boundary problem of electroelasticity for vibrations of an infinite piezoceramic cylinder with a thin
rigid inclusion is considered. Using the developed integral representation of the solution, the boundary problem is reduced
to a system of singular integro-differential equations of the second kind with resolvent kernels. Calculations yeild the amplitude-frequency
characteristics of the piecewise homogeneous cylinder. The behaviour of electroelastic fields, both within the cylinder and
on its boundary, is given. 相似文献