共查询到20条相似文献,搜索用时 0 毫秒
1.
Andrzej Tylikowski 《Archive of Applied Mechanics (Ingenieur Archiv)》2008,78(1):49-60
The dynamical stability of carbon nanotubes embedded in an elastic matrix under time-dependent axial loading is studied in
this paper. The effects of van der Waals interaction forces between the inner and outer walls of nanotubes are taken into
account. Using continuum mechanics, we apply an elastic layered shell model to solve the transverse parametric vibrations
of a carbon nanotube. Both the Gaussian wide-band axial temperature changes and physically realizable temperature changes
with known probability distributions are assumed as the tube axial loading. The energy-like functionals are used in the stability
analysis. The emphasis is placed on a qualitative analysis of dynamic stability problem. Stability domains in the space of
geometric, material and loading parameters are presented in analytical forms. 相似文献
2.
G. P. Gulgazaryan 《International Applied Mechanics》2008,44(5):534-554
The natural vibrations of a cantilever thin elastic orthotropic circular cylindrical shell are studied. Dispersion equations
for the determination of possible natural frequencies of cantilever closed shells and open shells with Navier hinged boundary
conditions at the longitudinal edges are derived from the classical dynamic theory of orthotropic cylindrical shells. It is
proved that there are asymptotic relationships between these problems and the problems for a cantilever orthotropic strip
plate and for a cantilever rectangular plate and the eigenvalue problem for a semi-infinite closed orthotropic cylindrical
shell with free end and for the same but open shell with Navier hinged boundary conditions at the longitudinal edges. A procedure
to identify types of vibrations is presented. Orthotropic cylindrical shells with different radii and lengths are used as
an example to find approximate values of the dimensionless natural frequency and damping factor for vibration modes
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Translated from Prikladnaya Mekhanika, Vol. 44, No. 5, pp. 68–91, May 2008. 相似文献
3.
Natural Vibrations Of Corrugated Cylindrical Shells 总被引:1,自引:0,他引:1
A method for determining the natural frequencies and modes of corrugated noncircular cylindrical shells is presented. The influence of the length and amplitude of corrugations on the fundamental frequency of unloaded and axially compressed shells is examined. The difference between the dependences of frequencies and critical loads on shell geometry is shown. The possibility of optimizing shells in frequencies and critical loads is established__________Translated from Prikladnaya Mekhanika, Vol. 41, No. 5, pp. 58–67, May 2005 相似文献
4.
S. Yu. Fialko 《International Applied Mechanics》2004,40(1):83-90
The paper sets forth a modified preconditioned conjugate-gradient method with shifted aggregated multilevel preconditioning (MPCG_AMIS). The method is intended to solve large-scale natural-vibration problems. Such problems are typical for the finite-element analysis of buildings and other complex structures and bodies. Using a proper shift in preconditioning improves considerably the spectral properties of the preconditioner and, hence, improves convergence. Using the MPCG_AMIS allows us to avoid lock of convergence, which is the case in the conventional PCG method. The performance of the method is illustrated by examples 相似文献
5.
V. F. Sivak 《International Applied Mechanics》2007,43(9):1024-1027
A technique and results of experimental determination of vibrational stresses in a system of two truncated conical shells
joined by three thin plates are presented. An analysis of the data obtained shows that the stress peaks near the added point
mass at resonance
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Translated from Prikladnaya Mekhanika, Vol. 43, No. 9, pp. 93–97, September 2007. 相似文献
6.
杂交元本征应力模式和应力子空间的性质研究 总被引:3,自引:0,他引:3
详细讨论了有限元本征应力模式和应力子空间的性质,并着重讨论和进一步完善了与杂交应力有限元应力子空间有关的一些定理,为提出新方法提供了理论基础,主要包括:(1)证明了杂交元特征值不大于对应位移元的特征值;(2)证明了矩阵H非奇异的充分必要条件是假设应力模式线性无关;(3)证明了杂交元所对应位移元的本征应力模式形成的杂交元与该位移元相同;(4)证明了等价假设应力模式形成相同的杂交元;(5)证明了确定杂交元本征应力模式的充分必要条件是其范数平方等于所形成杂交元的变形模态特征值;(6)证明了杂交元假设应力模式与变形模态的能量一一对应的充分必要条件是假设应力模式彼此正交且与所对应位移元的本征应力模式除了一一对应者之外都正交。 相似文献
7.
Norio Kondo 《International Journal of Computational Fluid Dynamics》2014,28(6-10):461-476
It is well known from a lot of experimental data that fluid forces acting on two tandem circular cylinders are quite different from those acting on a single circular cylinder. Therefore, we first present numerical results for fluid forces acting on two tandem circular cylinders, which are mounted at various spacings in a smooth flow, and second we present numerical results for flow-induced vibrations of the upstream circular cylinder in the tandem arrangement. The two circular cylinders are arranged at close spacing in a flow field. The upstream circular cylinder is elastically placed by damper-spring systems and moves in both the in-line and cross-flow directions. In such models, each circular cylinder is assumed as a rigid body. On the other hand, we do not introduce a turbulent model such as the Large Eddy Simulation (LES) or Reynolds Averaged Navier-Stokes (RANS) models into the numerical scheme to compute the fluid flow. Our numerical procedure to capture the flow-induced vibration phenomena of the upstream circular cylinder is treated as a fluid-structure interaction problem in which the ideas of weak coupling is taken into consideration. 相似文献
8.
R. Heuer 《Nonlinear dynamics》1994,5(1):25-38
A dynamic nonlinear theory for layered shallow shells is derived by means of the von Karman-Tsien theory, modified by the generalized Berger-approximation. Moderately thick shells with polygonal planform composed of multiple perfectly bonded layers are considered. The shell edges are assumed to be prevented from in-plane motions and are simply supported. A distributed lateral force loading is applied to the structure, and additionally, the influence of a static thermal prestress, corresponding to a spatial distribution of cross-sectional mean temperature, is taken into account. In the special case of laminated shells made of transversely isotropic layers with physical properties symmetrically distributed about the middle surface, a correspondence to moderately thick homogeneous shells is found. Application of a multi-mode expansion in the Galerkin procedure to the governing differential equation, where the eigenfunctions of the corresponding linear plate problem are used as space variables, renders a coupled set of ordinary time differential equations for the generalized coordinates with cubic as well as quadratic nonlinearities. The nonlinear steady-state response of shallow shells subjected to a time-harmonic lateral excitation is investigated and the phenomenon of primary resonance is studied by means of the perturbation method of multiple scales. A unifying non-dimensional representation of the nonlinear frequency response function is presented that is independent of the special shell planform. 相似文献
9.
This study is devoted to the experimental validation of a theoretical model of large amplitude vibrations of thin spherical
shells described in a previous study by the same authors. A modal analysis of the structure is first detailed. Then, a specific
mode coupling due to a 1:1:2 internal resonance between an axisymmetric mode and two companion asymmetric modes is especially
addressed. The structure is forced with a simple-harmonic signal of frequency close to the natural frequency of the axisymmetric
mode. The experimental setup, which allows precise measurements of the vibration amplitudes of the three involved modes, is
presented. Experimental frequency response curves showing the amplitude of the modes as functions of the driving frequency
are compared to the theoretical ones. A good qualitative agreement is obtained with the predictions given by in the model.
Some quantitative discrepancies are observed and discussed, and improvements of the model are proposed. 相似文献
10.
Natural vibrations of shallow cylindrical shells with rectangular plan and varying thickness are studied using a spline-approximation
method developed previously. Computation is carried out for different types of boundary conditions. The effect of the curvature
of the midsurface on the natural frequencies is examined. The natural frequencies of shells with constant and varying thickness
are compared
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Translated from Prikladnaya Mekhanika, Vol. 43, No. 4, pp. 89–98, April 2007. 相似文献
11.
E. K. Ankyanets 《International Applied Mechanics》2005,41(8):924-928
The vibrations of a cylindrical shell reinforced with ring ribs attached to the shell by means of elastic elements are studied.
The problem is solved by the finite-element method. The shell and ribs are modelled by a plane four-node finite element, which
is a combination of a four-node plane stress element and a four-node flexural element. The effect of the stiffness of the
elastic elements on the natural frequencies and modes is examined
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Translated from Prikladnaya Mekhanika, Vol. 41, No. 8, pp. 105–110, August 2005. 相似文献
12.
Summary An integral equation formulation for the dynamic biaxial response of slightly curved elastic-viscoplastic beams is presented
in the context of a multiple field analysis, which takes into account the geometrically nonlinear influence of moderately
large deflections. Materials are considered in the regime of rate-dependent plasticity and are subjected to accumulated ductile
damage. The latter is modeled by the growth of voids in the plastic zones of an initially porous elastic material. Inelastic
defects of the material are considered in the linear elastic background beam by a second imposed strain field (eigenstrains).
Geometrically nonlinear effects of large deflections under conditions of immovable supports are approximately taken into account.
By inspection, they render another “strain field” to be imposed on the linear background beam. Superposition applies in the
linear elastic background in an incremental formulation. Linear methods, as those based on Green's functions and Duhamel's
integral, are used to account for the given loads as well as for the resultants of the imposed strain fields. The intensity
and the distribution of the imposed strain fields are calculated incrementally in a time-stepping procedure. They are determined
by the constitutive law and by application of the nonlinear geometric relations. The numerical procedure resulting from the
multiple fields in the elastic background is illustrated for two cases: (1) a preloaded viscoplastic beam of rectangular cross
section is subjected to oblique flexural vibrations when forced by a sinusoidal load, and (2) an I-beam with a prescribed
initial curvature is severely impacted and thus driven into the plastic regime.
Accepted for publication 22 November 1996 相似文献
13.
IntroductionTheproblemofdelaminationbucklingofcompositelaminateshasgeneratedsignificantresearchinterestsandhasbeenthesubjectofmanytheoreticalinvestigationsinthisdecade.Afiniteelementmodel[1]waspresentedtosolvethepost_bucklingproblemofcompositeplateswit… 相似文献
14.
We demonstrate the new specific phenomenon of the long-time resonant energy exchange in the carbon nanotubes (CNTs) in the two optical branches - the Circumferential Flexure Mode (CFM) and Radial Btreathing Mode (RBM). It is shown that the modified nonlinear Schrödinger equation, obtained in the framework of nonlinear elastic thin shell theory, allows to describe the CNT nonlinear dynamics connected with considered frequency bands. Comparative analysis of the oscillations of the CFM and RBM branches shows the principal difference between nonlinearity effects. If the nonlinear resonant interaction of the low-frequency modes in the CFM branch leads to the energy capture in the some domain of the CNT, the same interaction in the RBM branch does not appear any tendency to the energy localization. The reason of such a distinction is the difference of the non-linear terms in the equations of motion. If the CFMs are specified by the soft power nonlinearity, the RBM dynamics is determined by the hard gradient nonlinearity. Moreover, in contrast to CFM the importance of nonlinearity in the case of RBM oscillations decreases with increasing of the length to radius ratio. The numerical integration of the thin shell theory equations confirms the results of the analytical study. 相似文献
15.
E. K. Ankyanets 《International Applied Mechanics》2005,41(10):1177-1181
The vibrations of a cylindrical shell reinforced with circular ribs attached to it by means of discrete elastic elements are
studied. The problem is solved by the finite-element method. The shell and ribs are modeled by a plane four-node finite element,
which is a combination of a four-node plane stress element and a four-node flexural element. The effect of the stiffness of
the elastic elements on the natural frequencies and modes is examined
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Translated from Prikladnaya Mekhanika, Vol. 41, No. 10, pp. 108–113, October 2005. 相似文献
16.
We investigate the control of friction-induced vibrations in a system with a dynamic friction model which accounts for hysteresis in the friction characteristics. Linear time-delayed position feedback applied in a direction normal to the contacting surfaces has been employed for the purpose. Analysis shows that the uncontrolled system loses stability via. a subcritical Hopf bifurcation making it prone to large amplitude vibrations near the stability boundary. Our results show that the controller achieves the dual objective of quenching the vibrations as well as changing the nature of the bifurcation from subcritical to supercritical. Consequently, the controlled system is globally stable in the linearly stable region and yields small amplitude vibrations if the stability boundary is crossed due to changes in operating conditions or system parameters. Criticality curve separating regions on the stability surface corresponding to subcritical and supercritical bifurcations is obtained analytically using the method of multiple scales (MMS). We have also identified a set of control parameters for which the system is stable for lower and higher relative velocities but vibrates for the intermediate ones. However, the bifurcation is always supercritical for these parameters resulting in low amplitude vibrations only. 相似文献
17.
18.
Yu. V. Skosarenko 《International Applied Mechanics》2006,42(3):325-330
This paper outlines a technique of determining the natural frequencies and modes of an elastic structure consisting of a cylindrical
shell and noncrossing rectangular plates inserted into it. The influence of the position, number, and thickness of the plates
on the natural frequencies and modes is analyzed
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Translated from Prikladnaya Mekhanika, Vol. 42, No. 3, pp. 89–96, March 2006. 相似文献
19.
D. A. Khodzhaev B. Kh. Éshmatov 《Journal of Applied Mechanics and Technical Physics》2007,48(6):905-914
The problem of vibrations of a viscoelastic plate with concentrated masses is studied in a geometrically nonlinear formulation.
In the equation of motion of the plate, the action of the concentrated masses is taken into account using Dirac δ-functions.
The problem is reduced to solving a system of Volterra type ordinary nonlinear integrodifferential equations using the Bubnov-Galerkin
method. The resulting system with a singular Koltunov-Rzhanitsyn kernel is solved using a numerical method based on quadrature
formulas. The effect of the viscoelastic properties of the plate material and the location and amount of concentrated masses
on the vibration amplitude and frequency characteristics is studied. A comparison is made of numerical calculation results
obtained using various theories.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 6, pp. 158–169, November–December, 2007. 相似文献
20.
M. Dimentberg 《Nonlinear dynamics》1996,11(4):401-405
A single-degree-of-freedom (SDOF) system with bilinear restoring force and damping characteristics is excited by a white-noise force. For the case of small damping the asymptotic method of quasi-conservative stochastic averaging is applied, which reduces the problem to that of a single Ito stochastic differential equation (SDE) for total energy of the response. A special case of the isochronous system is considered, where the static equilibrium position coincides with the slope discontinuity point of the system's characteristics, such as that of a moored body without slack and pretension in the mooring cable. For this case an analytical solution is obtained for autocorrelation function of the response energy. For the limiting case of a vibroimpact system the results are shown to agree with the exact solution. 相似文献