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1.
A reduction of friction by vibrations has been observed in various experiments. This effect can be applied to actively control
frictional forces by modulating vibrations. Moreover, common methods of controlling friction rely on lubricants and suitable
material combinations. The superimposition of vibrations can further reduce the friction force. This study presents a theoretical
approach based on the Dahl friction model that describes the friction reduction observed in the presence of the tangential
vibrations at an arbitrary angle. Analysis results indicated that the tangential compliance should be considered in modeling
the effect of vibrations in reducing friction. At any vibration angle, the tangential compliance of the contacts reduces the
friction reduction effect. The vibrations parallel to the macroscopic velocity are most effective for friction reduction. 相似文献
2.
Summary The paper investigates two important aspects, friction and spring motion, of the dynamics of a spring-actuated cam system.
The characteristics of the friction on the camshaft are analyzed using the nonlinear pendulum experiment, while the parameters
of the friction model are estimated using the optimization technique. The analysis reveals that the friction of the camshaft
depends on stick–slip, Stribeck effect and viscous damping. Spring elements are found to have much influence on the dynamic
characteristics. Hence, they are modeled as four-degrees-of-freedom lumped masses with equivalent springs. The lumped masses
and equivalent springs are obtained to match the static stiffness and natural frequency of the actual spring. The appropriateness
of the derived friction and spring model are verified by its application to a vacuum circuit-breaker mechanism of the cam-follower
type.
Received 23 March 2000; accepted for publication 21 November 2000 相似文献
3.
I. Sevostianov V. Levin M. Kachanov 《Archive of Applied Mechanics (Ingenieur Archiv)》2001,71(11):733-747
Summary Piezoelectric transversely isotropic matrix containing spheroidal piezoelectric inclusions with different properties and
of, generally, diverse aspect ratios is considered. A full set of ten effective electrostatic constants is derived, using
the method of effective field. The case, when the inclusions are circular cylinders (fibers) is analyzed in detail. The results
are compared with those of several earlier works. They constitute the theoretical framework for the design of piezocomposites
with prescribed overall properties.
Received 3 May 2001; accepted for publication 26 June 2001 相似文献
4.
Discontinuous fold bifurcations in mechanical systems 总被引:1,自引:0,他引:1
Summary This paper treats discontinuous fold bifurcations of periodic solutions of discontinuous systems. It is shown how jumps in
the fundamental solution matrix lead to jumps of the Floquet multipliers of periodic solutions. A Floquet multiplier of a
discontinuous system can jump through the unit circle, causing a discontinuous bifurcation. Numerical examples are treated,
which show discontinuous fold bifurcations. A discontinuous fold bifurcation can connect stable branches to branches with
infinitely unstable solutions.
Received 20 September 2000; accepted for publication 26 June 2001 相似文献
5.
Statistics of ultrasonic speckles reflected from a rough surface 总被引:1,自引:0,他引:1
Summary First- and second-order statistical properties of ultrasonic speckles reflected from a rough interface are studied theoretically
and experimentally in this paper. A theoretical model for predicting statistical properties of ultrasonic speckles is constructed,
based on the Fresnel-Huygens principle and three basic assumptions. Distributions of the amplitude and phase of ultrasonic
speckles in a scattering space are studied; the study shows that they are in the form of Rayleigh and uniform distribution,
respectively. Using the proposed model, the average transverse size of the speckles within a scattering domain, which are
received by a focus probe, is investigated. The average transverse size is found to be dependent on the characteristics of
the measuring system only, and does not vary with the position in the domain. To verify the applicability of the theoretical
model, a special experimental set-up was designed. The corresponding experiments were conducted for measuring the sound pressure
of the ultrasonic speckles reflected from a rough interface between water and aluminium alloy. The numerical results are compared
with the experimental ones. The comparison demonstrates that the theoretical model and the three related assumptions are suitable
for analysing statistical properties of ultrasonic speckles reflected from a rough interface.
Received 26 January 2001; accepted for publication 27 November 2001
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ID=" This work was supported by National Natural Science Foundation of China under project 10074017. 相似文献
6.
Summary This paper concerns the application of the constant deflection-contour method to problems involving nonlinear vibrations.
Two specific problems are considered: a clamped circular plate and an annular plate with free inner boundary. For the linear
case, the results obtained offer excellent agreement with previous studies, indicating significant potential for the utilization
of this method in different nonlinear cases. The analysis may be applied to other types of geometrical structures. Notwithstanding
the fact that only a first-term approximation has been made for the deflection function, in conjunction with the Galerkin
procedure, excellent agreement has been found. Additional analytical calculations could be made to improve accuracy, indicating
that the method could prove particularly useful when employed with a symbolic manipulation package.
Received 13 June 2001; accepted for publication 6 November 2001 相似文献
7.
X.-F. Li 《Archive of Applied Mechanics (Ingenieur Archiv)》2003,72(10):745-758
Summary The dynamic problem of an impermeable crack of constant length 2a propagating along a piezoelectric ceramic strip is considered under the action of uniform anti-plane shear stress and uniform
electric field. The integral transform technique is employed to reduce the mixed-boundary-value problem to a singular integral
equation. For the case of a crack moving in the mid-plane, explicit analytic expressions for the electroelastic field and
the field intensity factors are obtained, while for an eccentric crack moving along a piezoelectric strip, numerical results
are determined via the Lobatto–Chebyshev collocation method for solving a resulting singular integral equation. The results
reveal that the electric-displacement intensity factor is independent of the crack velocity, while other field intensity factors
depend on the crack velocity when referred to the moving coordinate system. If the crack velocity vanishes, the present results
reduce to those for a stationary crack in a piezoelectric strip. In contrast to the results for a stationary crack, applied
stress gives rise to a singular electric field and applied electric field results in a singular stress for a moving crack
in a piezoelectric strip.
Received 14 August 2001; accepted for publication 24 September 2002
The author is indebted to the AAM Reviewers for their helpful suggestions for improving this paper. The work was supported
by the National Natural Science Foundation of China under Grant 70272043. 相似文献
8.
M. Abu-Hilal 《Archive of Applied Mechanics (Ingenieur Archiv)》2003,72(9):637-650
Summary The transverse vibrations of elastic homogeneous isotropic beams with general boundary conditions due to a moving random
force with constant mean value are analyzed. The boundary conditions considered are: pinned–pinned, fixed–fixed, pinned–fixed,
and fixed–free. Based on the Bernoulli beam theory, the problem is described by means of a partial differential equation.
Closed-form solutions for the variance and the coefficient of variation of the beam deflection are obtained and compared for
three types of force motion: accelerated, decelerated and uniform. The effects of beam damping and speed of the moving force
on the dynamic response of beams are studied in detail.
Received 3 December 2001; accepted for publication 30 April 2002 相似文献
9.
Summary The thermal instability of a Rivlin–Ericksen fluid in a porous medium is considered in the presence of a uniform vertical
magnetic field to include the effect of Hall currents. For the case of stationary convection, the magnetic field has a stabilizing
effect on the system, whereas the Hall current has a destabilizing effect on the system. The medium permeability has both
stabilizing and destabilizing effects, depending on the Hall parameter M. The kinematic viscoelasticity has no effect on stationary convection. Graphs have been plotted by giving numerical values
to the parameters, to depict the stability characteristics. The magnetic field (and corresponding Hall currents) introduces
oscillatory modes in the system, which would be nonexistent in their absence. The sufficient conditions for the nonexistence
of overstability are also obtained.
Received 20 May 1999; accepted for publication 8 March 2000 相似文献
10.
Summary The problem of an interface edge crack between two bonded quarter-planes of dissimilar piezoelectric materials is considered
under the conditions of anti-plane shear and in-plane electric loading. The crack surfaces are assumed to be impermeable to
the electric field. An integral transform technique is employed to reduce the problem under consideration to dual integral
equations. By solving the resulting dual integral equations, the intensity factors of the stress and the electric displacement
and the energy release rate as well as the crack sliding displacement and the electric voltage across the crack surfaces are
obtained in explicit form for the case of concentrated forces and free charges at the crack surfaces and at the boundary.
The derived results can be taken as fundamental solutions which can be superposed to model more realistic problems.
Received 10 November 2000; accepted for publication 28 March 2001 相似文献
11.
Summary In a hybrid laminate containing an interfacial crack between piezoelectric and orthotropic layers, the dynamic field intensity
factors and energy release rates are obtained for electro-mechanical impact loading. The analysis is performed within the
framework of linear piezoelectricity. By using integral transform techniques, the problem is reduced to the solution of a
Fredholm integral equation of the second kind, which is obtained from one pair of dual integral equations. Numerical results
for the dynamic stress intensity factor show the influence of the geometry and electric field.
Received 29 June 2001; accepted for publication 3 December 2001 相似文献
12.
S.-M. Kwon H.-S. Choi K.-Y. Lee 《Archive of Applied Mechanics (Ingenieur Archiv)》2002,72(2-3):160-170
Summary The steady-state of a propagation eccentric crack in a piezoelectric ceramic strip bonded between two elastic materials under
combined anti-plane mechanical shear and in-plane electrical loadings is considered in this paper. The analysis based on the
integral transform approach is conducted on the permeable crack condition. Field intensity factors and energy release rate
are obtained in terms of a Fredholm integral equation of the second kind. It is shown for this geometry that the crack propagation
speed has influence on the dynamic energy release rate. The initial crack branching angle for a PZT-5H piezoceramic structure
is predicted by the maximum energy release rate criterion.
Received 23 January 2001; accepted for publication 18 October 2001 相似文献
13.
Summary Transversal vibrations of a uniformly moving two-mass oscillator on a Timoshenko beam of infinite length supported by a viscoelastic
foundation are studied. By using integral transforms, the characteristic equation for the oscillator's vibrations is obtained.
It is shown that the equation may have a root with a positive real part. The existence of such a root leads to the exponential
increase of the amplitude of the oscillator vibrations, i.e. to instability. The reasons for the instability to occur are
discussed. By employing the method of D-decomposition, the instability domains are found in the space of the system parameters.
Received 30 October 2000; accepted for publication 28 March 2001 相似文献
14.
Electro-mechanical analysis of an interfacial crack between a piezoelectric and two orthotropic layers 总被引:1,自引:0,他引:1
Summary The problem of an interfacially cracked three-layered structure constructed of a piezoelectric and two orthotropic materials
is analyzed using the theory of linear piezoelectricity and fracture mechanics. Anti-plane shear loading is considered, and
the integral transform technique is used to determine the stress intensity factor. Numerical examples show the electro-mechanical
effects of various material combinations and layer thicknesses on the stress intensity factor. Interesting results are obtained
in comparison with earlier solutions for interfacially cracked piezoelectric structures.
Received 29 December 2000; accepted for publication 3 May 2001 相似文献
15.
Summary In automotive traction drives, power is transmitted by friction forces. The friction forces result from the shear stresses
developed in lubricated and highly loaded contacts between rolling bodies. Due to the kinematics of a traction drive, shear
velocities occur in both the rolling direction and perpendicular to it. Due to these shear velocities and by normal pressure,
the lubricant is forced to build up shear stresses. The increase of the shear stresses may be modelled by a nonlinear viscous
element. The describing differential equations are coupled by the equivalent shear stress, which defines the nonlinear behaviour
of the element. A fast method is described to evaluate the coupled differential equations. By using a known analytical approximation
for the equivalent shear stress, the differential equations are decoupled and can be solved analytically. In an iterative
procedure the equivalent shear stress is updated, and the complete solution is found. The iterative method is extended to
account for thermal effects in the contact.
Received 17 June 1999; accepted for publication 26 October 1999 相似文献
16.
Summary A piezoelectric layer bonded to the surface of an elastic structure is considered. The piezoelectric and the elastic layers
are infinite along the x-axis and have finite thickness in the y-direction. The polarization direction of the piezoelectric material is along the y-axis. By means of the method of singular integral equations, the solution in a Laplace transform plane is demonstrated. Laplace
inversion yields the results in the time domain. Numerical values of the crack tip fields under in-plane transient electromechanical
loading are obtained. The influence of layers thickness on stress and electric displacement intensity factors is investigated.
Received 16 March 2000; accepted for publication 16 August 2000 相似文献
17.
Transient response of an insulating crack between dissimilar piezoelectric layers under mechanical and electrical impacts 总被引:1,自引:0,他引:1
Summary The dynamic response of an interface crack between two dissimilar piezoelectric layers subjected to mechanical and electrical
impacts is investigated under the boundary condition of electrical insulation on the crack surface by using the integral transform
and the Cauchy singular integral equation methods. The dynamic stress intensity factors, the dynamic electrical displacement
intensity factor, and the dynamic energy release rate (DERR) are determined. The numerical calculation of the mode-I plane
problem indicates that the DERR is more liable to be the token of the crack growth when an electrical load is applied. The
dynamic response shows a significant dependence on the loading mode, the material combination parameters as well as the crack
configuration. Under a given loading mode and a specified crack configuration, the DERR of an interface crack between piezoelectric
media may be decreased or increased by adjusting the material combination parameters. It is also found that the intrinsic
mechanical-electrical coupling plays a more significant role in the dynamic fracture response of in-plane problems than that
in anti-plane problems.
Received 4 September 2001; accepted for publication 23 July 2002
The work was supported by the National Natural Science Foundation under Grant Number 19891180, the Fundamental Research Foundation
of Tsinghua University, and the Education Ministry of China. 相似文献
18.
Summary The paper presents an efficient two-dimensional approach to piezoelectric plates in the framework of linear theory of piezoelectricity.
The approximation of the through-the-thickness variations accounts for the shear effects and a refinement of the electric
potential. Using a variational formalism, electromechanically coupled plate equations are obtained for the generalized stress
resultants as well as for the generalized electric inductions. The latter are deduced from the conservative electric charge
equation, which plays a crucial role in the present model. Emphasis is placed on the boundary conditions at the plate faces.
The model is used to examine some problems for cylindrical bending of a single simply supported plate. Number of situations
are examined for a piezoelectric plate subject to (i) an applied electric potential, (ii) a surface density of force, and
(iii) a surface density of electric charge. The through-thickness distributions of electromechanical quantities (displacements,
stresses, electric potential and displacement) are obtained, and compared with results provided by finite element simulations
and by a simplified plate model without shear effects. A good agreement is observed between the results coming from the present
plate model and finite element computations, which ascertains the effectiveness of the proposed approach to piezoelectric
plates.
Received 17 July 2000; accepted for publication 26 September 2000 相似文献
19.
Noncontact measurement of internal temperature distribution in a solid material using ultrasonic computed tomography 总被引:1,自引:0,他引:1
Numerical simulations and experiments have been carried out for a noncontact measurement of the internal temperature distribution in a solid material using ultrasonic computed tomography (CT). The method is based on the fact that the sound propagation velocity in a material depends on its temperature as well as its density and structure. From the numerical simulations, the convolution method is found to be an effective algorithm for the reconstruction of the sound velocity distribution. To obtain an accurate temperature distribution, it is found to be necessary to measure the sound propagation time with a resolution of 1 ns. In the experiments, the temperature distributions are measured in an agar-gel cylinder of 40 mm in diameter, along the center axis of which a platinum wire with 0.1 mm in diameter is located. By comparing the experimental results with the theoretical ones, the temperature distribution inside the agar-gel can be reconstructed with an error of 0.1 K, except for the region close to the platinum heater wire where temperature gradient is high. Further, the effects of an obstacle to the sound propagation, such as an acrylic resin cylinder inside the agar-gel, are investigated. Although the obstacles causes a part of projection to be missed, by using a linear-interpolation method to compensate for the incomplete projection, the temperature distribution can be reconstructed well but with a little larger error of 0.2 K, except for the regions close to the platinum heater wire and obstacle. 相似文献
20.
F. I. Stepanov 《Journal of Applied Mechanics and Technical Physics》2015,56(6):1071-1077
The axisymmetric contact problem of sliding of two solid parabolic indenters on a viscoelastic half-space with constant velocity is considered. Shear stresses modeling the adhesive component of the friction force act in the contact area. The model of the foundation material is described by an integral operator with an exponential kernel characterized by one relaxation time. The problem is solved by the boundary element method. The dependences of the contact characteristics on the sliding velocity, the normal load, and the distance between the centers of the indenters is analyzed. The results can be used to study the effect of the roughness elements modeled by two indenters on the contact characteristics and the deformation component of the friction force. 相似文献