Antiplane Problem of Electroelasticity for a Hollow Piezoceramic Cylinder Excited by a System of Surface Electrodes

An antiplane mixed boundary-value problem of electroelasticity is considered for a hollow piezoceramic cylinder with an arbitrary system of active surface electrodes generating its harmonic vibrations. The problem is solved using a method elaborated earlier for investigating vibrations of a solid piezoceramic cylinder with a system of active surface electrodes. The scheme of numerical solution of the obtained singular integro-differential equations of the boundary-value problem is based on the quadrature method. Calculation results are presented that describe the amplitude-frequency characteristics of a hollow cylinder and the behavior of some mechanical and electric quantities both within the cylinder and on its boundary.     

Free Cavitational Deceleration of a Circular Cylinder in a Liquid after Impact

The problem is considered about the vertical continuous impact and subsequent free deceleration of a circular cylinder semi-immersed in a liquid. The specificity of this problem is that, under certain conditions, some areas of low pressure near the body appear and the attached cavities are formed. The separation zones and the motion law of the cylinder are unknown in advance and have to be determined in solving the problem. The study of the problem is conducted by a direct asymptotic method effective for small spans of time. Some nonlinear problem with unilateral constraints is formulated that is solved together with the equation defining the law of motion of the cylinder. In the case when the space above the external free surface of a liquid is filled with a gas with low pressure (vacuum), an analytical solution of the problem is constructed. To determine the main hydrodynamic characteristics (the separation point and acceleration of the cylinder), we derive a system of transcendental equations with elementary functions. The solution of this system agrees well with the results obtained by the direct numerical method.     

A robot-balancer on a cylinder

The problem of stabilizing the equilibrium of a robot placed on a cylinder which can roll along a horizontal plane is investigated. There is no slip in any of the external contacts. Control is achieved by means of the electromechanical angular acceleration of a flywheel on the robot. Steady motions are studied. The basic procedures for stabilizing the robot in a vertical position are analysed in a non-linear formulation. It is shown that the corresponding linear system is completely controllable. A coordinate and velocity controller with saturation is constructed. The domain in which the system can be stabilized is found in connection with the boundedness of the control function. The effect of measurement errors is examined. The control characteristics are calculated for certain actual robot parameters.     

The antiplane problem of electroelasticity for a cylinder with a tunnel crack excited by an arbitrary system of surface electrodes

The antiplane mixed boundary-value problem of electroelasticity of the oscillations of an infinite piezoceramic cylinder, weakened by a curvilinear tunnel crack, is considered. Using special integral representations of the solution, the boundary-value problem is reduced to a system of singular integro-differential equations of the second kind with discontinuous kernels. The results of a numerical realization of the algorithm, characterizing the amplitude-frequency characteristics of a piecewise-uniform cylinder and the behaviour of the components of the electroelastic field in the region and on the boundary of the cylinder under conditions of the inverse piezoelectric effect, are presented.     

Antiplane strain of an elliptical cylinder with a crack

The antiplane strain of an anisotropic elliptical cylinder with a crack is examined. An infinite system of linear algebraic equations is obtained from the boundary conditions on the cylinder surface to determine the constants in the complex potential of the problem. Detailed numerical investigations are performed of the influence of the geometric and elastic characteristics of the cylinder on the magnitude of the stress intensity coefficients near the outer edge.Translated from Teoreticheskaya i Prikladnaya Mekhanika, No. 18, pp. 28–34, 1987.     

Method of homogeneous solutions in the mixed problem for a finite circular cylinder : PMM vol. 43, no. 6, 1979, pp. 1073–1081

The mixed axisymmetric problem of elasticity theory on the torsion of a finite circular cylinder by a stamp is considered. The stamp is fixed rigidly to one plane face of the cylinder, the other plane face is fixed, and conditions for no displacements or stresses are given on the cylinder surface. The problem is investigated by the method of homogeneous solutions [1], which permits obtaining its approximate solution for practically any values of the parameters. Such efficiency of the method is determined by the fact that the solution of the problem reduces to investigating an infinite algebraic system of the Poincaré — Koch normal systems type. When the ratio of the cylinder height to the radius of the stamp is sufficiently large, the system coefficients, the contact stresses, and the other characteristics of the problem are evaluated to any degree of accuracy, and effective asymptotic expressions are obtained for small values of this ratio. Results of numerical computations are presented.

A solution of the problem for the case of a large value of the ratio (R − a) /h and small values of the ratio λ = h / a is obtained in [2].     

Modelling and simulation of a sphere rolling on the inside of a rough vertical cylinder

A classical problem of nonholonomic system dynamics—the motion of a sphere on the inside of a rough vertical cylinder—is extended to rolling friction. The case study is modelled in independent coordinates. Due to the nonholonomic constraints imposed on the sphere, the governing equations arise as a set of differential-algebraic equations. The results of numerical simulations show the transition of the sphere from a sinusoid path on the vertical cylinder surface to a fall with slip. The physics of the ‘paradoxical’ motion is explained in detail.     

Vibrations of a cylinder in a concentric vessel filled with a two-layer fluid

A hybrid vibrational system containing a solid (a cylinder) with an elastic connection to a coaxial cylindrical cavity, completely filled with a heavy ideal stably stratified two-layer fluid, is considered. The combined self-consistent vibrations of the body and the fluid (of the internal waves) are studied. An explicit solution of the internal boundary value problem of an inhomogeneous liquid in an annular domain for a specified motion of the body is obtained. An integrodifferential equation of the Newton type is constructed on the basis of this. This equation describes the self-consistent oscillations of the cylinder. In the case of weak coupling of the interaction between the solid and the medium, an approximate solution is obtained using asymptotic methods and an analysis is carried out. Qualitative effects of the mutual effect of the motions of the cylinder and the fluid are found.     

Short-time dynamics of an elliptic cylinder moving in a viscous incompressible free-surface flow

The joint motion of a viscous incompressible fluid and a completely submerged elliptic cylinder is analyzed at short times. The cylinder is assumed to start from rest and move horizontally at a constant acceleration. A feature of the problem is that, at high accelerations, the fluid becomes detached from the cylinder surface and a cavity is formed. The problem is generalized to an elliptic cylinder floating on the surface of a viscous fluid.     

The scattering of acoustic waves by a cylinder with a non-uniform elastic coating

The problem of the scattering of a plane acoustic wave by a solid cylinder with a radially non-uniform elastic coating is considered. An analytical expression describing the scattered acoustic field is obtained. The equations of motion of the non-uniform elastic cylindrical layer are reduced to a system of ordinary differential equations, the boundary-value problem for which is solved by the power-series method. The results of calculations of the directional pattern of the scattered field are presented.     

The steady motion of an elastic cylinder compressed by a fixed shell

The steady mixed problem of the motion of a transversely isotropic elastic circular cylinder, compressed by a finite elastic shell, is solved by the method of piecewise-homogeneous solutions [1]. One of the relations of generalized orthogonality obtained for homogeneous solutions is used. Two special cases are considered: (1) a semi-infinite shell is placed on a movable cylinder with a specified negative allowance the edge of the shell is stress-free, and there is no preloading, and (2) a concentrated encircling load acts on the shell. The solution of the problem of a semi-infinite shell and the system of piecewise-homogeneous solutions are constructed in quadratures by the Wiener-Hopf method. (A similar problem was investigated in [2] in a static formulation. Steady mixed contact problems were investigated previously in [3–10]).     

Propagation of unsteady waves in a hollow magnetoelastic cylinder in contact with liquid media

A numerical-analytic solution is constructed for the problem of magnetoelasticity for a hollow cylinder immersed in a liquid and loaded from inside by an impulse-type axisymmetric mechanical pressure. Nonconducting and compressible internal and external media have different densities and elastic moduli, with their motion described by wave equations. The hollow cylinder is assumed to be an ideal conductor, and its motion is described by a linearized system of equations of magnetoelasticity; on internal and external boundaries, the conditions of conjugation hold. The problem is solved by the method of integral Laplace transforms in the time domain, and the inverse transforms are found by numerical inversion. The solutions obtained for the bounded problem are compared with solutions for a simplified unbounded problem.Translated from Teoreticheskaya i Prikladnaya Mekhanika, No. 18, pp. 83–87, 1987.     

Solution of an axisymmetric problem of free vibrations of piezoceramic hollow cylinders of finite length by the spline collocation method

An axisymmetric problem of longitudinal free vibrations of piezoceramic hollow cylinders for some types of boundary conditions on the end faces is considered. The lateral surfaces of the cylinder are covered with thin short-circuited electrodes. The polarization of piezoceramics is directed along the axis of the cylinder. Using the method of separation of variables and method of spline collocation along the length of the cylinder, we reduce the problem to a system of ordinary differential equations, which is solved by the method of step-by-step search. We present results of calculations for a PZT 4 piezoceramic cylinder.     

On a damped motion of a hydromechanical system

We obtain an exact solution to the problem of damped rotation of a solid cylinder and the surrounding viscous liquid which is at rest at infinity. We uncover a series of nontrivial characteristics of the dynamics of this hydromechanical system and establish in particular that the liquid can move faster than the boundary of the body.     

Packing cylinders on a cylinder with contact constraints

The problem of cylinder packing is investigated. The specific problem is to determine the maximum number of congruent cylinders that can be packed around a core cylinder of arbitrary dimensions. The constraint is that their circular face must keep in contact with the core cylinder and there may be no overlapping. Only right circular cylinders are considered. Mathematically, a lower and upper bound is determined. A quantitative result is also found using a modified genetic algorithm. The algorithm was found to reproduce the published results for the top and bottom circular faces of the core which reduces to the problem of packing congruent circles within a circle. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Cavity formation at the inclined separated impact on a circular cylinder under a free surface of a heavy liquid

Under study is a dynamic mixed problem concerning the impact on a circular cylinder and its subsequent movement with a constant speed in an ideal incompressible liquid. The influence is investigated of the physical and geometrical parameters of the problem on the cavity form and the configuration of the external free surface of the liquid for small times. An asymptotic analysis is carried out for the inner free boundary of liquid taking into account the dynamics of separation points. The reaction force of the medium on the cylinder is determined. The necessity is substantiated of introducing additional cavitation zones in the dynamic problem of impact.     

Numerical analysis of the dispersion of electroelastic waves in a cylinder whose physical properties have a longitudinal axis of symmetry

We develop a numerical method of analyzing the dispersion of electroelastic waves in a hollow circular cylinder. The method is based on the reduction of the wave problem to a spectral problem for a system of ordinary differential equations. This system is solved numerically. The roots of the dispersion equation are determined by the method of bisection. The practical convergence of the algorithm is shown using a specific example. One figure. Bibliography: 3 titles. Translated fromTeoreticheskaya i Prikladnaya Mekhanika, No. 28, 1998, pp. 151–156.     

Asymptotics of the reduced logarithmic capacity of a narrow cylinder

We consider the Dirichlet problem for the Laplace operator in the exterior of a narrow infinite cylinder with periodically varying directrix. The solution is sought in the class of functions logarithmically increasing as the distance from the cylinder is increased. The reduced logarithmic capacity is defined as a generalization of the logarithmic capacity (of the outer conformal radius).We construct and justify the asymptotics of the solution of the problem as the ratio of the diameter of the cross-section of the cylinder to its period tends to zero.     

Controlling chaos in a fluid flow past a movable cylinder

The model of a two-dimensional fluid flow past a cylinder is a relatively simple problem with a strong impact in many applied fields, such as aerodynamics or chemical sciences, although most of the involved physical mechanisms are not yet well known. This paper analyzes the fluid flow past a cylinder in a laminar regime with Reynolds number, Re, around 200, where two vortices appear behind the cylinder, by using an appropriate time-dependent stream function and applying non-linear dynamics techniques. The goal of the paper is to analyze under which circumstances the chaoticity in the wake of the cylinder might be modified, or even suppressed. And this has been achieved with the help of some indicators of the complexity of the trajectories for the cases of a rotating cylinder and an oscillating cylinder.     

Diffraction of a plane acoustic wave by a non-uniform thermoelastic cylindrical layer bounded by inviscid heat-conducting fluids

The diffraction of sound by a radially laminated isotropic thermoelastic cylindrical shell is considered. The system of equations for small perturbations of a hollow thermoelastic cylinder is reduced to a system of ordinary differential equations, the boundary-value problem for which is solved by the spline-collocation method. Expressions are obtained describing the wave field outside the cylindrical layer. Results of calculations of polar radiation patterns of the amplitude of the scattered acoustic wave in the far zone are presented.