Cylindrical Vibration Research Articles

Investigation of coupled response on cylindrical eccentricity induced vibration and flow induced vibration

The eccentric vibration and flow induced vibration of the drilling pipe is closely related to the safety of drilling engineering. To reveal the influence of eccentric vibration of the drilling pipe on the flow induced vibration, the effects of the eccentricity on the vibration characteristics of cylindrical flow induced vibrations are emphatically concerned in this paper. Combining the eccentric vibration model and the cylindrical flow induced vibration model, a coupled vibration model is established. The results show that the peak amplitude of the cylinder rises with the increase of the eccentric ratio. The vibration contains both the hydrodynamic frequency and the eccentric frequency, and the eccentric frequency gradually becomes the dominant frequency with the increasing eccentric ratio. The hydrodynamic frequency is locked at 1/2 rotation frequency due to the eccentricity. Eccentricity leads to phase differences in fluid force coefficients and displacements and a weakened correlation between fluid forces and displacements. The wake patterns show a tendency from 2S to P+S and finally to multi-vortex shedding with increasing eccentric ratio, which is the same as the trend of rising amplitude. Both the periodicity of the cylindrical vibrations and the stability of the wake flow decrease with the evolution of the wake flow.

Investigation of the combined effect of control rods and forced rotation on a cylinder

A novel structure combining the application of control rods and forced rotation on a cylinder is proposed based on the cylindrical vibration suppression, and the combined structure is numerically simulated at a low Reynolds number of 200, an attack angle of 0°–105°, and a rotation rate of 0−1. The vortex-induced vibration responses, fluid forces, and cylindrical wake evolution are analyzed, and the VIV suppression is compared and discussed. The results show that the merging of the vortex layers on the cylinder and control rods promotes cylindrical vortex shedding, causing a high amplitude cylinder response. The cylinder vibrates at a low amplitude for no vortex layer merging. Rotation causes increased directional sensitivity of the control rod to cylindrical amplitude suppression. A 98%-cylinder amplitude suppression can be achieved by combining the control rod and rotation, while only 60% can be achieved by the control rods or rotation alone, indicating that the combined structure is highly effective for amplitude suppression.

Longitudinal-transverse (“breathing”) vibration modes of orthotropic plates with and without account of its interaction with the surrounding acoustic media

Based on the previously obtained improved equations of motion, the problem of free cylindrical vibration of a hingedly supported plate surrounded by acoustic media is considered. Plate motion equations are obtained taking into account the internal friction of the plate material according to the Kelvin – Voigt model. The motion of acoustic media is described by two-dimensional generalized Helmholtz wave equations, compiled taking into account the internal dissipation of energy by introducing into consideration the complex sound velocity according to Skudrzyk. Based on the obtained solution, a study of resonant nonclassical shearless longitudinal-transverse (“breathing”) forms of free vibrations has been carried out at various values of the physical-mechanical properties of the plate material and the parameter characterizing energy dissipation in the acoustic media surrounding the plate.

Temperature dependence of mode coupling effect in piezoelectric vibrator made of [001]c-poled Mn-doped 0.24PIN–0.46PMN–0.30PT ternary single crystals with high electromechanical coupling factor**Project supported by the Basic Scientific Research Foundation of College and University in Heilongjiang Province, China (Grant No. 2018QNL-16), the Guiding Science and Technology Project of Daqing City (GSTPDQ), China (Grant No. zd-2019-03), and the National Natural Science Foundation

The influence of temperature on mode coupling effect in piezoelectric vibrators remains unclear. In this work, we discuss the influence of temperature on two-dimensional (2D) mode coupling effect and electromechanical coupling coefficient of cylindrical [001]c-poled Mn-doped 0.24PIN–0.46PMN–0.30PT piezoelectric single-crystal vibrator with an arbitrary configuration ratio. The electromechanical coupling coefficient kt decreases with temperature increasing, whereas k33 is largely invariant in a temperature range of 25 °C–55 °C. With the increase of temperature, the shift in the ‘mode dividing point’ increases the scale of the poling direction of the piezoelectric vibrator. The temperature has little effect on coupling constant Γ. At a given temperature, the coupling constant Γ of the cylindrical vibrator is slightly greater than that of the rectangular vibrator. When the temperature changes, the applicability index (M) values of the two piezoelectric vibrators are close to 1, indicating that the coupling theory can be applied to piezoelectric vibrators made of late-model piezoelectric single crystals.

Low Frequency Vibration Isolation Performance of the Plate with Periodic Cylindrical Oscillators

The paper is devoted to the vibration reduction and isolation performance of a periodic structure with cylindrical vibrators. A plate with periodic oscillators was investigated using finite element technic. In the finite element analysis, test specimens were modelled with finite element software. With appropriate geometric and material parameters, the structure can obtain elastic wave band gaps, where vibrations are prohibited. So, the structure can be regarded as a kind of vibration isolation material. The dispersion curve and transmission spectrum of the structure were calculated to find the range of the band gaps. Both the longitudinal vibration and flexural vibration of the plate are studied. The results show that the designed plate with proper parameters has a low frequency range of band gaps. It has a wide application prospect in the field of low frequency vibration isolation.

Flexural Vibrations of a Plate under Changes in the Mean Pressure on Its Surfaces

Abstract—The influence of the mean excess pressure on a cylindrical static bend and vibrations of a plate is studied. Increasing and decreasing this pressure lead to a decrease and increase in deflection, respectively. In the first case, the plate shape stabilizes under the action of longitudinal forces, while in the second case, destabilization takes place. The critical value of the mean pressure is determined. The dynamic modes of plate deformation under a sharp increase and decrease in pressure are analyzed. In the first case, vibrations with increased frequency are excited, while in the second case, the excited vibrations have a reduced frequency compared to the natural frequency of the unloaded plate. For deep evacuation, an exponential increase in deflection with time is observed. A method for solving the problem for complex pressure changes has been developed.

Open Loop Active Control Technique on Segmented Marine Riser Vibration Using Electromechanical Actuator

Recently, works have been focusing on suppression of the segmented cylindrical marine riser vibration caused by vortex-induced vibration experimentally as an open loop active vibration control (OLAVC) model. The main objective of this research is employing the OLAVC theory using double control rods driven by double motors as an electromechanical actuator at two locations which are: control rods located beside (CRBR) and in front–back (CRFBR) to the riser. Passive control technique has been verified before employing the power to the motor for both locations. The electromechanical actuators consisted of double control rods driven by double motors (12 V DC) and connected by couplings. The results revealed that the passive control technique was inadequate to suppress the cylinder vibration in both locations. Therefore, OLAVC techniques were developed with four voltages: 6, 8, 10, and 12 V which are, respectively, equivalent to 50, 75, 83, and 100% of the motor power to rotate the control rods. Eventually, a motor counter-clockwise (CCW) direction of rotation provided a better suppression compared with the clockwise direction. Moreover, an OLAVC system seemed to be adequate to reduce the vibration at all the supplied voltages at CCW direction and the maximum suppression has been obtained at 12 V for all actuator positions and water flow speeds where the maximum vibration suppressed up to 65.13 and 69.81% at the CRFBRP and CRBRP positions, respectively, with superior performance of CRBR position.

Detachment of electrons from atmospheric oxygen molecules in a high electric field

The results of experiments on the electrical breakdown of air in a quasi-optical microwave beam with a deeply subcritical initial field have been reported. Breakdown has been initiated by a cylindrical vibrator with spherically rounded ends and a vibrator with a tapered end. The experimental data suggest that the amount of initial breakdown-initiating electrons in a breakdown area can be provided by the detachment of electrons from atmospheric oxygen molecules. The effect of detachment depends on the field strength.

Freezing of gait in Parkinson’s disease: Evidence of sensory rather than attentional mechanisms through muscle vibration

IntroductionThe role of proprioceptive integration impairments as the potential mechanism underlying Freezing of gait (FOG) in Parkinson’s disease (PD) is still an open debate. The effects of muscle vibration (a well-known manipulation of proprioception) could provide the answer to the debate. The aim of this study was to determine whether proprioceptive manipulation, through muscle vibration, could reduce FOG severity. MethodsSixteen PD patients who experience FOG were required to walk with small step lengths (15 cm). Cylindrical vibration devices were positioned on triceps surae tendon. Three vibration conditions were tested: No vibration (OFF), vibration on the less affected limb (LA), or on the more affected limb (MA). Additionally, we assessed the effects of applying vibration before and after FOG onset. The FOG duration and the foot used to take the next step were assessed. ResultsFOG significantly decreased only with vibration of LA in comparison to OFF, and when vibration was applied after FOG onset. ConclusionOur results show that muscle vibration is a promising technique to alleviate the severity of FOG. Improvements to FOG behavior were restricted to the less affected limb, suggesting that only the less damaged side of the basal ganglia may have preserved capacity to process sensory feedback. These results also suggest the likelihood of sensory deficits in FOG that cannot be explained by cognitive mechanisms, since vibration effects were only observed unilaterally.

Cylindrical Bending and Vibration of Polar Material Laminates

This article considers a plane strain problem, which is known in conventional linear elasticity as cylindrical bending of simply supported plates and cross-ply laminates. By considering fibrous composites containing fibers resistant to bending, it formulates and solves corresponding polar elasticity equations governing the static and dynamic behavior of beam-like components made of a homogeneous or layered transversely isotropic material; each layer has embedded a single family of fibers. Fiber bending stiffness is accounted for through involvement of an extra elastic modulus, which, unlike its conventional elasticity counterparts that have dimensions of stress, has dimensions of force. Its involvement in the analysis implies existence of some intrinsic material area or length parameter, which may be associated, for instance, with fiber thickness of fiber spacing. A considerable amount of relevant numerical results are presented for thick beam components made of either homogeneous or two-layered transversely isotropic material. For the static bending problem, these include a detailed presentation of through-thickness distributions of displacements, stresses, as well as couple-stress. For the dynamic problem, attention is focused on the influence that fiber bending stiffness exerts on fundamental frequency parameters.

Random Vibration Spectrum Analysis Based on Finite Element Method of High-Pressure Cylindrical Cylinders

In order to solve the vibration problems of car high-pressure cylindrical cylinders, Plate and Shell Vibration Theory is used for the calculation and analysis of the vibration characteristics. The vibration frequencies and modes of such cylinders are obtained. At the same time, the corresponding results are gotten through ANSYS12.0 simulation calculation. The similarities and differences of the both vibration frequencies and the changes of the respective modes are compared and analyzed to support the farther safety performance analysis of such cylinders in the vibration environment.

Vibration Analysis of High-Pressure Cylindrical Cylinders

In order to solve the vibration problems of car high-pressure cylindrical cylinders, Plate and Shell Vibration Theory is used for the calculation and analysis of the vibration characteristics. The vibration frequencies and modes of such cylinders are obtained. At the same time, the corresponding results are gotten through ANSYS12.0 simulation calculation. The similarities and differences of the both vibration frequencies and the changes of the respective modes are compared and analyzed to support the farther safety performance analysis of such cylinders in the vibration environment.

Multi-dimensional extreme learning machine

As an important branch of neural network, extreme learning machines (ELMs) have attracted wide interests in the fields of pattern classification and regression estimation. However, when facing learning problems with multi-dimensional outputs, named multi-dimensional regression, the conventional ELMs could not generally get satisfactory results because it is incapable of exploiting the relatedness among outputs efficiently. To solve this problem, a new regularized ELM is firstly proposed in this paper by introducing a hyper-spherical loss function as regularizer. As the regularization form with this loss function cannot be solved directly, an solution with iterative procedure is presented. For improving the learning performance, the algorithm proposed above is further reformulated to identify the inner grouping structure hidden in outputs by assuming that the grouping structure is determined by different linear combinations of a small number of latent basis neurons. This is achieved as a mixed integer programming, and finally an alternating minimization method is presented to solve this problem. Experiments on two multi-dimensional data sets, a toy problem and a real-life dynamical cylindrical vibration data set, are conducted, and the results demonstrate the effectiveness of the proposed algorithm.

Mathematical modelling of cylindrical electromagnetic vibration energy harvesters

In this paper the first steps for the derivation of a mathematical model to describe the mechanical behaviour of a cylindrical electromagnetic vibration energy harvester, designed to extract energy from human gait to power biomedical implantable devices, are provided. As it is usual, in the modelling of such devices, the proposed mechanical model is also based on the solution of Newton's second law, but here a nonlinear closed-form expression is used for the resulting magnetic force of the system, unlike what has been done in previous works where, traditionally, that expression is a linear or is a nonlinear approximation of the real one. The main feature of this mechanical model is that it depends on several parameters which are related to the main characteristics of this kind of devices, which constitutes a major advantage with respect to the usual models available in the literature since these characteristics can always be changed in order to optimize the device.

On the Validity of Flat-Plate Finite Strip Approximation of Circular Cylindrical Shells

The validity of modeling curved shell panels using flat-plate finite strips has been demonstrated in the past by comparing finite strip numerical results with analytical solutions of a few benchmark problems; to date, no mathematical exact solutions of the method or its explicit forms of error terms have been rigorously derived to demonstrate analytically its validity. Using a unitary transformation approach (abbreviated as the U-transformation herein), an attempt is made in this paper to derive mathematical exact solutions of flat-plate finite strips in cylindrical shell vibration analysis. Unlike the conventional finite strip method which involves assembly of the global system of matrix equation and its numerical solution, the U-transformation method makes use of the inherent cyclic symmetry of cylindrical shells to decouple the global matrix equation into one involving only a few unknowns, thus rendering explicit form of solutions for the flat-shell finite strip to be derived. Such explicit solutions can be subsequently expanded into Taylor's series whose results reveal directly their convergence to the exact solutions and the corresponding rate of convergence.

Noise Radiation Measure-Sound Power and its Test Methods

This study mainly aims to study the characteristics and theory of sound radiation of steady-state vibration. Study shows that sound radiation power of steady-state vibration is constant. And taking excavator for experimental object by hemisphere surface method, the radiated sound power of the excavator is the same as testing the sound pressure on various surfaces based on relevant international standard. Finally, a test method of radiated sound power for cylindrical vibration object is proposed.

Intrinsic mode characteristic analysis and extraction in underwater cylindrical shell acoustic radiation

Target dimension is important information in underwater target classification. An intrinsic mode characteristic extraction method in underwater cylindrical shell acoustic radiation was studied in this paper based on the mechanism of shell vibration to gain the information about its dimension instead of accurate inversion processing. The underwater cylindrical shell vibration and acoustic radiation were first analyzed using mode decomposition to solve the wave equation. The characteristic of acoustic radiation was studied with different cylindrical shell lengths, radii, thickness, excitation points and fine structures. Simulation results show that the intrinsic mode in acoustic radiation spectrum correlates closely with the geometry dimensions of cylindrical shells. Through multifaceted analysis, the strongest intrinsic mode characteristic extracted from underwater shell acoustic radiated signal was most likely relevant to the radiated source radius. Then, partial information about unknown source dimension could be gained from intrinsic mode characteristic in passive sonar applications for underwater target classification. Experimental data processing results verified the effectiveness of the method in this paper.

Dynamic stiffness of hollowed cylindrical rubber vibration isolators — The wave-guide solution

The dynamic stiffness of hollowed cylindrical vibration isolators using a wave-guide modelling approach is given. The isolators consist of rubber and metal elements in series. The boundary conditions at the lateral and radial surfaces of each rubber component are locally non-mixed and simultaneously satisfied by using the modes corresponding to the dispersion relation for axial waves in infinite hollow cylinders while the metal plates are assumed rigid, following Newton’s second law. The modes of the rubber elements exactly satisfy the stress free boundary conditions at the curved radial boundaries, while the displacement conditions on the flat cylinder ends are satisfied in mean by a mode matching approach. The rubber is modelled as nearly incompressible with deviatoric visco–elasticity based on a fractional derivative, standard linear solid. The stiffness is found to depend strongly on frequency, displaying resonances and anti-resonances. Further, results indicate a great potential for optimising vibration isolators of the studied kind. By choosing appropriate combinations of metal plates and rubber elements, the dynamic transfer stiffness in higher frequency bands can be suppressed to be magnitudes lower than the static stiffness, a highly sought feature in vibration isolators. Finally, simplified models including mass-spring systems and the long rod theory are implemented and compared to the derived formulation.

Research on Energy Harvesting Behaviors of Different Shapes of Piezoelectric Vibrator

Shapes and geometry parameters of piezoelectric vibrator have a greatly influences on its energy harvesting ability. In this paper, both of static and modal characteristics of piezoelectric vibrators were respectively simulated by using the finite element analysis software Ansys, where influences from stress and the exciting force’s frequency on the outputting voltage of a cylindrical piezoelectric vibrator and a triangular cantilever piezoelectric vibrator were analyzed. The numerical simulation results show that its geometry sizes of triangular cantilever piezoelectric vibrator could result in its outputting voltage and first-order natural frequency’s shift, however, the exciting frequency of the external force has no any influences on its outputting voltage of the cylindrical vibrator. Besides, an optimized design was researched in order to improve its power generation capacity per unit volume for the triangular cantilever piezoelectric vibrator.

Induced field of an electromagnetic vibrator above a conducting screen placed in a microwave beam

The induced field of a cylindrical electromagnetic vibrator with spherically rounded ends is calculated. The vibrator is above a flat screen placed in a linearly polarized quasi-optical microwave beam. The plane of the screen is perpendicular to the Poynting vector of the radiation. The axis of the vibrator is aligned with the vector of the exciting field electrical component. In calculation, the length of the vibrator and the vibrator-screen distance were varied, while its diameter and the initial field were kept constant. It is found that the induced field of the vibrator with a length close to the half-wavelength of the field is maximal at the ends of the vibrator and the field strength resonantly depends on the length of the vibrator. The shortening of the “half-wavelength” vibrator that provides a maximal induced field is determined. The result of numerical simulation is to an extent intriguing. It is revealed that the induced field of a resonance half-wavelength vibrator rises considerably when the vibrator-screen distance becomes shorter than the quarter-wavelength of the field. The Q factor of an equivalent electromagnetic oscillating circuit characterizing the vibrator also grows, and the induced field more and more concentrates between the screen and the surface of the vibrator’s ends facing the screen. Full-scale experiments qualitatively support theoretical predictions. The results allow researchers to considerably extend the application area of vibrators as initiators of breakdown in high-pressure gases to ignite microwave discharges in quasi-optical beams with a low initial field.