Fifth international congress on sound and vibration

FifthillternationalcongressonsoundandvibrationwillbeheldatTheUniversityofAdelaide,SouthAustralia,Dec.15-18,l997.ThedeadllneforabstractsisMarch15,1997,andtheaddresstosendabstractsis'Dr.ColinHHansenSecretariatFifthinternationalCongressDept.ofMechanicalEngineeringUniversityofAdelaide,SouthAustralia5oo5,AUSTRALIAFifth international congress on sound and vibration…     

Influence of ultrasonic vibration on friction force

1IntroductionTheinIluenceofultrasonicvibrationonfrictionforceekistswidelyinmanyfields,includingultrasonicprocessing,ultrasonicweldingandultrasonicmotor.Accordingtotheclassicalslidingfrictiontheoryfrictionforceonlydependsonloadandmaterialproperty-IthasbeenprovdexperimeDtallythatabovetheorycanonlybeusedforaPpr~ation.UndermaDyconditions,especiallyunderultrasonicvibration,colitactarea,vibrationamplitude,slldingvelocity)etc.,alsoinIluencethefrictionforce.Moreandmorescholarspayattelltiontotheindu…     

Experimental studies on the vibration of perforated sheet

In the experiment we have measured the resonant frequencies of per-forated sheets with perforation rates from 0.008 to 0.30.Compared those fre-quencies with the corresponding resonant frequencies of homogeneous,orun-perforated one we obtained an empirical relationship between the resonantfrequency and perforation rate,which can be used for industrial purpose.Wehave also studied the change of vibrational energy distribution of perforatedsheet related to that of homogeneous.     

Enhancing vibration measurements by Mössbauer effect

The measurement of the Mössbauer effect in a system excited with a periodic perturbation can provide information about it. For that purpose, the Mössbauer absorption of a source-absorber set which hyperfine parameters are well known, is measured at a constant relative velocity (i.e. at a defined spectral energy). The resulting Mössbauer absorption periodic signal provides information of the sample ac perturbation response. This approach has been used time ago to measure small tympanic vibrations (mechanical perturbations). In this work we present an extension of the vibration experiments, by measuring them at various absorber-source relative velocities within a constant-velocity strategy. As a demonstration test, the frequency response of a piezoelectric diaphragm in the 100 Hz–5 kHz range is obtained with a custom electronic counter. The experiments are performed using a ⁵⁷Co(Rh) source and a 25- $\upmu$ m-thick stainless-steel absorber fixed to a piezoelectric diaphragm. Phase shifts and amplitude vibrations with velocities in the range from 1.5 $\upmu$ m/s to 20 mm/s are well characterized, extending the linearity limit well beyond the earlier suggested one of 1 mm/s.     

Non-linear theory of vibration and aesthetics of raga music

The non-linear theory of vibration has recently been applied toa number of problems in physics and was found to give many interestingresults which were absent in the case of linear vibration.It is natural tothink of the outcome of application of non-linear theory to raga music,atopic which has hitherto been unexplored.It has been found that a newrealm of musical idea is obtained if one considers the effects ofnon-linearity in physics on the understanding of the aesthetics and beautyin raga music when two notes are sounded simultaneously.     

Free vibration of non-uniform nanobeams using Rayleigh–Ritz method

In this article, boundary characteristic orthogonal polynomials have been implemented in the Rayleigh–Ritz method to investigate free vibration of non-uniform Euler–Bernoulli nanobeams based on nonlocal elasticity theory. Non-uniform cross section of nanobeams has been considered by taking linear as well as quadratic variations of Young's modulus and density along the space coordinate. Detailed analysis has been reported for all the possible cases of such variations. The objective of the present study is to analyze the effects of nonlocal parameter, boundary condition, length-to-diameter ratio and non-uniform parameter on the frequency parameters. It is found that clamped nanobeams are having highest frequency parameters than other types of boundary conditions for a particular set of parameters. It is also observed that frequency parameters decrease with increase in scaling effect parameter. First four deflection shapes of non-uniform nanobeams have also been incorporated. In this analysis, some of the new results in terms of boundary conditions have also been included.     

Free vibration of rectangular nanoplates using Rayleigh–Ritz method

Vibration analysis of isotropic rectangular nanoplates based on the classical plate theory in conjunction with Eringen's nonlocal elasticity theory is considered. Nanoplates are one of the structural units that are used in nanoscale applications. In this study, Rayleigh–Ritz method with algebraic polynomial displacement function is used to solve the vibration problem of isotropic rectangular nanoplates subjected to different boundary conditions. The advantage of the method is that one can easily handle the specified boundary conditions at the edges. A comparison of the results with those available in the literature has been made. The proposed method is also validated by convergence studies. Frequency parameters are given for different nonlocality parameters, length of nanoplates and boundary conditions. The study highlights that nonlocality effects increase with the increase in mode number and the influence of nonlocal effects becomes increasingly pronounced for higher order vibration modes. Three-dimensional mode shapes for the specified nanoplates have also been presented.     

Temperature-insensitive fiber cantilever vibration sensor based on a fiber-to-fiber structure

A simple optical fiber cantilever vibration sensor consisting of two opposite aligned bare optical fibers sealed in a quartz capillary is presented.The fiber with the longer bare section is suspended in air and acts as a cantilever.By detecting the transmission power of the sensor directly,the environmental vibrational frequencies and amplitudes may be obtained.By adjusting the cantilever's natural deflection angle,the sensor can achieve high sensitivity,good response linearity,and a wide dynamic range.Coupling conditions are optimized to minimize temperature effects by simply setting an appropriate air gap between the bare fibers.     

Computational analysis of vibration modes of disk-shaped piezoelectric traveling wave motors

IIntroductlon The working principle ofdlsk-shaped travelingwave ultrasonic motors Is:due to Inverseplezoeffect,the stator composed of plezoelectrlc and metal wafers bonded together transformsthe electrical energy to ultrasonic vibrations with an elliptical locus between contact Interfaces,and transforms the micro mechanical vibrations to a continuous rotation of＊theon rotor by us-lug magnification mechanism of＊theism tooth.In this course.there exist two ener取 conversationprocesses:electric…     

Rotation and vibration of diatomic molecule oscillator with hyperbolic potential function

The explicit expressions of energy eigenvalues and eigenfunctions of bound states for a three-dimensional diatomic molecule oscillator with a hyperbolic potential function are obtained approximately by means of the hypergeometric series method. Then for a one-dimensional system, the rigorous solutions of bound states are solved with a similar method. The eigenfunctions of a one-dimensional diatomic molecule oscillator, expressed in terms of the Jacobi polynomial, are employed as an orthonormal basis set, and the analytic expressions of matrix elements for position and momentum operators are given in a closed form.     

The characteristic of power flow in broad band dynamic vibration absorber

DVA (dynamic vibration absorber) is good for restrain of the resonance vibration in low frequency, especially under the condition that there are only one mode or two modes in a frequency band. It seems rather difficult to control the resonance vibration of elastic structures in high frequency, since usually there are so many modes in high frequency band. The broad band DVA is brought forward to reduce the resonance vibration of elastic structures. The broad band DVA is designed on the basis of the characteristic of power flow in structure in this paper. The broad band DVA is effective on absorbing the resonance vibration power flow of the most important modes. The ability of absorbing vibration for the broad band DVA is analyzed in detail. The results obtained in this paper provide a basis for the optimization design of the broad band DVA and the optimization positions on structures.     

A multi-stage high-speed railroad vibration isolation system with “negative” stiffness

The intensity of mechanical vibrations generated by a moving train increases at high speeds. Conventional railroad vibration isolation systems are either insensitive or inefficient in the infra-low frequency range, which is the range most hazardous to humans. In this work, an approach for upgrading a multi-stage system for engineers, crew, passengers, and people living near railroads is presented. The approach involves the design of geometrically similar redundant mechanisms with “negative” stiffness that could be compactly inserted into all system stages without degrading structure and safety. The approach is implemented in the design of seat suspensions. Finally, a concept relevant to the design of mechanisms for vehicle spring hangers and track bed elements is discussed in terms of the dimensional analysis.     

Study on rectangular ultrasonic radiator of flexural resonant vibration in high modes

Based on the theory of coupling vibration and flexural vibration of thin rod of rectangular cross section, the fiexural vibration of rectangular thin plate was studied. The frequency equation was derived under the condition of freeboundaries. The normal modes and the relation between the normal modes and the resonant frequency were obtained. Experiments showed that the calculated resonant frequencies agree well with the measured results, and the rectangular thin plate in flexural vibration has abundant resonant frequencies. The radiator of flexural vibration used in ultrasonic cleaning and other techniques has the advantages of large acoustic radiating area, uniform acoustic field and easy adjustment of resonant frequencies, proving that it is a promising ultrasonic source.     

Power flow transmission influenced by vibration source impedance for a compound system

I.IntroductionVeryofteninengineeringpracticemachinesareusuallyinstalledonflexiblestructures.Buildingfloors,shipdecks,aircraftfuselages,carortrainChassisarebutafewexamplesthatfallintothiscategory.Themachinetransmitsvibrationtothereceivingstructureandresultsinstructure-bornesoundtransmission.Especiallywhenaheaviermachinerunningathighspeedismoulltedonaflekib1efoundation,thesourceandthereceiverwillpresentsimilardynamiccharacteristicsattheirinterface.Asaresult,theconventionalanalysiscannotbeappli…     

Torsional vibration of crankshaft in an engine–propeller nonlinear dynamical system

Theoretical and experimental studies on torsional vibration of an aircraft engine–propeller system are presented in this paper. Two system models—a rigid body model and a flexible body model, are developed for predicting torsional vibrations of the crankshaft under different engine powers and propeller pitch settings. In the flexible body model, the distributed torsional flexibility and mass moment of inertia of the crankshaft are considered using the finite element method. The nonlinear autonomous equations of motion for the engine–propeller dynamical system are established using the augmented Lagrange equations, and solved using the Runge–Kutta method after a degrees of freedom reduction scheme is applied. Experiments are carried out on a three-cylinder four-stroke engine. Both theoretical and experimental studies reveal that the crankshaft flexibility has significant influence on the system dynamical behavior.     

Electrostatic vibration energy harvester with 2.4-GHz Cockcroft–Walton rectenna start-up

In this paper, we propose the design, fabrication and experiments of a macro-scale electrostatic vibration energy harvester (e-VEH), pre-charged wirelessly for the first time with a 2.4-GHz Cockcroft–Walton rectenna. The rectenna is designed and optimized to operate at low power densities and provide high voltage levels: 0.5 V at 0.76 μW/cm² and 1 V at 1.53 μW/cm². The e-VEH uses a Bennet doubler as a conditioning circuit. Experiments show a 23-V voltage across the transducer terminal, when the harvester is excited at 25 Hz by $1.5g$ of external acceleration. An accumulated energy of 275 μJ and a maximum available power of 0.4 μW are achieved.     

Optimized design of suspension systems for hand–arm transmitted vibration reduction

This paper describes a systematic approach for optimizing suspension systems to reduce the vibrations transmitted to workers by hand-held power tools. The optimization is based on modeling tool-operator interactions using a mobility scheme. The tool is modeled as a vibration generator, and its internal impedance is included. A hand–arm impedance matrix is used to model the operator upper limbs. The mobility model is used to identify the optimal suspension characteristics, which in our study were the set of parameters that minimizes the frequency-weighted acceleration at the hand–tool interface. Different handling conditions (one and two hands) and different working cycles with the same tools can be included in the optimization process. The constraints derived from the limitation on the increase in the tool mass and the static deflection of the mounting system under the working loads are also considered. The proposed method has been applied to the reduction of the vibrations transmitted to the operator by a small pneumatic hammer. The designed system reduced the worker’s exposure so that it is within the limits of the EU directive. The agreement between the model predictions and the measured suspension performances validates the effectiveness of this approach.     

The equivalent circuit of ultrasonic coupling vibration of a longitudinally-excited short column

On the basis of apparent elasticity method,we derived the equiva-lent circuit of coupling vibration of a short column and discussed its frequencyequation and the effects of the load impedance on the resonant frequency of theshort column.By the equivalent circuit,we calculated the input mechanicalimpedance of the longitudinally-excited short column and the curves of the ap-parent vibration velocity ratio versus the geometrical dimensions of the column.It shows that the equivalent circuit method is a simple and convenient one toanalyze and calculate the coupling vibration of the short column.