Home HomeAnatoly T. Sukhodolsky, General Physics Institute (Russia)
Any amount of mechanical energy is known to be transformed into heat without any restriction. The principle of Carnot is to restrict any creation of mechanical energy from heat in heat engines on basis of entropy concept. The aim of this paper is to give an introduction to thermodynamics of the natural processes when effective generation of mechanical energy takes place without any devices owing to self-organization of a heat cycle. The main topics to discuss are: an advanced interpretation of Carnot principle and non-equilibrium entropy of light, the theorem of Carnot and maximum thermal eciency available for generation of vibrations.
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TOPLarisa A. Rybak, Russian Academy of Sciences (Russia)
Application of vibration isolation systems with kinematic operation principle is a perspective trend in the development of protection systems against basement vibrations impact . Connections of the object with its basement represent stiff/rigid mechanisms wich concrol relative position of the object and of its basement with help of information obtained from sensors of relative position of the object, its basement and accelerometers too, that are installed both at the object and on its basement. In case of basement motion absence, similar systems are insensitive to dynamic forces applied to the object, and only basement motion excitation sets the object in a relative motion with help of accelerometers. The vibration isolation problem could be achived by the creation of digital control methods of drive actuation. Here two approaches could be used. The first one is based on invariant control principle. We can create such a mode when we compensate acceleration on the object in such a way that it coues to zero due to the processing of accelerometer sygnal placed on the basement. The second way cousists of traditioual methods to produce lower frequency filter. A third idea is to combine in a certain way these two approaches.
sv970564.pdf (Scanned) sv970564.pdf (From Postscript) TOPLeonard L Koss, Monash University (Australia)
The mechanical action of a Yo Yo has several attributes which may give the toy a useful function as a vibration exciter for structures which have relatively low natural frequencies such as bridges and towers. The first attribute is that when a Yo Yo is released from a structure, the structure is exposed to a step input due to the loss of mass of the Yo Yo. The second attribute is that of an almost impulsive force input to the structure when the body of the Yo Yo reaches the bottom of its stroke due to the change in linear momentum over a short period of time. The third attribute is associated with the return of the Yo Yo body to its starting point if certain conditions on initial angular momentum, damping and string length are satisfied.Both a theoretical study and practical measurement have been undertaken to demonstrate the above attributes. Thus, in a cycle of Yo Yo motion the structure attached to the string of the Yo Yo is excited twice into vibration, the impulsive excitation being the greater source of vibration generation.The matrix equations of motion of a Yo Yo attached to a simple are spring mass systemwhere ml is the mass of the structure, m2is the linear mass of the Yo Yo, r is the radius of the Yo Yo spindle, I is the moment of inertia of the Yo Yo body, g is the gravitational constant, k is the structural stiffness, c1is structures viscous damping coefficient, c2 is the Yo Yo viscous damping coefficient and xl and X2are the coordinates which specify the position of the structure and Yo Yo, respectively. These equations are solved simultaneously using the Matlab computer code. A typical simulation result is shown below. Results and comparisons of theory and experiment will be given in the paper.
sv970111.pdf (Scanned) TOPDumitru Caruntu, University of Bucharest (Romania)
The annular plates are used in many structural applications. Therefore, the analysis of the annular plates' vibrations is of interest to many mechanical, aeronautical and civil engineers. We base our considerations on the classical plates' theory. The paper involves factoring the fourth-order linear differential operator, which appears in the equation of motion, into a pair of second order operators. For the annular plates with variable thickness, the conditions in which factorization is possible are presented. In this way, all the annular plates whose thickness varies with the radius for which this method is applicable are found. For example, the paper determines the general solution of vibrations differential equation and solves the eigenfrequencies' problem of annular plates with parabolic thickness.
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R.M. Heidecker, University of Western Australia (Australia)
S.J. Drew, University of Western Australia (Australia)
Brian J. Stone, University of Western Australia (Australia)
Torsional vibration in ball mills can be a serious problem - even leading to failure. In the design of such mills it is therefore important to be able to design them so that such vibration will not be a problem. It is thus desirable to be able to model the torsional vibration of a rotating system which includes a ball mill. The major difficulty with modelling torsional vibration is the low level of damping in rotating systems and insufficient information about its magnitude. This paper describes an experimental investigation of the torsional vibration of a ball mill with a particular emphasis on the damping of the mill itself. It was considered possible that the mill could be a significant source of energy dissipation for torsional vibration. A small batch ball mill was investigated using a servo motor as both the drive and a torsional exciter. The main parameters of the rig were varied and a systematic series of tests was performed for each combination of parameters. The inertia and damping of the mill were studied and the results are presented.
sv970549.pdf (Scanned) TOPKazem Abhary, University of South Australia (Australia)
Unlike complex lumped parameter rectilinear vibratory systems which can be easily and exactly formulated and then solved by widely available commercial computer packages, the solution of complex lumped parameter torsional vibratory systems is lengthy and time consuming. These systems can be solved by either the Holzer's method or the Transfer Matrix method. The former is unable to handle damped systems and the application of the latter upon damped systems is cumbersome. Both methods are numerical and the solution time dramatically increases by the increase in the number of branches of the torsional system, such that the inclusion of even an example of a four-branch system in mechanical vibrations textbooks has become prohibitive, let alone a complex multi-branch torsional system. In this paper, bond graphs have been used as a medium to facilitate the rectilinear modelling of complex torsional systems. It has been demonstrated that through elimination of the transformers, the bond graph of a torsional system will be converted to the bond graph of a rectilinear system on the basis of which the rectilinear model of the torsional system can be established. The model has been proven to follow a simple pattern and to be very rapidly constructible, irrespective of the complexity of the system. This approach has converted the project-type problems (via the Holzer's and Transfer Matrix methods) to simple class-room tutorials.
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Sead Spuzic, King Fahd University of Petroleum and Minerals (Saudi Arabia)
Ian Reid, University of South Australia (Australia)
Milorad Zec, Norwegian University of Science and Technology (Norway)
Mechanisms comprising oscillating components have important engineering applications. These systems are often based on forced oscillatory motion of vital elements. Solid surfaces, involved in dynamic contact, almost always experience sliding and wear along the active interface. This effect becomes extremely significant in mechanisms designed to perform multiple automatic motions. The recursive motion, intended to follow a precise kinematic pattern, ultimately shows adverse deviations. Engineering technologies developed to combat these deviations, e.g. the hardfacing, need the appropriate criteria to evaluate the maintenance economy. In addition to geometric degradation, the disadvantageous vibrations occur as the result of growing dissipative forces. The number of material attributes, e.g. the elastic moduli, can significantly change with the sliding distance. Presently, the theory of kinematics does not provide complete models for sliding distance for rolling-sliding contact. Currently, the fundamental concepts of circular motion and oscillations are presented without addressing this important aspect of the motion gradient with respect to contacting surfaces. This paper presents the mathematical derivation of the general case of interfacial motion. The presented kinematic relations are important for large class of dynamic systems that comprise interfacial motion, e.g. rail-wheel contact. Reference is made to practical cases where the proposed model can be applied.
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Sadao Azuma, College of Science and Technology, Tohoku (Japan)
Hiroyuki Ishida, College of Science and Technology, Tohoku (Japan)
Shunichi Kono, College of Science and Technology, Tohoku (Japan)
This paper deals with an analysis concerning the chattering phenomenon of the one-degree-of -freedom systems with collision. The objective of authors is to investigate the state of rebound and contact time when the mass element of the vibratory systems run into the optional collision surface. The collision surface, on paper, is equivalently substituted by the stiffness-surface that possesses a spring and a damper. It is characterized with relative to some properties of the system model, and moreover the considerations, which is so easy in practice as for analysis of collision systems by the applications of nonlinear equivalent stiffness-surface, is indicated as a result of examine.
sv970508.pdf (Scanned) TOPDave Anderson, Arup Acoustics (Australia)
The Bridgewater Hall in Manchester, UK, forms the new home for the Halle orchestra and a major international venue for symphonic and classical music. The hall comprises a 2400 seat auditorium together with orchestral accommodation and backstage facilities. This paper presents the design of the vibration isolation system used to prevent excessive groundborne noise from the adjacent railway. Predictions and measurements are compared, showing reasonable agreement of overall results but with significant differences in source levels, propagation losses and isolation insertion loss.
sv970488.pdf (Scanned) sv970488.pdf (From Postscript) TOPBoris M Efimtsov, TsAGI, Central Aerohydrodynamic Institute (Russia)
On the theoretical analysis basis the principal trends and regularities of the plate vibration connected with the elasto-inertial features of stif-feners are studied. The dynamic bending and torque strenth of stiffeners is taken into account in this case. The effect of these points-on frequencies and forms of the plate vibration connected with stiffeners is illustrated. The conditions are formulated at which the lowest eigen-frequency of the stiffened plate exeedes the first frequency of eigen-vibrations of its freely-supported isolated span and the distance between the knot lines of the respective vibrations form is not higher than the stiffener step. These conditions determine the relations between the elasto-inertial parameters of the plate and the stiffeners at which an essential atten-uation of the acoustic radiation of the stiffened plate at low frequencies can be realized at the expense of reducing the distance between the knot lines of its lowest forms.
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Stanley G Hutton, University of British Columbia (Canada)
Guoping Chen, Nanjing University of Aeronautics and Astronautics (China)
An investigation aimed at determining the complex moduli for a number of polymer materials is discussed. The complex moduli are determined over a limited range on the basis of transmissibilities measured on mass loaded cubic specimens subjected to controlled base harmonic excitation. Different mathematical models of the response of the specimens are reviewed and relations between the measured transmissilbility and the moduli presented. Consideration is given to the manner in which the experimental data may be fitted and to the errors that are involved.
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Oskar Bschorr, Aeroacoustics Munich (Germany)
H. Albrecht, Aeroacoustics Munich (Germany)
Alternating forces on a motor vehicle induce structure vibrations, and secondary noise is emitted. The means for damping this type of noise - structure borne noise - are summarised, for instance, in VDI standard 3727: Schallschutz durch Koerperschalldaempfung The basic means comprise a damping layer, a constrained layer, and a vibration absorber. The set-up, effect and dimensioning of the vibration absorber and the metallic damping layer, both of which were developed at the Aeroacoustic Laboratory in Ottobrunn, are described in the following. Vibration absorbers have been used in rail vehicles for over a decade. Wheel-vibration absorbers on the ICE train reduce noise emission at 200 km/h by 8 dB(A).
sv970448.pdf (Scanned) TOPBenjamin A. Cray, Naval Undersea Warfare Center (U.S.A.)
This paper examines a simple model: the vibration of an infinite string resting on sets of periodic supports, which are modeled as linear spring-mass-damper systems. The q-th. set of periodic supports may be offset by a distance xq. These offsets can thus be used to create spatiallydistributed gratings along the length of the string. The objective here is to gain an understanding of the physical mechanisms that govern the vibration response of more complicated arbitrarily-stiffened elastic structures.
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Yun S. Ryu, Hyundai Motor Company (Korea)
Chong D. Choi, Hyundai Motor Company (Korea)
Hee B. Cho, Hyundai Motor Company (Korea)
The coupled vibration of wheel-railway track system has been considered as that of a mass moving on a beam. In this paper, an analytical model is proposed to analyze the coupled vibration when the wheel travels on railway track. The railway track supported by sleepers is considered as a beam on Winklers foundations, and the wheel traveling on the railway track at constant speed is considered as a moving mass. Hertzs contact stiffness is assumed between the wheel and railway track. Numerical results are compared with experimental ones to verify the validity of the numerical method. The numerical method is found to be efficient to analyze this system. Based on the numerical simulation, the appropriate analysis range of the beam model and the characteristics of coupled vibration are discussed.
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R.A. Heller, Virginia Polytechnic Institute & State University (U.S.A.)
S. Thangjitham, Virginia Polytechnic Institute & State University (U.S.A.)
A. Szekeres, Technical University of Budapest (Hungary)
Under dynamic load conditions thermal stresses and moisture induced stresses require the solution of coupled problems. Thermal expansion, moisture expansion (swelling) and elastic displacements may be analyzed independently for static or quasi-static loads and slowly varying temperature or moisture inputs. In that case displacements produced by Fourier heat conduction and the analogous Fick moisture transport may be dicoupled from elastic displacements. On the other hand, in hygroscopic materials, due to the Soret and Dufour effects cross-coupling takes place when either of these inputs: thermal, hygroscopic and mechanical, are applied at a high rate. [equations omitted]. Using the equations, the problem of a vibrating rod immersed in an environment whose temperature and mositure content varies harmonically is solved. For comparison the stress distributions due to the individual inputs as well as due to the combined inputs will be calculated.
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Samo Zupan, University of Ljubljana (Slovenia)
Ivan Prebil, University of Ljubljana (Slovenia)
Pavle Kaiba, University of Ljubljana (Slovenia)
During the design of rotational connections used in various applications (transport machines, cranes, technological equipment, and military machines) many problems emerge already in the phase of development and analysis of substructures, i.e. various large dimension rolling bearings, screw connections between bearing rings and supporting structures, and gear pairs. Inconsistent computer support in this phase causes much difficulty and delay in the search for the optimal solution. Therefore we decided to design a complete program system for the analysis and optimisation of the above mentioned substructures of a rotational connection, and the adaptation of their geometric relations. All the necessary data will be stored in a common data base. For some typical rotational connections completely automated preparation of the technical documentation will be possible, using this data base. Even in the case of non typical designs we expect the automation of up to 75% of designer's work.
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Juergen Buellesbach, Universitaet der Bundeswehr Muenchen (Germany)
Oliver Fischer, Bilfinger + Berger Bau AG (Germany)
Starting with an introductory description of parametrically excited stability phenomena, a short outline is given of analyses found in literature.Next, a kinetic stability theory is explained which is the basis of the stability analyses performed in the following, and which can be applied to arbitrary shell constructions. In view of a numerical solution the stability equations are then transformed into a compact equation of work by applying the principle of virtual displacements. The portions obtained by this can be grouped together to form the contributions of the virtual internal deformation work and the virtual kinetic energy. Then the equations are modified with regard to buckling analyses of plates. In consideration of the time-dependent fundamental state due to the pulsating load application, a method is presented which can be used to solve the derived time differential equation system of HILLs type. This time differential equations system yields instability regions containing all unstable load-frequency combinations. Furthermore, it can be proved that periodically solutions, which can be represented by fourier series, exist along their boundaries.The application of the theory mentioned above and its numerical realization is explained for two plates with different boundary-conditions subjected to pulsating loads. The noteworthy new results found out show instability regions starting at the expected resonance point at (Omega) = 2 . (omega). Moreover the effects of damping are illustrated and the resonance phenomena due to inertia portions of the fundamental state are discussed.
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V.I. Babitsky, Loughborough University
A.M. Veprik, Ricor, En Harod Ihud (Israel)
Modern condensed design often do not permit the effective use of linear flexural suspension as a universal solution for the limitation of energy transmission from machine to its foundation and vice versa. As soon as an application Involves exposure to a high level of shock, wide band random or frequency varying vibration, the internal impacts against the limiters of motion becomes the subject of serious concern. The presence of bumpers turns the vibration isolator into the strongly nonlinear (vlbro-impact) structure. The idea of this novel vlbratlon isolatlon arrangement is based on the co-operative use of lightly damped linear vibration isolation and specially tuned heavily damped bumpers. The bumpers are installed with minor oscillation space sufficient to allow impactless operation under nominal excitation and to restrict effectively excessive deflections. The main advantages of this scheme are due to the removal of motion limitation and damping duties from the flexural elements and concentrating these in the bumpers with the intelligent utilization of dynamical properties of the vibro-impact system. The study of the dynamics of a . nonlinear system of vibration isolation exposed to kinematic excitation of sine sweep, wide band random and saw-tooth shock types was conducted. Special attention was paid to the simulation of the response to suddenly applied gross intensity shock. As a result, the generalised optimal parameters of nonlinear isolation were found. The results of the simulation are compared with a series of full-scale vibration tests of a flexibly suspended linear compressor of a split Stirling cryocooler for a vibration sensitive electro-optical device.
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Xiaoquan Wang, The Hong Kong Polytechnic University (Hong Kong)
K.T. Chan, The Hong Kong Polytechnic University (Hong Kong)
A modified transfer matrix method is developed to obtain exact solution of natural frequencies and mode shapes of a cantilever beam loaded with distributed mass over an intermediate span. The eigenvalue problem is analytically derived, then eigenvalues and eigenfunctions are calculated numerically. As verification, free vibration of a cantilever beam with concentrated mass is studied and the computational natural frequencies agree very well to the data available in the open literature. Computational results are presented to demonstrate influence of added mass position and length on natural frequencies and mode shapes of the mass-loaded cantilever beam. It is shown that as the distributed mass shifts from the clamped end to the free one, the fundamental natural frequency decreases while the natural frequencies of higher modes vary cyclically. The nodal points of mode shapes shift with the distributed mass in a swing manner, and the amplitudes of mode shapes are suppressed at the locality of the mass. As the mass position is fixed, the effect of mass length is found to be significant for natural frequencies of higher modes, implying that in this case error will appear if a distributed mass is modeled by a concentrated one. However, when the length of the distributed mass is made rather small, say 1/1000 of the beam length, then it can be regarded as a concentrated one with great accuracy.
sv970289.pdf (Scanned) TOPAdolf E. Blach, Concordia University (Canada)
A tall fractionator tower, part of a super fractionation unit in an aromatics plant of a petroleum refinery was originally built by a very reputable pressure vessel fabricator with extensive experience. The fractionator used in the production of Xylene performed well for a number of years without any difficulties. Then, suddenly, when a drop in price of aromatics led to a shutdown of the unit, the empty tower started to vibrate violently at moderate wind velocities. As soon as the tower was filled with liquid, the vibrations stopped; however, over a period of 10 years with on and off vibrations, the anchor bolts were apparently stretched beyond the yield point of the material. An investigation into the strength of the foundation also showed insufficient safety against overturning. This paper describes the accumulated damage done to both, tower and foundation, also the very expensive repair work required to make the tower structurally sound. The repair took almost one year to completion, partly due to the fact that work had to be done while the refinery was on-stream. The repair, of course, did not fully eliminate the reasons for the vibrations. An automatic system had to be devised to sense vibratiom during periods of shutdown of the process unit, and automatically initiate a sequence to fill the tower with liquid whenever excessive vibrations are detected.
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Yoshiaki Terumichi, University of Tokyo (Japan)
Shinichi Ohno, University of Tokyo (Japan)
Self-excited vibration in cylindrical grinding is always experienced if the work speed is high. In this paper, the effect of the work speed on the occurrence of self-excited vibration is investigated analytically and numerically, and the amplitude and phase shift of the work vibration in steady state is also determined, using the averaging method with the nonlinearity of the damping force taken into consideration. The main results are as follows: First, if the work speed is low, self-excited vibration does not occur. On the other hand, if the work speed is high, self-excited vibration always occurs. The critical speed of the work revolution is given using Nyquists stability criterion. Second, if the grinding rate is large, the amplitude of the self-excited vibration increases with increase of the work speed. In the steady state, the phase of the work displacement is delayed by pi/2 to that of previous grinding for all work speed. The above theoretical result about the critical work speed is in good agreement with the experimental one.
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Dimitrije Jankovic, University of Belgrade (Yugoslavia)
Svetozar Jankovic, University of Belgrade (Yugoslavia)
The transportation of original measure (OM) and measurement devices (MD) is frequently performed by motor vehicles. The unusual conditions which occur due to vibrations, and temperature impact loads, as well as other disruptions during transportation have influence on the metrological characteristics of OM and MD.Due to this fact, and in the desire to choose, that is, design a motor vehicle for the transportation of OM and MD, there has been made a classification of OM and MD according to their sensitivity to vibrations and other loads, as well as to the method of packing of same and storage facilities in the vehicle, all for the purpose of securing the preservation of the metrological characteristics in transportation.
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T.Ho. Babayan, Institute of Geophysics & Engineering Seismology (Armenia)
S. Karapetyan, Institute of Geophysics & Engineering Seismology (Armenia)
H. Abrahamyan, Institute of Geophysics & Engineering Seismology (Armenia)
This work is devoted to survey the variations of amplitude-period character of microseisms in epicentral areas of expected seismic events, with the aim to solve the problem of short-term prediction of earthquakes. The investigations were carried out in the area of intersection of the south shoots of the Spitak fault and Achourian seismogeneous fault in two stages: September 1995 and June-July 1996. Earthquakes source areas has been determined by traditional (geophysical-seimological) and non-traditional (biolocation) methods, before some months of seismic events. The graphs were made up, which show that interesting results were obtained. At the first stage of investigations it turned out, that some houres before the seismic events anomal increasing of amplitudal level and periods of high frequency microseisms occured. After the events they are decreased to phon level. At the second stage of the works it occured again the same but only for amplitude levels, without changing of periods. As a conclusion to this studies investigations of microseisms in source areas paving seismic events make it possible to realize short term prediction of the earthquakes.
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