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1
Content available remote Powstawanie rezonansowych drgań uzwojeń w transformatorach energetycznych
Witczak P.
Przegląd Elektrotechniczny
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2017
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R. 93, nr 7
1--4
PL
W pracy opisano metodykę obliczeń drgań uzwojeń w transformatorach energetycznych przy pomocy metody elementów skończonych 3D zarówno w dziedzinie elektromagnetycznej jak i mechanicznej. Obliczenia uwzględniają rzeczywistą geometrię uzwojeń oraz ich strukturę materiałową.
EN
The paper describes the calculation method of winding zone in power transformers which uses the 3D finite elements both in electromagnetic and in structural domain. Calculations take into account the realistic geometry and material structure of windings.
2
Content available remote Kinematically Excited Vibration of an Asymmetric Rotor/Bearing System With Magnetic Lubricant
Perek A., Kurnik W.
Machine Dynamics Research
|
2015
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Vol. 39, No. 4
5-19
EN
The paper is concerned with transverse dynamics of a rigid rotor supported in a semi-active slide bearing lubricated with a magnetic fluid. Attention is focused on modeling and simulation of forced vibrations of an asymmetric rotor supported in a rolling bearing at one end and in a slide bearing, on the other one. The slide bearing is treated as a nonlinear flexible support with visco-elastic properties controlled by an external magnetic field via a ferrofluid used as a bearing lubricant. The considered dynamical system is a discrete model of real rotor of Rotor Kit RK-4 by Bentley Nevada, a laboratory device being used for educational and research purposes. The aim of the study is to find how a magnetically induced modification of the magnetic fluid affects the resonant behavior of the rotor under harmonic kinematic excitation by the rotor housing movement. Computer simulations are used to obtain resonant curves of nonlinear relative rotor/housing vibrations. The effects of magnetically controlled viscosity of the lubricant fluid are presented as changes of shape and maximum values of the resonant curves as well as a shift of the resonance zone in the excitation frequency domain.
3
Content available remote Changes of the resonant vibration frequencies for different concrete beams
Buda-Ożóg L.
Zeszyty Naukowe Politechniki Rzeszowskiej. Budownictwo i Inżynieria Środowiska
|
2009
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z. 52 [264]
25-32
EN
This paper provides information about changes of resonant vibration frequencies for concrete and reinforced concrete (RC) beams. The objects of research were concrete beams of different dimensions and RC beams. The concrete beams were damaged by stage of cutting but RC beams were damaged by stage of static loading. After each stage of damage, the resonant vibration frequencies were determined. The parameters change their values while cutting or loading the beams due to cracking. On the basis of the obtained results from different beams, an effort was made to correlate the different dimension of beams, influence of reinforce and the damage of the tested beams with the changes of the modal parameters.
4
Content available remote Resonant Vibration of a Rotor with Magnetic
Dziedzic K., Kurnik W.
Machine Dynamics Problems
|
2007
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Vol. 31, No. 1
43-52
EN
The paper is concerned with the dissipative effect of the magnetic hysteresis in transverse dynamics of a rigid rotor supported in hydrodynamic bearings with magnetic actuation. Attention is focused on the influence of magnetic damping induced in the ferromagnetic core of a single magnetic actuator on the stability domain and the resonant behaviour of a rotor under constant gravity load and harmonic excitation. The dynamic relation between the magnetic field and magnetic induction in the core is described in form of a differential equation based on the hypothesis of magneto-rheologic analogy. Nonlinear magnetization curve reflecting magnetic saturation is included.
5
Content available The resonant vibration of the asymmetrical rotor supported in the slide bearings with the floating bearing shell
Starczewski Z.
Mechanics / AGH University of Science and Technology
|
2006
|
Vol. 25, no. 3
143-147
EN
In the paper resonance vibrations of the asymmetric rotor supported on journal bearings are analysed. The profile of bushes is circular and additionally bushes are encased in floating ring with controlled elastic and dumping properties. It was proved that through modification of the elastic and dumping properties it is possible to limited the amplitude of resonance vibrations as well as it possible to control frequency at which frequency the resonance occurs. The diagrams with investigation results are given.
PL
W pracy zamieszczono rozważania na temat drgań rezonansowych asymetrycznego wirnika podpartego w łożyskach ślizgowych. Zarys panewek jest kołowy i dodatkowo osadzone są one w pływającym pierścieniu o regulowanych własnościach sprężysto-tłumiących. Wykazano, iż poprzez zmianę, tych własności można ograniczać amplitudę drgań w rezonansie, a także sterować częstością, przy której występuje rezonans. W pracy zamieszczono odpowiednie wykresy.
6
Content available remote Rezonansowe poziome drgania parametryczne podwieszonych kładek dla pieszych
Grosel J., Wójcicki Z.
Zeszyty Naukowe Politechniki Rzeszowskiej. Mechanika
|
2005
|
z. 65 [222]
137-144
EN
The possibility of exciting parametric resonance vibration in a suspended pedestrian bridge as a result of a premeditated action of a group of people, or of crowd movement, is analysed. Large horizontal transverse vibration are caused by the vertical periodic synchronised movement of people, which is analogical to the movements of a person on a swing. The problem studied is how large a group of people is able to excite dangerous parametric vibration in the system.
7
Content available remote Effect of geometrical orientation of three-lobe slide bearings on amplitude of resonant vibration of an unsymmetric supported rotor
Starczewski Z.
Mechanics and Mechanical Engineering
|
2004
|
Vol. 7, nr 2
145-151
EN
In the paper the effect of geometric orientation of bearing shells on damping of forced vibration of journals of an asymmetric rotor has been analysed. Considerable influence of mutual position of the shells, has been confirmed as far as decrement of the vibration amplitude was concerned. The effect of asymmetry oil clearances and journal lengths has been taken into account. The results are shown in appropriate graphs.
8
Content available remote Active reduction of resonant vibration in rotating shafts made of piezoelectric composites
Przybyłowicz P.M.
Archives of Control Sciences
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2003
|
Vol. 13, no. 3
327-337
EN
The paper concers dynamic properties of rotating shafts, subjected to structural unbalance that excites transverse vibration. The shaft is made of an active composite containing piezoceramic fibers (so-called Piezoelectric Fiber Composites- PFCs). Efficiency of the applied method of active reduction of the vibration is discussed in the paper. Theoretical fundamentals of the method based on the proportional and velocity feedbacks are presented. Simulation results are shown in the form of aplitude-frequency characteristics. The investigations prove that the application of the active laminates, as elements structurally integrated with piezoelectric actuators, is an efficient tool for reducing resonant vibration amplitude in rotating shafts.
9
Content available remote Ocena zmian sztywności węzłów na podstawie widma częstości drgań rezonansowych
Buda-Ożóg L., Kozłowski A., Łakota W.
Zeszyty Naukowe Politechniki Rzeszowskiej. Mechanika
|
2002
|
z. 60 [197]
51-58
EN
Method of the stiffness assessment of the beam-to-column top and seat angle bolted connection has been presented in the paper. Static and dynamic methods were used in the analysis. Statical tests made on joint sample were used to obtain M-ɸ characteristic of the joint. Dynamic method relies on the measurements of the response of the structure to the impulse excilation. Correlation between resonance frequency response and joint stiffness, which rely on bolt tightening, has been demonstrated.
10
Content available remote Aktywne tłumienie drgań rezonansowych sztywnego wirnika podpartego w łożyskach o zarysach niekołowych w przypadku wymuszenia kinematycznego
Starczewski Z.
Zeszyty Naukowe Politechniki Rzeszowskiej. Mechanika
|
2002
|
z. 60 [197]
555-560
EN
In the paper the possibility of damping of resonant vibration of a rigid rotor supported on pericycloidal journal bearings with the multiplication factor Kn=3 (three-lobe bearings) is discussed. The effect of application of 2 and 3 pairs of magnetic actuators on limitting resonance amplitudes is examined. As the excitation motion of the fundament (kinematic excitation) is assumed. Exemplary diagrams showing resonant displacements of the rotor and concluding remarks are included in the paper.
11
Content available remote Redukcja drgań rezonansowych stalowych fundamentów ramowych pod maszyny obrotowe
Grosel J., Klasztorny M.
Zeszyty Naukowe Politechniki Rzeszowskiej. Mechanika
|
1999
|
z. 52 [174]
57-64
EN
A matrix dynamic equation of motion of a steel frame foundation for rotary machines, equipped with passive dynamic absorbers, is formulated. Transoms and columns of the foundation are made as thin walled bars of an open contour. The machines are treated as vibroisolated rigid bodies. The spatial thin walled frame is discretised with FEM. The system satisfies some orthogonality conditions, used in the assembly process. The absorbers are optimally localised as well as optimally tuned with respect to selected modal systems of the original structure and are applied for reducing steady-state forced vibrations of the light damped foundation in the resonant zones. A computer algorithm and programme are written, useful for dynamic analysis of engineering structures undertaken. Dynamic analysis of a realistic foundation for a turboset is performed.
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