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1
Content available remote Experimental Beam Structure With Magnetically Controlled Damping Blocks
Bajkowski J. M., Dyniewicz B., Bajer C.
Machine Dynamics Research
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2017
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Vol. 41, No. 1
77--88
EN
This study considers the dynamic response of an experimental system combining two thin, aluminium beams with damping blocks attached. Damping blocks made of magnetorheological elastomer were placed at the tips of the beams and sequentially clamped using electromagnets to obtain energy dissipation. We analyse whether the magnetorheological elastomers can be effectively used in controlled damping systems with varying levels of stiffness and friction. The experimental results demonstrate that residual vibrations can be suppressed faster when the switching control is applied than if the electromagnetic actuator is turned on constantly. The effectiveness of the solution is discussed, based on the experimental results. The decay of vibration amplitude, damping and the system frequency is provided.
2
Content available remote Semi-active control of track subjected to an inertial moving load
Dyniewicz B., Pisarski D., Konowrocki R.
Vibrations in Physical Systems
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2012
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Vol. 25
147--152
EN
The paper deals with the problem of stabilization of vibrations of the load carrying structure via adaptive damping performed with a smart material. The properties of such a material must ensure reduction of vibrations, especially accelerations and displacements of selected stationary or follower points in a higher range than in the case of the material with homogeneous bilateral characteristics. Analytical calculations and numerical simulations proved the efficiency of the approach. Results obtained with the testing system equipped with magnetorheological controlled dampers will allow us to prove experimentally assumed control strategies and rheological properties of the filling material.
3
Content available remote Non-Hertzian contact model in wheel/rail or vehicle/track system
Dyniewicz B., Bajer C.
Vibrations in Physical Systems
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2012
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Vol. 25
141--146
EN
In the paper the spring-mass system describing the moving load, determined with the Hertz theory, was replaced with the spring-mass system with an inertial part being in contact with the beam, rail, or a track. Computational problems can be reduced significantly. Results are qualitatively and quantitatively improved, especially at higher range of the speed, related to critical values.
4
Content available remote General numerical description of a mass moving along a structure
Dyniewicz B., Bajer C.
Vibrations in Physical Systems
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2012
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Vol. 25
135--140
EN
The paper deals with vibrations of structures under a moving inertial load. The space-time finite element, approach has been used for a general description of the moving mass particle. Problems occur when we perform computer simulations. In the case of wave problem numerical description of the moving inertial loads requires great mathematical care. Otherwise we get a wrong solution. There is no commercial computing packages that would enable us direct simulation of moving loads, both gravitational and inertial.
5
Content available remote Numerical methods for vibration analysis of Timoshenko beam subjected to inertial moving load
Dyniewicz B., Bajer C. I.
Vibrations in Physical Systems
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2010
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Vol. 24
87--92
EN
The paper deals with the problem of modeling of the moving mass particle in numerical computation by using the finite element method in one dimensional wave problems in which both the displacement and angle of the pure bending are described by linear shape functions. The analysis is based on the Timoshenko beam theory. We consider the simply supported beam, in a range of small deflections with zero initial conditions.
PL
Praca omawia problem modelowania numerycznego poruszającej się cząstki masowej metodą elementów skończonych w zadaniu jednowymiarowym. Przemieszczenia i obroty opisano liniowymi funkcjami kształtu. Analizę oparto na teorii belki Timoshenki.
6
Content available remote Symulacja komputerowa ruchomych obciążeń inercyjnych
Dyniewicz B., Bajer Cz.
Drogi i Mosty
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2010
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nr 1
5-30
PL
W pracy przedstawiono algorytmy numeryczne metody elementów skończonych, dotyczące analizy drgań konstrukcji pod ruchomym obciążeniem bezwładnościowym. Niektóre problemy dynamiki konstrukcji trudno jest rozwiązać metodą elementów skończonych, stosowaną do zmiennych przestrzennych i metodą Newmarka, stosowaną do zmiennej czasu. Osobliwe cechy analitycznych rozwiązań równań różniczkowych, opisujących drgania wywołane ruchomym punktem masowym, muszą znaleźć swoje odzwierciedlenie również w ich rozwiązaniach numerycznych. Duże gradienty przebiegu rozwiązań, skoki wartości lub nieciągłości rozwiązań trudno jest uzyskać numerycznymi metodami dyskretnymi. Metody te same wymagają przybliżeń i wnoszą błędy, których oszacowanie jest trudne. W pracy omawiamy rozwiązania numeryczne, pozwalające uzyskać wyniki dokładne w pełnym zakresie prędkości przejazdu obciążenia bezwładnościowego.
EN
The paper presents algorithms for numerical finite element analysis of vibrations of structures under a moving inertial load. Some problems of dynamics of the structure are complex to be solved by the finite element method applied to spatial variables and by the Newmark method used for time domain. Peculiar features of analytical solutions of differential equations describing vibrations caused by a moving point mass must effect also their numerical solutions. Large gradients of solutions, jumps or discontinuities of solutions is difficult to obtain by the numerical discrete methods. These methods require approximations and introduce errors, which are difficult to be estimated. In this paper we discuss numerical solutions which allow us to obtain accurate results in a full range of velocity of the inertial load.
7
Content available remote Pomiary wielkości dynamicznych w transporcie kolejowym z wykorzystaniem czujników piezoelektrycznych
Dyniewicz B., Sekuła K., Dębowski T.
Drogi i Mosty
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2010
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nr 1
31-44
PL
Prawidłowe funkcjonowanie sieci kolejowej wymaga poznania stanu eksploatowanego toru oraz podtorza. Diagnozowanie sieci kolejowej wymaga m. in. budowy poprawnego modelu numerycznego, symulującego możliwie wiernie badany układ, zachowując przy tym rozsądny czas obliczeń. W pracy przedstawiono wyniki eksperymentów zrealizowanych na doświadczalnym stanowisku polowym. W pomiarach wykorzystano czujniki piezoelektryczne wykonane w formie płytek o prostokątnym kształcie. Otrzymane wyniki porównano z rezultatami obliczeń numerycznych wykonanych metodą elementów czasoprzestrzennych. Wykazano skuteczność symulacji komputerowych w opisie dynamiki rzeczywistych torów kolejowych.
EN
For proper operation of a railway system, identification of the track parameters is necessary. In orderto perform the monitoring, a numerical model of the railway system is required. The model should be as accurate as possible but it should also ensure moderate numerical costs of the computations. The paper presents experimental results taken in situ. The measurements were performed using piezoelectric sensors of a rectangular plate shape. The experimental measurements have been compared to the results of numerical simulations obtained using the method of space-time finite elements method. The effectiveness of the numerical simulation in modeling of the track dynamics has been proved.
8
Content available remote New feature of the solution of a Timoshenko beam carrying the moving mass particle
Dyniewicz B., Bajer C. I.
Archives of Mechanics
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2010
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Vol. 62, nr 5
327-341
EN
The paper deals with the problem of vibrations of a Timoshenko beam loaded by a travelling mass particle. Such problems occur in a vehicle/track interaction or a power collector in railways. Increasing speed involves wave phenomena with significant increase of amplitudes. The travelling speed approaches critical values. The moving point mass attached to a structure in some cases can exceed the mass of the structure, i.e. a string or a beam, locally engaged in vibrations. In the literature, the travelling inertial load is often replaced by massless forces or oscillators. Classical solution of the motion equation may involve discussion concerning the contribution of the Dirac delta term, multiplied by the acceleration of the beam in a moving point in the differential equation. Although the solution scheme is classical and successfully applied to numerous problems, in the paper the Lagrange equation of the second kind applied to the problem allows us to obtain the final solution with new features, not reported in the literature. In the case of a string or the Timoshenko beam, the inertial particle trajectory exhibits discontinuity and this phenomenon can be demonstrated or proved mathematically in a particular case. In practice, large jumps of the travelling inertial load is observed.
9
Content available remote String-beam under moving inertial load
Dyniewicz B., Bajer C.
Vibrations in Physical Systems
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2008
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Vol. 23
115--120
EN
The paper deals with the original analytical-numerical approach to the Bernoulli-Euler beam with additional tensile effect under a moving inertial load. The authors applied the 2nd kind Lagrange equation to derive a motion differential equation of the problem. The moving mass can travel through the string-beam with a whole range constant speed, also overcritical. The analytical solution requires a numerical calculation in the last stage and is called a semi-analytical one.
10
Content available remote Moving inertial load and numerical modelling
Bajer C., Dyniewicz B.
Vibrations in Physical Systems
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2008
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Vol. 23
65--70
EN
The paper presents the numerical approach to the moving mass prob¬lem. We consider the string and beam discrete element carrying a mass particle. In the literature efficient computational methods can not be found. The same disadvantage can be observed in commercial codes for dynamic simulations. Classical finite element solution fails. The space-time finite element approach is the only method which now results in convergent solutions and can be successfully applied in practice. Characteristic matrices and resulting solution scheme are briefly described. Examples prove the efficiency of the approach.
11
Content available remote Discontinuous Trajectory of the Mass Particle Moving on a String or a Beam
Dyniewicz B., Bajer C. I.
Machine Dynamics Problems
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2007
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Vol. 31, No. 2
66-79
EN
The paper deals with a new solution of the string or beam vibrating under a moving mass. Numerous solutions published up to date exhibit incorrect solutions. Moreover, they are not sufficiently simple and can not be applied to a whole range of the mass speed, also in over-critical range. We propose the solution of the problem that allows us to reduce the problem to the second order matrix differential equation. Its solution is characteristic of all features of the critical, sub-critical and over-critical motion. Results exhibit discontinuity of the mass trajectory at the end support point. The closed solution in the case of massless string is analysed and the discontinuity is mathematically proved. Numerical results obtained for inertial string demonstrate similar features. Small vibrations are analysed and that is why the effect discussed in the paper is of pure mathematical interest. However, the phenomenon can increase the complexity in discrete solutions.
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