Wyniki wyszukiwania - Biblioteka Nauki

1

Natural frequencies and modes shapes of two rigid bladed discs on the shaft

100%

Rządkowski R. , Sokołowski J.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2004

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tom Vol. 8, No 1

51-69

EN

The dynamic behavior of a rotor consisting of two bladed discs on a solid shaft is considered. The effect of shaft flexibility on the dynamic characteristics of the bladed discs and the coupling effects between the shaft and bladed disc modes are investigated. Results presented for various cases with differing blade flexibility show clearly the coupling effects in a bladed disc-shaft system. Interference diagrams are developed, from which the dynamic behavior of a system can be predicted for differing flexibility relationships between the solid shafts and the bladed discs. In this study, the global rotating mode shapes of flexible bladed disc-shaft assemblies have been calculated. Rotational effects such as centrifugal stiffening have been accounted for, and all the possible couplings between the flexible parts have been allowed. Gyroscopic effects have been included in the shaft with two discs. Calculated natural frequencies obtained from the blade, shaft, bladed disc and shaft with two discs have been checked to determine resonance conditions and coupling effects. The calculations have shown the influence of the shaft on the natural frequencies of the bladed discs up to one nodal diameter frequencies. The torsional frequency of the shaft with two discs is coupled with the zero nodal diameter modes of the single bladed discs. The bending modes of the shaft are coupled with one nodal diameter modes of the bladed discs. It is shown that including the shaft in the bladed discs model is important from a designer's point of view and can change the spectrum of frequencies considerably.

2

Recursive differentiation method: application to the analysis of beams on two parameter foundations

80%

Hassan M. T. , Doha E. H.

Journal of Theoretical and Applied Mechanics

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2015

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tom Vol. 53 nr 1

15--26

EN

The recursive differentiation method (RDM) is introduced and employed to obtain analytical solutions for static and dynamic stability parameters of beams resting on two-parameter foundations in various different end conditions. The present analysis reflects the reliability, efficiency and simplicity of the proposed RDM in tackling boundary value problems. In fact, it is widely common that the critical load accompanied with the first buckling mode is the smallest critical load, and then it is the dominant factor in the static stability analysis. In contrast, the present analysis indicates that such a conclusion is correct only for the case of beams without foundations or in the case of a weak foundation relative to the beam. It is proved that critical loads accompanied with higher buckling modes may be smaller than those accompanied with the lower modes and then it may control the stability analysis. The same phenomenon exists for natural frequencies in the presence of an axial load. Several illustrations are introduced to highlight the effects of both the foundation stiffness and beam slenderness on the critical loads and natural frequencies.

3

Structure numerical model updating on the results of experimental dynamic tests

80%

Sidorov V.

Structure and Environment

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2012

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tom Vol. 4, no. 3

5--7

EN

The paper presents an algorithm of structure calculation model adjustment by the values of free oscillations frequencies of structures, obtained as a result of experimental research. It is considered that the experimental test of a construction can obtain some values of the natural frequencies of the object and identify the corresponding forms of free oscillations.

4

Numerical Study of the Natural Oscillations of Perforated Vibrating Surfaces with Holes of Complex Geometry

80%

Kharchenko S. , Samborski S. , Kharchenko F. , Paśnik J.

Advances in Science and Technology. Research Journal

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2023

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tom Vol. 17, no 6

73--87

EN

The widespread use of perforated vibrating surfaces in various industries requires maximum productivity and construction reliability. The research task is to determine the significant factors and their degree of influence on the natural oscillations of vibrating surfaces with multiple holes of complex geometry. For this purpose, studies were carried out for three samples of plates: non-perforated, with basic round holes and holes of complex geometry in the form of a five-petal epicycloid. Studies of the natural oscillations of perforated vibrating surfaces have been conducted using the finite element method in Abaqus, which has proved sufficient accuracy of calculations. The dependencies of the natural oscillation frequency of perforated surface samples on their thickness, partition width between the holes, material type, and fixing method have been obtained. In addition, the analysis involved the study of eight modes of oscillation common in practice. The dependencies of the natural oscillation frequency of perforated surface on the relative parameters of ligament efficiency and stiffness coefficient have also been obtained. These parameters take into account the ratios of the partition width between the holes to the plate thickness and the dimensions of the holes. The research results allow to obtain levels of influence of the perforated vibrating surface parameters on their natural oscillations frequency. The obtained research results make it possible to further determine the absence of damage between the holes and predict the durability of perforated vibration surfaces in the presence of holes of complex geometry.

5

An Analysis of the Load Exerted on a Bearing-Type Transferring Fixed on the Frame at the Top or at the Bottom

80%

Fandáková M. , Sága M.

Machine Dynamics Problems

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2004

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tom Vol. 28, No. 3

95-100

EN

A building line is a common type of equipment used in the rubber-processing industry to build radial truck tyres in the semi-automatic production mode. The bearing-type transferring is part of the equipment. The paper presents an analysis of the load exerted on the bearing-type transferring depending on its fixation at the top of the frame. The paper also presents results of the stress and frequency analysis of the transferring.

6

A brief review and comparison of selected experimental methods for measuring natural frequencies of circular saw blades

80%

Kaczmarek A. , Orlowski K. A. , Javorek L.

Drewno : prace naukowe, doniesienia, komunikaty

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2016

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tom vol. 59, nr 197

231--239

EN

Different methods for the empirical determination of the natural frequencies of circular saw blades are presented. Stationary methods, such as the harmonic and impulse tests, are discussed and the results of related comparison are given. The comparison of the methods revealed their degree of practical usefulness and their accuracy in determining natural frequencies. A combination of specific methods is proposed, which should allow optimal results.

7

Dynamics of thermally activated shape memory alloy reinforced laminated beams

80%

Pietrzakowski M.

Journal of Theoretical and Applied Mechanics

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1998

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tom nr 4

879-893

EN

A way of use of shape memory alloy (SMA) fibers for dynamics response modification of laminated beams is presented in the paper. The considered concept of adaptive control is based on the ability to change the Young modulus during a temperature activated, reversible, martenstic transition that is specific to SMAs. It is assumed that the laminate is midplane symmetric and the corresponding layers of the same fiber orientation are activated simultaneously, and the SMA fibers can freely elongate in the matrix. A cantilever laminated beam with mass distributed on its free edge is subject to numerical analysis. Due to the quasi-steady one-dimensional model of heat conduction, martensite fraction and natural frequency time relations for the phase transition of SMA have been obtained. The influence of temperature on natural frequencies of the system has been analysed for some different locations of activated plies and directions of SMA fibers. The frequency response functions varying with the material phase transformation for a harmonic load acting on the free end of the beam have also been presented.

PL

W pracy przedstawiono zastosowanie włókien ze stopu z pamięcią kształtu (SMA) do modyfikacji właściwości dynamicznych belek laminowanych. Koncepcję adaptacyjnego sterowania oparto na unikalnej zdolności stopów SMA do wyraźnej zmiany wartości modułu Younga w procesie odwracalnej przemiany martenzytycznej wywołanej temperaturą. Założono, że warstwy laminatu są ułożone i uaktywniane symetrycznie względem powierzchni środkowej, a włókna SMA mogą swobodnie odkształcać się w osnowie. Symulacja numeryczna dotyczy belki laminowanej utwierdzonej wzdłuż jednego brzegu, z masą równomiernie rozłożoną na swobodnym, przeciwległym brzegu. Zgodnie z przyjętym stacjonarnym, jednowymiarowym modelem przewodnictwa cieplnego, wyznaczono przebiegi czasowe temperatury i zawartości martenzytu we włóknach SMA, oraz przebiegi podstawowej częstości własnej w zakresie przemiany fazowej. Zbadano wpływ temperatury na częstości własne zmieniając położenie warstw uaktwnianych a także kierunek ułożenia włókien SMA. Zakładając wymuszenie harmoniczne działające na swobodny brzeg belki, wyznaczono charakterystyki amplitudowo-częstotliwościowe odpowiadające pełnemu zakresowi transformacji fazy materiałowej.

8

New design of circular saw blade body and its influence on critical rotational speed

70%

Droba A. , Javorek L. , Svoreň J. , Paulíny D.

Drewno : prace naukowe, doniesienia, komunikaty

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2015

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tom vol. 58, nr 194

147--157

EN

Oscillation is an unwelcome state as it has adverse effects not only on the work piece but also on the tool. This paper deals with the problem of circular saw blade oscillation and the effect of modification of the circular saw blade body on the natural frequency as well as on the critical rotational speed. The calculation and experimental investigation of the natural frequencies and node shapes on two types of circular saw blades were carried out. Two methods used to determine the natural frequencies are presented: the first, modal analysis (FEM), a theoretical method, and the second, experimental measurement. The results of the investigation were used to compare the FEM and experimental methods and to show which modification achieved a higher critical rotational speed. Both methods were conducted on two circular saw blades for continual cutting with 36 teeth and slots.

9

A simple formula for predicting the first natural frequency of transverse vibrations of axially loaded helical springs

70%

Michalczyk K. , Bera P.

Journal of Theoretical and Applied Mechanics

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2019

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tom Vol. 57 nr 3

779--790

EN

A new formula that allows the first natural frequency of transverse vibrations of axially loaded steel helical springs to be determined has been presented in the paper. The relationship is easy to use and allows finding the first natural frequency of spring vibrations without the necessity of solving analytical or numerical models. According to the authors’ knowledge, this is the first such a formula and, consequently, when this frequency becomes zero, it enables determination of the critical axial force or deflection causing the buckling of the spring. The way of obtaining the described formula is presented in the paper. The results of this formula are compared with those obtained using FEM and experiments. The advantages, drawbacks and limitations of the proposed relationship are also discussed.

10

An influence of the d311 effect on the behavior of the cantilever beam-shaped piezoelectric activator made of two layers of pvdf with inverse polarity

70%

Teter A. , Gawryluk J. , Warmiński J.

Applied Computer Science

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2014

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tom Vol. 10, no 3

23--33

EN

In the present work an example of the numerical modeling of electro-mechanical coupling of the activator in the form of cantilever beam made of two layers PVDF subjected to an inverse polarity is described. Calculations were done for static deflections at the selected voltage levels and for modal analysis with an included and excluded piezoelectric effect. The effect of active material on the behavior of the beam was examined. In order to validate the model, results of the static calculation were compared with the strict analytical solution and the results presented by other authors.

11

Influence of the variability of the shape of short axisymmetric rods on the value of basic natural frequency of longitudinal vibrations

60%

Kozień M. S.

Vibrations in Physical Systems

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2021

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tom Vol. 32, nr 2

art. no. 2021212

EN

Rods with a relatively short length in relation to their transverse dimensions with a variable cross-section along the axis, subjected to longitudinal vibrations, have the character of stocky rods, for which the classic geometric principles used for rods are not fully met. For small engineering elements, the postulated design frequencies of natural vibrations in the very high cycle fatigue analyses reach the values of a dozen or so, small, several dozen kHz. In the article, the sensitivity of the value of the basic natural frequency to the change in the shape of the element is analysed and discussed. The analysis is conducted using finite element method.

12

Solution of plate free vibrations problem by method of fundamental solutions

60%

Uściłowska A.

Vibrations in Physical Systems

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2008

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tom Vol. 23

383--388

EN

In this paper, a meshless method for solving the natural vibration of plates problem is proposed. For this particular problem the method of fundamental solutions has been implemented. due to its features, the final resolving system can be solved with the classical approaches by using standard numerical procedures. To asses the formulation, the free vibration of some plates were calculated and the results compared with those obtained using other solution techniques. The present results are in good agreement with those found in the literature showing the accuracy and effectiveness of the proposed approach.

13

Influence of Double-Panel Structure Modification on Vibroacoustical Properties of a Rigid Device Casing

60%

Chrapońska A. , Rzepecki J. , Mazur K. , Wrona S. , Pawełczyk M.

Archives of Acoustics

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2020

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tom Vol. 45, No. 1

119--127

EN

Nowadays, noise generated by devices is a serious issue in industry and in everyday life, because it may cause health damage to humans. In this research, a cubic rigid device casing built of double-panel thin steel walls is employed to reduce noise emitted from an enclosed noise source. Double-panel structure is used because of good sound insulation it provides. There exist three main groups of noise reduction methods, i.e. passive, semi-active and active. In this paper, a semi-active modification of double-panel structure is applied and examined. The bistable actuator (solenoid) mounted between incident and radiating plates changes its state due to applied constant voltage, causing the coupling of plates. Experimentally measured natural frequencies and modeshapes of the structure are compared to the simulation results. The influence of proposed modification on dynamical properties of the structure is analyzed and discussed.

14

Effect of exciting force amplitude on occurrence of parametric resonance phenomenon in vibrating screen

60%

Bąk Ł. , Stachowicz E. , Noga S. , Skrzat A.

Vibrations in Physical Systems

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2016

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tom Vol. 27

42--46

EN

The paper considers the effect of exciting force amplitude on occurrence of parametric resonance phenomenon in vibrating screens by using experimental methods. The measuring test is performed for three cases of excitation force levels. For each force level sieve parametric vibrations are excited by using proper excitation frequency. It is shown that an increase of the excitation force results in an increase in the sieve vibration amplitude. The dependence between excitation force and sieve parametric vibrations is nonlinear. The value of excitation force has an effect on the sieve vibration mode shape. Two vibration mode shapes are detected. It is found that the excitation frequency influenced the vibration amplitude. An increase of sieve preload has no effect on the amplitude level, however it results in an increase of the sieve vibration frequency.

15

Influence of Double-Panel Structure Modification on Vibroacoustical Properties of a Rigid Device Casing

60%

Chrapońska A. , Rzepecki J. , Mazur K. , Wrona S. , Pawełczyk M. , Chrapońska A. , Rzepecki J. , Mazur K. , Wrona S. , Pawełczyk M.

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16

Vlianie gidrostaticeskoj zestkosti uplotnitel'nyh kolec na sobstvennye kolebania rotornoj sistemy

60%

Nikiforov A.

Zeszyty Naukowe Politechniki Świętokrzyskiej. Nauki Techniczne

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2008

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tom Z. 10, Vol. 1

55-62

EN

Natural oscillations of system "flexible rotor - liquid film - sealing ring" on base of finite element model are researched. The hydrostatic stiffness effect on natural (partial) frequencies and mode shapes for rotor and ring is discussed. Simulation veracity is confirmed by analytical calculation of natural frequencies for researched system.

17

The experimental investigation of the screen operation in the parametric resonance conditions

60%

Bąk Ł. , Noga S. , Stachowicz F.

Acta Mechanica et Automatica

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2015

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tom Vol. 9, no. 4

191--194

EN

In this paper the experimental studies of the screen working in the parametric resonance condition are discussed. The investigations are conducted for laboratory parametric resonance screen. The measuring test is performed for four cases of tension force values. The full sheet metal instead of the sieve is used. For each considered case the natural frequency of the plate and the parameter modulation frequency are determined.The achieved results are presented and discussed. It is shown that the highest sieve plate amplitude is obtained when the parameter modulation frequency is two times larger than natural frequency of the sieve plate. This parametric resonance vibration was observed only for tension force equal to 4000 N because of the rotational speed limits of electrical vibratos.

18

Analiza eksperymentalna i numeryczna zjawiska rezonansu parametrycznego w przesiewaczu wibracyjnym

60%

Bąk Ł. , Noga S. , Stachowicz F.

Mechanik

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2016

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tom R. 89, nr 3

214--215

PL

Przedstawiono metodykę i wyniki badań eksperymentalnych oraz obliczeń numerycznych dotyczących pracy przesiewacza wibracyjnego z sitem drgającym w warunkach rezonansu parametrycznego. Określono wpływ siły naciągu na częstotliwość i amplitudę drgań parametrycznych sita

EN

Discussed in this paper are the test methods and numerical studies on the vibrating screen operation in parametric resonance conditions. Also the effect of tension force on the sieve vibration frequency and amplitude is determined.

19

To describe of admixture effects on thin films free frequences

60%

Nahirnyj T. , Hrytsyna O.

Vibrations in Physical Systems

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2002

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tom Vol. 20

236--237

20

Calculation of natural frequency and mode shapes for a high speed bevel gear

60%

Michalska A. , Marciniec A.

International Journal of Applied Mechanics and Engineering

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2008

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tom Vol. 13, no 2

415-426

EN

The aim of this article is to analyze free vibrations of the tower shaft that drives the accessory gearbox used in a turbofan aircraft engine. The engine is used to power a midsize business jet. The problem was solved in two ways: by a frequency response measurement test and by employing the dynamic FEA (Finite Element Analysis) that can predict the modal shapes quite accurately (Ramil et al., 2004 and Li et al., 2004). The analysis conducted on an accurate model shows that results were very close to those achieved during the frequency response measurement test. However, working with such a complex model is time-consuming, impossible for preliminary analysis and, as demonstrated in this article, unnecessary. The purpose of this study was to work out a method that would minimize the total time necessary to conduct the analysis while maintaining the good level of accuracy.