Wyniki wyszukiwania - Biblioteka Nauki

1

Capabilities of estimation of rotor dynamic state on the ground of trajectories of bearing journals

100%

Rybczyński J.

Transactions of the Institute of Fluid-Flow Machinery

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2005

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tom nr 116

43-56

EN

In the paper presented are capabilities of advanced rotary machinery diagnostics based on the analysis of trajectories of slider bearing journals. Outlined and characterized have been the categories of rotary machine malfunctioning, which can be detected and discriminated on the basis of images of the journal center trajectory. Discussed have been these elements of trajectories, which bear information about the dynamic state of the machine and which can contribute to differentiation of the machine defects. Principles of diagnostics of the machine state have been analysed from the point of view of relations between the trajectory feature and the rotor dynamic state. Presented problems are based on author's own expertise and have been illustrated by sample images stemming from author's own experimental investigations as well as numerical simulations conducted using own computer codes. The material contained in the paper can be helpful in practical diagnostic applications.

2

Journal Bearing Fault Detection Based on Daubechies Wavelet

100%

Narendiranath B. T. , Himamshu H. S. , Prabin K. N. , Rama P. D. , Nishant C.

Archives of Acoustics

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2017

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tom Vol. 42, No. 3

401--414

EN

Journal bearings are widely used to support the shafts in industrial machinery involving heavy loads, such as compressors, turbines and centrifugal pumps. The major problem that could arise in journal bearings is catastrophic failure due to corrosion or erosion and fatigue, which results in economic loss and creates major safety risks. Thus, it is necessary to provide suitable condition monitoring technique to detect and diagnose failures, and achieve cost savings to the industry. Therefore, this paper focuses on fault diagnosis on journal bearing using Debauchies Wavelet-02 (DB-02). Nowadays, wavelet transformation is one of the most popular technique of the time-frequency-transformations. An experimental setup was used to diagnose the faults in the journal bearing. The accelerometer is used to collect vibration data, from the journal bearing in the form of time domain. This was then used as input for a MATLAB code that could plot the time domain signal. This signal was then decomposed based on the wavelet transform. The fast Fourier transform is then used to obtain the frequency domain, which gives us the frequency having the highest amplitude. To diagnose the faults various operating conditions are used in the journal bearing such as Full oil, half loose, half oil, fault 1, fault 2, fault 3 and full loose. Then the Artificial Neural Networks (ANN) is used to classify faults. The network is trained based on data already collected and then it is tested based on random data points. ANN was able to classify the faults with the classification rate of 85.7%. Thus, the test process for unseen vibration data of the trained ANN combined with ideal output target values indicates high success rate for automated bearing fault detection.

3

Charakterystyki dynamiczne 5-o powierzchniowego łożyska ślizgowego

100%

Strzelecki S.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2001

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tom z. 70

149-156

PL

Łożyska ślizgowe 5-powierzchniowe stosowane są w lekko obciążonych, wysokoobrotowych maszynach wirnikowych. Niezawodna konstrukcja łożyska może być zapewniona poprzez wyznaczenie i analizę jego charakterystyk statycznych i dynamicznych. W referacie przedstawiono charakterystyki dynamiczne łożyska ślizgowego 5-powierzchniowego obciążonego statycznie.

EN

The paper introduces the results of calculation of dynamic characteristic of 5-lobe journal bearing for the different relative length of the bearing. Adiabatic conditions of oil film and aligned axis fo journal and bush have been assumed.

4

Obliczanie odkształceń łożyska ślizgowego metodą CASE

100%

Strzelecki S.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2001

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tom z. 70

165-172

PL

W referacie przedstawiono metodę rozwiązania zagadnienia termosprężystych odkształceń łożyska ślizgowego z panewką o zarysie kołowym. Założono równoległość osi czopa i panewki oraz adiabatyczny model filmu smarowego oraz adiabatyczny, laminarny film. Obliczenia prowadzono w warunkach statycznego położenia równowagi czopa.

EN

The paper presents the results of iterative procedure computation of bearing structure deflections for assumed relative length of the bearing. Adiabatic conditions of oil film and aligned axis of journal and bush have been assumed.

5

Odkształcenia wahliwego łożyska ślizgowego 5-o segmentowego

100%

Strzelecki S. , Kuśmierz L.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2001

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tom z. 70

157-164

PL

Referat przedstawia wyniki obliczeń odkształceń segmentów łożyska wahliwego 5-o segmentowego. Obciążenia łożyska w postaci rozkładu ciśnienia i temperatury wyznaczono przy założeniu laminarnego, adiabatycznego filmu smarowego.

EN

The paper introduces the results of calculations of segments deformations of 5-lobe tilting pad journal bearing for the different relative length of the bearing. Adiabatic conditions of oil film and aligned axis of journal and bush have been assumed.

6

Zmiany struktury warstwy wierzchniej w łożysku ślizgowym samochodu przy tarciu suchym badane metodą anihilacji pozytonów

100%

Polak A. , Dryzek J. , Grzych K.

Czasopismo Techniczne. Mechanika

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2004

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tom R. 101, z. 7-M/2

463--469

PL

Celem artykułu było przedstawienie zmian w warstwie wierzchniej łożyska ślizgowego w czasie tarcia suchego. Badania przeprowadzono metodą anihilacji pozytonów. Wykazano przydatność metody w tego typu badaniach.

EN

The aim of this paper was to describe the changes in superficial laser during material transfer in metal-graphite and metal-polymer journal bearing. This phenomenon was studied many times, but the mechanism of the transfer film formation requires further explanation. In this paper we intend to present also the possibilities offered by positron annihilation spectroscopy in the study of subsurface zone in friction processes.

7

Test stand in university of applied science giessen for friction forces measurements in slide bearing using the acoustic emission method

100%

Ziegler B. , Wierzcholski K. , Miszczak A.

Journal of KONES

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2008

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tom Vol. 15, No. 3

591-595

EN

The present paper shows particularly description of the construction of the test stand for experimental research performed in University of Applied Science Giessen and connected with the measurements of hydrodynamic friction forces in journal slide bearings by using the Acoustic Emission Method. The test stand is adapted for the friction force measurements for the low bearing load and for the high bearing load. For such test stand in the case of low and high loads the dependencies between friction forces and time can be exactly obtained. During the measurements the temperature changes are expected. The advantage of this method is the fact that oscillations of measured friction values can be executed directly from the source to the sensor, what enables us to do an "online-measurement". The Acoustic Emission Analysis is (in opposite to the aforementioned Friction Power measurement) a relative method, which means, that the absolute amount of a RMS-Value depends on the measuring chain.

8

Capacity and friction force in slide journal bearing gap by laminar unsteady lubrication

100%

Krasowski P.

Journal of KONES

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2010

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tom Vol. 17, No. 3

231-238

EN

This paper shows results of numerical solutions modifled Reynolds equations for laminar unsteady oil flow in slide Journal bearing gap. Laminar unsteady oil flow is performed during periodic and unperiodic perturbations of bearing load or is caused by the changes of gap height in time. During modelling crossbar bearing operations in combustion engines, bearing movement perturbations from engine vertical vibrations causes velocity flow perturbations of lubricating oil on the bearing race and on the bearing slider in the circumferential direction. Above perturbations occur mostly during the starting and stopping of machine. This solution example applies to isothermal bearing model with infinity length. Lubricating oil used in this model has Newtonian properties and constant dynamic viscosity. Results are presented in the dimensionless hydrodynamic pressure and tangential tension distribution diagrams. Diagrams also presents capacity and friction force change during the time ofvelocity perturbations. Received solutions were compared with the solution received by the stationary lubrication flow in the slide Journal bearing, which were made with the same parameter assumption by constant dynamie oil viscosity. Isothermal bearing model is similar to friction node model by steady-state heat load conditions. Described effect can be used as on example of modelling the bearing friction node operations in reciprocating movement during exploitation of engines and machines.

9

Bearing condition monitoring using vibration measurements and a new signal enhancement technique

100%

Klamecki B. E.

Applied Mechanics and Engineering

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1999

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tom Vol. 4, no spec.

51-56

EN

This paper describes work aimed at assessing main journal bearing wear in a spark ignition engine using vibration measurements. A large number of tests were run with varying sensor location, engine speed, oil viscosity and bearing wear simulated by machining away material from bearing surfaces. Results show that signal magnitude can be used to characterize bearing operation and wear. Engine speed and oil grade have effects on the signals obtained. In addition it is shown that weak parts of signals can be enhanced with the addition of noise of appropriate level. Random noise was added to vibration signals and noise of an appropriate level enhanced weak parts of accelerometer signals.

10

Vlianie nesimmetricnogo nagreva vala ne ego traektoriu v sektornom cilindriceskom podsipnike

100%

Grigoriev B. , Fedorov A.

Zeszyty Naukowe Politechniki Świętokrzyskiej. Nauki Techniczne

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2008

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tom Z. 10, Vol. 1

101-108

EN

Influence of asymmetrical heating of an unbalanced shaft on a trajectory of a synchronous whirl in the pad journal bearings is considered. The mathematical model including both the thermogydrodynamic analysis of bearings and the calculation of shaft heating with its subsequent bend is developed. As an example the system consisting of two bearings in which shaft with overhung disk rotates was considered.

11

On partial hydrodynamic lubrication effects in the journal bearings

100%

Szolc T. , Sosnowski W.

Computer Methods in Materials Science

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2007

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tom Vol. 7, No. 1

94-100

EN

The objective of this research is to include mixed friction effects into existing models of hydrodynamic journal bearings described e.g. in [1]. The problem of partial hydrodynamic lubrication caused by roughness of sliding surfaces has been investigated for many years by numerous researchers. But majority of theoretical studies in this field were focused on very fundamental aspects taking into consideration general principles of bearing operation from the viewpoint of flow determination between sliding surfaces of various roughness description, [2]. The considerations in this paper are devoted to partial hydrodynamic lubrication effects in typical cylindrical transverse journal bearings applied for supporting of heavy rotor-shafts of the rotating machines. For this purpose there is used the average flow theory for an oil film interaction with rough journals and bushings. In order to carry out a qualitative analysis of the problem a simple mechanical model of the partially lubricated “super-bearing” is assumed. This model consists of the rigid mass rotating with constant speed and performing translational in-plane motion within the non-rotating rigid ring which is elastically suspended in this plane. The rigid mass represents the entire inertia of the rotating parts of the rotor machine and the rigid ring corresponds to the housing of such “super bearing”. Translational in-plane motion of the rigid mass is coupled with translational motion of the rigid ring by means of mass-less springs and dampers representing respectively visco-elastic properties of the oil film in the “super-bearing” with rough sliding surfaces. These visco-elastic properties of the oil film in such bearing are determined by numerical solving of the average Reynolds equation describing partial oil flow between the rough journal and bushing. Here, according to [2], the pressure flow factors and the shear flow factors standing in the average Reynolds equations are determined analytically using proper empirical formulae obtained by numerical simulations of the model flows between partially lubricated surfaces for various roughness geometry and average oil film thicknesses. Solving in this way the average Reynolds equation for the entire oil gap by means of the finite difference method enables us to determine resultant viscous friction retarding force as well as transverse hydrodynamic load of the bearing. For various roughness geometry the former enables us to determine the frictional power yielded by the bearing and the latter makes possible calculation of stiffness and damping coefficients of the mass-less springs representing visco-elastic properties of the oil film in the assumed model of the “super-bearing”. In the numerical examples numerous roughness amplitudes of the journal and the bushing surface as well as various directional orientations of roughness asperities, which follow from final machining of the journal and the bushing, are taken into consideration in order to investigate their influence on kineto-static and dynamic behaviour of the transverse oil-film bearing. In the next steps of research in this field, beyond the partial lubrication, also the metal-to-metal friction effects are going to be investigated, i.e. for so high loadings of the journal bearing, when the hydrodynamic lubrication theory for the oil film stops to be in force.

PL

Celem pracy jest przedstawienie algorytmu, który umożliwi uwzględnienie tarcia mieszanego w łożyskach ślizgowych. Zaproponowano takie modyfikacje równania Reynoldsa, które pozwolą uwzględnić wysokość nierówności na powierzchniach waha i panwi. Następnie założono możliwość wystąpienia warunków tarcia mieszanego, do którego może dojść, gdy najmniejsza odległość wału i panewki zmniejszy się osiągając wartość przy której może dojść do kontaktu obydwu współpracujących części. Przyjęto, że w takim przypadku tarcie mieszane zostanie opisane z wykorzystaniem klasycznego modelu Coulomba. Podstawą obliczeń jest prosty algorytm numeryczny wbudowany w program IZOTER prof. Kicińskiego (1996, 2005) oparty na Metodzie Różnic Skończonych i przeznaczony do symulacji zjawisk towarzyszących pracy łożysk ślizgowych. Zaproponowany algorytm przetestowano na przykładzie łożyska stosowanego w turbinie siłowni energetycznej.

12

New approach to analysis of additional effects of journal bearings

100%

Malenovský E. , Pochylý F.

Zeszyty Naukowe Katedry Mechaniki Stosowanej / Politechnika Śląska

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2001

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tom z. 15

293-298

EN

The new theoretical approach to the analysis of rigid body motion (for example rotating shaft) is presented in this article. The solution is derived in curvilinear co-ordinates, which is completely different from contemporary approach. The theoretical analyse is done for different boundary conditions and it is also possible to include the division of velocity and pressure along the axis of the shaft.

PL

W pracy przedstawiono nowe podejście teoretyczne do analizy ciał sztywnych (np. wirujących wałów). Rozwiązanie wyprowadzone we współrzędnych krzywoliniowych, co jest zupełnie różne od obecnie stosowanego podejścia. Analizę teoretyczną przeprowadzono dla różnych warunków brzegowych. Możliwe jest również wyprowadzenie rozkładu prędkości i ciśnienia wzdłuż osi wału.

13

Pressure And Capacity Changes In Slide Journal Bearing For Laminar Unsteady Oil Flow

100%

Krasowski P.

Journal of Polish CIMAC

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2007

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tom Vol. 2, no 1

281-290

EN

This paper presents numerical solutions of the modified Reynolds equation of laminar unsteady lubrication in a cylindrical slide journal bearing. Laminar, unsteady oil flow is performed during periodic and unperiodic perturbations of bearing load or is caused by the changes of gap height in the time. Above perturbations occur during the starting and stopping of machine. The particular solutions are limited to the isothermal models of bearing with infinite length and lubricated by Newtonian oil with the dynamic viscosity dependent on pressure. The disturbances are related to the unsteady velocity of oil flow on the sleeve and on the surface Diagram shows the results of hydrodynamic pressure and capacity forces in the dimensionless form in time intervals of displacement duration.

14

Pressure and velocity distribution in slide journal bearing lubricated micropolar oil

100%

Krasowski P.

Journal of Polish CIMAC

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2010

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tom Vol. 5, no 1

119-126

EN

This paper shows results of numerical solutions an modified Reynolds equations for laminar unsteady oil flow in slide journal bearing gap. Laminar unsteady oil flow is performed during periodic and unperiodic perturbations of bearing load or is caused by the changes of gap height in time. During modelling crossbar bearing operations in combustion engines, bearing movement perturbations from engine vertical vibrations causes velocity flow perturbations of lubricating oil on the shaft in the circumferential direction. This solution example apply to isothermal bearing model with infinity length. Lubricating oil used in this model has Newtonian properties and constant dynamic viscosity. Results are presented in the dimensionless hydrodynamic pressure and tangential tension distribution diagrams. Diagrams also presents capacity and friction force change during the time of velocity perturbations. Received solutions were compared with the solution received by the stationary lubrication flow in the slide journal bearing, which were made with the same parameter assumption by constant dynamic oil viscosity. Isothermal bearing model is similar to friction node model by steady-state heat load conditions. Described effect can be used as on example of modeling the bearing friction node operations in reciprocating movement during exploitation of engines and machines.

15

Pressure In Slide Journal Bearing Lubricated Oil With Micropolar Structure

100%

Krasowski P.

Journal of Polish CIMAC

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2008

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tom Vol. 3, no 2

9-13

EN

Present paper shows the results of numerical solution Reynolds equation for laminar, steady oil flow in slide bearing gap. Lubrication oil is fluid with micropolar structure. Properties of oil lubrication as of liquid with micropolar structure in comparison with Newtonian liquid, characterized are in respect of dynamic viscosity additionally dynamic couple viscosity and three dynamic rotation viscosity. Under regard of build structural element of liquid characterized is additionally microinertia coefficient. In modeling properties and structures of micropolar liquid one introduced dimensionless parameter with in terminal chance conversion micropolar liquid to Newtonian liquid. The results shown on diagrams of hydrodynamic pressure in dimensionless form in dependence on coupling number N2 and characteristic dimensionless length of micropolar fluid A1. Presented calculations are limited to isothermal models of bearing with infinite length.

16

Automatic Fault Classification for Journal Bearings Using ANN and DNN

100%

Narendiranath Babu T. , Aravind A. , Rakesh A. , Jahzan M. , Rama Prabha D. , Ramalinga Viswanathan M.

Archives of Acoustics

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2018

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tom Vol. 43, No. 4

727--738

EN

Journal bearings are the most common type of bearings in which a shaft freely rotates in a metallic sleeve. They find a lot of applications in industry, especially where extremely high loads are involved. Proper analysis of the various bearing faults and predicting the modes of failure beforehand are Essentials to increase the working life of the bearing. In the current study, the vibration data of a journal Bering in the healthy condition and in five different fault conditions are collected. A feature extraction metod is employed to classify the different fault conditions. Automatic fault classification is performed using artificial neural networks (ANN). As the probability of a correct prediction goes down for a higher number of faults in ANN, the method is made more robust by incorporating deep neural networks (DNN) with the help of autoencoders. Training was done using the scaled conjugate gradient algorithm and the performance was calculated by the cross entropy method. Due to the increased number of hidden layers in DNN, it is possible to achieve a high efficiency of 100% with the feature extraction method.

17

Surface topography of slide journal bearings

100%

Miszczak A. , Czaban A.

Journal of KONES

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2011

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tom Vol. 18, No. 3

279-285

EN

In this article the measurements results of surface topography of different types of slide bearings sleeves have been presented. The research has been conducted with the use of atomic force microscope (AFM). The results of measurements of surface topography were presented in the form of surface topography maps, three-dimensional graphs and some examples of selected cross-sections of investigated surface in the form of profile graphs. Measurements of surface topography were made for thin-walled sleeves of slide journal bearings covered with PTFE, POM, bronze and white metal layers. Operated and new sleeves have been considered with the use of Atomic Force Microscope NT-206produced in MTM in Minsk, Republic of Belarus [2]. Atomic Force Microscope NT-206 provides information for samples with maximum roughness value plus or minus 1 mi m. Max. field in one scanning process is up to 32)um x 32mi m. Measurements were preceded with resolution 256x256points. Presented in the work results of surface topography measurements also include the calculated values of average deviation profile Ra and Rq and the value of fixed distance between the lowest and highest inequality. The application SurfaceXplorer was used for processing and visualization of the data obtained from AFM NT-206, which besides from generating 2D, 3D and profile diagrams, was used to calculate and draw graph of height distribution. The comparison of received data will allow verifying type and amount of surface wear of discussed journal micro-bearings parts in micro and nanoscale and will help to design surface layers with improved tribological properties.

18

Friction forces measurements by the acoustic emission for slide bearing test stand in uni of applied science Giessen

88%

Ziegler B. , Wierzcholski K. , Miszczak A.

Journal of KONES

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2008

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tom Vol. 15, No. 4

627-633

EN

The present paper describes the results of measurements performed in University of Applied Science Giessen and determined hydrodynamic friction forces in journal slide bearings by using the Acoustic Emission Method. It describes the use of the Acoustic Emission Analysis as an indicator of the bearing friction at slide bearings. The investigations were made at two different test stands. The test stand at Maritime University Gdynia covers the hydrodynamic operation range, the test stand at University of Applied Science Giessen the mixed friction area. The successive steps of measurements of the hydrodynamic friction forces are presented in this paper. Hardness and roughness of cooperating surfaces is in this paper particularly described. The friction values and its boundary conditions at the test were measured for the low bearing load and for the high bearing load. In both cases, the dependencies between friction forces and time are exactly obtained. During the measurements, the temperature is taken into account. The advantage of this method is the fact that these oscillations can be executed directly from the source to the sensor, what enables us to do an "online-measurement". The Acoustic Emission Analysis is (in opposite to the aforementioned friction power measurement) a relative method, which means, that the absolute amount of a RMS-Value depends on the measuring chain. The results are compared and discussed with other results obtained in experiments performed in Maritime University Gdynia.

19

Friction forces measurements for slide bearing test stand in maritime university Gdynia using the acoustic emission method

88%

Ziegler B. , Wierzcholski K. , Miszczak A.

Journal of KONES

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2008

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tom Vol. 15, No. 2

571-577

EN

The present paper determines the results of experimental research performed in Gdynia Maritime University and connected with the measurements of hydrodynamic friction forces in slide journal slide bearings by using the Acoustic Emission Method. A new method for mechanical friction force measuring was carried out at this test stand, simultaneously the friction force will be indicated by an optimized Acoustic Emission System. The friction conditions at the test were measured by two different methods. At the one hand the friction power measurement and at the other hand the Acoustic Emission Analysis. One characteristic of the friction power measurement is the rather inert reaction to the oscillations of the slide bearing. The advantage of the method is the fact that one can measure absolute values of the friction power. In opposite to that, the Acoustic Emission Analysis measures the high frequency oscillations caused by the hydrodynamic friction between the oil molecules. The advantage of this method is the fact that this oscillations can be executed directly from the source to the sensor, what enables us to do an "online-measurement". The Acoustic Emission Analysis is (in opposite to the aforementioned friction power measurement) a relative method, which means, that the absolute amount of a RMS-Value depends on the measuring chain. The results are compared and discussed with other results obtained in experiments performed in University of Applied Science Giessen.

20

Asymmetric Rigid Rotor System Supported on Journal Bearings with Piezoactive Elements

88%

Przybyłowicz P. M.

Machine Dynamics Problems

|

2003

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tom Vol. 27, No. 2

87-106

EN

In the paper, the problem of stability of an asymmetric journal bearing system enhanced with piezoelectric elements is considered. Journal bearings are known to exhibit dynamic loss of stability in the form of flutter-type vibration while exceeding the critical rotation speed. By making use of piezoelectric actuators pushed in between the bearing housing and shell it is possible to affect the size of thebearing gap, which directly influences the critical rotation speed and the moment when the system losses its stability. In the paper, the critical speed is examined on the grounds of linearised equations of motion describing a 4-DOF mechanical system. The length of the rotor is taken into account. The equations of motion include terms corresponding to the gyroscopic effect. The position of application of the external load is assumed arbitrarily. It is proved that the incorporated method enables semi-active control of dynamic properties of the examined system. Results of carried out simulations are presented in the form of trajectories of eigenvalues, static equilibrium curves and stability zones versus the applied gain in the control system.