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Tesi sul tema "Bearings (Machinery)"

Autore: Grafiati
Pubblicato: 4 giugno 2021
Ultima modifica: 1 agosto 2024

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1

Li, Yawei. "Dynamic prognostics of rolling element bearing condition". Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/15847.

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2

Frew, David Anthony. "The design, development and vibration analysis of a high-speed aerostatic bearing". Thesis, Link to the online version, 2007. http://hdl.handle.net/10019/362.

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3

Zhang, Cheng. "Defect detection and life prediction of rolling element bearings". Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/17658.

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4

Jakeman, R. W. "Analysis of dynamically loaded hydrodynamic journal bearings with particular reference to misaligned marine sterntube bearings". Thesis, Nottingham Trent University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233019.

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5

Pu, Guang. "Hybrid air bearings for high speed turbo machinery". Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7789/.

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This PhD project is set out to develop a type of hybrid journal air bearings with reduced reliance on the supply of compressed air for mobile turbomachinery applications. The research work covers hydrostatic and hybrid journal air bearings with non-compliant clearance boundaries. The approach adopted combined numerical analysis based on CFD and experimental verification of the designs. The research can be divided into three sections. In the first section, numerical approaches to model hydrostatic and hybrid journal air bearings with a fixed clearance boundary were developed based on finite difference method (FDM) and finite volume method (FVM) respectively. In the second and third section, theoretical and experimental studies were performed on hydrostatic and hybrid journal air bearings. Performance of the bearings was investigated in non-rotational and rotational conditions. The analysis on stability and natural frequencies of rotor bearing system was performed using the linear bearing model. The unbalance responses of the rotor in the test rig were predicted using non-linear transient analysis and measured experimentally from 50k rpm to 120k rpm in rotor speed. Through the theoretical and experimental investigations of the hybrid journal air bearings, the objectives of the project have been implemented and the aims have been met.
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6

Mur, Miranda José Oscar 1972. "Feasibility of electrostatic bearings for micro turbo machinery". Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/9823.

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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1998.
Includes bibliographical references (p. 97-98).
by José Oscar Mur Miranda.
M.Eng.
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7

Roach, Christopher James. "Development of porous ceramic air bearings". Thesis, Cranfield University, 2001. http://dspace.lib.cranfield.ac.uk/handle/1826/3693.

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Porous air bearings enjoy some important advantages over conventional air bearing types such as increased load carrying capacity, higher stiffness and improved damping. However, these types of bearings have yet to find widespread acceptance due to problems with obtaining materials with consistent permeability, instability issues relating to the volume of gas trapped at the bearing surface in the pores, and manufacturing the bearing without altering the permeability. Using a series of fine grades of alumina powder to minimise surface pore volume it has been demonstrated that it is possible to consistently and reproducibly manufacture porous bearings by injection moulding and slip casting. The relationship between powder size, processing conditions, porosity, mechanical properties and fluid flow characteristics were experimentally determined. The temperature of processing and the green density were found to be the controlling parameters in the resulting fluid flow properties for a given powder size, Test bearings were produced from the range of processing conditions investigated. It was found that the fine powder size bearings were stable over the entire range of test conditions irrespective of their initial manufacturing route. The most important consideration for the bearing performance was the quality of manufacture. The bearings were found to be sensitive to the flatness of their working surface and quality of fit in their test holder. The bearings were compared with published theories for load capacity and stiffness. A reasonable agreement was found with load carrying capacity once a correction for surface roughness was incorporated. Stiffness predictions provided a useful tool for the analysis and prediction of properties such as optimum values of permeability for a given geometry, if certain allowances are made.
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8

Chong, F. S. "Variation analysis of hybrid bearings". Thesis, Liverpool John Moores University, 1985. http://researchonline.ljmu.ac.uk/5560/.

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9

Lin, Juhn-Shyue. "Experimental analysis of dynamic force transmissibility through bearings". Connect to resource, 1989. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1207597697.

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10

Stack, Jason R. "Fault signature detection for rolling element bearings in electric machines". Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/13276.

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11

Moodie, Craig Alexander Simpson. "An investigation into the condition monitoring of large slow speed slew bearings". Access electronically, 2009. http://ro.uow.edu.au/theses/3035.

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12

Hassan, Mohd Firdaus Bin. "Nonlinear analysis of rotating machinery running on foil-air bearings". Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/nonlinear-analysis-of-rotating-machinery-running-on-foilair-bearings(b16f6146-676b-42c2-aeae-cab321831d78).html.

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Abstract (sommario):
The recently-developed simultaneous solution scheme for solving nonlinear rotordynamic systems running on foil-air bearings (FABs) has overcome the practice of decoupling the air film, foil and rotor equations that has been typically followed to reduce computational burden at the expense of accuracy. However, the published works using the simultaneous solution technique have been limited to a simple bump foil model in which the individual bumps were modelled as independent spring-damper (ISD) subsystems. The overall aim of this thesis is to present methods that enable more realistic FAB models to be integrated into the simultaneous solution scheme, without compromising its efficiency. Two such alternative approaches are presented: (1) the full foil structure modal model (FFSMM) of the bump foil structure; (2) non-parametric system identification of the entire FAB i.e. foil and air film. The FFSMM provides a more realistic model of the bump foil structure since it considers the interaction between the bumps and foil inertia. Although the foil damping is still assumed to be linear, the model presented is adaptable to nonlinear friction forces. The dynamics of the bump foil structure are studied by finite element methods and experimentally validated using a purpose-made corrugated foil structure. The FE result shows that the effect of bump interaction increases the effective stiffness of the FAB. Foil inertia is not important for the range of speeds considered in the thesis, but the experimentally validated fundamental foil resonance of around 2 kHz is within the operating speed range of high-speed turbomachinery. The FFSMM can take into account the curvature of the bearing sleeve, but the effect of this feature is proven to be negligible for the size of bearing used in the study. The FFSMM simulation results are correlated against ISD model results and published experimental maximum film thickness and locus of the journal response. The results of the FFSMM were then compared against experimental results under unbalance response conditions measured from a purpose-built test rig. The rotor was mathematically modelled using rigid body equations of motion, which were validated by modal analysis. The unbalance rotor response results obtained from the FFSMM and experiment both show that the sub-synchronous motion is not only mainly influenced by the increment of unbalance mass, but, to a greater extent, the increment of rotor speed. The findings show good agreement between the model and experimental results. This thesis also presents the non-parametric system identification of a FAB, which is also adaptable to the simultaneous solution scheme. This work is motivated by two advantages: (a) it removes computational limitations by replacing the whole bearing equations by a displacement/force relationship, where the air film effect is taken into account; (b) it can capture complications that cannot be easily modelled, if the identification is based on empirical data. A Recurrent Neural Network (RNN) is trained to identify the full numerical model of a FAB over a wide range of speeds. The identified model of the FAB is adapted into the frequency domain rotor-dynamic simultaneous solution technique by using harmonic balance (HB) methods, thus directly producing the steady-state orbit response. Excellent correlation is demonstrated between the identification technique and the full numerical model under two validation processes: (i) using different sets of input/output data; (ii) the application of the identified RNN-FAB model to HB analysis in lieu of the full numerical model of the FAB.
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13

Dawson, Benedict E. "Design and implementation of magnetic bearings and associated controllers". Thesis, University of Sussex, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360583.

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14

Collins, D. "The vibrational characteristics of oil lubricated plain journal bearings". Thesis, University of Leeds, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373844.

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15

Williams, Tracy Denise. "Remote condition monitoring of rolling element bearings with natural crack development". Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/17243.

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16

Ujjin, Rapee Mechanical &amp Manufacturing Engineering Faculty of Engineering UNSW. "Prediction of bearing failure in pin-loaded laminates". Awarded by:University of New South Wales. School of Mechanical and Manufacturing Engineering, 2007. http://handle.unsw.edu.au/1959.4/28197.

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This thesis presents the results of an investigation of bearing failure at a loaded hole in carbon fibre composite laminates. The investigation included finite element analysis and a program of experimental testing for quasi-isotropic laminates, uni-directional laminates and laminates with fibres steered along predefined trajectories. The investigation formed part of a research program in the Cooperative Research Centre for Advanced Composite Structures Ltd (CRC-ACS) support by the Office of Naval Research from the United States. Work in progress in the CRC includes research defined in this thesis including the addition of nano-particles to the resin to improve the bearing strength. The literature survey undertaken in this thesis identified that the micro-buckling theory proposed by Professor C.T. Sun from Purdue University, Indiana USA, is the best analysis procedure for initial bearing failure in pin-loaded laminates. This failure theory has therefore been implemented in a Fortran program using the results from a finite element analysis for the nonlinear contact problem of a pin bearing on a hole in a composite laminate. The finite element analysis is executed using the commercial finite element system MSC.MARC. The numerical predictions have been validated by a test of progressive failure with the aid of an acoustic emission monitoring system. The acoustic emission parametric and frequency analysis is performed using the acoustic emission software Vallen Systeme. Fast fourier transformation of the waveform have been achieved to distinguish and identify microfailure mode. Failure mechanisms have been verified by post-mortem microstructural examination. There are 3 failure mechanisms associated with bearing failure in carbon fibre reinforced epoxy composite, the first is fibre matrix interfacial failure, followed by fibre fracture, and subsequently matrix splitting. The application of AE technique has been applied successfully to characterise the development of failure.
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17

Roach, M. P. "Vibration control in rotating machinery using variable dynamic stiffness hydrostatic squeeze-films". Thesis, Staffordshire University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254234.

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18

Bara, Richard J. "Rupture point movement in journal bearings". Link to electronic thesis, 2004. http://www.wpi.edu/Pubs/ETD/Available/etd-0607104-105624/.

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19

Whitfield, Robert Ian. "An investigation into the tilt of turbo - generator rotor bearings". Thesis, Northumbria University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245265.

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20

Klos, Gerhard P. J. "The development of a process for the radius hardening of diesel engine crankshaft journals". Thesis, Cape Technikon, 1992. http://hdl.handle.net/20.500.11838/2231.

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Thesis (M. Diploma (Mechanical Engineering))--Cape Technikon, 1992.
Radius hardening on journals of forged steel Diesel engine crankshafts is performed in order to increase fatigue life characteristics. This requirement may be necessary if the demands for engine power are to be increased, but where the existing crankshaft design is close to its fatigue limit, such that an increase in loading will cause it to'fail. Induction hardening of journal radii changes the make-up of the material from a coarse to a fine crystalline structure which alters the features of crack propagation. As a consequence of this higher loads can be applied onto the crankshaft without ultimately resulting in catastrophic material failure. Extending the induction hardened zone from the bearing surfaces into the radii of journals, culminates in process difficulties which are not experienced in non-radius hardened Hardening of journal radii induces crankshafts. as well as releases stresses in the crankshaft webs. This results in a deformation of the crankshaft which can be measured in the form of journal runout. Such a problem cannot be overcome by straightening the crankshafts in order to reduce runout, since this will cause Straightening hand induces the radii to crack once hardened. in the unhardened state on the other stresses which will be released again after hardening. This results in an increase in runout. High runout indicates that stresses have been induced into the crankshaft material. This is undesirable since this will make critical manufacturing processes such as grinding, governing of journal lengths, uncontrollable. It can furthermore result in creep of the crankshaft long after the manufacturing date. This results in crankshaft deformation, noticeable through an increase in runout. Since the crankshaft cannot be straightened after hardening, the consequence is that it will be unusable. The process must therefore be developed in such a manner, that all variables which can contribute towards stress induction resulting in journal 'runout, must be investigated and resolved.
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21

Ciabattoni, Dino. "A CADAM interface for the computer-aided selection of Timken tapered roller bearings". Thesis, Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/101171.

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This thesis presents an interactive computer-graphics geometry interface that simplifies the tapered roller bearing selection procedure. An applications program has been developed that links the CADAM data base to SELECT-A-NALYSIS (SAN), Timken's bearing selection and analysis program. The independent modular format of the SAN preprocessor eliminates the ambiguity and difficulty associated with conventional bearing selection routines. Interactive-graphic menu selection allows program logic to be followed while design geometry is selected from a CADAM model. In addition to the discussion of the program development and structure, step-by-step instructions for an example problem are provided. Complete program listings are also supplied to facilitate future additions and modifications to the preprocessor.
M.S.
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22

Emmanouilidis, Christos. "Evolutionary multi-objective feature selection and its application to industrial machinery fault diagnosis". Thesis, University of Sunderland, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391024.

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23

McLarnon, Christopher Norman. "The non-linear response of overhung rotors in floating ring bearings". Thesis, Heriot-Watt University, 1997. http://hdl.handle.net/10399/613.

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24

Yang, Da-Ming. "Development of novel intelligent condition monitoring procedures for rolling element bearings". Thesis, University of Aberdeen, 2001. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU151909.

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The primary aim of this thesis is to develop a novel procedure for an intelligent automatic diagnostic condition monitoring system for rolling element bearings. The applicability of this procedure is demonstrated by its implementation in a particular electric motor drive system. The novel bearing condition diagnostic procedure developed involves three stages combining the merits of advanced signal processing techniques, feature extraction methods and artificial neural networks. This procedure is the effective combination of these techniques and methods in a holistic approach to the rolling element bearing problem which provides the novelty in this thesis. Maintenance costs account for an extremely large proportion of the operating costs of machinery. In addition, machine breakdowns and consequent downtime can severely affect the productivity of factories and the safety of products. It is therefore becoming increasingly important for industries to monitor their equipment systematically in order to reduce the number of breakdowns and to avoid unnecessary costs and delays caused by repair. The rolling element bearing is an extremely widespread component in industrial rotating machinery and a large number of problems arise from faulty bearings. Therefore, proper monitoring of bearing condition is highly cost-effective in reducing operating cost. The advanced signal processing techniques used here are bispectral-based and wavelet-based analyses. The bispectral-based procedures examined are the bis-pectrum, the bicoherence, the bispectrum diagonal slice, the bicoherence diagonal slice, the summed bispectrum and the summed bicoherence. The wavelet-based procedure uses the Morlet wavelet. These methods greatly enhance the ability of an automated diagnostic process by linking the increased capability for signal analysis to the predictive capability of artificial neural networks. The bearing monitoring scheme based on bispectral analysis is shown to provide greater insight into the structure of bearing vibration signals and to offer more diagnostic information than conventional power spectral analysis. The wavelet analysis provides a multi-resolution, time-frequency approach to extract information from the bearing vibration signatures. In order to effectively interpret the wavelet map, the time-frequency domain is used instead of the time-scale domain by plotting the associated time trace and power spectrum.
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25

Jintanawan, Thitima. "Vibration of rotating disk-spindle systems with hydrodynamic bearings /". Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/7149.

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26

Evans, M. H. "White structure flaking failure in bearings under rolling contact fatigue". Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/355966/.

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White structure flaking (WSF) as a premature wear failure mode in steel rolling element bearings is caused by white etching cracks (WECs) and perhaps butterflies formed in the ~1 mm zone beneath the contact surface under rolling contact fatigue (RCF). WECs are branching crack systems typically several millimetres in length that have a microstructural change called ‘white etching area’ (WEA) associated with the crack. Butterflies are smaller cracks initiating at material defects and impurities that form WEA wings that revolve around their initiators. Hydrogen diffusion into the bearing steel during service and transient operating conditions have been suggested as drivers of white etching features (butterflies, WEA and WECs). However the initiation and propagation mechanisms as well as the thresholds for WEC formation are not well understood. This is due to the difficulties of creating WECs repeatedly under laboratory conditions and the lack of a method established for mapping WECs in detail or 3 dimensions as typically only limited metallographic analyses are conducted over several cross-sections. A series of RCF tests have been conducted in this study to investigate the formation drivers and formation mechanisms of WECs using a two-roller RCF machine. WECs were successfully created in hydrogen charged 100Cr6 martensitic steel rollers under low-moderate concentrations of diffusible hydrogen (~1 ppm) and service realistic loading conditions (Pmax 1.5 – 2 GPa). However, only butterflies were formed under transient conditions with non-hydrogen charged rollers. One such butterfly was analysed in detail to further understanding of crack formation mechanisms and carbide dissolution as part of the WEA microstructural change. Based on the evidence obtained from the SEM, FIB tomography and STEM/TEM analysis, a void/cavity coalescence theory for initial butterfly crack formation and iron chromium carbide dissolution as part of the WEA formation mechanism is proposed. Metallography was extensively used in this project to view cross-sections of the wear zones subject to RCF. A metallographic serial sectioning technique was established to quantitatively map wear zones for the first time. Mapping WECs in their entirety and 3D modelling revealed the 3-dimensional morphology and orientation of WECs and maximised detection of possible WEC initiators. This study has for the first time quantitatively investigated the influence of diffusible hydrogen, load and rolling cycles on white etching feature formation and the thresholds of formation. The hydrogen charged tests showed that the formation of butterflies was independent of the concentration of diffusible hydrogen with the test parameters used, but dependent on contact pressure and number of rolling cycles up to a threshold. WEC formation thresholds were found at certain values of the concentration of diffusible hydrogen, contact pressure and number of rolling cycles. Extensive serial sectioning and 3D modelling of WECs also demonstrated that the orientation of WECs differed depending on the sectioning direction. It was found that the vast majority of WECs were contained in the subsurface wear zone and did not make any connection with the surface, thus dismissing surface initiation. The WECs often interacted with inclusions that were judged to be crack initiators and evidence was found that butterfly cracks could propagate to form WECs. The white etching features initiated predominately at short sulfide type inclusions, small globular manganese sulfide oxide inclusions and small globular oxide inclusions. Therefore strong evidence was observed for a subsurface initiation mechanism of WECs from non-metallic inclusions. A comparison of the WEC formations in the hydrogen charged two-roller tests was made with serial sectioning investigations of WEC formation in wind turbine gearbox bearings obtained from the field and those tested on a large-scale transient test rig (non-hydrogen charged). This was performed to understand if a difference in the WEC initiation and propagation mechanism occurs under the differing conditions. The comparison showed correlation between the WEC formation mechanisms as a high number of inclusions interacted with the WECs that were judged to be crack initiators and small/short sized inclusions predominated as the crack initiators. Therefore based on the serial sectioning analysis across various test specimens and bearings it is proposed that one mechanism of WEC formation is due to multiple linking of extended butterflies or small WECs in the subsurface to form larger WEC networks that eventually propagate to the surface resulting in WSF. The data also suggests that steel cleanliness standards analysing inclusion density (as opposed to maximum inclusion lengths) are more relevant in understanding butterfly/WEC initiation. However steel cleanliness standards used should record inclusions that are only a couple of micrometer’s in length/diameter.
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27

Roberts, Thomas Patton. "A model of cavitating journal bearing performance under dynamic loads". Thesis, Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/18887.

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28

Baseer, M. A. "Control of vibration in a flexible rotor-bearing system". Thesis, University of Bath, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254323.

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29

Park, Jung Seo. "Effects of asymmetry on the vibration of rotating disk/spindle systems /". Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/7084.

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30

Ayandokun, O. K. "The incremental motion encoder : a sensor for the integrated condition monitoring of rotating machinery". Thesis, Nottingham Trent University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245075.

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31

Khan, A. F. "Condition monitoring of rolling element bearings : a comparative study of vibration-based techniques". Thesis, University of Nottingham, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292225.

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32

Ishii, Toshiyasu. "Transient response technique applied to active magnetic bearing machinery during rotor drop". Thesis, Virginia Tech, 1990. http://hdl.handle.net/10919/41937.

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The active magnetic bearing (AMB) is a relatively new technology which has many advantages compared with conventional bearing design. In an AMB system, the rolling-element back-up bearings are indispensable to protect the magnetic bearing rotor and stator, and other stationary seals along the rotor shaft. In this paper, a theoretical formulation is proposed and solved numerically to examine the transient response of the flexible rotor, from the time just previous to the AMB shuts down and including the rotor drop onto the back-up bearing. The backward whirl of the rotor, which may lead to the destructive damage of the machinery, has been analytically predicted at very light support damping and very high support damping. Also, the vibration due to the non-linearity of the contact point geometry has been included in the analysis. The influence of the support damping on the displacement of the disk and also the contact force between the journal and the inner-race of the back-up bearing have been computed for various rotor system parameters. By comparing these results with the optimum support damping for the simple flexible rotor model, it is shown that this support damping optimization can be applicable for specifying the required optimum range of support damping for the back-up bearings of AMB systems.
Master of Science

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33

Mansoor, Yousuf Ali. "The effect of oil feed pressure on friction and cavitation in plain bearings". Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/48377/.

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Experimental and theoretical studies of the influence of oil supply pressure on the friction torque in plain bearings have been carried out. The focus of the work has been the reduction in bearing friction that might be achieved by reducing oil supply pressure and the mechanisms by which the changes in friction occur, with potential applications to reducing bearing friction in internal combustion engines. A single bearing test rig has been used to investigate the impact of feed oil pressure on the extent of cavitation and the role of increased film cavitation on friction under light, steady loads for a bearing with a 180° groove, using an SAE 5W-30 oil. Film visualization shows that cavitation area increases when the oil feed pressure is reduced and the extent of the full width film reduces primarily as the angle of film reformation is retarded. Both load and speed increases reduce the full width film extent. At constant film viscosity, friction torque was reduced by up to 20% by increased cavitation which reduced the film area and the eccentricity ratio. The latter reduces the surface shear stress in the load-bearing region of the film and overall, the circumferential average. As load increases, the reduction in film area accounts for an increasing proportion of the friction torque reduction. The effect of load, speed, lubricant formulation and clearance on bearing friction and film pressure has been investigated. Increases in load led to increases in friction and peak film pressures with smaller percent reductions in friction torque as the supply pressure was reduced. Bearing friction torque was found to show a linear dependence on oil viscosity in the hydrodynamic regime where friction could be substantially reduced by using low viscosity oils. The effect of increased clearance was to reduce bearing friction and increase peak film pressures. The effects of reduced oil supply pressure on friction in crankshaft main bearings during cold-start warm-ups have been investigated. Friction reductions have been found to be most significant during cold running conditions at light loads. The thermal coupling between the bearing films and engine structure influences the film warm-up. Initially there is a rapid rise in film temperatures after which the warm-up is held back by the temperature of the surrounding metal. In addition to reducing bearing friction, reducing oil supply pressure also reduces the oil pumping work required; this represents an additional benefit which can be particularly significant under cold operating conditions.
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34

Mahajan, Manoj Deepak Jackson Robert Lloyd. "Experimental and analytical investigation of a dymanic gas squeeze film bearing including asperity contact effects". Auburn, Ala., 2006. http://repo.lib.auburn.edu/Send%2012-15-07/MAHAJAN_MANOJ_5.pdf.

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35

Billington, Scott Alexander. "Sensor and machine condition effects in roller bearing diagnostics". Thesis, Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/17796.

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36

Kannan, Vigneshwar. "Intelligent Approaches for the Improved Condition Monitoring of Rolling Element Bearings". Thesis, Griffith University, 2022. http://hdl.handle.net/10072/419770.

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Abstract (sommario):
Rotational machinery is used for various applications and is commonplace in industry and aviation sectors. Rolling Element Bearings (REBs) play a vital part in the optimal functioning of rotational machinery. They can naturally develop faults through standard operation of machinery over time or at an accelerated rate due to external factors. Undetected faults in REBs that have not been addressed with the appropriate maintenance actions can cause severe damage to the machine. Maintenance and repairs once damage reaches this stage will be relatively more expensive. This will lead to unexpected machine downtime which could affect revenue dependant on the operation of these machines. Furthermore, such machine damage could cause machinery to behave erratically making it dangerous for those in the immediate vicinity. Therefore, it is essential to ensure the REB used are in good condition. Traditionally, maintenance was scheduled to occur at a certain time when components were expected to fail. However, this would mean that faults occurring sooner than expected will affect machinery operations. It is also possible for these components to remain in good condition past its expected use making maintenance actions unnecessary. A more cost-effective solution that was since developed was condition-based maintenance. This involved monitoring the health condition of machinery through sensor output using appropriate techniques. Condition monitoring can be achieved using various sensors, each presenting their own advantages. Modern approaches to condition monitoring have also utilised multiple sensors for improved detection and diagnosis of faults. The aim of this research was to develop intelligent approaches for the improved accuracy and reliability of REB condition monitoring. Three gaps in literature were identified and addressed in this thesis. Envelope analysis is a technique that has been widely used for the detection and diagnosis of bearing defects. Defect related frequencies are uncovered through the process by selecting an ideal frequency band for demodulation. The use of this frequency band yields an envelope spectrum with more pronounced defect frequencies. Many studies have been carried out for the selection of an ideal frequency band and is considered a major challenge. To address this issue, a real-coded genetic algorithm (GA) with a novel fitness function and crossover selection method was developed. The proposed method was tested on bearing data from two different rotor-bearing systems and was proven to be capable of fault detection. The method was also benchmarked against the fast kurtogram method, a well-established approach used in the fault detection of bearings. The comparison showed that although a much better demodulation band could be identified using the proposed method, the fast kurtogram method obtained results much faster. Harsh operating conditions and environmental factors can affect information acquired by sensors. This can, in turn, negatively influence the accuracy of fault detection and diagnosis. While signal distortions can be distinguished through visual inspection, this is not always practical especially with the rise of automated condition monitoring systems. Research in the area of signal quality assessment is generally limited in the context of machinery condition monitoring. An anomaly detection method was proposed for the detection of vibration signal quality issues and was intended to be used as a pre-processing step to fault diagnosis. This involved the training of a one-class support vector machine (OCSVM) on features pertaining to good quality signals from various machine health conditions. It was found that the approach worked very well in identifying signal issues for trained health conditions. Though misclassifications occurred for untrained conditions, it could be observed that they fell close to the decision boundary generated by the OCSVM. A countermeasure was also proposed to allow untrained condition signals of good quality to be correctly classified by relaxing the decision boundary. Condition monitoring of machinery using multiple sensors has become quite common due to their increasing availability. Data from different sensors are commonly fused at one of the three information fusion levels to attain a more reliable diagnosis on machine health. It is likely that in the event of sensor issues or sensor failure, the reliability of the sensor output will suffer. Distortions in signals can easily pollute the overall classification and go unnoticed due to a majority of these monitoring systems operating automatically. To address this problem, an approach that was capable of assigning a lower influence to low quality sensor signals in the overall diagnosis was proposed. This involved first computing integrity scores for each sensor in the system using OCSVMs. Individual health classifications for each sensor were derived using support vector machines (SVMs). Finally, fusion was conducted at the decision-level by aggregating the integrity scores of corresponding sensors for each class from which the highest was considered the overall classification. This method was validated on a heterogeneous sensor system that consisted of a triaxial-accelerometer and one Acoustic Emission (AE) sensor. The data used in testing included different machine conditions with signals that were of both good and poor quality. Testing showed that a high reliability was achieved through such an approach. This shows that despite some sensor signals being unreliable, the method would be able to accurately distinguish this and reduce its influence on the final diagnosis. The research gaps identified in condition monitoring of REB were successfully addressed using intelligent algorithms. The presented solutions can be implemented for an increased accuracy and reliability of fault detection and diagnosis of bearings, thereby achieving the aim of the study.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Eng & Built Env
Science, Environment, Engineering and Technology
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37

Rothwell, Benjamin Charles. "Design of robust PTFE faced bearings for performance and reliability in large rotating machinery". Thesis, University of Leeds, 2016. http://etheses.whiterose.ac.uk/13348/.

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In this thesis a Finite Element Modelling (FEM) approach is proposed for modelling the visco-plastic creep effects that a PTFE-faced thrust bearing would undergo during normal operating conditions. A thermal elastic hydrodynamic lubrication (TEHL) model is developed, which uses the Reynolds equations for a fluid film, coupled with Hertzian contact theory and the energy equation to predict the pressure and film thickness on the PTFE face as well as the temperature and thickness of the fluid. These variables are then used with a Norton creep function to predict the secondary creep effects on the PTFE surface. This change in PTFE thickness due to visco-plastic effects are taken into account within the film thickness equations and the effects over a bearing’s operational life span studied. The Norton creep function is obtained from experimental creep results conducted on filled PTFE samples at the University of Leeds. This experimental method allowed for the displacement of the samples to be recorded over a 7 day test period at a representative range of pressure and temperature conditions and a Norton creep function to be obtained from the results. The Norton creep function was then included within the simulations to allow for the visco-plastic creep effects to be studied. Results obtained showed that whilst the secondary creep had a small effect on the pressure profile of the pad, the peak pressure was significantly affected during the duration of the pads operational life. It was concluded that this was due to the pad deformation changing, meaning a smaller peak pressure was observed, but the tilt angle did not change greatly, meaning the profile did not change. The pad and film thickness also changed as time passed, with the pad getting thinner in areas of high pressure and temperature, due to the secondary creep effects. It was also observed that the peak temperature of the pad also decreased as time passed, due to the film thickness increase in areas of high temperature.
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Snider, James M. "Zinc pot bearing material wear and corrosion characterization". Morgantown, W. Va. : [West Virginia University Libraries], 2004. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=3716.

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Thesis (Ph. D.)--West Virginia University, 2004.
Title from document title page. Document formatted into pages; contains xx, 272 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 207-208).
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Rachamalla, Vishnu V. "A model of stabilizer roll bearing for a continuous hot-dip galvanizing line". Morgantown, W. Va. : [West Virginia University Libraries], 2006. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4948.

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Thesis (M.S.)--West Virginia University, 2006.
Title from document title page. Document formatted into pages; contains x, 82 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 74-75).
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Carlsson, Björn. "Development and implementation of test rig for investigation of reciprocating polymeric journal bearing wear and friction in a controlled atmosphere". Ohio : Ohio University, 1992. http://www.ohiolink.edu/etd/view.cgi?ohiou1172085651.

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Yoon, Jungkeun. "Shock response of a rotating disk & spindle system with fluid dynamic bearings (FDB) under high shock environments /". Thesis, Connect to this title online; UW restricted, 2008. http://hdl.handle.net/1773/7139.

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Tseng, Chaw-Wu. "Vibration of rotating-shaft design spindles with flexible bases /". Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/7129.

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Worley, Stacy K. "Bearing failure detection in farm machinery using low-cost acoustic techniques". Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06302009-040529/.

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44

Alley, Erick Shaw. "Influence of microstructure in rolling contact fatigue of bearing steels with inclusions". Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28127.

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Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Neu, Richard; Committee Member: Damm, E. Buddy; Committee Member: Gall, Ken; Committee Member: Gokhale, Arun; Committee Member: McDowell, David; Committee Member: Zhou, Min
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Cannon, Jesse R. "Compliant mechanisms to perform bearing and spring functions in high precision applications /". Diss., CLICK HERE for online access, 2004. http://contentdm.lib.byu.edu/ETD/image/etd599.pdf.

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46

Zieliński, Piotr. "The influence of surface roughness and solid contaminants on the performance of hydrodynamic journal bearings". Thesis, Queensland University of Technology, 1997.

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47

Larsen, Christopher G. "Structural FRF Measurements up to 50 kHz to Assist Frequency Band Selection for Machinery Health Monitoring". University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1337715377.

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48

Snider, James M. "Zinc pot bearing material wear rate as a function of contact pressure and velocity". Morgantown, W. Va. : [West Virginia University Libraries], 2002. https://etd.wvu.edu/etd/controller.jsp?moduleName=documentdata&jsp%5FetdId=2721.

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Thesis (M.S.)--West Virginia University, 2002.
Title from document title page. Document formatted into pages; contains x, 80 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 69-70).
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Jackson, Robert Lee III. "An investigation of the wear and lubrication of a thrust washer system in an automatic transmission planetary gearset". Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/16853.

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Guilherme, Karen de Lolo. "Modelagem dinamica de compressores alternativaos". [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/264561.

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Orientador: Paulo Roberto Gabriel Kurka
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: Este trabalho tem como objetivo propor um modelo de dinâmica flexível dos componentes de um compressor alternativo monocilíndrico de refrigeração. Tal modelo representa um aperfeiçoamento da modelagem dinâmica utilizada, que supõe mancais rotativos fixos ou pinados. A modelagem dinâmica flexível do compressor é útil na analise dos esforços de natureza elástica e dissipativa que ocorrem nos mancais de sustentação do conjunto. Esses resultados podem também ser utilizados numa correta medição da energia dissipada pelos mancais. O modelo dinâmico utiliza um mecanismo biela-manivela, pistão e eixo, sujeitos ao carregamento da pressão que o fluido refrigerante exerce sobre o pistão no interior do cilindro. A modelagem incorpora efeitos giroscópicos e utiliza mancais flexíveis nos acoplamentos dos componentes, o que proporciona maior mobilidade ao modelo. O Método de Newton Euler é utilizado na analise das forças e momentos atuantes no sistema para a obtenção das equações diferenciais que representam o seu movimento. As equações dinâmicas, por sua vez, são resolvidas numericamente através do método de Runge-Kutta. Observou-se que a modelagem da oscilaãoo dos componentes rotativos no conjunto eixo-biela-manivela é capaz de produzir esforços diferenciados nos mancais do compressor quando comparado aos esforços de mancal presentes num modelo pinado
Abstract: The work consists in fiding a flexible dynamics model of a single cylinder, reciprocating refrigeration gas compressor. The model represents an improval to the current dynamic model of compressors, that use fixed or pinned rotation journal bearings. An efficient dynamic model of the compressor is useful in the analysis of elastic and dissipative loads that occur in the system¿s internal bearings. The results produced by the model can also be employed in the correct measurement of the energy dissipated at the bearings. The dynamic model consists of a rotor, cranckshaft, connecting rod and piston, all subject to the load from compression of the refrigerant fluid. The model incorporates gyroscopic effects and utilizes flexible bearing couplings, which yield greater mobilty to the moving mechanisms. The Newton-Euler method is used in the analysis of acting forces and torques, establishing the necessary differential equations that describe the movement of the system. A numerical solution of the dynamic equations is obtained through use of the Runge-Kutta method. Application of the model shows that oscillations of the rotating internal components of the compressor yield increased loads to the bearings, as compared to a pinned rotation model
Doutorado
Mecanica dos Sólidos e Projeto Mecanico
Doutor em Engenharia Mecânica
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