Dissertations / Theses on the topic 'Ball Bearings'
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El-Tayeb, Nabil Said Mohamed. "The dynamic properties of ball bearings." Thesis, University of Leeds, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366386.
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Holland, Michael L. "Assembly Optimization for Double Row Ball Bearings." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/37009.
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This thesis is a treatise on optimal assembly methods for double row ball bearings. As with common single row bearings, double row ball bearings, consist of four general components, namely, an inner ring, an outer ring, a complement of balls and a cage or retainer to keep the balls separate. Unlike single row bearings, however, double row ball bearings have two complements of balls in two distinct parallel races. Although this double row configuration is desirable in a number of applications, it makes the bearings more difficult and expensive to assemble. In addition, current manual assembly procedures require a great deal of digital manipulation, leading to concern about carpal tunnel syndrome and other long-term repetitive motion injuries.
This thesis attempts to develop an improved assembly process for all types of double row bearings. Although the work is intended to be general, the Torrington 5203 double row ball bearing is adopted as a specific application example. This bearing's assembly difficulties and additional cost are a result of its manual Conrad assembly method and a rubber O-ring and groove used solely for bearing assembly. In the assembly process, the O-ring supports the upper balls temporarily until the two rings can be aligned concentrically, thus snapping the balls into the bearing races. This thesis addresses the replacement of the rubber O-ring and explores opportunities for bearing assembly automation.
Design synthesis of a retractable or reusable assembly component to replace the rubber O-ring supporting the upper balls during assembly is presented. A large group of design concepts are developed and evaluated, resulting in a small group of feasible designs. These feasible solutions are then tested, and a design that has the potential immediate implementation in an improved manual assembly process is proposed. In addition, two design concepts are presented as candidates for possible implementation in an automated assembly process.
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Ribadeneira, M. Xavier. "Ball bearing diagnostics with multiple sensors." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/18963.
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Levesque, George. "Critical flaw size in silicon nitride ball bearings." [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0041089.
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Shakya, Piyush. "Data fusion based diagnosis and prognosis of ball bearings." Thesis, IIT Delhi, 2015. http://eprint.iitd.ac.in:80//handle/2074/8174.
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Sandström, Tobias. "Condition Monitoring of Ceramic Ball Bearings in an Engine Testing Dynamometer." Thesis, KTH, Maskinkonstruktion (Inst.), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-183126.
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The choice of the topic addressed in this thesis aims to improve the service and maintenance on ceramic ball bearings in a specific test dynamometer and through an engineering approach develop tools for condition monitoring. The company connected to this thesis, AVL, is the world's largest privately owned company for development, simulation and testing technology of powertrains for passenger cars, trucks and large engines. Engine testing is a critical part of the business at AVL Sweden and unexpected bearing failure can result in long repair times and great economic losses due to loss of the testing time. In short terms, the methodological approach followed the following steps; first a thorough information retrieval regarding bearings and analysis was conducted. The search was deepened around areas such as hybrid ball bearings, bearing failure mechanisms, bearing defect frequencies, signal analysis and condition monitoring. After this a table for bearing damage detection was developed and a “step by step” guidance for condition monitoring. The tools where afterwards verified by simple testing to detect complications within the chosen system. The existing condition monitoring system that is used today revealed weaknesses as it lacked the feature of taking preventive measures. The system that is based on temperature measurements isn’t satisfactory enough, especially when it’s missing visual clarity. Service and maintenance according to specifications from the manufacturer should be scheduled to ensure operational and guarantees. Currently mounted accelerometers on the housing of the Dynas3 engine should be connected for collecting data and the total sum of energy should be calculated for simple monitoring of historical progression. This should be done by following the guidance in order to ensure proper data acquisition. The best way to implement condition monitoring showed to be by performing multi-parameter monitoring. The design of the condition monitoring system is highly connected to what to monitor and at what stage. One main consideration to keep in mind is that it’s very rare that manufacturing defects are the reason for bearing failure. Instead it derives from improper storage, transport, handling or dimensional errors and even in some cases by improperly implemented force analysis prior to bearing selection.Huvudämnet som behandlas i detta examensarbete syftar till att förbättra service och underhåll på keramiska kullager i en viss testdynamometer och genom ett ingenjörsmässigt tillvägagångsätt utveckla verktyg för tillståndsövervakning. Företaget som är ansluten till detta examensarbete är AVL som är världens största privatägda företag för utveckling, simulering och testteknik för drivlinor för personbilar, lastbilar och stora motorer. Motorprovning är en viktig del av verksamheten vid AVL Sverige, och ett oväntat lagerhaveri kan leda till långa reparationstider och stora ekonomiska förluster på grund av utebliven test tid. I korta termer följde den metod som använts följande steg, först genomfördes en grundlig informationssökning om lager och tillhörande analyser. Efter det fördjupades sökande kring områden som hybrida kullager, lagerskademekanismer, frekvenser kopplade till lagerskador, signalanalys och tillståndsövervakning. Efter detta framställdes en tabell för detektering av lagerskador, samt en ”steg för steg” guide för tillståndsövervakning. Verktygen för tillståndsövervakning kontrolleras efteråt, genom att enkla tester genomfördes för att upptäcka komplikationer inom det valda systemet. Det övervakningssystem som används idag avslöjade svagheter genom att sakna funktionen att vidta förebyggande åtgärder. System som är baserat på temperaturmätningar är inte tillräckligt tillfredsställande, speciellt när det saknar en visuell tydlighet. Den service och underhåll som enligt tillverkarens föreskrifter påvisas bör planeras för att säkerställa drift och garantier. Nuvarande monterade accelerometrar fästa vid motorhöljet bör anslutas för att insamla data, och den totala summan av energin bör beräknas för en enkel övervakning av det historiska utvecklingsförloppet. Detta bör göras genom att följa de riktlinjer som framställts för att säkerställa korrekt datainsamling. Det bäst passande sättet att genomföra tillståndsövervakning på i detta fall visade sig vara att utföra multiparameterövervakning. Framställningen av tillståndsövervakningssystemet är starkt förknippat med vad som skall övervakas och i vilket skede. En huvudsaklig bidragande faktor att komma ihåg är att det är mycket ovanligt att fabrikationsfel är orsaken till lagerhaveri. Istället härstammar haveriet från felaktig förvaring, transportering, hantering eller dimensioneringsfel och i vissa fall av felaktigt genomförd kraftanalys inför lagerval.
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Gunduz, Aydin. "Multi-Dimensional Stiffness Characteristics of Double Row Angular Contact Ball Bearings and Their Role in Influencing Vibration Modes." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1326397623.
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Akturk, Nizami. "Dynamics of a rigid shaft supported by angular contact ball bearings." Thesis, Imperial College London, 1993. http://hdl.handle.net/10044/1/7359.
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Khanam, Sidra. "Vibration analysis and feature extraction of ball bearings with local defect." Thesis, IIT Delhi, 2016. http://localhost:8080/xmlui/handle/12345678/7033.
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Pinckney, Francis Douglas. "Air-oil mist lubrication of small bore ball bearings at high speeds." Thesis, Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/104537.
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Martin, M. J. "Elastohydrodynamic films and scuffing behaviour in high speed angular contact ball bearings." Thesis, Cardiff University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.543267.
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Tuomas, Roger. "Properties of oil and refrigerant mixtures : lubrication of ball bearings in refrigeration compressors /." Luleå : Division of Machine Elements, Luleå University of Technology, 2006. http://epubl.ltu.se/1402-1544/2006/70/.
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Sum, Wei Wern. "Dynamic analysis of angular-contact ball bearings and the influence of cage geometry." Thesis, University of Nottingham, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.423977.
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Yin, Zidong. "Modeling and design of a miniature high precision linear stage on ball bearings." Compiègne, 2010. http://www.theses.fr/2010COMP1914.
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Aujourd'hui, la miniaturisation est une tendance forte dans le développement technologique des produits industriels, avec les exigences en composants microtechniques. Le micro / usinage conventionnel à l'outil est de plus en plus important, car il peut créer des pièces en 3-D avec des matériaux divers et il présente de nombreux avantages en efficacité, productivité, flexibilité et rentabilité, etc. Us guidages linéaires miniatures sont des composants clés des méso machines-outils. Cette thèse porte sur la conception d'une table linéaire miniature sur roulements à billes avec une raideur élévée, apte à satisfaire les exigences des méso machines-outils de haute précision. Deux critères de conception de base sont considérés: le premier est que les paliers à billes doivent être en mesure de supporter la charge maximale d'utilisation tout en conservant un comportement élastique et maximisant la rigidité ; l'autre est que l'influence des tolérances sur le diamètre des billes et la planéité de la paroi sur les mouvements parasites doit rester en dessous de l'erreur maximale autorisée sur la surface usinée. Un palier ouvert avec des erreurs géométriques est étudié en premier lieu par la théorie de He. Ensuite, une structure de palier fermé précontraint est proposée pour sa capacité à soutenir une charge relativement élevée, avec une grande rigidité, dans un encombrement limité. Sur la base des éléments de palier fermé proposés, une méthode de modélisation et de minimisation d'un guidage a été développée pour répondre aux exigences d'une taille limite de 70x 140 mrra, une capacité de charge > 250N et une rigidité > 500N/gm. Une évaluation théorique des erreurs de rectitude et de tangage d'un mini guidage avec des paliers sur roulements précontraints a été développée et analysé pour différentes préchuges, erreurs géométriques et charges externes. L'erreur de rectitude du mouvement peut ainsi être réduite à environ 1/10' de l'erreur de fabrication, ou moins selon la longueur d'onde de l'erreur de planéité des parois. Une optimisation des profils d'entrée sous le chariot est étudiée pour réduire les mouvements parasites et les excitations vibratoires induits par l'effet de bord du contact de roulement. Enfin, un prototype de mini-rail de guidage pour méso machines-outils a été conçu et fabriqué. La course est de 80 mm. S parois du roulement sont en acier GCr15 et les billes sont en céramique Si3N4, pour son niveau élevé de résistance à la compression et sa dureté. Les dimensions de la structure de la table miniature ont été déterminées avec des évaluations par éléments finis ; l'épaisseur des parois doit être >Ilmm. Les erreurs de tangage et de rectitude du mouvement du prototype ont été étudiées. Pour une erreur maximale du diamètre des billes d'environ 0,13gm et des erreurs de profil des parois d'environ 1,0 à 3,0gm, l'erreur de rectitude du guidage est d'environ 0,25gm sur une course de avec une précontrainte géométrique de 6gm. Ces résultats sont en bon accord avec les prédictions théoriquesIn actual technological developments, the trend to miniaturization of industrial products requtes micro components. Tool based micro/meso-scale machining is becoming increasingly important, since it cm create 3-D parts in various engineering materials and has many advantages in productivity, efficiency, flexibility and cost effectiveness, etc. Mini-guideways are key components of meso-machine tools. This thesis fuses on the design of an ultra precision miniature linear guideways on bail bearings, able to fulfilling the requirements of ultra predision meso-machine tools with a high stiffness. Two basic design criteria are consider: one is that the bail bearing elements must be able to bear the maximum working load while keeping an elastic behaviour and maximizing the stiffness; the other is that the influence of halls diameter and wall flatness tolerances on peasidc movements must be kept below the maximum error allowed to surface machining. Firstly, based on Hertzian contact theory, an open bearing with geometrical errors is studied. Then a structure of preloaded closed bearing element is proposed for its potential ability to supporting a heavy load with a high stiffness in a limited size. Based on the proposed closed bearing elements, a method of modeling and minimisation of a guideway is developed, targeting at fulfilling the conditions of a limited size of 70x140 mm, load capacity >250N and stiffness >500N/gm. A Theoretical evaluation of straightness error and pitch error of the motion of the mini-guideway with closed bearing elements is developed and is analyzed with various specified preloads, geometrical errors and external loads. Straightness error of motion of the mini-guideway may be reduced to about 1610 times the given fabrication error or even less, for specified appropriate wavelength of surface error of the walls. To lower the puasitic motion and excitation generated by bUls entering or exiting from under the cage, opdMzation of the cage's profiles is discussed to minimize the edge effect on rolling contact. At last, a prototype of mini-guideway for meso machine tools has been design and manufactured. The travel is80 mm. The beuings walls have been made of steel GCr15 and the bans are in ceramics Si4, rince they have a high level of compressive strength and hardness. The dimension of the ni-guideway structure have been dened via evaluations with the Finite Element Method (FEM); thickness of the walls of the ni-guideway should be >11 mm. Fitch errors and straighness error of motion of the prototype have been invesfigated. For a diameter error of balls of about 0. 13gm and straightness profile errors of the walls aof about I. 0-3. 0gm, the straightness motion error of the mini-guideway is about 0. 251tm over a travel of 5m with a geometrical preload of 6jrm. These results agree well with the theoretical prédictions
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Karlsson, Alexander, and Eric Marcus. "Evaluation of Strain and Temperature Measurements with Fiber Bragg Grating for Loss Verification and Heat Transfer of Ball Bearings." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-86149.
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Volvo Cars is in a change of producing only electric and hybrid cars by 2025.Subcomponent testing is a crucial part to ensure the quality of the individual buildingblocks in an electric machine. Any way of making these tests more reliable and less timeconsuming is of great interest at Volvo. Force and temperature on bearings are especiallyhard to measure accurately, because of their placement and dynamic behavior. Accurateand reliable measurements is also a vital part in creating realistic Computer-AidedEngineering (CAE) models for simulation purposes. Simulations on bearings could lead tobetter bearing choices and accelerate the design process. This could increase bearing lifeand increase the Electrical Vehicle (EV) range due to minimized friction losses. FiberBragg Grating (FBG) sensors is a technology that has some key advantages overconventional sensors. They are immune to EMI, smaller in size, can have multiple sensorsin one fiber and can measure multiple physical quantities at the same time. Volvo Cars isinterested in investigating whether this sensor technology could be a candidate forreplacing some of the current measurement setup configurations.The project was divided into three parts, validating sensor equipment, find method forinstallation and measurement on a bearing and development of a CAE model for bearinglosses and heat transfer. To validate the sensor equipment a Measurement SystemAnalysis (MSA) was performed on two FBG fibers, one FBG isolated from strain fortemperature measurement and one FBG array with multiple sensing points. From theMSA it could be seen that the FBG temperature sensor had a total uncertainty of 3.4 °CThe FBG array had a strain uncertainty of 1.04 μ𝜀 and a temperature uncertainty of 0.4 °C.The uncertainty of both the FBG array and the FBG temperature sensor is highlydependent on the calibration of the sensitivity constant. The force measurement on thebearing was done with a concept based on the wavelength difference, produced by strain,between two FBG sensors. The concept was tested in a dynamic component rig where anaxial force could be applied, and the wavelength difference measured. The temperatureon the outer ring of the bearing was measured using an FBG isolated from strain. The testresults were promising, but since the FBG is sensitive to temperature and strain theincreased temperature difference between the two fibers affected the results. Thecalibration method needs to be compensated for the increased temperature differencebetween the fibers which is generated when the rotational speed is increased, and thiscould not be done with a single temperature measurement. The two developed CAEmodels was both constructed in MATLAB and showed similar behavior with experimentaltests done by others. To validate the models, physical test for heat transfer and bearinglosses should be performed.
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Huq, Fazul, and dpmeng@bigpond com. "Development of Life Prediction Models for Rolling Contact Wear in Ceramic and Steel Ball Bearings." RMIT University. Aerospace, Mechanical and Manufacturing Engineering, 2007. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080215.145624.
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The potential for significant performance increases, using ceramic materials in un-lubricated rolling element bearing applications, has been the subject of research over the past two decades. Practical advantages over steel include increased ability to withstand high loads, severe environments and high speeds. However, widespread acceptance has been limited by the inability to predict wear life for ceramic bearing applications. In this thesis, the rolling contact wear of 52100 bearing steel and Over-aged Magnesia-Partially-Stabilised Zirconia (OA-Mg-PSZ) ceramic are examined using a newly developed rolling contact wear test rig. The new wear test rig simulates the system geometry of an un-lubricated hybrid (ceramic and steel) ball bearing. The new wear test rig is versatile in that it allows low cost samples to be utilised resulting in a larger number of samples that can be tested. Wear samples of 52100 bearing steel and OA-Mg-PSZ produced by the new wear test rig were examined for mass loss and wear depth. The wear behavior of both the steel and ceramic material showed a dependence on operating variables time and load. Load was varied between 300N to 790N. Typical mass loss after 1 hour of testing 52100 bearing steel at 790N was 0.03 grams as compared to OA-Mg-PSZ which was 0.001 grams. The rolling contact wear of the OA-Mg-PSZ was an order of magnitude lower than that of the 52100 bearing steel. The wear mechanism for 52100 bearing steel was typical of plastic deformation and shearing near and below the surface of rolling contact. Once cracks extend to reach the surface, thin flat like sheets are produced. In OA-Mg-PSZ the wear mechanism initially is that of plastic deformation on the scale of the surface asperities with asperity polishing occurring followed by lateral cracks and fatigue spallation. Results obtained using the new rolling contact wear test rig led to the establishment of a new equation for wear modeling of 52100 bearing steel and OA-Mg-PSZ ceramic materials.
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Chen, Qi. "Benchmarking of temperature and friction in axial ball bearings lubricated by a novel polymer thickened grease." Thesis, KTH, Maskinkonstruktion (Inst.), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-183007.
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This project concerns the benchmarking of a novel polymer thickened grease with a lithium thickened one. The new grease has shown low temperature property in the previous bearing tests on SKF-R2F. A DAQ interface was implemented using lab View for a modified four-ball machine. The result shows the temperature and friction torque profiles of the greases at different speeds. The raw data is attached with a suggested improvement for friction measurement.Det här projektet avser att jämföra ett nytt polymerbaserat fett med ett lithiumbaserat fett. Det nya fettet har påvisat låga temperaturegenskaper i det tidigare testet med ett lager av typen SKF-R2F. Ett DAQ-gränssnitt implementerades med Lab View för en modifierad fyr-kulig maskin. Resultaten visar temperaturer och friktionsmoment av fetterna vid olika hastigheter. Förslag på förbättring av friktionsmomentet är presenterat tillsammans med rådata.
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Kirchner, William Thomas. "Ultrasonic acoustic health monitoring of ball bearings using neural network pattern classification of power spectral density." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/36130.
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This thesis presents a generic passive non-contact based acoustic health monitoring approach using ultrasonic acoustic emissions (UAE) to facilitate classification of bearing health via neural networks. This generic approach is applied to classifying the operating condition of conventional ball bearings. The acoustic emission signals used in this study are in the ultrasonic range (20-120 kHz), which is significantly higher than the majority of the research in this area thus far. A direct benefit of working in this frequency range is the inherent directionality of the microphones capable of measurement in this range, which becomes particularly useful when operating in environments with low signal-to-noise ratios. Using the UAE power spectrum signature, it is possible to pose the health monitoring problem as a multi-class classification problem, and make use of a multi-layer artificial neural network (ANN) to classify the UAE signature. One major problem limiting the usefulness of ANN's for failure classification is the need for large quantities of training data. Artificial training data, based on statistical properties of a significantly smaller experimental data set is created using the combination of a normal distribution and a coordinate transformation. The artificial training data provides a sufficient sized data set to train the neural network, as well as overcome the curse of dimensionality. The combination of the artificial training methods and ultrasonic frequency range being used results in an approach generic enough to suggest that this particular method is applicable to a variety of systems and components where persistent UAE exist.Master of Science
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Perrelli, Valeria. "Six Sigma Approach to Halve the Cycle Time of a Grinding Process on Carbonitrided Parts : Case analysis and solution executed at SKF-Bari Factory, Italy." Thesis, KTH, Industriell produktion, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-102794.
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The main purpose of this thesis work was to halve the cycle time of a grinding process of the groove of carbonitrided ball bearings rings. The study was conducted as a Six Sigma project at SKF in Bari, Italy. Reaching the goal was important for the company as it meant avoiding the purchase of another grinding machine. The groove grinding process on carbonitrided rings features double the cycle time than the same process on through hardened rings and halving it was required to fulfill the volumes demanded. The Six Sigma methodology was applied through the implementation of DMAIC. The analysis of the problems and identification of areas for improvement were carried out deploying different tools such as an Ishikawa diagram, Hypothesis Testing and Statistical Process Control. The outcome of this was the need to optimize the carbonitriding process minimizing the depth of the layer without enlarged carbides in order to render the design of the part easier to machine and subsequently find the process parameters for the groove grinding yielding a cycle time of six seconds. Many trials were conducted with the supplier of carbonitriding, until the carbon and ammonia potentials were set at levels resulting in a depth of the layer allowing the change of the design. An optimizing DOE was instead performed for the grinding process which highlighted the parameters settings yielding the target cycle time. Finally actions and controls to perform in order to maintain the gains were defined.
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Kucukyilmaz, Ali. "Experimental Investigation Of Residual Stresses Introduced Via Shot Peening And Their Effect On Fatigue Life Of Ball Bearings." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/2/12611494/index.pdf.
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In this study, residual stresses introduced via application of shot peening on the raceways of bearing rings and their effect on the fatigue life was investigated experimentally. For improvement of residual compressive stress state, shot peening operation with different parameters was utilized. Residual stress measurements were conducted via X-ray diffraction technique. Optimization of residual stress state during the production of ball bearings is the main target of this study. Process parameters for shot peening and super-finishing were studied for determination of the parameters that induce the most favorable residual stress state. The fatigue life of ball bearings were determined by life cycle tests and tabulated to show the results of the study. The results of the thesis are believed to help for optimization of residual stress distribution and improvement of service life of ball bearings.
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Bainbridge, Emma. "'Ball-bearings all the way, and never a dull moment!' : an analysis of the writing of G.V. Desani." Thesis, University of Kent, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399648.
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CABRAL, Adriano de Sousa. "Estudo termográfico de auxílio à detecção de falhas por desgaste mecânico em rolamento autocompensador de esferas." Universidade Federal de Campina Grande, 2017. http://dspace.sti.ufcg.edu.br:8080/jspui/handle/riufcg/1497.
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O objetivo desta pesquisa foi analisar se a Termografia pode auxiliar na detecção de falhas em elementos de máquinas, notadamente rolamentos autocompensadores com 2 carreiras de esferas. A motivação surgiu da necessidade de verificar os pontos de falhas existentes nestes elementos mecânicos visando minimizar e/ou eliminar paradas inesperadas que possam comprometer o bom funcionamento dos mesmos e consequentemente das máquinas às quais estão inseridos. A pesquisa é classificada como investigativa, documental, prescritiva, qualitativa e quantitativa. A metodologia utilizada fez uso de bancada de testes composta por elementos mecânicos diversos a citar: motor elétrico controlado por inversor de frequência, amortecedores de vibração (vibra-stop), polias e correias, mancais de rolamentos, carga em eixo, câmera térmica e rolamentos autocompensadores modificados com defeitos nas pistas interna e externa em cenário com condições de controle e não-controle de temperatura ambiente, umidade relativa, rotação do motor, velocidade do ar, temperatura refletida e emissividade. Como resultado, observou-se que houve alteração significativa de temperatura nas pistas interna e externa dos rolamentos com falha do tipo sulco. Por outro lado, não foram percebidas alterações significativas nas pistas interna e externa do rolamento com falha por desgaste por abrasão. Por fim, conclui-se, neste trabalho, que a hipótese inicial foi parcialmente confirmada, isto é, a Termografia pode sim auxiliar a detectar as falhas mecânicas, mas falhas do tipo sulco e não as falhas do tipo desgaste abrasivo.
The aim of this study was to verify if Thermography can help in the diagnosis of failures in machine elements, notably self-aligning bearings with 2 rows of balls. The motivation arose from the need to verify the fault points existing in these mechanical elements to minimize and / or eliminate unexpected stops that could compromise the proper functioning of themselves and consequently of the machines of which they are part of. This study is classified as investigative, documentary, prescriptive, qualitative and quantitative. The methodology made use of test bench composed of several mechanical elements: electric motor controlled by frequency inverter, vibration-stop buffers, pulleys and belts, house bearings, radial load, thermal camera and self-aligning bearings with inner and outer race fault in a scenario with control conditions and non-control of ambient temperature, relative humidity, engine speed, air velocity, reflected temperature and emissivity. It was confirmed that there was a significant temperature change in the inner and outer races of groove-type failure bearings. On the other hand, no significant changes were observed in the inner and outer races of the bearing with abrasion wear failure. Finally, it was concluded in this work that the initial hypothesis was partially confirmed, that is, the Thermography can help to detect mechanical failures in groove type failures but not abrasive wear type failures.
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Masotti, Paulo Henrique Ferraz. ""Metodologia de monitoração e diagnóstico automatizado de rolamentos utilizando lógica paraconsistente, transformada de wavelet e processamento de sinais digitais"." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/85/85133/tde-28052007-165556/.
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A área de monitoração e diagnóstico vem apresentando um acentuado desenvolvimento nos últimos anos com a introdução de novas técnicas de diagnóstico bem como vem contando com a contribuição dos computadores no processamento das informações e das técnicas de diagnósticos. A contribuição da inteligência artificial na automatização do diagnóstico de defeito vem se desenvolvendo continuamente e a crescente automação na indústria vêm de encontro a estas novas técnicas. Na área nuclear, é crescente a preocupação com a segurança nas instalações, e têm sido procuradas técnicas mais eficazes para aumentar o nível de segurança [59]. Algumas usinas nucleares já possuem instaladas, em algumas máquinas, sensores que permitem a verificação de suas condições operacionais. Desta forma, este trabalho também pode colaborar nesta área, ajudando no diagnóstico das condições de operação das máquinas, mais especificamente, no diagnóstico das condições dos rolamentos. O principal objetivo deste trabalho é detectar e classificar os tipos de defeitos apresentados pelos rolamentos analisados e para tal desenvolveu-se uma nova técnica de extração de característica dos sinais de aceleração, baseando-se no Zero Crossing da Transformada de Wavelet contribuindo com o desenvolvimento desta dinâmica área. Como técnica de inteligência artificial foi utilizada a Lógica Paraconsistente Anotada com dois valores (LPA2v), oferecendo a sua contribuição na automação do diagnóstico de defeitos, pois esta lógica pode tratar inclusive de resultados contraditórios que as técnicas de extração de características possam apresentar. Foi desenvolvido um programa de computador onde varias técnicas de extração de características foram utilizadas para realização de diagnóstico das condições de operação dos rolamentos. Este programa foi testado através de dados experimentais obtidas em uma bancada de ensaios para rolamentos onde defeitos previamente conhecidos foram utilizados para avaliar o desempenho das novas técnicas utilizadas. Este trabalho também se concentrou na identificação de defeitos em sua fase inicial procurando utilizar acelerômetros, pois são sensores robustos, de baixo custo e facilmente encontrados na indústria em geral. Os resultados deste trabalho foram obtidos através da utilização de um banco de dados experimental e verificou-se que os resultados de diagnósticos de defeitos mostraramse bons para defeitos em fase inicial.The monitoring and diagnosis area is presenting an impressive development in recent years with the introduction of new diagnosis techniques as well as with the use the computers in the processing of the information and of the diagnosis techniques. The contribution of the artificial intelligence in the automation of the defect diagnosis is developing continually and the growing automation in the industry meets this new techniques. In the nuclear area, the growing concern with the safety in the facilities requires more effective techniques that have been sought to increase the safety level. Some nuclear power stations have already installed in some machines, sensors that allow the verification of their operational conditions. In this way, the present work can also collaborate in this area, helping in the diagnosis of the operational condition of the machines. This work presents a new technique for characteristic extraction based on the Zero Crossing of Wavelet Transform, contributing with the development of this dynamic area. The technique of artificial intelligence was used in this work the Paraconsistente Logic of Annotation with Two values (LPA2v), contributing with the automation of the diagnosis of defects, because this logic can deal with contradictory results that the techniques of feature extraction can present. This work also concentrated on the identification of defects in its initial phase trying to use accelerometers, because they are robust sensors, of low cost and can be easily found the industry in general. The results obtained in this work were accomplished through the use of an experimental database, and it was observed that the results of diagnoses of defects shown good results for defects in their initial phase.
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Nelias, Daniel. "Contribution à l'étude des roulements." [S.l.] : [s.n.], 1999. http://csidoc.insa-lyon.fr/these/1999/nelias/index.html.
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Knauf, Stefan [Verfasser], and Rolf [Akademischer Betreuer] Rannacher. "Numerical simulations for ball bearings considering fluid-structure interaction problems and non-Newtonian fluids with a free boundary / Stefan Knauf ; Betreuer: Rolf Rannacher." Heidelberg : Universitätsbibliothek Heidelberg, 2011. http://d-nb.info/1179229290/34.
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Gao, Wenjun. "Modelling of windage and churning losses in high speed rolling element bearings." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEI048/document.
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Dans un système de machines rotatives comme un moteur à turbine, les paliers d'éléments roulants à grande vitesse jouent un rôle important dans le support de l'arbre ou du rotor rotatif, et ont besoin d'une lubrification pour assurer leur fonction. Sauf qu'une petite quantité d'huile est nécessaire pour former le film lubrifiant élastohydrodynamique dans la zone de contact, la plus grande partie du lubrifiant reste en suspension dans l'air, formant un mélange huile/air. Ce phénomène entraîne des pertes hydrauliques parasitaires excessives lorsque les éléments roulants se translatent et tournent dans l'environnement fluide, ce qui peut constituer une partie relativement importante de la perte de puissance totale du roulement, appelée traînée d'enroulement et pertes de barattage. Pour une vitesse de rotation jusqu'à 3× 106 Ndm, la contribution de la traînée/dérive au total peut atteindre 50%. Cependant, jusqu'à présent, il existe peu d'approches utilisées directement pour l'estimation des pertes par traînage, qui ne pouvait fournir qu'une approximation plutôt grossière. Dans cette thèse, la méthode CFD est utilisée pour analyser d'abord l'écoulement autour d'un cylindre circulaire de longueur finie avec deux extrémités libres dans un espace ouvert. Ensuite, le modèle est remplacé par plusieurs cylindres circulaires en ligne pris en sandwich par deux parois plates, ce qui représente une approche simplifiée. Le fluide est ici considéré comme incompressible, représentant un fluide monophasé équivalent pour l'écoulement diphasique huile/air à l'intérieur de la cavité de palier avec des propriétés de fluide spécifiées. Les résultats indiquent que l'écoulement autour de l'élément de rouleau de longueur finie est perturbé par ses deux extrémités libres, les anneaux environnants, la cage et d'autres éléments roulants. Il est proposé une relation entre le coefficient de traînée et le nombre de Reynolds approprié pour un cylindre circulaire dans les roulements à rouleaux (1In a rotating machinery system like turbine engine, high speed rolling element bearings play an important role in supporting the rotating shaft or rotor, and need lubrication to insure their function. Except a small quantity of oil is needed to form the elastohydrodynamic lubricant film in the contact zone, most of lubricant remains in suspension in air, forming an oil/air mixture. This phenomenon leads to excessive parasitic hydraulic losses when rolling elements translate and rotate into the fluid environment, which may constitute a relatively large portion of the bearing's total power loss, named windage drag and churning losses. For high speed applications, i.e. for rotational speed up to 3× 10^6 Ndm, the contribution of drag/windage loss to the total one may reach up to 50%. However, so far there are few approaches used directly for drag and churning losses estimation, which could only provide a rather gross approximation. In this thesis, the Computational Fluid Dynamics (CFD) method is employed to analyze first the flow around one finite-length circular cylinder with two free ends in an open space. Then the model is changed to several in-line circular cylinders sandwiched by two flat walls, which represents a simplified approach. The fluid here is regarded as incompressible, representing an equivalent one-phase fluid for the oil/air two-phase flow inside the bearing cavity with specified fluid properties. The results indicate that the flow around the finite length roller element is perturbed by its two free ends, the surrounding rings, the cage and other rolling elements. A relationship between the drag coefficient and the Reynolds number suitable for circular cylinder in roller bearings (1
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Carvalho, Rafael Vischi. "Análise dinâmica de rolamentos de esfera." [s.n.], 2010. http://repositorio.unicamp.br/jspui/handle/REPOSIP/263050.
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Orientador: Katia Lucchesi Cavalca DediniDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
Made available in DSpace on 2018-08-16T18:19:16Z (GMT). No. of bitstreams: 1 Carvalho_RafaelVischi_M.pdf: 7127919 bytes, checksum: 2c7a6895f35098e4e4f46ed38b158980 (MD5) Previous issue date: 2010
Resumo: Rolamentos de esfera são elementos de máquinas de forma simples mas utilizados em aplicações envolvendo altas velocidades, altas temperaturas e diferentes carregamentos. O modelo para o carregamento é fundamental para análise dinâmica do mancal e por esse motivo é necessário definir com precisão o desempenho desses mecanismos usando métodos analíticos. O objetivo deste trabalho é analisar o rolamento de esferas baseando-se, em um primeiro momento, em referências bibliográficas de diversos autores para, em seguida, iniciar o equacionamento e simulação para analisar as influências do momento giroscópico, das velocidades geradas nos diversos componentes do rolamento e do carregamento nas esferas. A partir de um rolamento padrão, aplicou-se uma metodologia de testes por simulação numérica variando os principais fatores críticos de um rolamento do ponto de vista estático, cinemático e dinâmico. Conclui-se que a rotação e o ângulo de contato influem nas forças de atrito que resistem ao momento giroscópico e nas velocidades geradas na zona de contato entre esfera e pistas interna e externa. Em altas rotações, quanto maior os seus valores, maior a influência nos ângulos de precessão e de nutação, causando o efeito de escorregamento. Verificou-se, ainda, o valor do ângulo de nutação no qual a velocidade normal ao contato é nula, isto é, validou-se o efeito de outer raceway control. Assim, o modelo apresentou-se consistente com a aproximação para as velocidades e acelerações presentes no elemento rolante, fatores estes fortemente relacionados à condição de lubrificação de mancais de esferas
Abstract: Ball bearings are simple machine elements but largely used in several applications involving high velocities, high temperatures and different loads. The load model is fundamental for the ball bearing's dynamic and for this reason it is necessary to define with accuracy the mechanisms performance using analytical methods. The objective of this thesis is to analyze the ball bearings using, firstly, the most relevant books and papers from several authors as reference and then initiate the modeling and simulation to analyze the influences from the gyroscopic moment and from the velocities created due to the bearing's components and also to the load. Based on a basic bearing, a numeric simulation's test methodology was applied modifying the main critical factors from the bearing and considering the kinematical, dynamical and statical behaviors. The conclusion is that the rotation and the contact angle have influence at the friction forces that resist to the gyroscopic moment and to the velocities that are created at the contact zones between balls and inner and outer raceways. Under high rotations, as higher its value is, higher is the influence at the precession and nutation angles, causing sliding. It was also verified the nutation angle in which the normal velocity at contact is zero, validating the outer raceway control. The model presented itself very consistent with the approximation for the velocities and accelerations presented at rolling element, factors that are highly related to the lubrication condition from the ball bearings
Mestrado
Mecanica dos Sólidos e Projeto Mecanico
Mestre em Engenharia Mecânica
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Radaelli, Gustavo Zarpelon 1989. "Determinação do carregamento dinâmico em mancais de esfera de contato angular." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/264178.
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Orientador: Kátia Lucchesi Cavalca DediniDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: Os mancais possuem um papel expressivo dentre os componentes de um sistema rotativo, tendo o suporte de um elemento rotativo como sua principal função. Por trabalharem na interface entre elementos fixos e rotativos, os mancais constituem a origem de grande parcela das falhas ocorrentes em um sistema. Dentre estes, os mancais de rolamento de contato angular estão entre os mais utilizados, principalmente pela indústria automobilística. Apesar da ampla gama de aplicações, esses mancais usualmente estão sujeitos a falhas por fadiga de superfície, o que torna imprescindível um estudo aprofundado dos esforços e das velocidades aplicados às esferas e, consequentemente, às pistas interna e externa. A descrição dos esforços e das velocidades nas esferas é um desafio considerável, uma vez que as esferas estão sujeitas a uma lubrificação elastohidrodinâmica, que por sua vez, depende integralmente dos esforços e das velocidades das esferas para ser modelada, gerando assim um processo iterativo. O principal objetivo deste trabalho é analisar o rolamento de esferas de contato angular, com embasamento teórico na literatura clássica para, em seguida, iniciar o equacionamento do equilíbrio de forças nas esferas e no mancal, o qual por sua vez, resulta na força de contato associada à condição de lubrificação. Para tanto, um programa computacional para simulação numérica das análises cinemáticas e dinâmicas foi desenvolvido e seus resultados comparados com a literatura. Após realizar a validação inicial do modelo com a literatura, uma solução mais completa é proposta para reproduzir de uma forma mais detalhada o que se encontra em aplicações práticas. Os resultados encontrados pelas diversas simulações foram condizentes com os resultados encontrados na literatura clássica, atestando que o programa computacional desenvolvido é consistente
Abstract: The bearings are of great importance and its major function is to support a rotating element. Due to the mandatory role of these components in the interface between fixed and rotating elements, the bearings are the source of a great percentage of the possible faults on a system. The rolling bearings of angular contact are one of the most utilized, mainly by the automotive industry. In spite of the great applications field, these bearings are usually subject to damage by superficial fatigue, which makes of great significance the detailed study of the efforts and the velocities on the spheres and, consequently, on the external and internal railways. The description of the efforts and velocities acting on the spheres is a considerable challenge, once the spheres are subject to an elastohidrodynamic lubrication that fully depends on the efforts and velocities of the spheres, generating an iterative process. The main objective of this work is to analyze the rolling bearings of angular contact, under theoretical bases, in order to accomplish the forces balance for the balls and for the bearing, which in turn results in the contact forces associated to the lubrication condition. The analysis requires the development of a computational program to numerically simulate the kinematic and dynamic conditions and, then, some of the results can be compared with the literature. After the initial validation of the model with the literature, a more complete solution is proposed to make it closer to practical applications. Results obtained by several simulations are compatible with those found in theoretical bases, attesting that the computational program developed is consistent
Mestrado
Mecanica dos Sólidos e Projeto Mecanico
Mestre em Engenharia Mecânica
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Ivan, Knežević. "Analiza dinamičkog ponašanja kugličnih ležaja primenom veštačkih neuronskih mreža." Phd thesis, Univerzitet u Novom Sadu, Fakultet tehničkih nauka u Novom Sadu, 2020. https://www.cris.uns.ac.rs/record.jsf?recordId=114949&source=NDLTD&language=en.
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Predmet ove doktorske disertacije je analiza dinamičkog ponašanjakotrljajnih ležaja primenom veštačkih neuronskih mreža. Na bazirezultata eksperimentalnog ispitivanja obučene su veštačkeneuronske mreže koje su sposobne da predvide amplitude brzinevibracija ležaja. Vibracije koje ležaj generiše zavise od nizauticajnih parametara koji se mogu podeliti na konstrukcione,tehnološke i eksploatacione. Modeli dobijeni primenom veštačkihneuronskih mreža određuju zavisnosti između uticajnih parametara iamplituda brzine vibracija koje ležaj generiše. Validacijaneuronskih modela izvršena je na osnovu eksperimentalnih rezultata.Analiziran je uticaj svakog parametra ležaja na amplitude brzinevibracija u karakterističnim područjima frekvencija. U radu suprikazani i rezultati međusobnog uticaja više parametara. Modelimasu dobijene preporučene vrednosti uticajnih parametara ležaja. Prianalizi tehnoloških parametara uvedeni su: parametar ekvivalentnepovršinske hrapavosti, parametar ekvivalentne valovitosti iparametar ekvivalentnog odstupanja od kružnosti staza kotrljanja.Novouvedeni parametri omogućavaju bolje razumevanje uticaja nadinamičko ponašanje. U radu je pokazano da su neuronski modelisposobni da na osnovu parametara ležaja predvide klasu kvalitetaležaja.The subject of this doctoral dissertation is the analysis of the dynamicbehavior of ball bearings using artificial neural networks. Based on theresults of the experimental test, artificial neural networks were trained to beable to predict the amplitudes of the bearing vibration velocity. The vibrationsgenerated by the bearing depend on a number of influential parameters thatcan be divided into construction, technological and exploitation. Modelsobtained by applying artificial neural networks determined the dependencesbetween the influencing parameters and the amplitudes of the vibrationvelocity generated by the bearing. Validation of neural models wasperformed based on experimental results. The influence of each parameteron the vibration velocity amplitudes in the characteristic frequency rangeswas analyzed. The paper also presents the results of the mutual influence ofseveral parameters. The models obtained the recommended values of theinfluential bearing parameters. In the analysis of technological parameters,the following parameters were introduced: the parameter of equivalentsurface roughness, the parameter of equivalent waviness and the parameterof equivalent roundness error of raceways. The newly introduced parametersprovide a better understanding of the impact on dynamic behavior. The papershows that neural models are able to predict the bearing quality class basedon bearing parameters.
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Hjalmarsson, Joel, and Anes Memic. "FE Analysis of axial-bearing in large fans : FE analys av axialkullager i stora fläktar." Thesis, Linnaeus University, School of Engineering, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-6663.
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Detta examensarbete har utförts på Fläktwoods AB i Växjö, som producerar stora axialfläktar för olika industriapplikationer. Syftet är att öka kunskapen om fettsmorda axiella kullager genom FE analyser.
Projektet har genomförts i fem delsteg för att avgöra påverkan av en eller några få parametrar i taget. De studerade parametrarna är: elementstorlek, kontaktstyvhet, last, lagergeometri (dvs. oskulation), ickelinjär geometri och ickelinjära materialegenskaper (dvs. plasticitet).
Slutsatsen är att elementstorleken bör väljas fint nog för att ge ett jämnt resultat men grovt nog för att beräkningstiden skal vara rimlig. Kontaktstyvheten har inte stor, men tydlig, inverkan på kontakttrycket och penetrationen. Förändringar av oskulationen leder till förändringar i kontaktellipsens form medan olika laster inte påverkar formen på ellipsen, utan snarare storleken. När det handlar om plasticitet är sträckgränsen den viktigaste faktorn att beakta.
This thesis project was carried out at Fläktwoods AB in Växjö who produces large axial fans for different industry applications. The purpose is to increase the knowledge of grease lubricated axial ball bearings through FE analyses.
The project was executed into five sub steps to determine the influence of one or few parameters at a time. The studied parameters are: mesh density, contact stiffness, load, bearing geometry (i.e. osculation), geometrical nonlinearity and material nonlinearity (i.e. plasticity).
It is concluded that the mesh density should be selected fine enough to give a smooth result but course enough to give a reasonable calculation time. The contact stiffness has not a major, but a clear, impact on the contact pressure and penetration. Changes of the osculation lead to changes of the contact ellipse shape and applying different load level does not affect the shape of the ellipse but rather the size. When dealing with plasticity the yield strength is the most important factor to take in consideration.
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Niel, Dimitri. "Etude du comportement thermomécanique de paliers à roulements pour une application hautes vitesses." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI007/document.
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Avec l’apparition de moteur électrique dans le secteur automobile, les réducteurs mécaniques fonctionnent à des vitesses de rotation de plus en plus élevées. Pour ce type de réducteur, les pertes de puissance au niveau des paliers à roulements peuvent être prédominantes pour des vitesses de rotation élevées. Ces pertes sont fortement dépendantes du comportement thermique du palier à roulement. D’où l’intérêt de développer des outils numériques permettant d’estimer les puissances générées au sein d’un palier à roulement. Cette estimation permettra en phase de pré-étude de développer un dispositif de refroidissement adapté afin d’éviter tout risque de dégradation du palier à roulement. Cette thèse présente une nouvelle approche permettant d’étudier le comportement thermomécanique de palier à roulement. Cette approche intermédiaire requiert un minimum de paramètres d’entrée (géométrie externe du palier à roulement et condition de fonctionnement). Elle utilise la méthode dite « des réseaux thermiques » pour obtenir une interconnexion entre les pertes de puissance et le comportement thermique du palier à roulement. Enfin cette approche permet de calculer la puissance dissipée au sein d’un roulement et les températures des bagues et du lubrifiant principalement pour une application hautes vitesses. Cette approche est développée pour des roulements à billes à gorge profonde et contact oblique. Des valeurs expérimentales sont nécessaires pour valider cette nouvelle approche. C’est pourquoi, un nouveau banc d’essai modulaire dédié à l’étude du comportement thermomécanique de palier à roulement a été développé. Sur ce nouveau moyen d’essai, une grande variété de paliers à roulements peut être testée pour différentes conditions de fonctionnement. Pour les premiers essais, un roulement à billes à gorge profonde lubrifié par injection est testé pour un fonctionnement hautes vitesses (produit (n×D_m) supérieur au million)Rolling Element Bearing (REB) is an essential component in mechanical transmission to reduce friction between rotating parts. Now, with the development of electrical motor in mechanical industry, REBs may work at very high rotation speed. It leads to an increase of REB power losses and temperatures. Theses power losses are strongly coupled with the REB thermal behaviour. The oil temperature has a significant impact on the kinematic viscosity which in turn affects the REB power losses. Based on thermal network approach, an intermediate model is developed in this study. This new model allows obtaining lumped information (temperature of rings) with a minimum of input data (REB external geometry and operating condition only) and by using global power loss models. This intermediate model is developed for angular contact ball bearing and deep groove ball bearing under oil jet lubrication for high speed application. Experimental data are required to validate this new approach. That why, a modular test rig is designed to obtain information on the REB thermomechanical behaviour. The new test rig developed in this study is dedicated to a wide range of REB dimensions and for different operating conditions. For the first test, a deep groove ball bearing under oil jet lubrication is studied for high speed application ((N.dm) product is higher than one million.)
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Alegranzi, Selvino Bork. "Construção e adequação de uma bancada de ensaios para investigações de técnicas não destrutivas de detecção de falhas incipientes em rolamentos." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2012. http://hdl.handle.net/10183/60683.
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O monitoramento de vibração de máquinas rotativas é de grande interesse da indústria, uma vez que se tem a possibilidade de detectar, com certa antecedência, problemas relacionados à condição de funcionamento do equipamento, possibilitando reparos, ajustes ou consertos e, assim, minimizando custos no caso de falhas graves ou paradas inesperadas. Neste trabalho é feita a adequação de uma bancada de testes para estudo de técnicas de detecção de falhas em rolamentos de esferas por análise de vibração. O objetivo é o de localizar falhas em rolamentos utilizando o monitoramento dos sinais das vibrações (aceleração) no mancal que suporta o rolamento de teste e o posterior processamento com o auxílio de alguma técnica de detecção. Neste trabalho a técnica do envelope foi escolhida. A bancada, assim desenvolvida, permite a retirada e colocação dos rolamentos em estudo de maneira simples e rápida, permitindo a execução de diversos testes com rapidez. A investigação da detecção de falhas em rolamentos é feita comparando-se rolamentos em condições normais com rolamentos que têm um defeito induzido. Inicialmente é apresentada a descrição das origens e formas de propagação das falhas em elementos de rolamentos e também as formas como estas falhas são induzidas em locais específicos de cada rolamento. Uma breve revisão sobre métodos de detecção de falhas no domínio do tempo e da frequência é feita. Ênfase é dada ao método do envelope que faz uso da transformada de Hilbert (Hilbert Transform) conjuntamente com a transformada Rápida de Fourier (Fast Fourier Transform). Em seguida, descreve-se como foram geradas as falhas e separados os grupos de teste, também é descrito como os ensaios foram executados com os danos induzidos em local pré-determinado no rolamento. Os resultados obtidos possibilitaram identificar as origens das falhas induzidas tanto na pista externa quanto na interna dos rolamentos analisando os sinais de vibração do mancal onde está montado o rolamento em teste com o pós-processamento dos mesmos com a técnica investigada. Os testes simulam as condições extremas encontradas em sistemas rotativos de equipamentos industriais através da imposição de cargas verticais ao rolamento. Este estudo de detecção das falhas em rolamentos propiciou uma melhor compreensão e análise do processo de falha nestes componentes.The vibration monitoring of rotating machines is of great interest to industries since it has the ability to detect, in advance, problems related to the operational condition of the equipment, enabling fixing, adjustments or repair, and thus, minimizing the cost in case of faults or unexpected downtime. In this work, the study of the adequacy of a test bench for detecting faults in ball bearings by vibration analysis techniques is developed. It aims at locating faults in ball bearings using vibration monitoring signals (acceleration) in the journal bearings that support this elements and further processing with the aid of some detection technique. In this work the envelope technique was chosen. The developed test bench thus allows the removal and placement of the bearings in a simple and fast way allowing running quickly several tests. The investigation of detecting faults in ball bearings is made by comparing the bearings under normal conditions with bearings which have an induced defect. First of all is presented a description of the origins and forms of propagation of faults in bearing elements and also the ways in which these failures are induced in specific locations of each bearing. A brief review of methods for detecting faults in the time and frequency domain is made. Emphasis is given to the Envelope Method which uses the Hilbert Transform with the Fast Fourier Transform. Then it is described how the tests were accomplished with the induced damage in predetermined sites in the bearing. The results obtained allowed to identify the origins of the induced bearing failures in both outer and inner races just by reading the vibration signals and post-processing them with the investigated technique. The tests take care to simulate conditions close to those found in actual rotatory systems of industrial equipment by imposing vertical loads to the bearing. This study in detecting flaws in balls bearings provided a better understanding of the analysis failure process in these components.
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Xin, Ge. "Sparse representations in vibration-based rolling element bearing diagnostics." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI051/document.
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Bien que le diagnostic des roulements par analyse vibratoire soit un domaine très développé, la recherche sur les représentations parcimonieuses des signaux de vibration est encore nouvelle et difficile pour le diagnostic des machines tournantes. Dans cette thèse, de méthodes nouvelles ont été développées, au moyen de différents modèles stochastiques, associées à des algorithmes efficaces afin de servir l’industrie dans le diagnostic des roulements. Tout d’abord, les modèles parcimonieux présentés dans la littérature sont revus. Les principales publications concernant le diagnostic des machines tournantes ont également été considérées. Enfin, en discutant des avantages et des inconvénients des représentations parcimonieuses, une interprétation des structures creuses d’un point de vue Bayésien est proposée, ce qui donne lieu à deux nouveaux modèles de diagnostic des machines tournantes. Dans un second temps, un nouveau modèle stochastique est proposé : il introduit une variable cachée relative à l’apparition d’impacts et estime le contenu spectral des transitoires correspondants ainsi que le spectre du bruit de fond. Cela donne lieu à un algorithme de détection automatique - sans besoin de pré-filtrage manuel - à partir duquel les fréquences de défaut peuvent être révélées. Le même algorithme permet également de filtrer le signal de défaut de manière très efficace par rapport à d’autres approches basées sur l’hypothèse stationnaire. La performance de l’algorithme est étudiée sur des signaux synthétiques. L’efficacité et la robustesse de la méthode sont également vérifiées sur les signaux de vibration mesurés sur un banc d’essai (engrenages et paliers). Les résultats sont meilleurs ou au moins équivalents à ceux de l’analyse d’enveloppes classique et du kurtogramme rapide. Dans un troisième temps, un nouveau schéma pour l’extraction de signaux cyclostationnaires (CS) est proposé. En considérant la variance périodique en tant que variable cachée, un filtre temporel est conçu de manière à obtenir la reconstruction intégrale des signaux CS caractérisés par une fréquence cyclique préétablie, qui peut être connue à priori ou estimée à partir de la corrélation spectrale. Un intérêt particulier de la méthode est sa robustesse lorsqu’elle est appliquée sur des données expérimentales ainsi qu’une capacité d’extraction supérieure par rapport au filtre de Wiener conventionnel. Finalement, ces exemples expérimentaux témoignent de l’utilisation polyvalente de la méthode à des fins de diagnostic de signaux composés. Pour finir, une analyse comparée utilisant le calcul rapide de la corrélation spectrale est réalisée sur une base de données publiquement disponible et largement utilisée. C’est un point crucial qui fixe un défis non-trivial à résoudreAlthough vibration-based rolling element bearing diagnostics is a very well-developed field, the research on sparse representations of vibration signals is yet new and challenging for machine diagnosis. In this thesis, several novel methods have been developed, by means of different stochastic models, associated with their effective algorithms so as to serve the industry in rolling element bearing diagnostics. First, the sparsity-based model (sparse code, in natural image processing) is investigated based on the current literature. The historical background of sparse representations has been inquired in the field of natural scenes. Along three aspects, its mathematical model with corresponding algorithms has been categorized and presented as a fundamental premise; the main publications are therefore surveyed in the literature on machinery fault diagnosis; finally, an interpretation of sparse structure in the Bayesian viewpoint is proposed which then gives rise to two novel models for machinery fault diagnosis. Second, a new stochastic model is introduced to address this issue: it introduces a hidden variable to indicate the occurrence of the impacts and estimates the spectral content of the corresponding transients together with the spectrum of background noise. This gives rise to an automatic detection algorithm – with no need of manual prefiltering as is the case with the envelope spectrum – from which fault frequencies can be revealed. The same algorithm also makes possible to filter out the fault signal in a very efficient way as compared to other approaches based on the stationary assumption. The performance is investigated on synthetic signals with a high noise-to-signal ratio and also in the case of a mixture of two independent transients. The effectiveness and robustness of the method are also verified on vibration signals measured on a test-bench (gears and bearings). Results are found superior or at least equivalent to those of conventional envelope analysis and fast kurtogram. Third, a novel scheme for extracting cyclostationary (CS) signals is proposed. By regularizing the periodic variance as hidden variables, a time-varying filter is designed so as to achieve the full-band reconstruction of CS signals characterized by some pre-set characteristic frequency. Of particular interest is the robustness on experimental data sets and superior extraction capability over the conventional Wiener filter. It not only deals with the bearing fault at an incipient stage, but it even works for the installation problem and the case of two sources, i.e. bearing and gear faults together. Eventually, these experimental examples evidence its versatile usage on diagnostic analysis of compound signals. Fourth, a benchmark analysis by using the fast computation of the spectral correlation is provided. One crucial point is to move forward the benchmark study of the CWRU data set by uncovering its own unique characteristics
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Bezerra, Roberto de Araujo. "Detecção de falhas em rolamentos por analise de vibração." [s.n.], 2004. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265232.
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Orientador: Robson PederivaTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: Neste trabalho, é feito um estudo comparativo entre diversas técnicas de detecção de falhas em rolamentos por análise de vibração. Inicialmente, as técnicas foram aplicadas a modelos matemáticos de falhas nas pistas interna, externa e nas esferas dos rolamentos; sendo, em seguida, feito um estudo comparativo entre as técnicas. As técnicas foram aplicadas também a rolamentos com falhas induzidas nas pistas e esfera com diferentes tamanhos de falhas e submetidos a diferentes velocidades, para uma melhor compreensão das técnicas. Finalmente, as técnicas foram usadas para o monitoramento da evolução das falhas em um conjunto de doze rolamentos que foram submetidos a condições próximas as de trabalho, o que possibilitou um estudo mais detalhado do processo de evolução dessas falhas. Os resultados obtidos mostraram que, de todas as técnicas utilizadas, o envelope com filtro adaptativo foi a mais eficiente, sendo capaz de detectar pequenos amassamentos e o surgimento de falhas na gaiola. O estudo em condições próximas a realidade possibilitou uma melhor compreensão do processo de evolução das falhas em rolamentos
Abstract: In this thesis, it is made a comparative study among several vibration analysis techniques of fault detection. Initially, the techniques were applied to inner and outer race and rolling element mathematical models of faults, and so, it was possible to compare the techniques. It was used the same techniques on the races and rolling elements with different size of induced faults, submitting to different speeds. With those studies it was possible to understand how to use the technique in a better way. Finally, we monitored a group of twelve bearings to analyse the evolution of faults, close to real conditions. The results showed that the most efficient techniques is the envelope with adaptive filter, it detects small dentings and the begging of cage failure. It was possible to get a better understanding of the failure evolution process in bearings, studying it in close conditions to the reality
Doutorado
Mecanica dos Sólidos e Projeto Mecanico
Doutor em Engenharia Mecânica
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Rommelaere, Simon. "Ball Bearing Design Tool Evaluation." Thesis, KTH, Rymdteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-219425.
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This report has been written during my internship/master thesis at Thales Alenia Space, Cannes, FRANCE. The subject of the thesis is ball bearing design, and is focused on the software RBSDyn. This software has been developed by CNES, the French Center for Space Studies, and is used to simulate bearings behaviors under various conditions. My mission was to verify, test and implement this software for the company. In order to do so, the first step was to understand the bearing theory, which is the first part of this report. The second step was to use the software and verify its results, which is presented in the second section. Eventually, the final goal of this internship was to create a sequence to help Thales Alenia Space engineers to design and select bearings, using this software and an Excel tool that needed to be created. Note that for confidentiality reasons, the values and names used for internal TAS mechanisms have been removed of this document.Denna rapport sammanfattar ett examensarbete som utfördes vid Thales Alenia Space, Cannes, Frankrike. Ämnet var utformning av kullager för utfällbara strukturer inom rymdindustrin och fokuserade på mjukvaran RBSDyn. Denna mjukvara har utvecklats av det franska rymdcentret CNES och används för att simulera kullagers beteende när de utsätts för olika laster. Uppdraget i examensarbetet var att verifiera, testa och implementera denna mjukvara för Thales Alenia Space. Det första steget i detta arbete var att gå igenom viktiga grundläggande samband inom kullagerteori. Det andra steget var att att verifiera resultaten från RBSDyn med de grundläggande sambanden. Det sista steget var att skapa en lämplig procedur för utformning av kullager; en procedur som ingenjörerna på Thales Alenia Space kan följa för att välja och utforma kullager för olika utfällbara strukturer. Proceduren innefattar mjukvarorna RBSDyn och Excel. Av sekretessskäl så har vissa värden och namn på utfällbara strukturer utelämnats i denna rapport.
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Rullich, Markus [Verfasser], Thomas [Akademischer Betreuer] Frauenheim, and Ciacchi Lucio [Akademischer Betreuer] Colombi. "Experimental and Computational Investigation of the Influence of a Plasma-Enhanced Chemical Vapor Deposition Amorphous Carbon Fluorine Coating on Sliding Friction in Hybrid Ball Bearings / Markus Rullich. Gutachter: Thomas Frauenheim ; Lucio Colombi Ciacchi. Betreuer: Thomas Frauenheim." Bremen : Staats- und Universitätsbibliothek Bremen, 2012. http://d-nb.info/107204658X/34.
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Amami, Lassad. "Analyse expérimentale de la réponse dynamique d'un rotor vertical guidée par desroulements avec jeu." Thesis, Poitiers, 2016. http://www.theses.fr/2016POIT2254.
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L'objectif de cette thèse est l’étude expérimentale d’un rotor vertical, complexe supporté par deux paliers à roulements et deux paliers aérostatiques. Le fort comportement non-linéaire du rotor est dû aux jeux fonctionnels existants entre les bagues extérieures des roulements et les pièces du carter en vis-à-vis.Les paliers aérostatiques sont destinés à simuler la présence des joints d’étanchéité annulaires et d’apporter de l’amortissement au rotor.Le boitier d’essai est composé d'un rotor représentatif en termes de dimensions, de masse et de répartitions des inerties d’une machine réelle. Il est constitué d’un arbre et de trois disques représentant les rouets et la turbine. Le rotor est entrainé en rotation par une turbine-Pelton et guidé par deux paires de roulements et deux paliers aérostatiques à injection radiale. Le poids du rotor monté verticalement est supporté par une butée aérostatique. Un jeu fonctionnel est prévu entre les bagues extérieures des roulements et leur logement. Les essais ont visé trois valeurs de ce jeu radial (faible, modéré et élevé). L’instrumentation du banc permet la mesure des déplacements radiaux des trois disques suivant deux directions perpendiculaires et des bagues extérieures des roulements suivant une seule direction. Les analyses vibratoires sont représentées sous formes des diagrammes « waterfalls », des diagrammes « full-spectrum » et des orbites.Les réponses dynamiques des disques et des bagues extérieures des roulements ont montré l’instauration d’un comportement non-linéaire du rotor avec l’augmentation du jeu fonctionnelThe aim of this dissertation is the experimental analysis of a vertical, complex rotor supported by two pair of ball bearings and two aerostatic bearings. The strong non-linear behavior of the rotor is due to the deadband clearance between the outer rings of the bearings and the stator.Aerostatic bearings are intended to simulate the presence of annular seals and provide damping to the rotor.The test rig is composed of a rotor that reproduces the dimensions, the weight and the inertia of a real machine. It rotor consists of a shaft and three disks representing the impellers and the turbine. The rotor is entrained by a Pelton turbine and is guided by two pairs of bearings and two radial injection aerostatic bearings. An aerostatic thrust bearing supports the weight of the vertically mounted rotor. A dead-band clearance exists between the outer rings of the bearings and the housing. The tests covered three values ofthe radial clearance, small, average and large. The instrumentation of the test rig allows the measurement of radial displacements of the three disks in two perpendicular directions and of the outer rings of the bearings in one direction. The results of the vibration analysis are presented as "waterfalls" diagrams, full-spectrum diagrams and orbits. The dynamic responses of the discs and of the outer rings of the bearings showed the appearance of a non-linear behavior of the rotor with increasing the dead-band clearance
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Hergert, Robert J. "Rotary micro-ball bearing designs for MEMS applications." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/40060.
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Micro-electro-mechanical systems (MEMS) technology allows the fabrication of small mechanical systems in silicon using standard micro-fabrication pro- cesses. MEMS techniques have found wide acceptance in such devices as ac- celerometers, micro-mirrors, resonators, probes, and micro-tweezers to name a few. Though small linear motions are common in MEMS applications, few devices exhibit reliable rotary motion. This work explores several methods of fabricating rotary bearings using micro-balls as the support mechanism. Micro-ball bearings have several advantages over other MEMS bearing tech- nologies in that they provide robust mechanical support, require no external control systems, and basic designs require very few fabrication steps. Ball cages or retainers are common in macro-scale bearings, providing uniform spacing between the balls. Several cage designs are proposed and explored in this work: a radial ball bearing with an integrated ball cage, a dual-row style cage, and ve unique cage geometries integrated into silicon micro-turbines (SMTs.) Also, an example of a curved or angular contact race- way is presented as an example of this type of raceway geometry in MEMS devices. Each is presented with a discussion of the design considerations and fabrication process. This is followed by a characterization of the performance of each design. These studies found that the integrated cage in the radial ball bearing performs well at speeds ranging up to 20 000RPM. Minimal wear was ob- served after 6 hours of continuous testing. However, the solder bond in the cage was a common failure point in these devices, limiting the reliability and longevity. The dual groove style cage was designed to eliminate the solder bond. However, the higher frictional forces between the ball and the cage in this design resulted in higher losses during operation. Taking into account the higher losses and the added complexity of the design, it seems unlikely that this approach would be appropriate for further study. However, the design does represent a novel approach for releasing multi-wafer rotary structures and is presented here as example of this technique. Testing of the cage de- signs for the SMTs indicated that a full ring design (a full annulus with holes for the balls) performed the best of the 5 cage geometries. However, these devices do not perform as well as cage-less designs for high speed applications due to higher ctional forces and increased raceway wear at the interface be- tween the ball and the raceway edge. Finally, the curved raceway has shown excellent performance up to 2500RPM with normal loads up to 40mN in tribometer testing. SMTs with this raceway desing were also tested for over 10 million revolutions and at speeds over 70 000RPM. The test results for all of the bearings designs presented here show that the devices exhibit stable operation at low to moderately high speeds.
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Adolfsson, Erik. "Simplified finite element bearing modeling : with NX Nastran." Thesis, Uppsala universitet, Tillämpad mekanik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-255398.
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This report was produced at the request of ABB Robotics and the work was conducted at their facilities in Västerås, Sweden. In the development of industrial robots the structures are slimmed to increase the accuracy and speed. When conducting finite element analysis on the robots the accuracy of the component modelling and definitions of the boundary conditions becomes more important. One such component is the ball bearing which consist of several parts and has a nonlinear behavior where the balls are in contact with the rings. The task given was to develop new methods to model roller bearings in Siemens finite element modelling software NX Nastran. Then conduct a strain measurement, to compare the methods to real experimental values. The goal with the report is to find one or more methods to model roller bearings, with accurate results, that can beused in their development work. The report was conducted by first doing a study on bearings and finite element modeling, and learning to use the software NX Nastran. Then the development of the methods were done by generating ideas for bearing models and testing them on simple structures. Nine methods was produced and a tenth, the method used to model bearings today, was used as a reference. The methods was used to build bearing models in a finite element model of a six axis robot wrist. Simulations were done on the models with different load cases and the results were compared to a strain measurement of the wrists real counterpart. Only six of the models were analyzed in the result, since four of the models returned results that were deemed unusable. When compiling the result data no model was found to accurately recreate the stresses in every load case. Three methods, that allow deformation, performed similarly. One of them is suggested to be used as modelling method in the future. Worst of the methods, according to the results compiled, was found to be the method used today. It fails to describe local stresses around the bearing. For continued work it is suggested that linear contact elements is studied further. Four out of five models constructed with linear contact elements failed to return satisfactory results.
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Omar, Farah Samatar. "Modélisation multiphysique des roulements à billes par la Méthode des Éléments Discrets en régime Élasto-Hydro-Dynamique." Electronic Thesis or Diss., Amiens, 2022. http://www.theses.fr/2022AMIE0059.
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Le travail réalisé dans le cadre de cette thèse a contribué au développement d'un outil numérique dédié à la simulation des roulements à billes en conditions de service Elasto-Hydro-Dynamiques (EHD). Une modélisation originale, adaptée à ces organes de guidage en rotation, est donc mise en œuvre dans le cas des roulements à billes à contact radial SKF 6208 et à contact oblique SKF 7208. De par leur caractère multi-contact, les deux roulements sont modélisés par la Méthode des Eléments Discrets, avec une formulation hertzienne du contact elliptique pour déterminer les interactions billes/pistes de roulement et déformations aux contacts. En considérant, dans un premier temps, des indicateurs standards, à la fois cinématiques et dynamiques, les modèles discrets de roulements à billes 6208 et 7208, sont testés puis validés en conditions statiques et dynamiques. L'implémentation, dans un deuxième temps, d'un modèle rhéologique piézo-visco-élastique du lubrifiant a, quant à elle, contribué à mettre en évidence l'influence du pilotage en vitesse, du chargement imposé, ou encore, du jeu diamétral sur le régime de lubrification du roulement. Le couplage, dans un troisième temps, des propriétés rhéologiques et diélectriques du lubrifiant a permis de montrer la pertinence de la réponse électrique du roulement, en particulier pour l'identification de son régime de lubrification. En effet, la corrélation de l'épaisseur de film fluide à sa capacitance électrique s'est révélée un bon indicateur de l’état du contact lubrifié. Cette corrélation est corroborée par une bonne adéquation des prédictions numériques, obtenues avec le modèle discret de roulement à billes à contact radial 6208, et résultats expérimentaux issus de la littérature. En conclusion, la capacitance électrique du contact lubrifié est un indicateur fiable, pouvant être utilisé comme moyen de prédiction du régime de lubrification pour assurer une durée de vie optimale au roulementDuring this PhD thesis, we have focused on a digital tool for modeling ball bearing operating under elstohydrodynamic (EHD) regime. Based on an original description involving the discrete element method (DEM), the developed digital tool integrates all the components of ball bearings and enables realistic behavior under mechanical loading and kinematic conditions. Two models of ball bearings were considered and simulated with the digital tool, namely SKF 6208 radial contact ball bearing and SKF 7208 angular contact ball bearing. In order to check the standard indicators recommended by most ball bearing manufactures, a stiffness model for elliptical hertzian contact and an improved EHD formulation for lubricated contact are implemented in the discrete model of ball bearings. In addition, we have introduced into the discrete modeling an electrical capacitance model coupling rheological and dielectric properties of the lubricant with the Hertz's pressure at the contact between the ball and the raceways. The numerical predictions of lubricant film capacitance provided by numerical simulations are in good accordance, both qualitatively and quantitatively, with the experimental data available in the literature. The combination of the discrete modeling and the electrical approach enables efficient solutions to be provided in terms of lubrication regime in relation to the lubricant properties to optimize the bearing lifetime
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Westsson, David. "Simulation of torque caused by the lubrication fluid in a ball bearing." Thesis, Umeå universitet, Institutionen för matematik och matematisk statistik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-126563.
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Mutyala, Kalyan Chakravarthi. "Influence of Metallic, Dichalcogenide, and Nanocomposite Tribological Thin Films on The Rolling Contact Performance of Spherical Rolling Elements." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1447751680.
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Bovet, Christophe. "Contribution à la modélisation du comportement dynamique des paliers à roulements de réducteurs aéronautiques." Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4022.
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La quête de minimisation du ratio poids-puissance, omniprésente dans l'industrie aéronautique, conduit à une plus grande souplesse structurelle des boîtes de transmission de puissance d'hélicoptères.Cette souplesse structurelle, associée aux sollicitations sévères mises en jeu, entraîne des déformations non négligeables des arbres et carters, et nuit naturellement à la tenue en service des roulements.S'il n’est pas maîtrisé, le désalignement des portées de roulements accroît fortement les efforts vus par la cage et peut conduire à sa rupture en fatigue.Le travail proposé s'intéresse à la modélisation du comportement dynamique des roulements de réducteurs aéronautiques et vise plus particulièrement à anticiper ce mode de ruine.Le modèle développé permet d'estimer les sollicitations de la cage en fonctionnement.Ces informations, précieuses aux ingénieurs, permettront de mieux maîtriser, et donc d'optimiser le processus de dimensionnement des roulementsThe quest for minimizing the power to weight ratio, omnipresent in the aircraft industry, has led to greater structural flexibility of helicopter gearboxes.This increasing flexibility combined with the severe loads which it involves, causes significant strains on shafts and housings, and may be detrimental to rolling bearing service life expectancy.An unchecked misalignment of bearing seats greatly increases cage stresses and it may cause its premature fatigue failure.The present work focuses on modeling the dynamic behavior of rolling bearings of aeronautical gearboxes and it specifically anticipates this failure mode.The model developed is able to estimate cage stresses in operation. This information is valuable to engineers, it allows a better control and thus an optimization of the rolling bearings design process
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Hirst, Derek John. "Failure of the elastohydrodynamic lubrication of ball bearing components at very high speeds." Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.676730.
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Zhang, Qingning. "Experimental and analytical investigation into the two stage turbocharging systems for diesel engines." Thesis, University of Bath, 2016. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.707566.
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The work described in this thesis aims to conduct a systematic study of the two stage turbocharging system to improve the Diesel engine transient performance as well as NOX and CO2 emissions with a focus on the improved turbocharger matching and the control of the charging system, through the use of high fidelity engine models backed by experimental results. To perform the analytical study, commercial 1D simulation software has been used in the process of system characterisation and control strategy design. To validate the analytical results, a two stage turbocharging system was installed on a production diesel engine and tested on a transient engine test bench. The test results were then used to further calibrate the 1D engine/turbocharger model. Several other technologies were also investigated in simulation to explore their potential to further improve the system. Unlike most studies in the literature, this project focused on the system benefit of the engine and turbochargers, instead of conducting optimisation solely at the component level. The engine global parameters, such as the engine fuel consumption, emission levels and the transient response were the main parameters to be considered and were also best suited to the strengths of the 1D simulation method. The interactive use of both the analytical and experimental methods was also a strong point of this study. A novel control strategy for the system was proposed and demonstrated in the simulation. Experiments confirmed the validity of this control strategy and provided data for further model calibration. The comparison of the test results of the baseline engine to those obtained with the two stage turbocharged engine system verified the benefits of the novel turbocharging arrangement and control scheme. Transient response (T1090) was improved, with a 50% faster torque rise at 1000 rpm; the fuel consumption over the NEDC was 4% lower and NOx emissions over the NEDC were 28% lower. In the meantime, the study also revealed shortcomings of the system, such as the lack of EGR control at low speed, low load condition and a mid-speed fuel consumption deterioration of 13% on average at 3000 rpm due to excessive back pressure. With a novel 1D model corroborated using test results, exploratory simulation was done to rectify the aforementioned shortcomings and to further improve the system. Simulation results showed that by implementing VGT and ball bearing technology in the high pressure stage of the two stage system, the EGR controllability at low speed was regained and the excessive back pressure at high speed was improved. Consequently, the fuel consumption was only increased by 1.3% compared to the baseline NEDC operation and the transient response was on par with the original two stage system, with only 0.05s slower in torque rise at 1000 rpm, and still 48% faster than the baseline VGT system. Furthermore, the NOx emission can be expected to be greatly improved in the upcoming more intensive drive cycles compared to the NEDC cycle, with simulation showing NEDC NOX emissions dropped by 1%, comparing to a substantial reduction of 11% in WLTC.
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Dyson, John Edwin. "Aspects of the behaviour and design of dental high speed ball bearing air turbine handpieces." Thesis, University of London, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324587.
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Endicott, Roger A. "Immunoregulation of T-lymphocyte proliferative activity by alveolar macrophages from mice bearing Lewis lung carcinoma tumors." Virtual Press, 1986. http://liblink.bsu.edu/uhtbin/catkey/458971.
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The immune regulatory abilities of alveolar macrophages from C57B1/6 mice bearing a metastatic variant of Lewis lung carcinoma were determined. During early stages of tumor development, or before tumors metastasized to the lungs, alveolar macrophages did not affect or slightly enhanced T-lymphocyte proliferation; as tumor growth progressed, or following tumor metastasis, alveolar macrophages suppressed the T-cell response. Macrophage suppressor activity was probably not mediated by their production of PGE, since macrophages of tumor-bearing mice secreted less 2 PGE than did macrophages of normal mice. Normal alveolar 2 macrophages or macrophages preincubated in tumor cell supernatant for a short period stimulated T-cell blastogenesis and secreted PGE during in vitro culture. However, with 2 longer exposure to tumor cell supernatant, alveolar macrophages lost the capacity to augment T-cell proliferation and secreted less PGE 2.Ball State UniversityMuncie, IN 47306
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Liao, Xin-Wei, and 廖信瑋. "Radial passive magnetic bearing in ball bearings supporting rotor system applications." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/yvcpxc.
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碩士中原大學
機械工程研究所
102
Nowadays, magnetic systems have been applied in the industry systems widely due to the frictionless property of magnetic systems. Magnetic systems have two kinds: passive and active magnetic systems. Active magnetic systems use electronic magnet to control the subjects, such as rotors or platforms, by controlling the current to adjust the size of magnetic force. The advantage is the system stability can be confirm via tuning the magnetic force by the feedback signals, but the disadvantage is the magnetic system need additional control system and will consume the power. Passive magnetic systems use the permanent magnets to produce magnetic force. The advantage is it can be used a widely range, but the disadvantage is its magnetic force can’t be controlled, need to calculate the magnetic force. A passive magnetic bearing and a ball bearing are combined to form a hybrid bearing system in this paper. The passive magnetic bearing is used to increase the maximum radial load capacity and reduce the ball bearing load then promote the bearing life. The reasons we chosen a passive magnetic bearing are that the passive magnetic bearing system has no friction, does not need additional control, widely using environment and cheaper than the active magnetic bearing. The coordinate ball bearing is a deep groove ball bearing. The deep groove ball bearings are one of the most widely used ball bearings. Because the load capacity and life of the ball bearing are both lower than the steel ball bearing. This paper used a deep groove ball bearing with the inner radius is 10mm, the outer radius is 19mm, and the thickness is 10mm to be a test bearing. The experiment result showed that the proposed hybrid bearing can promote the bearing life. First, we calculated the radial force and axial force for the supporting system to determine the system specifications and capacity and the need of the supporting system. Then analyzed the relationship of forces and positions of the passive magnetic bearing according to the formula of the permanent magnet and to simulate the magnetic circuit with JMAG to choose a suitable set of permanent magnets to form a result with maximum radial force and minimum axial force. Finally, the passive magnetic bearing and the deep groove ball bearing are combined to test and confirm with the simulation results.
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Chih-Ming, Lin, and 林志明. "Analysis for the Stiffness of Ball Bearings." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/39170709352485704249.
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碩士中原大學
機械工程研究所
90
SKF deep groove bearing and angular contact bearing are analyzedfor displacement and stiffness coefficient. According to Hertz contact theory, Jones-Harris build the method for analyzing the displacement and stiffness coefficient of bearings under load. This investigation programs Jones-Harris Method (JHM) in Borland C++ to do trial and error repeatedly and accurately. Results from Finite Element Method (FEM) which fits the reality almost are compared to JHM and Palmgren’s empirical function. Palmgren’s method over evaluates the stiffness due to reduced assumptions. JHM still dose not fit reality exactly but approaches to FEM. The program based on JHM helps solving difficult calculation but is more sufficient than FEM and more accurate than Palmgren’s empirical function.
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Liu, Zhen-Gang, and 劉鎮綱. "Contact Stress Analysis of Hybrid Ceramic Ball Bearings." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/12293815737286854706.
Full textAbstract:
碩士國立聯合大學
機械工程學系碩士班
101
The hybrid ceramic ball bearing has low density, high hardness, low friction coefficient, non-magnetic, high wear resistance, good self-lubricating and rigidity characteristics, especially suitable for high speed, high precision and long life of the rolling elements. This study focuses on contact stress analysis of the hybrid ceramic ball bearing with inner and outer ring for various bearing materials. The segmented regression equations are derived by bearing parameters regression analysis. It can provide more convenient computing and applications for bearing parameters design. The numerical results show that the bearing stress error rate is very small, the regression analysis compared to the interpolation method. Therefore, the regression analysis can be achieved considerable accuracy. Further, 3D model of the hybrid ceramic ball bearing is constructed with SolidWorks software, and the image format file is converted to the ANSYS finite element software. For various bearing materials and bearing parameters, the effects of the contact stress on the hybrid ceramic bearings are investigated. By the finite element software, it can clearly understand the structural characteristics of the hybrid ceramic bearings. The results of this analysis will help the application of the hybrid ceramic bearings and provide the design of bearing manufacturing.