Dissertations / Theses on the topic 'Rolling contact fatigue (RCF)'
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1
Shen, Jialong. "Responses of alternating current field measurement (ACFM) to rolling contact fatigue (RCF) cracks in railway rails." Thesis, University of Warwick, 2017. http://wrap.warwick.ac.uk/93593/.
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Rolling contact fatigue (RCF) cracks are a widespread problem that impairs the service life of railway rails and wheels, with an associated high cost of labour and capital expenditure for remediation. Severe RCF cracks cause serious safety issues as they can turn down at a larger propagation angle into the rail potentially leading to a rail break. Rail grinding can effectively eliminate RCF cracks if they are detected when they are small enough to be removed. Alternating current field measurement (ACFM) is one of the electromagnetic (EM) techniques that can be used for defect detection and sizing in the rail industry. ACFM has been reported to be more accurate in providing length and depth information than conventional UT for small RCF cracks and is less sensitive to lift-off than eddy current methods. The aim of the present research is to analyse the response of ACFM signals to single and multiple RCF cracks in railway rails using experimental measurements and FE based modelling tools, focusing on the influences of crack vertical angle and multiple cracks (number, spacing, size, uniformity) on the ACFM signal to improve the accuracy of dimension predictions. A novel method (using the Bz signal) is proposed to determine the vertical angle of the RCF cracks, which then allows the crack vertical depth to be determined from the pocket length (standard output from ACFM measurements) and therefore the appropriate amount of rail grinding to remove the RCF cracks. It was found that the vertical angle influences the pocket length determined from the measured ΔBxmax/Bx value when the cracks are shallow (vertical angles < 30°), therefore greater accuracy can be obtained when compensating the ΔBxmax/Bx value using the determined vertical angle. It is shown that the variations of crack surface length, crack inner spacing and crack number for multiple cracks also influence the ΔBxmax/Bx values determined for multiple cracks. The influences of asymmetrical crack shapes on crack sizing are discussed, in general it has been found that for accurate sizing of RCF cracks using a single ACFM scan the cracks should be regular, where the assumption of semi ellipse shapes is appropriate. The methods developed in the project were assessed using calibration samples (machined cracks with different sizes and vertical angles) and rails removed from service containing single and multiple RCF cracks. It was found that the new approach proposed in this work allowed the vertical angle to be predicted well for single and multiple RCF cracks (difference to measurements < 14.3 %). In addition the error in pocket length prediction is greatly decreased when using the sizing method including compensation determined from the crack vertical angle.
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Reddy, Venkatarami. "Modelling and analysis of rail grinding and lubrication strategies for controlling rolling contact fatigue (RCF) and rail wear." Thesis, Queensland University of Technology, 2004. https://eprints.qut.edu.au/15864/1/Venkatarami_Reddy_Thesis.pdf.
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Rails play a significant role in transport of goods and passengers. In Australia railway transport industry contributes 1.6% of GDP with goods and services worth $AUD 8 billion each year which includes $ AUD 0.5 billion per year in exports (Australasian Railway Authority Inc, 2002).
Rail track maintenance plays an important role in reliability and safety. The Office for Research and Experiments (ORE) of the Union International des Chemins de Fer (UIC) has noted that maintenance costs vary directly (60-65 per cent) with change in train speed and axle load. It was also found that the increase in these costs with increased speed and axle load was greater when the quality of the track was lower
(ORR, 1999). Failures during operation are costly to rail players due to loss of service, property and loss of lives. Maintenance and servicing keep rail tracks in operating, reliable and safe condition. Therefore, technical and economical analysis is needed by rail players to reduce maintenance cost and improve reliability and safety of rail networks.
Over the past few years, there have been major advances in terms of increased speed, axle loads, longer trains, along with increased traffic density in corridors. This has led to increased risks in rail operation due to rolling contact fatigue (RCF) and rail wear. The infrastructure providers have less incentive to maintain a given infrastructure standard if its access charges are rigid and rolling stock standard is not achieved. It has been estimated that between 40 to 50 per cent of wagon maintenance costs and 25 per cent of locomotive maintenance costs are related to wheel
maintenance (Railway Gazette International, 2003). The economic analysis of Malmbanan indicates that about 50% of the total cost for maintenance and renewal were related to traffic on rails and 50% not related to traffic, such as signaling, electricity and snow-clearance. The results from the analysis have made it possible
for the mining company LKAB to start up the 30 Tonnes traffic with new wagons and locomotives on the Malmbanan line in year 2001 (Åhrén et al 2003). The rail infrastructure providers have challenges to maintain infrastructure due to government control on access charges and limited control on rail operations.
The aim of the research is to:
· Develop a maintenance cost model for optimal rail grinding for various operating conditions; and
· Develop integrated rail grinding and lubrication strategies for optimal
maintenance decisions.
In this research real life data has been collected, new models have been developed
and analysed for managerial decisions. Simulation approach is used to look into the
impact on various costs such as rail grinding, operating risk, down time, inspection,
replacement, and lubrication. The results of the models for costs and the effect of rail grinding and lubrication strategies are provided in this thesis.
In this research rail track degradation, rail failures and various factors that influence
rail degradation are analysed. An integrated approach for modelling rail track degradation, rail wear, rail grinding and lubrication is developed. Simulation model and cost models for rail grinding are developed and analysed. It has been found through this research that rail grinding at 12 MGT interval is economic decision for enhancing rail life. It was also found that lubrication is most effective compared to
stop/start and no lubrication strategies in steep curves.
Rail grinding strategies developed in this research have been considered by Swedish National Rail for analysing the effectiveness of their existing policies on grinding intervals. Optimal grinding and lubrication decisions have huge potential for savings in maintenance costs, improving reliability and safety and enhancing rail life.
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Reddy, Venkatarami. "Modelling and analysis of rail grinding and lubrication strategies for controlling rolling contact fatigue (RCF) and rail wear." Queensland University of Technology, 2004. http://eprints.qut.edu.au/15864/.
Full textAbstract:
Rails play a significant role in transport of goods and passengers. In Australia railway transport industry contributes 1.6% of GDP with goods and services worth $AUD 8 billion each year which includes $ AUD 0.5 billion per year in exports (Australasian Railway Authority Inc, 2002). Rail track maintenance plays an important role in reliability and safety. The Office for Research and Experiments (ORE) of the Union International des Chemins de Fer (UIC) has noted that maintenance costs vary directly (60-65 per cent) with change in train speed and axle load. It was also found that the increase in these costs with increased speed and axle load was greater when the quality of the track was lower (ORR, 1999). Failures during operation are costly to rail players due to loss of service, property and loss of lives. Maintenance and servicing keep rail tracks in operating, reliable and safe condition. Therefore, technical and economical analysis is needed by rail players to reduce maintenance cost and improve reliability and safety of rail networks. Over the past few years, there have been major advances in terms of increased speed, axle loads, longer trains, along with increased traffic density in corridors. This has led to increased risks in rail operation due to rolling contact fatigue (RCF) and rail wear. The infrastructure providers have less incentive to maintain a given infrastructure standard if its access charges are rigid and rolling stock standard is not achieved. It has been estimated that between 40 to 50 per cent of wagon maintenance costs and 25 per cent of locomotive maintenance costs are related to wheel maintenance (Railway Gazette International, 2003). The economic analysis of Malmbanan indicates that about 50% of the total cost for maintenance and renewal were related to traffic on rails and 50% not related to traffic, such as signaling, electricity and snow-clearance. The results from the analysis have made it possible for the mining company LKAB to start up the 30 Tonnes traffic with new wagons and locomotives on the Malmbanan line in year 2001 (Åhrén et al 2003). The rail infrastructure providers have challenges to maintain infrastructure due to government control on access charges and limited control on rail operations. The aim of the research is to: · Develop a maintenance cost model for optimal rail grinding for various operating conditions; and · Develop integrated rail grinding and lubrication strategies for optimal maintenance decisions. In this research real life data has been collected, new models have been developed and analysed for managerial decisions. Simulation approach is used to look into the impact on various costs such as rail grinding, operating risk, down time, inspection, replacement, and lubrication. The results of the models for costs and the effect of rail grinding and lubrication strategies are provided in this thesis. In this research rail track degradation, rail failures and various factors that influence rail degradation are analysed. An integrated approach for modelling rail track degradation, rail wear, rail grinding and lubrication is developed. Simulation model and cost models for rail grinding are developed and analysed. It has been found through this research that rail grinding at 12 MGT interval is economic decision for enhancing rail life. It was also found that lubrication is most effective compared to stop/start and no lubrication strategies in steep curves. Rail grinding strategies developed in this research have been considered by Swedish National Rail for analysing the effectiveness of their existing policies on grinding intervals. Optimal grinding and lubrication decisions have huge potential for savings in maintenance costs, improving reliability and safety and enhancing rail life.
4
Gergel, Matej. "Rekonstrukce stanice AXMAT." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2014. http://www.nusl.cz/ntk/nusl-231145.
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The master´s thesis deals with reconstruction of RCF test rig AXMAT. Main goal is design new hydraulic load system and his realization. The first part of thesis describes similar experimental machines and their pros and cons. This analysis is base for complete reconstruciton of AXMAT. New hydraulic load system allows dynamic programmable load cycles. Control system with close loop and feedback was created in software Matlab – Simulink. Main frame was reconstructed too. Control and action parts were asseble to station. Output of thesis is function sample.
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Juna, Anwar Pervez. "On the characterisation and detection of rolling contact fatigue (RCF) type cracks in railway vehicle wheels using an alternating current field measurement (ACFM) technique." Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7945/.
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The development of the alternating current field measurement (ACFM) technique for high-speed inspection of railway wheels/track is important to ensure the integrity of railway assets. The stress and conditions at the wheel/rail contact patch, severity of rolling contact fatigue (RCF) damage and changes in microstructure and hardness with tread depth for railway wheels are investigated. This study employs experimental measurement of RCF defects in railway wheels to understand ACFM sensor signal - RCF defect relationships. The influence of sensor frequency and speed, sensor angle relative to crack angle, lift-off distance, crack propagation angle and inter-crack spacing distance are investigated. Low rather than high frequency sensors are better suited at sizing cracks in railway wheels and track. The optimum signal is obtained when the sensor is oriented parallel to the crack angle. The signal is reduced at higher speeds. The maximum change in the normalised Bx signal component of the sensor’s magnetic field is greater for closely spaced cracks (< 5 mm) and thus overestimates the defect. Inter-crack spacing distances of 15-20 mm yield estimates for crack pocket depths that are oversized by 20-36%. The inner cracks in a cluster with four defects yields higher Bₓ values than expected and thus significantly over sizes the defects at 15-20 mm inter-crack spacing distances, whereas, the sensor provides reasonable depth estimates for the outer cracks. Crack propagation angle affects the signal. Scans conducted with the probe oriented at 90° to the cluster of cracks consisting of a deep central crack surrounded by shallow cracks results in a distinct central sensor Bₓ signal that consists of a peak due to a flux leakage effect, thus, identifying the critical defect.
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Popelka, Jakub. "Vliv cílené modifikace topografie na únavové poškozování třecích povrchů." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2008. http://www.nusl.cz/ntk/nusl-227904.
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Diploma thesis describes influence of directed modificated topography of frictional surfaces on fatigue wear non-conformal incurvate solids. It was created 3D parametric model of experimental test rig in modelling environment Autodesk Inventor. With the help of model was designed and carried reconstruction of experimental test rig so to possible obtain repeatable results under the sliding conditions of frictional surfaces. It enabled show influence of surface iregularities (dents) frictional surfaces on contact fatigue service life in conditions mixed lubrication regime and different values of slide to roll ratio.
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Zahradník, Radek. "Vliv topografie třecích povrchů na kontaktní únavu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-229384.
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This master thesis deals with influence of topography of friction surfaces on rolling contact fatigue. This influence is examined by newly reconstructed R-MAT station, whose reconstruction and fully report about it, is part of this master thesis. Influence is examined on area with higher surface's roughness which it wasn't examined before. Further research is made on area of surfaces with topographical modification with higher surface's roughness.
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Smith, Lindsey. "Rolling contact fatigue in wheel-rail contact." Thesis, University of Newcastle Upon Tyne, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.438385.
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Hadfield, Mark. "Rolling contact fatigue of ceramics." Thesis, Brunel University, 1993. http://bura.brunel.ac.uk/handle/2438/6622.
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Ceramic/ceramic and ceramic/steel contacts under lubricated rolling conditions are studied. This work is of interest to ball bearing manufacturers as the use of ceramics in the design of these components has some advantages over traditional bearing-steel materials. Low density and increased stiffness are the mechanical properties which gas-turbine and machine tool manufacturers are most likely to realise. Much research over the past two decades on material structure, quality control and manufacturing techniques has produced a material which can seriously challenge bearing steel in ball-bearing design. This is especially the case for hybrid ball-bearings, ie ceramic balls with steel bearing races which are now used as standard components. The purpose of this study is to examine the rolling contact fatigue failure modes of ceramics. This study concentrates on silicon nitride as this material has most potential for use by industry. The primary reason for studying ceramic balls is because of interest in ball-bearing applications, hence a modified four-ball machine is employed which correctly models ball motions and precisely defines ball load. Experimental and theoretical kinematic analysis of ball motion during modified four ball machine tests is presented. The kinematic analysis reveals that in practice, lower ball tracking exists at high speeds. Test conditions of lubricated contacts under high compressive stress show delamination type failures. Delamination failures are classified in terms of propagation and initiation from scanning electron microscope observations. Residual stresses are measured on delaminated surfaces, which implies plastic deformation of the ceramic. Also, chemical analysis implies that disruption of silicon, nitrogen and oxygen levels may take place on delaminated surfaces. Experiments illustrating various fatigue failure modes using artificially pre-cracked ceramic balls in contact with a steel upper ball are presented.
10
Wang, W. "Rolling contact fatigue of silicon nitride." Thesis, Bournemouth University, 2010. http://eprints.bournemouth.ac.uk/17764/.
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Silicon Nitride has traditionally been used as rolling contact bearing material owing to its superior performance compared to bearing steels. Its successful application as a bearing element has led to the development of Silicon Nitride in other rolling contact applications in the automotive industry and the power industry. However, a major limitation of its wider application is its high material and machining cost, especially the cost associated with the finishing process. In the present study, a low cost sintered and reaction-bonded Silicon Nitride is used to study the surface machining effects on its rolling contact fatigue performance. Studies have been carried out to link the surface strengths of Silicon Nitride derived from half-rod and C-Sphere flexure strength specimens to the rolling contact lives of Silicon Nitride rod and ball specimens. The rolling contact fatigue tests were carried out on ball-on-rod and modified four-ball machines. Three types of surface with coarse, fine and RCF-conventional finishing conditions were examined. Flexure strength tests on half-rod and C-Sphere showed an increasing surface strength from specimens with coarse, fine to RCF-conventionally machined conditions. During rolling contact fatigue tests of as-machined specimens, no failures were observed on either ball-on-rod or four-ball tests after 100 million stress cycles. However, a trend of decreasing wear volumes was measured on the contact path of rods and balls with coarse, fine and RCF-conventional conditions. In four-ball tests, spall failures were observed on pre-cracked specimens. There was a trend of increasing rolling contact fatigue lifetime from pre-cracked specimens with coarse, fine to RCF-conventional machining conditions. The study of Silicon Nitride machining was also carried out using an eccentric lapping machine to investigate the effect of eccentricity on the finishing rate of hot isostatically-pressed and sintered and reaction-bonded Silicon Nitride. The eccentricity had no significant impact on finishing rate as concluded in this study. The effect of lubricant viscosity and chemistry on the rolling contact fatigue performance of Silicon Nitride was also studied. The result is inconclusive.
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Hannes, Dave. "Growth of cracks at rolling contact fatigue." Thesis, KTH, Hållfasthetslära (Avd.), 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-33659.
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Rolling contact fatigue is a problem encountered with many machine elements.In the current report a numerical study has been performed in order to predictthe crack path and crack propagation cycles of a surface initiated rolling contactfatigue crack. The implementation of the contact problem is based on theasperity point load mechanism for rolling contact fatigue. The practical studiedproblem is gear contact. Different loading types and models are studied andcompared to an experimental spall profile. Good agreement has been observedconsidering short crack lengths with a distributed loading model using normalloads on the asperity and for the cylindrical contact and a tangential load on theasperity. Several different crack propagation criteria have been implemented inorder to verify the validity of the dominant mode I crack propagation assumption.Some general characteristics of rolling contact fatigue cracks have beenhighlighted. A quantitative parameter study of the implemented model hasbeen performed.Utmattning med rullande kontakter är ett ofta förekommande problem för många maskinelement. I den aktuella rapporten utfördes en numerisk studieför att förutsäga sprickvägen hos utmattningssprickor som initierats i ytan vidrullande kontakter. Implementeringen av kontaktproblemet bygger på asperitpunktlastmekanismen för rullande kontakter. Studien av kontaktproblemetär tillämpad till kugghjul. Olika belastningstyper och modeller studeradesoch jämfördes med profilen hos en experimentell spall. Bra överensstämmelseobserverades för korta spricklängder när en modell med fördelad belastninganvänds för en belastningstyp där en normalbelastning agerar på asperiten ochvid cylindriska kontakten och en tangentialbelastning införs på asperiten. Olikakriterier för spricktillväxt implementerades för att verifiera giltigheten av antagandetatt mode I spricktillväxt är dominant. Några generella kännetecken avutmattningssprickor med rullande kontakter framhävdes. En kvantitativ parameterstudie för den implementerade modellen utfördes.
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Hearle, Adrian Donald. "Deformation, shakedown and fatigue in rolling contact." Thesis, University of Cambridge, 1985. https://www.repository.cam.ac.uk/handle/1810/250858.
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Ahmed, Rehan. "Rolling contact fatigue of thermal spray coatings." Thesis, Brunel University, 1998. http://bura.brunel.ac.uk/handle/2438/5469.
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The practical advantages of thermal spray coatings like high deposition rates, low cost and tribological properties of high wear resistance have enabled these coatings to become an integral part of aircraft and automobile industry. Recent advancements in thermal spraying techniques like high particle speed and temperature call for new applications for these coatings. This experimental study addresses the Rolling Contact Fatigue performance of thermal spray coatings deposited by a variety of techniques like High Velocity Oxy-Fuel (HVOF), Detonation Gun (D-Gun) and Plasma spraying. RCF tests were conducted using a modified four ball machine in conventional steel ball bearing and hybrid ceramic bearing configurations. Tribological conditions during the RCF tests were varied by changing the test lubricant and the lubrication mechanism, contact load and shape of the drive coated rolling element to vary the roll/slip ratio. RCF tests were analyzed on the basis of the performance, coating failures using surface and subsurface observations, and residual stress studies. Experimental and theoretical studies of the ball kinematics have also been included. These tests revealed that the performance of the coated rolling elements was dependent upon the coating and the substrate properties. The coating thickness, substrate hardness, tribological conditions during the test, coating and substrate material as well as the coating process and the substrate preparation significantly affect the coating performance and the failure modes. Three different failure modes of these coatings have been discussed along with the changes in the near surface residual stress behaviour of the coated rolling elements.
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Alwahdi, Farag Abdullah Mohamed. "Wear and rolling contact fatigue of ductile materials." Thesis, University of Sheffield, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421003.
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Carroll, Robert Ian. "Surface metallurgy and rolling contact fatigue of rail." Thesis, University of Sheffield, 2006. http://etheses.whiterose.ac.uk/14639/.
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This thesis presents the results of an investigation into the effect of surface metallurgy on the rolling contact fatigue behaviour of rail. The investigation has used laboratory based rolling/sliding twin disc testing of samples with a surface metallurgical feature simulated on them. The samples used in laboratory testing have been compared with samples of rail removed from track. Two surface metallurgical features have been investigated: decarburisation and white etching layer. Decarburisation is the loss of carbon from the surface of the rail due to oxidation at high temperatures, resulting in a softer layer at the surface (180HV compared to 250HV bulk). The decarburised layer has been simulated in this research by heat treating discs in a laboratory furnace with an air atmosphere. The results show that by increasing the depth of decarburisation the growth rate of cracks within the sample, along with the wear rate, increases. At the maximum depth of decarburisation allowed on rail by the standard (O.5mm) there was little difference in the wear or rolling contact fatigue behaviour with or without decarburisation. White etching layer (WEL) forms on the surface of rail due to the action of the wheels and is a very hard layer (>850HV) up to 250mm deep. White etching layer has been simulated in two ways: spot welding and gross sliding of the discs. The results have shown that cracks initiate preferentially at weak spots at the surface, such as the interface between the WEL and pearlite or along proeutectoid ferrite boundaries. It has been found that the growth of cracks below the surface depends on the strain history of the subsurface pearlite. The results indicate that white etching layer is detrimental to rail life through either the promotion of rolling contact fatigue and/or wear.
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Sato, Meiji. "Wear and rolling contact fatigue of rail steels." The Ohio State University, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=osu1335372747.
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Quiney, Zak. "Rolling contact fatigue detection via high frequency acoustic emission." Thesis, Swansea University, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.678470.
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Qiu, Xiaonong. "Rolling contact fatigue behavior of three eutectoid rail steels /." Full text open access at:, 1987. http://content.ohsu.edu/u?/etd,153.
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Kim, Tae Hyun. "Fatigue of surface engineered steel in rolling-sliding contact." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325019.
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Yang, Yulin. "Evaluation of rolling contact fatigue resistance for coated components." Thesis, University of Hull, 2003. http://hydra.hull.ac.uk/resources/hull:8534.
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The thesis reviews and studies current evaluation mechanisms, techniques and machines for testing rolling contact fatigue failure resistance and load capacity of coated components. The thesis investigates both normal and accelerated rolling contact fatigue evaluation test mechanisms and their models, and evaluation test technique principles suitable to the appraisal of coated bearing components. A major contribution of the thesis is the design and development of a new rolling contact fatigue evaluation test machine for coated components. Tests of the rolling contact fatigue of coated bearing raceways under the oil lubricant, grease lubricant and no lubricant conditions, applying the new rolling contact fatigue evaluation mechanisms, evaluation technique principles and the new test machine, have been performed. The accelerated rolling contact fatigue tests of the coated bearing raceways use SiC powder in the oil lubricant. The new rolling contact fatigue test machine has been found suitable for evaluating the rolling contact fatigue resistance of components with superhard coatings. The accelerated rolling contact fatigue test method has been shown to give comparable rolling contact fatigue test results to those obtained in a normal rolling contact fatigue test, while being much faster. In the fatigue test, the cyclic maximum shear stress produces an initial fatigue crack near the substrate surface of the test bearing raceways. The observed phenomena are consistent with theory, although the location of the initial crack is much closer to the surface than would be predicted by a 'static' Hertzian analysis. Insufficient traction forces on the contact surface between the rolling elements of a test coated bearing makes gross skidding occur, leading to rapid wear, over-heating and final failure of the test coated bearing. The LSO fatigue life of the test coated bearing raceway tends to decrease with increase of the coating thickness and coating hardness of the test coated bearing raceway.
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Fish, Gareth. "The effect of emulsion chemistry on rolling contact fatigue." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/46297.
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Alshahrany, Shaya. "Rolling contact fatigue in heavily loaded gear transmission contacts." Thesis, Cardiff University, 2015. http://orca.cf.ac.uk/90422/.
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This thesis examines the influence of asperities such as found on the teeth of gears and discs, and failure mechanisms associated with rough surface Elastohydrodynamic Lubrication (EHL). The principal outcomes of the research provide a good insight into fatigue life, residual stress effects, damage prediction and surface contact failures. In particular, the study is intended to provide understanding into the residual stress distribution resulting from plastic deformation of surface asperities in the running in process. The residual stress is then added to the asperity elastic stress distribution and examined in detail to see the effects on fatigue damage and fatigue life. So, a theoretical model has been developed to assist design against the residual stress effect and surface contact fatigue, such as micropitting. The technique used in the study starts with developing an elastic plastic model of the rough surface by using the Abaqus Finite Element analysis software package. This is a nonlinear problem and ranges of applied loads have been applied to the as-manufactured surfaces causing the asperity features to experience varying degrees of plastic deformation. The pre and post running roughness profiles are studied in order to assess the level of plastic deformation actually occurring at significant surface asperity features by aligning the pre and post running profiles. This results in a new technique that has helped to identify the level of plastic deformation occurring in the practice, and also to make a comparison with FEA contact analysis for the same asperity features to identify the appropriate residual stress field. The residual stress field associated with the plastic deformation was extracted and evaluated. The extracted residual stress field was transferred to a form that facilitated IV inclusion in stress evaluation code to obtain the stress history for the material subject to loading in an EHL contact. The research carried out considers surface fatigue analysis with and without a residual stress field, so as to establish the influence of asperity plastic deformation on the fatigue properties of the surface. All the work is based on numerical simulation of surface fatigue failure in EHL situations and carried out numerically. The procedure can be applied quickly and gives the opportunity to apply several models and investigate the influence of all the model parameters on material deformation and fatigue life.
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Fu, Hanwei. "Microstructural alterations in bearing steels under rolling contact fatigue." Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/270311.
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The formation of microstructural alterations in bearing steels under rolling contact fatigue (RCF) is systematically studied. A literature review summarizes current understanding in this field, leading to the key to the formation of these microstructural features being carbon redistribution as a consequence of cyclic rolling contact. In this context, a novel theory is postulated to describe the migration of carbon caused by gliding dislocations. The theory combines the Cottrell atmosphere theory with the Orowan equation and is capable of quantifying the dislocation-assisted carbon flux. Based on the proposed theory, models are suggested for different types of microstructural alterations formed in rolling contact fatigued bearings – dark etching regions (DERs), white etching bands (WEBs) and white etching areas (WEAs). Very good agreement is obtained between the predications made by the models and the experimental data from both this research and the literature. Moreover, the models consider the effects of contact pressure, temperature, rotational speed and number of cycles, and thus can be applied for universal RCF testing conditions. The reproduced microstructural features are also characterized using advanced characterization techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atom probe tomography (APT), with the observation validating the postulated formation mechanisms. It is demonstrated that DERs, WEBs and WEAs follow the same principle during formation – strain induced carbon redistribution. This is the first time that these microstructural alterations are quantitatively described using a unified theory. The achievements obtained from this research can be far reaching. It not only leads to great progress in understanding the phenomenology of RCF in bearing steels, but also can be further extended to other scenarios with similar phenomena such as severe plastic deformation and hydrogen embrittlement.
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Ghaffari, Gharehbagh Mir Ali. "Multi-scale modeling and simulation of rolling contact fatigue." Diss., University of Iowa, 2016. https://ir.uiowa.edu/etd/2082.
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In this thesis, a hierarchical multiscale method was developed to predict rolling contact fatigue lives of mechanical systems. In the proposed multiscale method, the molecular modeling and simulation of lubricant was conducted to investigate the friction between rolling contact surfaces. The calculated friction coefficient was passed to the continuum model of rolling contact components to predict fatigue lives.
Molecular dynamics modeling and simulation of thin film lubrication and lubricated contact surfaces were carried out to investigate mechanisms of hydrodynamic lubrication at nano-scale first. Although various lubricant alkane chains were considered in the molecular model, the chain length of eight united molecules were mainly employed in this thesis. In addition, the effects of temperature and nano-particles (debris) on the friction forces were discussed. It was found that the existing of nano-particles (debris) could increase the friction force between contact surfaces with hydrodynamic lubrication.
In the continuum model of the developed multiscale method, finite element analysis was employed to predict rolling contact fatigue life of rolling contact components, including bearing and gear-tooth. Specifically, the fatigue crack initiation of bearing was studied, and then the fatigue crack initiation and propagation in gear-tooth. In addition, the enhancement of gear-tooth fatigue life by using composite patches was discussed as well. It should be noted that the friction coefficient used in the continuum model was calculated in the molecular model. It is one-way message passing in the developed multiscale method.
Another continuum method was studied and developed in this thesis to provide alternate methods for the continuum model in the proposed multiscale framework. Peridynamics method has advantages in modeling and simulation of discontinuities, including cracks, over the conventional finite element methods. The applications of Peridynamics in predicting fatigue crack initiation and propagation lives were discussed in this thesis.
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Dahlberg, Johan. "On the asperity point load mechanism for rolling contact fatigue." Doctoral thesis, Stockholm : Hållfasthetslära, Kungliga Tekniska högskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4569.
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Stewart, Simon Hardie. "The rolling contact fatigue of post-treated thermal spray coatings." Thesis, Heriot-Watt University, 2005. http://hdl.handle.net/10399/234.
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Iida, Yusuke. "The effects of magnetic fields on rolling contact fatigue wear." Thesis, Brunel University, 2007. http://bura.brunel.ac.uk/handle/2438/7405.
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The thesis describes the effects of the magnetic field in rolling contact tests of steel by using a two-disc machine and the investigation of its mechanism from contact stress analysis by using FEM and the agnetisation of a ferromagnetic substance. In the tests, two contact kinematic conditions, that is pure rolling and 10% rolling with sliding together with 1.1 and OAT [Tesla] of horizontal static magnetic fields created by permanent magnets were pplied. The results of optical and scanning electron microscopy observations show that finer wear particles and smoother worn surfaces are produced in the presence of the magnetic field. For the generation of the finer wear particles, it is considered necessary that the subsurface crack initiation point is moved towards the surface due to the magnetic field. Wear amounts of the discs are lowered III the magnetic fields under the pure rolling conditions. However, at 100/0 rolling with sliding, the wear amounts are increased in the magnetic fields even though finer particles and smoother surfaces are observed. Both tendencies are unified by calculating the number of cycles required to generate wear particles, which are reduced due to the magnetic field's presence. For these mechanisms, it is considered that domain walls near the contact region are caught by dislocations when the specimen is agnetised and part of the energy for magnetisation activates the dislocation movement resulting in crack initiation.
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Hanzal, Robert J. F. "Rolling contact fatigue failures in silicon nitride and their detection." Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/361698/.
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The project investigates the feasibility of using sensor-based detection and processing systems to provide a reliable means of monitoring rolling contact fatigue (RCF) wear failures of silicon nitride in hybrid bearings. To fulfil this investigation, a decision was made early in the project to perform a series of hybrid rolling wear tests using a twin disc machine modified for use on hybrid bearing elements. The initial part of the thesis reviews the current understanding of the general wear mechanisms and RCF with a specific focus to determine the appropriate methods for their detection in hybrid bearings. The study focusses on vibration, electrostatic and acoustic emission (AE) techniques and reviews their associated sensing technologies currently deployed with a view of adapting them for use in hybrids. To provide a basis for the adaptation, an understanding of the current sensor data enhancement and feature extraction methods is presented based on a literature review. The second part describes the test equipment, its modifications and instrumentation required to capture and process the vibration, electrostatic and AE signals generated in hybrid elements. These were identified in an initial feasibility test performed on a standard twin disc machine. After a detailed description of the resulting equipment, the thesis describes the calibration tests aimed to provide base data for the development of the signal processing methods. The development of the signal processing techniques is described in detail for each of the sensor types. Time synchronous averaging (TSA) technique is used to identify the location of the signal sources along the surfaces of the specimens and the signals are enhanced by additional filtering techniques. The next part of the thesis describes the main hybrid rolling wear tests; it details the selection of the run parameters and the samples seeded with surface cracks to cover a variety of situations, the method of execution of each test run, and the techniques to analyse the results. The research establishes that two RCF fault types are produced in the silicon nitride rolling element reflecting essentially different mechanisms in their distinct and separate development; i) cracks, progressing into depth and denoted in this study as C-/Ring crack Complex (CRC) and ii) Flaking, progressing primarily on the surface by spalls. Additionally and not reported in the literature, an advanced stage of the CRC fault type composed of multiple and extensive c-cracks is interpreted as the result of in duced sliding in these runs. In general, having reached an advanced stage, both CRC and Flaking faults produce significant wear in the steel counterface through abrasion, plastic deformation or 3-body abrasion in at least three possible ways, all of which are described in details.
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Evans, M. H. "White structure flaking failure in bearings under rolling contact fatigue." Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/355966/.
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White structure flaking (WSF) as a premature wear failure mode in steel rolling element bearings is caused by white etching cracks (WECs) and perhaps butterflies formed in the ~1 mm zone beneath the contact surface under rolling contact fatigue (RCF). WECs are branching crack systems typically several millimetres in length that have a microstructural change called ‘white etching area’ (WEA) associated with the crack. Butterflies are smaller cracks initiating at material defects and impurities that form WEA wings that revolve around their initiators. Hydrogen diffusion into the bearing steel during service and transient operating conditions have been suggested as drivers of white etching features (butterflies, WEA and WECs). However the initiation and propagation mechanisms as well as the thresholds for WEC formation are not well understood. This is due to the difficulties of creating WECs repeatedly under laboratory conditions and the lack of a method established for mapping WECs in detail or 3 dimensions as typically only limited metallographic analyses are conducted over several cross-sections. A series of RCF tests have been conducted in this study to investigate the formation drivers and formation mechanisms of WECs using a two-roller RCF machine. WECs were successfully created in hydrogen charged 100Cr6 martensitic steel rollers under low-moderate concentrations of diffusible hydrogen (~1 ppm) and service realistic loading conditions (Pmax 1.5 – 2 GPa). However, only butterflies were formed under transient conditions with non-hydrogen charged rollers. One such butterfly was analysed in detail to further understanding of crack formation mechanisms and carbide dissolution as part of the WEA microstructural change. Based on the evidence obtained from the SEM, FIB tomography and STEM/TEM analysis, a void/cavity coalescence theory for initial butterfly crack formation and iron chromium carbide dissolution as part of the WEA formation mechanism is proposed. Metallography was extensively used in this project to view cross-sections of the wear zones subject to RCF. A metallographic serial sectioning technique was established to quantitatively map wear zones for the first time. Mapping WECs in their entirety and 3D modelling revealed the 3-dimensional morphology and orientation of WECs and maximised detection of possible WEC initiators. This study has for the first time quantitatively investigated the influence of diffusible hydrogen, load and rolling cycles on white etching feature formation and the thresholds of formation. The hydrogen charged tests showed that the formation of butterflies was independent of the concentration of diffusible hydrogen with the test parameters used, but dependent on contact pressure and number of rolling cycles up to a threshold. WEC formation thresholds were found at certain values of the concentration of diffusible hydrogen, contact pressure and number of rolling cycles. Extensive serial sectioning and 3D modelling of WECs also demonstrated that the orientation of WECs differed depending on the sectioning direction. It was found that the vast majority of WECs were contained in the subsurface wear zone and did not make any connection with the surface, thus dismissing surface initiation. The WECs often interacted with inclusions that were judged to be crack initiators and evidence was found that butterfly cracks could propagate to form WECs. The white etching features initiated predominately at short sulfide type inclusions, small globular manganese sulfide oxide inclusions and small globular oxide inclusions. Therefore strong evidence was observed for a subsurface initiation mechanism of WECs from non-metallic inclusions. A comparison of the WEC formations in the hydrogen charged two-roller tests was made with serial sectioning investigations of WEC formation in wind turbine gearbox bearings obtained from the field and those tested on a large-scale transient test rig (non-hydrogen charged). This was performed to understand if a difference in the WEC initiation and propagation mechanism occurs under the differing conditions. The comparison showed correlation between the WEC formation mechanisms as a high number of inclusions interacted with the WECs that were judged to be crack initiators and small/short sized inclusions predominated as the crack initiators. Therefore based on the serial sectioning analysis across various test specimens and bearings it is proposed that one mechanism of WEC formation is due to multiple linking of extended butterflies or small WECs in the subsurface to form larger WEC networks that eventually propagate to the surface resulting in WSF. The data also suggests that steel cleanliness standards analysing inclusion density (as opposed to maximum inclusion lengths) are more relevant in understanding butterfly/WEC initiation. However steel cleanliness standards used should record inclusions that are only a couple of micrometer’s in length/diameter.
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Balcombe, Robbie. "A study of rolling contact fatigue cracks in lubricated contacts." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/9848.
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A novel method for coupling fluid pressure and crack deformation for the purpose of analysing rolling contact fatigue (RCF) cracks in lubricated, hydrodynamic and elastohydrodynamic, contacts is presented. The model addresses some of the simplifying assumptions applied to existing models presented in the literature such as: (i) using an imposed fluid pressure gradient inside the crack, (ii) using an imposed fluid pressure at the crack mouth, and (iii) adopting a surface contact pressure, Hertzian or EHL, that does not account for the fluid flow in and out of the crack during loading. The model has been used to model the effect of lubricant/crack interaction in various RCF configurations as the rolling element passes over the pre-formed crack; which has direct application to bearings and rail/wheel contacts. The results of the simulations performed with the fully-coupled fluid/solid solver developed by the author suggest that the cracked component/lubricant interaction contributes significantly to accelerate the rate of surface breaking crack growth in rolling element bearings and wheel/rail type contacts. It is shown through simulations that the lubricant works as a catalyst inside the crack to convert the compressive contact load into a crack opening, tensile fatigue mechanism, through the effect of fluid pressurisation inside the crack. The results obtained using such a model suggest that the opening associated with the fluid action within the crack induces large mode I stress intensity factors. This has been shown to be the principal factor that promotes and influences the rate of rolling contact fatigue crack growth in lubricated contacts. In addition to the modelling work, an experimental method of analysing RCF cracks in real time has been developed. The technique is based on laser induced fluorescence that allows the penetration of the fluid within the crack to be observed. Though the method would require development to be used to provide results that could be used for quantitative comparisons with crack models, some encouraging preliminary results have been obtained: the technique has been shown to be suitable for measuring, at least qualitatively, the real time evolution of the film thickness in RCF cracks.
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Al-Sabti, Sara Louise. "Failure modes of polymethylmethacrylate resulting from rolling line contact." Thesis, Brunel University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311264.
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Kang, JeeHyun. "Mechanisms of microstructural damage during rolling contact fatigue of bearing steels." Thesis, University of Cambridge, 2014. https://www.repository.cam.ac.uk/handle/1810/245255.
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Bearings are employed in a number of applications under extremely demanding conditions. During long operation times, the material undergoes rolling contact fatigue where microstructural damage manifests as dark-etching regions and white-etching areas, which display different properties from the surrounding region. The aim of this study is to identify the mechanisms for such damage and to suggest models that can explain the influence of the initial microstructure and test conditions. In order to appraise the stress state in rolling contacts, two testing techniques were employed and it was examined if the testing methods could reproduce the same damage as in bearing operation. During ball-on-rod fatigue testing, microcracks were generated adjacent to inclusions and some were decorated with white-etching areas. Repetitive push tests showed a similar extent of subsurface hardening compared to the ball-on-rod tests, and allowed the strain per stress cycle to be measured. The microstructural alterations in a white-etching area were studied both on a macroscale and on an atomic-scale. The degree of stress concentration near a microcrack was calculated employing a nite element method. The microstructure, as well as the segregation behaviour of alloying elements in the white-etching area, were investigated by employing transmission electron microscopy and atom probe tomography. A nanocrystalline structure with scattered carbide particles was observed in the white-etching area. Carbon and silicon segregation was highly pronounced in some boundaries of dislocation cell structures. Models were suggested to account for the microstructural alterations during rolling contact fatigue. Carbide coarsening in dark-etching regions was modelled by considering how carbon di usion is assisted by dislocation glide. The predicted hardness evolution was consistent with experimental observation. The kinetics of carbide dissolution in white-etching areas was calculated by taking two processes into account: deformation accumulation and carbon diffusion. These models suggest that the microstructural changes during bearing operation can be controlled by tailoring the initial microstructure and managing the test conditions.
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Everitt, Carl-Magnus. "Initiation of rolling contact fatigue from asperities in elastohydrodynamic lubricated contacts." Licentiate thesis, KTH, Hållfasthetslära (Avd.), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-222371.
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Rolling contacts are utilized in many technical applications, both in bearings and in the contact between gear teeth. These components are often highly loaded, which makes them susceptible to suffer from rolling contact fatigue. This work focuses on the rolling contact fatigue mechanism of pitting. In order to attain a better understanding of why pitting initiates and grows, detailed simulations of rolling contacts have been performed. In particular the contact between two gears in a truck retarder was here used as a case study. The investigated contact experienced elastohydrodynamic lubrication conditions since the load was high enough to causes the surfaces in contact to deform and the viscosity of the lubricant to increase significantly. In Paper A it was investigated if surface irregularities in the size of the surface roughness are large enough to cause surface initiated fatigue. The investigation focused on the pitch line since small surface initiated pits were found here even though there was no slip present. Since there were pits present at the pitch line, it is important that the theories of pitting can explain the development of pits also in the absence of slip. The conclusion of the work was that surface irregularities of the size of normal surface roughness are enough to cause surface initiated fatigue at the pitch line. In Paper B it was investigated why pits are more likely to initiate in the dedendum of pinion gears than in the addendum. In both areas slip is present but in different directions. In the dedendum the friction from slip is against the rolling direction which enhances the risk for pitting. The investigation was performed by studying the effect of the temperature rise in the contact caused by the slip. The conclusion drawn was that the temperature rise in the contact explained why pitting was more common in the dedendum than in the addendum.Rullande kontakter förekommer i många applikationer, till exempel i lager och mellan kugghjulständer. Både lager och kugghjul utsätts ofta för höga laster vilket gör att dess ytor löper stor risk att utmattas, vilket kallas rullande kontaktutmattning. Denna studie fokuserar på pitting, även kallat spalling, vilket är en typ av rullande kontaktutmattning där en utmattninsspricka växer fram som får delar av ytan att ramla av. För att få en bättre förståelse varför pittingskador uppkommer har noggranna simuleringar utförts av rullande kontakter. Kontakten mellan två tänder på kugghjul i en lastbilsretarder har används som underlag då många pittingskador påträffats på dem. För att minska friktionen och nötningen i kontakten mellan kuggtänderna användes smörjmedel. De höga lasterna lastbilsretardern utsattes för deformerade kuggarnas ytor elastiskt samtidigt de kraftigt ökade viskositeten hos smörjmedlet. Dessa förhållanden gör att kontakten kallas för elastohydrodynamiskt smord, vilket på engelska förkortas till EHL. I Artikel A undersöktes om små ytojämnheter kan orsaka ytinitierade pittingskador. Eftersom skadan påträffats i friktionslösa kontakter, så som vid rullcirkeln på de undersökta kugghjulen, är det viktigt att teorierna som förklarar uppkomsten inte är beroende av friktion. Undersökningen fokuserade därför på förhållandena vid rullcirkeln. Slutsatsen från arbetet var att små ytojämnheter, av samma storleksordning som ytojämnheterna på de undersökta kugghjulen, är tillräckligt stora för att orsaka utmattningsskador. I Artikel B undersöktes varför det är vanligare att pitts initieras i dedendum än addendum på drivande kugghjul. Kontakten på båda sidorna om rullcirkeln slirar svagt åt olika håll. Att kontakten slirar skapar friktion som är motriktad rullriktningen i dedendum vilket ökar risken för pittingskador. För att undersöka varför dessa förhållanden ökar risken för skador fördjupades analysen av kontakten genom att inkludera temperaturfältet. Simuleringarna visade att temperaturen ökar genom kontakten vilket orsakar en asymmetrisk spänningsfördelning. Denna asymmetriska spänningsfördelning gör att ytojämnheter i dedendum är troligare att orsaka skador än ytojämnheter i addendum.
QC 20180213
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Tyfour, Wa'il Radwan Ali. "Interaction between wear and rolling contact fatigue in pearlitic rail steels." Thesis, University of Leicester, 1995. http://hdl.handle.net/2381/34715.
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The work presented in this thesis is aimed at investigating the interaction between wear and rolling contact fatigue, which are two of the most serious forms of deterioration caused by the wheel on rail contact stresses. Wheel-rail contact conditions were simulated by a two disc contact using the LEROS (LEicester university ROlling-Sliding wear testing machine). Investigation of the wear behaviour of BS11 pearlitic rail steel showed that steady state wear behaviour is established after a certain number of rolling-sliding cycles. Contact surface failure by ratchetting (accumulation of unidirectional plastic strain) was found to be the dominant failure mechanism during the period leading to the steady state. This mechanism was confirmed by the drop in the wear rates when the direction of rolling-sliding; i.e. strain in the surface layer, was reversed at predetermined numbers of cycles. The effect of repeated rolling direction reversals on crack morphology, propagation and rolling contact fatigue (RCF) life of BS11 rail steel was also investigated. It was established that rolling direction reversal has a beneficial effect on RCF life. A new mechanism, the "variable crack face friction mechanism", was proposed to explain this effect. Interaction between wear and RCF fatigue was investigated through rolling-sliding experiments where specimens were run dry for certain number of cycles, to induce different levels of wear damage, before the fatigue performance was investigated. It was shown that initial dry cycles above a critical number causes sudden and significant deterioration in RCF life. This deterioration has been explained in terms of the role of the accumulation unidirectional plastic strain (ratchetting) in initiating and propagating the early cracks during the dry phase. A strong correlation was found between the total ratchetting strain induced during the dry phase and the deterioration in RCF life. An empirical relationship to estimate this deterioration was concluded.
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Frolish, Michael Fraser. "Design criteria for rolling contact fatigue resistance in back-up rolls." Thesis, University of Sheffield, 2002. http://etheses.whiterose.ac.uk/15083/.
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The demands placed on back-up rolls in hot strip mills have been investigated by a combination of literature and industrial studies. The tribological operating conditions have been established and the maximum local loads and pressure distributions at the work roll/back-up roll interface have been obtained by processing mill and roll schedule data using a computer program (commercial software developed by V AI Industries (UK) Ltd) and applying the theories of contact mechanics. After a study of the responses of the rolls to these demands and possible failure mechanisms, research has centred on surface initiated damage whereby cracks can propagate into the roll substrate potentially reaching the internal residual stress fields and leading to catastrophic failure. A proposed qualitative contact and fracture mechanics model, for the rolling contact fatigue and spalling failure, has been quantified theoretically using published methods for determining the stress intensity factors at the tips of pressurised and water lubricated, inclined rolling contact fatigue cracks. The predictions of the quantitative model in terms of crack directions and lengths have been validated by microscopic observation of the morphologies cracks produced in test discs used in the "SUROS" Rolling-Sliding Testing Machine and also in a sample of material spalled from a back-up roll. The quantitative failure model includes criteria for crack branching either upwards leading to micro spalling or downwards (potentially catastrophic) and the link between these two cases has been related quantitatively to the value of the mode I threshold for the roll material. After linking mechanics to microstructure and quantifying the interactions between wear and rolling contact fatigue in this case, practical quantitative recommendations have been made for the design of bainitic back-up roll materials, back-up roll redressing procedures and the surface roughness of both the work rolls and back-up rolls presented to the mill.
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Rycerz, Pawel. "Propagation of surface initiated rolling contact fatigue cracks in bearing steel." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/44525.
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The useful life of mechanical components which experience highly stressed rolling/sliding contacts, such as rolling element bearings or gears, is limited by rolling contact fatigue (RCF). Surface initiated pitting is a mode of RCF which has in recent years received particular attention from industry due to its frequent occurrence in service. This work focuses on the growth behaviour of RCF cracks before they develop into surface pits. A three-contact disc machine was used to perform pitting experiments on bearing steel samples. Preliminary tests showed that surface initiated cracks could be reproduced under high contact pressure and mixed lubrication regime. However, it was not possible to detect them using the vibration monitoring system installed on the test rig. This led to the development of a high sensitivity crack detection system which employs the principle of magnetic flux leakage (MFL). The existing test rig was modified to accommodate an inductive sensor and required signal acquisition electronics. In addition, a signal processing procedure was developed to enable analysis in real time. It was shown that the MFL technique is significantly more sensitive than commonly used alternatives. The system is capable of automatically finding cracks down to about 100 μm in length. In addition, results have shown a linear relationship between defect size and signal amplitude which enables in-situ sizing of cracks. Using the crack detector, a procedure to generate cracks and extract their growth rates was established. Crack growth was first studied under high contact pressure. It was found that initiation occurred very early in total life, which was attributed to high asperity stresses due to mixed lubrication regime. Total life to pitting was dominated by crack propagation, the speed of which was shown to depend on crack size. Small cracks grew at a steady and slightly decreasing rate until a critical size is reached at which propagation speed rapidly increases, shortly followed by pitting. Further study at lower loads confirmed that contact pressure is the main parameter controlling propagation speed. In order to identify a suitable crack propagation law, the measured crack growth rates were plotted against a stress intensity parameter expressed in terms of maximum contact pressure and crack size. The results suggest that after reaching certain length, rolling contact fatigue cracks grow according to a Paris-type power law, where the exponent of stress intensity parameter, and therefore contact pressure, was found to be approximately 7.5.
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Bulusu, Prashant. "Rolling contact fatigue predictions based on elastic-plastic finite element stress analysis and multiaxial fatigue /." abstract and full text PDF (free order & download UNR users only), 2006. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1437664.
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Thesis (M.S.)--University of Nevada, Reno, 2006."August, 2006." Includes bibliographical references (leaves 38-45). Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2006]. 1 microfilm reel ; 35 mm. Online version available on the World Wide Web.
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Sircar, Sager Dave [Verfasser], and A. [Akademischer Betreuer] Wanner. "Rolling Contact Fatigue of Hypoeutectoid Steel / Sager Dave Sircar. Betreuer: A. Wanner." Karlsruhe : KIT-Bibliothek, 2015. http://d-nb.info/1073204820/34.
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Rochard, Bernard P. "Rolling contact fatigue of railway rails and organisation design for its management." Thesis, University of Sheffield, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.445126.
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Alley, Erick Shaw. "Influence of microstructure in rolling contact fatigue of bearing steels with inclusions." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28127.
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Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2009.Committee Chair: Neu, Richard; Committee Member: Damm, E. Buddy; Committee Member: Gall, Ken; Committee Member: Gokhale, Arun; Committee Member: McDowell, David; Committee Member: Zhou, Min
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Hedmark, Björn, and Per Wallgren. "Influence of ANS Triboconditioning on friction and fatigue in rolling contact configurations." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-75597.
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The automotive industry is constantly being challenged by customers and authorities to enhance the efficiency of the internal combustion engine (ICE) in order to achieve improved fuel consumption and reduced emissions. There are several interfaces within the design of an ICE that causes frictional losses, one of them is the valvetrain. An approach to reducing the friction in the valvetrain of modern engines is to implement cam-follower rollers, resulting in a rolling rather than sliding contact when interacting with the camshaft. The prominent type of wear in rolling contacts is surface fatigue, and specifically a phenomenon called micropitting. The company in collaboration with this project is Applied Nano Surfaces Sweden AB (ANS), located in Uppsala, Sweden. The company have specialized in surface treatment methods of mechanical components. ANS has developed a mechano-chemical treatment method called ANS Triboconditioning, which have shown beneficial friction and wear reducing properties when applied to metal surfaces. This thesis was conducted to investigate how the ANS Triboconditioning would affect the frictional behaviour compared to established surface treatment methods and the occurrence of micropitting in rolling contact configurations. Two types of test programs was implemented into a Wazau UTM 2000 Twin-Disc Tribometer. No clear trend could be established from the micropitting tests and therefore no conclusion regarding if ANS Triboconditioning affects the occurrence of micropitting damage in a positive or negative manner could be stated. The results from the friction test indicated an overall reduction in friction for the test specimens that had been treated with ANS Triboconditioning when compared to specimens that only had been treated with already established surface treatment methods. Summarized, additional tests and analyses are necessary in order to statistically confirm the observed results and determine their respective trends.
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Yeung, Kwai-wing. "Elastic-plastic analysis of rolling elliptical contacts and the effects of axial superimposed stresses on rolling contact fatigue failure /." [Hong Kong] : University of Hong Kong, 1987. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12333669.
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Hannes, Dave. "On fatigue crack growth modelling of surface initiated rolling contact fatigue using the asperity point load mechanism." Doctoral thesis, KTH, Hållfasthetslära (Avd.), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-141151.
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Load transfer in applications or between machine components is generally achieved through contact. In case of recurrent high contact loads in combination with a rolling motion, i.e. with a relatively small amount of slip, the contact surface may eventually suffer from rolling contact fatigue (RCF). The damage consists then of cracks and craters or spalls, which can cause dysfunctionality of the application leading to inefficiency or increased maintenance costs. Ultimately the damage may cause total failure of the machine component. The damage process is still not fully understood due to the complexity of the problem. Different mechanisms have been suggested to explain initiation and propagation of RCF damage. The current work focused on crack growth modelling of surface initiated RCF in case hardened gear steel. The study was based on the asperity point load mechanism, which emphasizes the importance of the surface roughness in the damage process. Asperities on the contact surface act as stress raisers inducing locally high tensile surface stress when entering the contact. Improved understanding of the damage process and further validation of the asperity point load mechanism was achieved. In Paper A, the crack path of surface initiated RCF was simulated in the symmetry plane of the damage with the trajectory of the largest principal stress in the uncracked material. The mode I fracture mechanism was found applicable as well as linear elastic fracture mechanics (LEFM). The evolvement of the asperity contact parameters during the load cycle was determined through a finite element (FE) contact model based on an equivalent contact geometry. The predicted RCF crack path agreed with experimental spall profiles both in entry details as in overall shape. An experimental series was performed in Paper B to investigate the crack closure behaviour in presence of large negative minimum loads. The experimental results suggested a crack closure limit close to zero. The choice of the equivalent mixed-mode stress intensity factor range and especially the crack closure limit had a significant effect on the predicted RCF or spalling life. The two-dimensional crack growth model was further developed in Paper C and used to investigate the influence of asperity size, friction and residual surface stress on the simulated RCF damage. The simulations agreed qualitatively with experimental observations where reduced surface roughness, improved lubrication and compressive residual surface stress increased RCF resistance. In Paper D, a three-dimensional stationary crack was studied using an FE model and a simplified RCF load. A new crack geometry was proposed allowing the investigation of the spall opening angle of the typical vshaped damage. Crack arrest through crack closure was suggested as explaining mechanism. A qualitative study indicated increased spread of the surface damage with increased friction. The results also depended on the crack inclination angle. The different studies supported the asperity point load mechanism to explain not only fatigue initiation but also fatigue crack propagation.QC 20140210
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Spangenberg, Ulrich. "Reduction of rolling contact fatigue through the control of the wheel wear shape." Thesis, University of Pretoria, 2017. http://hdl.handle.net/2263/62796.
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Heavy haul railway operations permit the transport of huge volumes at lower cost than other modes of transport. The low cost can only be sustained if the maintenance costs associated with such railway operations are minimised. The maintenance costs are mainly driven by wheel and rail damage in the form of wear and rolling contact fatigue (RCF). Low wear rates in the wheel-rail interface have resulted in an increase in the prevalence of rail RCF, thereby increasing rail maintenance costs. The aim of this study is to develop an approach to reduce rail RCF on South Africa’s iron ore export line by managing the worn wheel shape. This approach is developed by evaluating wheel and rail profile shapes that contribute the most to RCF initiation, studying the influence of suspension stiffness and rail profile changes as well as a redesign of the wheel profile. The influence of wheel and rail profile shape features on the initiation of rolling contact fatigue (RCF) cracks was evaluated based on the results of multibody vehicle dynamics simulations. The damage index and surface fatigue index were used as two damage parameters to assess the influence of the different features. The damage parameters showed good agreement to one another and to in-field observations. The wheel and rail profile shape features showed a correlation to the predicted RCF damage. The RCF damage proved to be most sensitive to the position of hollow wear and thus bogie tracking. RCF initiation and crack growth can be reduced by eliminating unwanted shape features through maintenance and design and by improving bogie tracking. Two potential mitigation measures had been adapted from those published in literature to reduce RCF. The mitigation measures involved changes in suspension stiffness to spread wheel wear across the tread and the use of gauge corner relief rail profiles. These mitigation measures were evaluated by means of multibody dynamics and wear maintenance costs. These mitigation measures, however, did not prove to be successful in reducing RCF initiation while maintaining a low wheel wear rate. The current operating conditions on South Africa’s iron ore line, although still not optimal overall, were found to be better in terms of their wear and RCF performance than the two proposed RCF mitigation measures. Based on the finding of the study on two RCF mitigation measures it was recommended that a conformal wheel profile be developed to spread the wheel wear across the tread to reduce the occurrence and propagation of RCF cracks, while still maintaining low wheel wear rates. A comparative study of this new wheel profile design and the current wheel profile design was therefore performed using multibody dynamics simulation together with numerical wheel wear and RCF predictions. The advantages of the conformal wheel profile design were illustrated by evaluating the worn shape and resulting kinematic behaviour of the conformal design. The conformal design had a steadier equivalent conicity progression and a smaller conicity range compared with the current wheel profile design over the wheel’s wear life. The combination of a conformal wheel profile design with 2 mm hollow wear and inadequate adherence to grinding tolerances often result in two-point contact, thereby increasing the probability of RCF initiation. The conformal wheel profile design was shown to have many wear and RCF benefits compared with the current wheel profile design. However, implementation of such a conformal wheel profile must be accompanied by improved rail grinding practices to ensure rail profile compliance. Based on these findings an approach is proposed where the conformal wheel profile design together with improved compliance of the in-service rail profiles to the target rail profile are implemented. This has the potential to reduce RCF initiation on South Africa’s iron ore export line.Thesis (PhD)--University of Pretoria, 2017.
Mechanical and Aeronautical Engineering
PhD
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Willens, David C. "Improving the Fatigue Life of Cylindrical Thread Rolling Dies." Digital WPI, 2020. https://digitalcommons.wpi.edu/etd-dissertations/602.
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Thread rolling is a unique metal forming process which is commonly used to form screw threads on threaded fasteners and precision leadscrews at relatively high rates of speed. Threads are formed on a cylindrical blank by flat or cylindrical dies having the reverse form on them, which rotate and penetrate the blank simultaneously, to plastically deform it into a precise geometry. Thread rolling dies are exposed to a complex state of cyclical contact stresses that eventually cause the dies to fail by fatigue and wear. The stress state is not easily ascertained through standard analytical models due to complex geometry and process conditions. This research seeks to better understand the state of contact stresses present in cylindrical thread rolling dies as they form material, to aid in identifying and testing economical methods of improving thread rolling die fatigue life. Some work has been published on using FEA simulation software to model the thread rolling process, but no work has been published on using FEA software to analyze the stresses in thread rolling dies. DEFORM®-3D Forming Simulation Software by Scientific Forming Technologies Corporation in Columbus, Ohio was used to simulate the throughfeed thread rolling process and model the state of stresses in the dies. The results were compared to the Hertzian contact stress model and the Smith Liu equations for rolling and sliding friction. Fatigue life prediction methods involving S-N curves, surface fatigue strength, and Weibull probability distributions were tested using the simulation data against field results. An optimized die design was generated from a design of experiments simulating different die design geometry. Findings show that field failures correlate well to the DEFORM® simulation results. The Hertz model with Smith Liu equations improved correlation with the simulation. Fatigue life prediction models correlated reasonably well to field results using the simulation data for inputs. These findings can aid in selecting appropriate die materials, design parameters, and fatigue life treatments.
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Hannes, Dave. "Modelling of surface initiated rolling contact fatigue crack growth using the asperity point load mechanism." Licentiate thesis, KTH, Hållfasthetslära (Avd.), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-34005.
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Qiao, Hua. "Prediction of contact fatigue for the rough surface elastohydrodynamic lubrication line contact problem under rolling and sliding conditions." Thesis, Cardiff University, 2005. http://orca.cf.ac.uk/56019/.
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The study of elastohydrodynamic lubrication (EHL) with rough surfaces results in a transient problem due to time varying geometry. In conditions where the A ratio (the ratio of smooth surface film thickness to composite roughness) is low, significant pressure deviations from the corresponding smooth surface results occur. The relative motion of asperity features on the two surfaces leads to cycling of these pressure deviations as surface features move through the nominal contact area. Micropitting, which is a form of surface distress seen in gears, may well be viewed as rolling contact fatigue at the roughness asperity scale as a result of this load cycling. In order to understand the failure mechanism associated with rough surface EHL, a full theoretical model of lubrication of gear contacts under low A conditions is presented in this thesis. The model takes account of the real gear operating conditions in terms of loads, speeds, surface roughness and lubricant properties to predict pressures, film thickness, temperatures, and friction between the teeth. Subsequent contact stress analysis was performed to determine the stress history developed in the contacting solids. Conventional pitting is usually associated with failure beneath the surface of a rolling contact and in the past has been linked with the occurrence of the maximum shear stress that occurs in the classical Hertzian solution for smooth surfaces. In this thesis, a numerical procedure for predicting contact fatigue damage in an EHL line contact between two rough surfaces is developed to take the features of variable amplitude multiaxial fatigue into account due to the roughness effect. The way in which the calculated fatigue damage varies with changes in factors such as slide roll ratio, speed, viscosity, rough surface profiles, and A ratio adopted for the analysis is demonstrated in a series of numerical examples using roughness profiles taken from gears in micropitting experiments.
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Potier, Karl. "Effets des faibles oscillations sur la dégradation de contacts roulants avec glissement de composants aéronautiques." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLC035.
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Ces travaux de thèse concernent l’étude des effets des oscillations de faibles amplitudes sur la durée de vie en fatigue de contact pour des composants d’actionneurs de vol. Des outils théoriques et expérimentaux ont pour cela été employés.Un modèle semi-analytique de contact rugueux élasto-plastique a été codé puis utilisé. Celui-ci, couplé au modèle de Dang Van, a permis de réaliser une étude théorique de l’influence du sens de passage de contacts sur la durée de vie en fatigue. Une comparaison en fatigue entre mouvements continus et mouvements oscillants a ainsi pu être faite.Un banc bi-disque a été spécifiquement développé chez UTAS pour pouvoir réaliser des essais de fatigue de roulement aussi bien en mouvements continus qu’en mouvements oscillants. Des essais de lubrification ont été réalisés sur des éprouvettes en XD15NW et en CX13VD afin de caractériser le phénomène de faux effet Brinell. Des essais de fatigue en lubrification optimale ont finalement été réalisés sur les éprouvettes en XD15NW en mouvements continus et en mouvements oscillants, les résultats ont été comparés et mis en vis-à-vis avec ceux de l’analyse théoriqueThis PhD thesis is a study of small reciprocating motions effects on contact fatigue life of flight actuator components. Theoretical and practical tools are used for this purpose.A semi-analytical elasto-plastic rough contact code has been implemented and, then, used. This code, associated with Dang Van model, allowed us to perform a theoretical study of rolling direction effect on fatigue life. A comparison has been made between continuous motions and reciprocating motions.A twin-disc test bench has been specifically design at UTAS to allow us to perform rolling fatigue tests with continuous motions or with reciprocating motions. Lubrications tests have been done on XD15NW and CX13VD samples in order to study false brinelling phenomenon. Finally, fatigue tests in ideal lubrication conditions have been done on XD15NW samples with continuous motions and with reciprocating motions, results have been cross-checked each other and cross-checked with theoretical results
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Su, Xiaoyan. "Surface initiated rolling/sliding contact fatigue in pearlitic and low/medium carbon bainitic steels /." Full text open access at:, 1996. http://content.ohsu.edu/u?/etd,253.
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Bower, A. F. "Some aspects of plastic flow, residual stress and fatigue cracks due to rolling and sliding contact." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382514.
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