The Experts below are selected from a list of 417 Experts worldwide ranked by ideXlab platform
Rob S Dwyer-joyce - One of the best experts on this subject based on the ideXlab platform.
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2015Co-Authors: Rob S Dwyer-joyce, Tom Reddyhoff, B. W. Drinkwater, Key WordsAbstract:An ultrasonic pulse striking a thin layer of liquid trapped between solid bodies will be partially reflected. The proportion reflected is a function of the layer stiffness, which in turn depends on the film thickness and its bulk modulus. In this work, measu-rements of reflection have been used to determine the thickness of oil films in elastohydrodynamic lubricated (EHL) contacts. A very thin liquid layer behaves like a spring when struck by an ultrasonic pulse. A simple quasi-static spring model can be used to determine the proportion of the ultrasonic waves reflected. Experiments have been performed on a model EHL contact between a ball and a flat surface. A transducer is mounted above the contact such that the ultrasonic wave is focused onto the oil film. The reflected signals are captured and passed to a PC for processing. Fourier analysis gives the reflection spectrum that is then used to determine the stiffness of the liquid layer and hence its thickness. In further testing, an ultrasonic transducer has been mounted in the housing of a deep-groove ball bearing to measure the film generated at the Outer Raceway as each ball passes. Results from both the ball-flat and ball bearing measure-ments agree well with steady-state theoretical EHL predictions. The limits of the measuring technique, in terms of the measur-able rolling bearing size and operating parameters, have been investigated
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Monitoring of Lubricant Film Failure in a Ball Bearing Using Ultrasound
Journal of Tribology, 2006Co-Authors: Jie Zhang, Bruce W Drinkwater, Rob S Dwyer-joyceAbstract:A lubricant-film monitoring system for a conventional deep groove ball bearing (type 6016, shaft diameter 80 mm, ball diameter 12.7 mm) is described. A high-firequency (50 MHz) ultrasonic transducer is mounted on the static Outer Raceway of the bearing. The transducer is focused on the ball-Raceway interface and used to measure the reflection coefficient of the lubricant in the "contact" ellipse between bearing components. The reflection coefficient characterizes the lubricant film and can be used to calculate its thickness. An accurate triggering system enables multiple reflection measurements to be made as each lubricated contact moves past the measurement location. Experiments are described in which bearings were deliberately caused to fail by the addition of acetone, water and sand to the lubricant. The ultrasonic reflection coefficient was monitored as a function of time as the failure occurred. Also monitored were the more standard parameters, temperature and vibration. The results indicate that the ultrasonic measurements are able to detect the failures before seizure. It is also observed that, when us,ed in parallel, these monitoring techniques offer the potential to diagnose the failure mechanism and hence improve predictions of remaining life.
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Acoustic measurement of lubricant-film thickness distribution in ball bearings
The Journal of the Acoustical Society of America, 2006Co-Authors: Jie Zhang, Bruce W Drinkwater, Rob S Dwyer-joyceAbstract:An oil-film thickness monitoring system capable of providing an early warning of lubrication failure in rolling element bearings has been developed. The system is used to measure the lubricant-film thickness in a conventional deep groove ball bearing (shaft diameter 80 mm, ball diameter 12.7 mm). The measurement system comprises a 50 MHz broadband ultrasonic focused transducer mounted on the static Outer Raceway of the bearing. Typically the lubricant-films in rolling element bearings are between 0.1-1.0 μm in thickness and so are significantly smaller than the ultrasonic wavelength. A quasistatic spring model is used to calculate oil-film thickness from the measured reflection coefficient data. An accurate triggering system has been developed to enable multiple reflection coefficient measurements to be made as the contact ellipse sweeps over the measurement location. Experiments are described in which the loading conditions and rotational speed are varied. Lubricant-film thickness distributions measured ultrasonically are described and are shown to agree well with the predictions from classical elastohydrodynamic (EHD) lubrication theory, particularly at high radial loads and low rotary speeds. A range of parameters affecting the performance of the measurement are discussed and the limits of operation of the measurement technique defined. © 2006 Acoustical Society of America.
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The on-line measurement of lubricant film thickness for condition monitoring
Insight: Non-Destructive Testing and Condition Monitoring, 2004Co-Authors: Bruce W Drinkwater, Rob S Dwyer-joyceAbstract:The ultrasonic reflectivity of a lubricant layer between two solid bodies depends on the ultrasonic frequency, the acoustic properties of the liquid and solid, and the layer thickness. In this paper, ultrasonic reflectivity measurements are used as a method for determining the thickness of lubricating films in bearing systems. An ultrasonic transducer is positioned on the outside of a bearing shell such that the wave is focused on the lubricant film layer. The transducer is used to both emit and receive wideband ultrasonic pulses. For a particular lubricant film the reflected pulse is processed to give a reflection coefficient spectrum. The lubricant film thickness is then obtained from either the layer stiffness or the resonant frequency. The method has been validated using fluid wedges at ambient pressure between flat and curved surfaces. Experiments on the elastohydrodynamic film formed between a ball sliding on a flat were performed. Film thickness values in the range 50-500 nm were recorded which agreed well with theoretical film formation predictions. Similar measurements have been made on the oil film between the balls and Outer Raceway of a deep groove ball bearing.
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Operating limits for acoustic measurement of rolling bearing oil film thickness
Tribology Transactions, 2004Co-Authors: Rob S Dwyer-joyce, Tom Reddyhoff, B. DrinkwaterAbstract:An ultrasonic pulse striking a thin layer of liquid trapped between solid bodies will be partially reflected. The proportion reflected is a function of the layer stiffness, which in turn depends on the film thickness and its bulk modulus. In this work, measurements of reflection have been used to determine the thickness of oil films in elastohydrodynamic lubricated (EHL) contacts. A very thin liquid layer behaves like a spring when struck by an ultrasonic pulse. A simple quasi-static spring model can be used to determine the proportion of the ultrasonic waves reflected. Experiments have been performed on a model EHL contact between a ball and a flat surface. A transducer is mounted above the contact such that the ultrasonic wave is focused onto the oil film. The reflected signals are captured and passed to a PC for processing. Fourier analysis gives the reflection spectrum that is then used to determine the stiffness of the liquid layer and hence its thickness. In further testing, an ultrasonic transducer has been mounted in the housing of a deep-groove ball bearing to measure the film generated at the Outer Raceway as each ball passes. Results from both the ball-flat and ball bearing measurements agree well with steady-state theoretical EHL predictions. The limits of the measuring technique, in terms of the measurable rolling bearing size and operating parameters, have been investigated.
Dick Petersen - One of the best experts on this subject based on the ideXlab platform.
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varying stiffness and load distributions in defective ball bearings analytical formulation and application to defect size estimation
Journal of Sound and Vibration, 2015Co-Authors: Dick Petersen, Carl Q Howard, Zebb PrimeAbstract:Abstract This paper presents an analytical formulation of the load distribution and varying effective stiffness of a ball bearing assembly with a Raceway defect of varying size, subjected to static loading in the radial, axial and rotational degrees of freedom. The analytical formulation is used to study the effect of the size of the defect on the load distribution and varying stiffness of the bearing assembly. The study considers a square-shaped Outer Raceway defect centered in the load zone and the bearing is loaded in the radial and axial directions while the moment loads are zero. Analysis of the load distributions shows that as the defect size increases, defect-free Raceway sections are subjected to increased static loading when one or more balls completely or partly destress when positioned in the defect zone. The stiffness variations that occur when balls pass through the defect zone are significantly larger and change more rapidly at the defect entrance and exit than the stiffness variations that occur for the defect-free bearing case. These larger, more rapid stiffness variations generate parametric excitations which produce the low frequency defect entrance and exit events typically observed in the vibration response of a bearing with a square-shaped Raceway defect. Analysis of the stiffness variations further shows that as the defect size increases, the mean radial stiffness decreases in the loaded radial and axial directions and increases in the unloaded radial direction. The effects of such stiffness changes on the low frequency entrance and exit events in the vibration response are simulated with a multi-body nonlinear dynamic model. Previous work used the time difference between the low frequency entrance event and the high frequency exit event to estimate the size of the defect. However, these previous defect size estimation techniques cannot distinguish between defects that differ in size by an integer number of the ball angular spacing, and a third feature of the vibration response is therefore required to distinguish between such defects. It is hypothesized and validated through simulations that when the static load remains constant, the third distinguishing feature is the characteristic frequencies of the low frequency event.
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analysis of bearing stiffness variations contact forces and vibrations in radially loaded double row rolling element bearings with Raceway defects
Mechanical Systems and Signal Processing, 2015Co-Authors: Dick Petersen, Carl Q Howard, Alireza Moazen Ahmadi, Nader Sawalhi, Sarabjeet SinghAbstract:Abstract A method is presented for calculating and analyzing the quasi-static load distribution and varying stiffness of a radially loaded double row bearing with a Raceway defect of varying depth, length, and surface roughness. The method is applied to ball bearings on gearbox and fan test rigs seeded with line or extended Outer Raceway defects. When balls pass through the defect and lose all or part of their load carrying capacity, the load is redistributed between the loaded balls. This includes balls positioned outside the defect such that good Raceway sections are subjected to increased loading when a defect is present. The defective bearing stiffness varies periodically at the ball spacing, and only differs from the good bearing case when balls are positioned in the defect. In this instance, the stiffness decreases in the loaded direction and increases in the unloaded direction. For an extended spall, which always has one or more balls positioned in the defect, this results in an average stiffness over the ball spacing period that is lower in the loaded direction in comparison to both the line spall and good bearing cases. The variation in bearing stiffness due to the defect produces parametric excitations of the bearing assembly. The qualitative character of the vibration response correlates to the character of the stiffness variations. Rapid stiffness changes at a defect exit produce impulses. Slower stiffness variations due to large wavelength waviness features in an extended spall produce low frequency excitation which results in defect components in the velocity spectra. The contact forces fluctuate around the quasi-static loads on the balls, with rapid stiffness changes producing high magnitude impulsive force fluctuations. Furthermore, it is shown that analyzing the properties of the dynamic model linearized at the quasi-static solutions provides greater insight into the time–frequency characteristics of the vibration response. This is demonstrated by relating the low frequency event that occurs when a ball enters a line spall to the dynamic properties of the bearing assembly.
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analyses of contact forces and vibration response for a defective rolling element bearing using an explicit dynamics finite element model
Journal of Sound and Vibration, 2014Co-Authors: Sarabjeet Singh, Uwe G Kopke, Carl Q Howard, Dick PetersenAbstract:Abstract This paper provides insights into the physical mechanism by which defect-related impulsive forces, and consequently, vibrations are generated in defective rolling element bearings. A dynamic nonlinear finite element model of a rolling element bearing with an Outer Raceway defect was numerically solved using the explicit dynamics finite element software package, LS-DYNA. A hypothesis was developed to explain the numerical noise observed in the predicted vibrations and contact forces, and the noise frequencies were analytically estimated. In-depth analyses of the numerically estimated dynamic contact forces between the rolling elements and the Raceways of a bearing, which are not measured in practice, and have not been reported previously, are presented in this paper. Several events associated with the traverse of the rolling elements through the Outer Raceway defect are elaborated, and the impulsive force generating mechanism is explained. It was found that the re-stressing of the rolling elements that occurs near the end of a Raceway defect generates a burst of multiple short-duration force impulses. The modelling results also highlight that much higher contact forces and accelerations are generated on the exit of the rolling elements out of defect compared to when they strike the defective surface. A bearing with a machined Outer Raceway defect was tested in a controlled experiment; the measured acceleration response compared favourably with the numerically modelled acceleration results, thereby, validating the low- and high-frequency characteristics of the de-stressing and re-stressing of the rolling elements, respectively.
Sarabjeet Singh - One of the best experts on this subject based on the ideXlab platform.
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analysis of bearing stiffness variations contact forces and vibrations in radially loaded double row rolling element bearings with Raceway defects
Mechanical Systems and Signal Processing, 2015Co-Authors: Dick Petersen, Carl Q Howard, Alireza Moazen Ahmadi, Nader Sawalhi, Sarabjeet SinghAbstract:Abstract A method is presented for calculating and analyzing the quasi-static load distribution and varying stiffness of a radially loaded double row bearing with a Raceway defect of varying depth, length, and surface roughness. The method is applied to ball bearings on gearbox and fan test rigs seeded with line or extended Outer Raceway defects. When balls pass through the defect and lose all or part of their load carrying capacity, the load is redistributed between the loaded balls. This includes balls positioned outside the defect such that good Raceway sections are subjected to increased loading when a defect is present. The defective bearing stiffness varies periodically at the ball spacing, and only differs from the good bearing case when balls are positioned in the defect. In this instance, the stiffness decreases in the loaded direction and increases in the unloaded direction. For an extended spall, which always has one or more balls positioned in the defect, this results in an average stiffness over the ball spacing period that is lower in the loaded direction in comparison to both the line spall and good bearing cases. The variation in bearing stiffness due to the defect produces parametric excitations of the bearing assembly. The qualitative character of the vibration response correlates to the character of the stiffness variations. Rapid stiffness changes at a defect exit produce impulses. Slower stiffness variations due to large wavelength waviness features in an extended spall produce low frequency excitation which results in defect components in the velocity spectra. The contact forces fluctuate around the quasi-static loads on the balls, with rapid stiffness changes producing high magnitude impulsive force fluctuations. Furthermore, it is shown that analyzing the properties of the dynamic model linearized at the quasi-static solutions provides greater insight into the time–frequency characteristics of the vibration response. This is demonstrated by relating the low frequency event that occurs when a ball enters a line spall to the dynamic properties of the bearing assembly.
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analyses of contact forces and vibration response for a defective rolling element bearing using an explicit dynamics finite element model
Journal of Sound and Vibration, 2014Co-Authors: Sarabjeet Singh, Uwe G Kopke, Carl Q Howard, Dick PetersenAbstract:Abstract This paper provides insights into the physical mechanism by which defect-related impulsive forces, and consequently, vibrations are generated in defective rolling element bearings. A dynamic nonlinear finite element model of a rolling element bearing with an Outer Raceway defect was numerically solved using the explicit dynamics finite element software package, LS-DYNA. A hypothesis was developed to explain the numerical noise observed in the predicted vibrations and contact forces, and the noise frequencies were analytically estimated. In-depth analyses of the numerically estimated dynamic contact forces between the rolling elements and the Raceways of a bearing, which are not measured in practice, and have not been reported previously, are presented in this paper. Several events associated with the traverse of the rolling elements through the Outer Raceway defect are elaborated, and the impulsive force generating mechanism is explained. It was found that the re-stressing of the rolling elements that occurs near the end of a Raceway defect generates a burst of multiple short-duration force impulses. The modelling results also highlight that much higher contact forces and accelerations are generated on the exit of the rolling elements out of defect compared to when they strike the defective surface. A bearing with a machined Outer Raceway defect was tested in a controlled experiment; the measured acceleration response compared favourably with the numerically modelled acceleration results, thereby, validating the low- and high-frequency characteristics of the de-stressing and re-stressing of the rolling elements, respectively.
Edward Holweg - One of the best experts on this subject based on the ideXlab platform.
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a semi analytical bearing model considering Outer race flexibility for model based bearing load monitoring
Mechanical Systems and Signal Processing, 2018Co-Authors: Stijn Kerst, Barys Shyrokau, Edward HolwegAbstract:Abstract This paper proposes a novel semi-analytical bearing model addressing flexibility of the bearing Outer race structure. It furthermore presents the application of this model in a bearing load condition monitoring approach. The bearing model is developed as current computational low cost bearing models fail to provide an accurate description of the more and more common flexible size and weight optimized bearing designs due to their assumptions of rigidity. In the proposed bearing model Raceway flexibility is described by the use of static deformation shapes. The excitation of the deformation shapes is calculated based on the modelled rolling element loads and a Fourier series based compliance approximation. The resulting model is computational low cost and provides an accurate description of the rolling element loads for flexible Outer Raceway structures. The latter is validated by a simulation-based comparison study with a well-established bearing simulation software tool. An experimental study finally shows the potential of the proposed model in a bearing load monitoring approach.
Bruce W Drinkwater - One of the best experts on this subject based on the ideXlab platform.
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Monitoring of Lubricant Film Failure in a Ball Bearing Using Ultrasound
Journal of Tribology, 2006Co-Authors: Jie Zhang, Bruce W Drinkwater, Rob S Dwyer-joyceAbstract:A lubricant-film monitoring system for a conventional deep groove ball bearing (type 6016, shaft diameter 80 mm, ball diameter 12.7 mm) is described. A high-firequency (50 MHz) ultrasonic transducer is mounted on the static Outer Raceway of the bearing. The transducer is focused on the ball-Raceway interface and used to measure the reflection coefficient of the lubricant in the "contact" ellipse between bearing components. The reflection coefficient characterizes the lubricant film and can be used to calculate its thickness. An accurate triggering system enables multiple reflection measurements to be made as each lubricated contact moves past the measurement location. Experiments are described in which bearings were deliberately caused to fail by the addition of acetone, water and sand to the lubricant. The ultrasonic reflection coefficient was monitored as a function of time as the failure occurred. Also monitored were the more standard parameters, temperature and vibration. The results indicate that the ultrasonic measurements are able to detect the failures before seizure. It is also observed that, when us,ed in parallel, these monitoring techniques offer the potential to diagnose the failure mechanism and hence improve predictions of remaining life.
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Acoustic measurement of lubricant-film thickness distribution in ball bearings
The Journal of the Acoustical Society of America, 2006Co-Authors: Jie Zhang, Bruce W Drinkwater, Rob S Dwyer-joyceAbstract:An oil-film thickness monitoring system capable of providing an early warning of lubrication failure in rolling element bearings has been developed. The system is used to measure the lubricant-film thickness in a conventional deep groove ball bearing (shaft diameter 80 mm, ball diameter 12.7 mm). The measurement system comprises a 50 MHz broadband ultrasonic focused transducer mounted on the static Outer Raceway of the bearing. Typically the lubricant-films in rolling element bearings are between 0.1-1.0 μm in thickness and so are significantly smaller than the ultrasonic wavelength. A quasistatic spring model is used to calculate oil-film thickness from the measured reflection coefficient data. An accurate triggering system has been developed to enable multiple reflection coefficient measurements to be made as the contact ellipse sweeps over the measurement location. Experiments are described in which the loading conditions and rotational speed are varied. Lubricant-film thickness distributions measured ultrasonically are described and are shown to agree well with the predictions from classical elastohydrodynamic (EHD) lubrication theory, particularly at high radial loads and low rotary speeds. A range of parameters affecting the performance of the measurement are discussed and the limits of operation of the measurement technique defined. © 2006 Acoustical Society of America.
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Acoustic measurement of lubricant-film thickness distribution in ball bearings
The Journal of the Acoustical Society of America, 2006Co-Authors: Jie Zhang, Bruce W DrinkwaterAbstract:An oil-film thickness monitoring system capable of providing an early warning of lubrication failure in rolling element bearings has been developed. The system is used to measure the lubricant-film thickness in a conventional deep groove ball bearing (shaft diameter 80mm, ball diameter 12.7mm). The measurement system comprises a 50MHz broadband ultrasonic focused transducer mounted on the static Outer Raceway of the bearing. Typically the lubricant-films in rolling element bearings are between 0.1–1.0μm in thickness and so are significantly smaller than the ultrasonic wavelength. A quasistatic spring model is used to calculate oil-film thickness from the measured reflection coefficient data. An accurate triggering system has been developed to enable multiple reflection coefficient measurements to be made as the contact ellipse sweeps over the measurement location. Experiments are described in which the loading conditions and rotational speed are varied. Lubricant-film thickness distributions measured ultr...
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The on-line measurement of lubricant film thickness for condition monitoring
Insight: Non-Destructive Testing and Condition Monitoring, 2004Co-Authors: Bruce W Drinkwater, Rob S Dwyer-joyceAbstract:The ultrasonic reflectivity of a lubricant layer between two solid bodies depends on the ultrasonic frequency, the acoustic properties of the liquid and solid, and the layer thickness. In this paper, ultrasonic reflectivity measurements are used as a method for determining the thickness of lubricating films in bearing systems. An ultrasonic transducer is positioned on the outside of a bearing shell such that the wave is focused on the lubricant film layer. The transducer is used to both emit and receive wideband ultrasonic pulses. For a particular lubricant film the reflected pulse is processed to give a reflection coefficient spectrum. The lubricant film thickness is then obtained from either the layer stiffness or the resonant frequency. The method has been validated using fluid wedges at ambient pressure between flat and curved surfaces. Experiments on the elastohydrodynamic film formed between a ball sliding on a flat were performed. Film thickness values in the range 50-500 nm were recorded which agreed well with theoretical film formation predictions. Similar measurements have been made on the oil film between the balls and Outer Raceway of a deep groove ball bearing.
