The Experts below are selected from a list of 4125 Experts worldwide ranked by ideXlab platform
M. Elforjani - One of the best experts on this subject based on the ideXlab platform.
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Detecting AE Signals from Natural Degradation of Slow Speed Rolling Element Bearings
Condition Monitoring of Machinery in Non-Stationary Operations, 2012Co-Authors: M. Elforjani, DavidAbstract:Rolling element Bearing diagnosis using high frequency Acoustic Emission (AE) signals has been on-going since the late 1960’s. This paper attempts to demonstrate the use of AE measurements to detect natural defect initiation and propagation in a rolling element Bearing. To facilitate the investigation a special purpose test-rig was built to allow for accelerated natural degradation of a Bearing Race. It is concluded that sub-surface initiation and crack propagation is detectable with AE technology.
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accelerated natural fault diagnosis in slow speed Bearings with acoustic emission
Engineering Fracture Mechanics, 2010Co-Authors: M. ElforjaniAbstract:Abstract Rolling element Bearings are the most common cause of rotating machinery failure. Over the past 20 years, Acoustic Emission (AE) technology has evolved as a significant opportunity to monitor and diagnose the mechanical integrity of rolling element Bearings. This paper presents results of an investigation to assess the potential of the Acoustic Emission (AE) technology for detecting and locating natural defects in rolling element Bearings. To undertake this task a special purpose test-rig was built that allowed for accelerated natural degradation of a Bearing Race. It is concluded that sub-surface initiation and subsequent crack propagation can be detected using a range of data analysis techniques on AE’s generated from natural degrading Bearings. The paper also investigates the source characterisation of AE signals associated with a defective Bearing whilst in operation. This study also attempted to identify the size of a natural defect on Bearings using AE technology. In conclusion, the results from this investigation show that whilst measurements on operational Bearings cannot be achieved as described in this paper, the method of identifying the onset of crack propagation can be employed as a quality control tool for Bearing manufacturers particularly for testing Bearing material homogeneity.
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Natural mechanical degradation measurements in slow speed Bearings
Engineering Failure Analysis, 2009Co-Authors: M. ElforjaniAbstract:Abstract Acoustic emission (AE) technology applied to condition monitoring is gaining acceptance as a useful complimentary tool. This paper demonstrates the use of AE measurements to detect, monitor the growth and locate natural defect initiation and propagation in a conventional rolling element Bearing. To undertake this task a special purpose test-rig was built to allow for accelerated natural degradation of a Bearing Race. It is concluded that crack initiation and its subsequent propagation is detectable with AE technology. The paper also investigates the source characterisation of AE signals associated with a defective Bearing whilst in operation.
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Assessment of natural crack initiation and its propagation in slow speed Bearings
Nondestructive Testing and Evaluation, 2009Co-Authors: M. ElforjaniAbstract:Monitoring of Bearings is an essential part of most condition monitoring programmes in rotating machinery. This paper demonstrates the use of acoustic emission (AE) measurements to detect, monitor and locate natural defect initiation and propagation in a thrust rolling element Bearing. To undertake this task a special purpose test-rig was built that allowed for accelerated natural degradation of a Bearing Race. It is concluded that sub-surface initiation and subsequent crack propagation can be detected using a range of time and frequency domain analysis techniques on AE's generated from natural degrading Bearings. The paper also investigates the source characterisation of AE signals associated with a defective Bearing whilst in operation.
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monitoring the onset and propagation of natural degradation process in a slow speed rolling element Bearing with acoustic emission
Journal of Vibration and Acoustics, 2008Co-Authors: M. ElforjaniAbstract:The monitoring and diagnosis of rolling element Bearings with the high frequency acoustic emission (AE) technology has been ongoing since the late 1960s. This paper demonstrates the use of AE measurements to detect, locate, and monitor natural defect initiation and propagation in a conventional rolling element Bearing. To facilitate the investigation a special purpose test rig was built to allow for accelerated natural degradation of a Bearing Race. It is concluded that subsurface initiation and subsequent crack propagation can be detected with the AE technology. The paper also presents comparative results between AE and vibration diagnosis.
P. Krasowski - One of the best experts on this subject based on the ideXlab platform.
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Velocity distribution in slide journal Bearing gap by laminar unsteady lubrication
Journal of KONES, 2011Co-Authors: P. KrasowskiAbstract:This paper shows results of numerical solutions the modified Reynolds equations for laminar unsteady oil flow in slide journal Bearing gap. Laminar unsteady oil flow is performed during periodic and unperiodic perturbations of Bearing load or is caused by the changes of gap height in time. Above perturbations occur mostly during the starting and stopping of machine. During modelling crossbar Bearing operations in combustion engines, Bearing movement perturbations from engine vertical vibrations causes velocity flow perturbations of lubricating oil on the Bearing Race and on the Bearing slider in the circumferential direction. This solution example applies to isothermal Bearing model with infinity length. Lubricating oil used in this model has Newtonian properties and constant dynamic viscosity. Perturbations connected with unsteady lubricating oil velocity in the circumferential direction on the slide Bearing and on the slider of Bearing were taken into consideration. Results are presented in the dimensionless hydrodynamic pressure and velocity distribution diagrams. Received solutions were compared with the solution received by the stationary lubrication flow in the slide journal Bearing, which were made with the same parameter assumption by constant dynamic oil viscosity. Isothermal Bearing model is similar to friction node model by steady-state heat load conditions.
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CAPACITY AND FRICTION FORCE IN SLIDE JOURNAL Bearing GAP BY LAMINAR UNSTEADY LUBRICATION
Journal of KONES, 2010Co-Authors: P. KrasowskiAbstract:This paper shows results of numerical solutions modified Reynolds equations for laminar unsteady oil flow in slide journal Bearing gap. Laminar unsteady oil flow is performed during periodic and unperiodic perturbations of Bearing load or is caused by the changes of gap height in time. During modelling crossbar Bearing operations in combustion engines, Bearing movement perturbations from engine vertical vibrations causes velocity flow perturbations of lubricating oil on the Bearing Race and on the Bearing slider in the circumferential direction. Above perturbations occur mostly during the starting and stopping of machine. This solution example applies to isothermal Bearing model with infinity length. Lubricating oil used in this model has Newtonian properties and constant dynamic viscosity. Results are presented in the dimensionless hydrodynamic pressure and tangential tension distribution diagrams. Diagrams also presents capacity and friction force change during the time of velocity perturbations. Received solutions were compared with the solution received by the stationary lubrication flow in the slide journal Bearing, which were made with the same parameter assumption by constant dynamic oil viscosity. Isothermal Bearing model is similar to friction node model by steady-state heat load conditions. Described effect can be used as on example of modelling the Bearing friction node operations in reciprocating movement during exploitation of engines and machines.
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PRESSURE AND VELOCITY DISTRIBUTION IN SLIDE JOURNAL Bearing GAP BY LAMINAR UNSTEADY LUBRICATION
Journal of KONES, 2009Co-Authors: P. KrasowskiAbstract:This paper shows results of numerical solutions an modified Reynolds equations for laminar unsteady oil flow in slide journal Bearing gap. Laminar unsteady oil flow is performed during periodic and aperiodic perturbations of Bearing load or is caused by the changes of gap height in time. Above perturbations occur mostly during the starting and stopping of machine. During modelling crossbar Bearing operations in combustion engines, Bearing movement perturbations from engine vertical vibrations causes velocity flow perturbations of lubricating oil on the Bearing Race and on the Bearing slider in the circumferential direction. This solution example applies to isothermal Bearing model with infinity length. Lubricating oil used in this model has Newtonian properties and constant dynamic viscosity. Perturbations connected with unsteady lubricating oil velocity in the circumferential direction on the slide Bearing and on the slider of Bearing were taken into consideration. Results are presented in the dimensionless hydrodynamic pressure and velocity distribution diagrams. Received solutions were compared with the solution received by the stationary lubrication flow in the slide journal Bearing, which were made with the same parameter assumption by constant dynamic oil viscosity. Isothermal Bearing model is similar to friction node model by steady-state heat load conditions.
A S Sekhar - One of the best experts on this subject based on the ideXlab platform.
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application of discrete wavelet transform for detection of ball Bearing Race faults
Tribology International, 2002Co-Authors: S Prabhakar, A R Mohanty, A S SekharAbstract:Bearing Race faults have been detected by using discrete wavelet transform (DWT). Vibration signals from ball Bearings having single and multiple point defects on inner Race, outer Race and the combination faults have been considered for analysis. The impulses in vibration signals due to Bearing faults are prominent in wavelet decompositions. It is found that the impulses appear periodically with a time period corresponding to characteristic defect frequencies. It has been shown that DWT can be used as an effective tool for detecting single and multiple faults in the ball Bearings.
David S. Mccann - One of the best experts on this subject based on the ideXlab platform.
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The International Space Station Solar Alpha Rotary Joint Anomaly Investigation
2010Co-Authors: Elliot P. Harik, Justin Mcfatter, Daniel J. Sweeney, Carlos F. Enriquez, Deneen M. Taylor, David S. MccannAbstract:The Solar Alpha Rotary Joint (SARJ) is a single-axis pointing mechanism used to orient the solar power generating arrays relative to the sun for the International Space Station (ISS). Approximately 83 days after its on-orbit installation, one of the two SARJ mechanisms aboard the ISS began to exhibit high drive motor current draw. Increased structural vibrations near the joint were also observed. Subsequent inspections via Extravehicular Activity (EVA) discovered that the nitrided case-hardened steel Bearing Race on the outboard side of the joint had extensive damage to one of its three rolling surfaces. A farreaching investigation of the anomaly was undertaken. The investigation included metallurgical inspections, coupon tests, traction kinematics tests, detailed Bearing measurements, and thermal and structural analyses. The results of the investigation showed that the anomaly had most probably been caused by high Bearing edge stresses that resulted from inadequate lubrication of the rolling contact. The profile of the roller Bearings and the metallurgical properties of the Race ring were also found to be significant contributing factors. To mitigate the impact of the damage, astronauts cleaned and lubricated the Race ring surface with grease. This corrective action led to significantly improved performance of the mechanism both in terms of drive motor current and induced structural vibration.
Sk Bhaumik - One of the best experts on this subject based on the ideXlab platform.
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Analysis of fractured Bearings of wheel hub of an aircraft
2011Co-Authors: M.l. Madan, M Sujata, Sk BhaumikAbstract:Damaged parts of Bearings of a wheel hub of an aircraft were sent to the laboratory for analysis. The parts of the inner Bearing were found to have extensive secondary damages which obliterated the primary signatures of failure, and hence the mechanism of failure could not be established. Examination of the outer Bearing Race indicated that it had failed by overload. The Bearing Race was manufactured from a carburizing grade steel and it was case carburized to effective case depth of 1.2 mm for 550 HV.
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Failure analysis of nose wheel hub of an aircraft
2011Co-Authors: M.l. Madan, M Sujata, Sk BhaumikAbstract:A rejected nose wheel hub with loose Race at the Bearing housing area was sent to this laboratory for investigation. Based on the signatures on the axle, and the outer and inner surfaces of the Bearing, it appeared that the looseness of the Race was due to inadequate fitment of the Bearing at the Bearing seating area of the wheel hub. There were no evidences to suggest that there was excessive axial load on the Bearing in the outward direction which could lead to detachment/looseness of the Bearing Race. It is, therefore, stated that this failure is not similar to the one that was investigated in this laboratory earlier (refer NAL Report No. MT-FA-1205-05-2010 dated May 14, 2010). In the earlier case, the dislodgement of the Bearing was by fracturing of the outer Race due to excessive axial load in the outward direction. Hence, these two failures need to be treated differently.