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Showing papers on "Bearing (mechanical) published in 2005"


Journal ArticleDOI
TL;DR: Wear of fixed bearing prostheses was reduced significantly when anterior-posterior displacement and internal-external rotation kinematics were reduced due to decreased cross shear on the articulating surface and a reduction in AP displacement.

315 citations


Journal ArticleDOI
TL;DR: In this paper, a new method for detecting localized bearing defects based on wavelet transform was proposed, which can be used for detecting single and multiple faults in ball bearing race faults.
Abstract: Due to the importance of rolling bearings as the most widely used machine elements, it is necessary to establish a suitable condition monitoring procedure to prevent malfunctions and breakages during operation. This paper presents a new method for detecting localized bearing defects based on wavelet transform. 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, ball fault and combination of these faults have been considered for analysis. Wavelet transform provides a variable resolution time–frequency distribution from which periodic structural ringing due to repetitive force impulses, generated upon the passing of each rolling element over the defect, are detected. It is found that the impulses appear periodically with a time period corresponding to characteristic defect frequencies. In this study, the diagnoses of ball bearing race faults have been investigated using wavelet transform. These results are compared with feature extraction data and results from spectrum analysis. It has been clearly shown that DWT can be used as an effective tool for detecting single and multiple faults in ball bearings. This paper also presents a new method of pattern recognition for bearing fault monitoring using hidden Markov Models (HMMs). Experimental results show that successful bearing fault detection rates as high as 99% can be achieved by this approach.

269 citations


Journal ArticleDOI
TL;DR: In this paper, a special measurement system using a non-contact electro-optical extensometer to measure hole elongation is proposed during static tensile testing, the response of bearing damage was monitored by acoustic emission measurement Several specimens were observed by means of soft X-ray radiography and SEM at different loading levels to assess internal damage.

224 citations


Journal ArticleDOI
TL;DR: In this article, a 3D progressive damage finite element model of multi-bolt, double-lap composite joints is developed in the non-linear finite element code ABAQUS and validated by comparing load-displacement characteristics and surface strains to experimental results.
Abstract: A 3D progressive damage finite element model of multi-bolt, double-lap composite joints is developed in the non-linear finite element code ABAQUS. The model is validated by comparing load–displacement characteristics and surface strains to experimental results. A study is then performed of the effects of variable bolt–hole clearance with results compared to experiments in which bolt loads were measured in joints loaded to ultimate failure. It is shown that clearance can cause major changes in the load distribution and damage mechanisms in the joint. It can also lead to a significant reduction in the load at which initial failure (due to bearing at one of the holes) occurs, making it an important variable to consider in the limit load design of aircraft. Unlike previous methods, the method presented here is capable of correctly accounting for bearing and bypass stresses, in the presence of damaged material properties, as well as the load re-distribution that occurs after bearing failure at one or more holes.

204 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present the results of an experimental study of the detection of mechanical faults in an induction motor by means of analysis of combinations of permeance and magneto-motive force (MMF) harmonics.
Abstract: This paper presents the results of an experimental study of the detection of mechanical faults in an induction motor. As is reasonably well known, by means of analysis of combinations of permeance and magneto-motive force (MMF) harmonics, it is possible to predict the frequency of air gap flux density harmonics which occur as a result of certain irregularities in an induction motor. In turn, analysis of flux density harmonics allows the prediction of induced voltages and currents in the stator windings. Reviewing this theory, equations which may aid in the identification of mechanical faults are presented. These equations include both those which indicate eccentric conditions and those which have been suggested to help identify bearing faults. The development of test facility to create eccentricity faults and bearing fault conditions is described. This test facility allows rapid access to the motor bearings, allowing an investigation into the ability to detect faulted bearing conditions using stator current monitoring. Experimental test results are presented, indicating that it may be possible to detect bearing degradation using relatively simple and inexpensive equipment.

133 citations


Proceedings ArticleDOI
16 Jun 2005
TL;DR: In this article, a passive EMI filter is proposed to eliminate bearing current and ground leakage current from an inverter-driven motor rated at 400 V and 3.7 kW.
Abstract: This paper presents a practical approach to eliminating both bearing current and ground leakage current from an inverter-driven motor rated at 400 V and 3.7 kW. When the shaft voltage with respect to the motor frame exceeds the dielectric breakdown voltage of thin lubricating grease films in two metal bearings at the drive and non-drive ends, an electrical discharge machining (EDM) current flows through the bearings. A passive EMI filter can keep the shaft voltage in check, as a result of having eliminated high-frequency common-mode voltage from the motor terminals. Hence, no dielectric breakdown occurs in the grease films, so that no EDM current flows in the bearings. Experimental results verify the viability and effectiveness of the passive EMI filter designed in this paper

115 citations


Journal ArticleDOI
TL;DR: In this paper, a CFD method has been applied to model lubricant flow behavior within linear pad bearing having large, closed pockets or recesses, and the presence of closed pockets can result in a significant reduction in bearing friction coefficient and that there are two different origins for this, depending on the bearing convergence ratio.
Abstract: A CFD method has been applied to model lubricant flow behavior within linear pad bearings having large, closed pockets or recesses. The study shows that the presence of closed pockets can result in a significant reduction in bearing friction coefficient and that there are two different origins for this, depending on the bearing convergence ratio. At high convergence ratios, as used in conventional thrust hearings, a pocket located in the high-pressure region of the bearing produces a reduction in local shear stress and thus friction. This friction reduction is larger than the reduction in load support resulting from the presence of the pocket so there is a net overall reduction in friction coefficient. In low convergence ratio bearings, each pocket also acts as an effectively-independent step bearing and thereby generates a higher local pressure than would otherwise he the case. This results in the overall hearing having enhanced load support and thus a reduced friction coefficient. This effect is particularly large at very low convergence ratios when cavitation occurs in the pocket inlet.

111 citations


Journal ArticleDOI
TL;DR: In this article, a new bearing fault detection and diagnosis scheme based on hidden Markov modeling (HMM) of vibration signals was introduced. But the proposed scheme was also adapted to diagnose multiple bearing faults.
Abstract: In this paper, we introduce a new bearing fault detection and diagnosis scheme based on hidden Markov modeling (HMM) of vibration signals. Features extracted from amplitude demodulated vibration signals from both normal and faulty bearings were used to train HMMs to represent various bearing conditions. The features were based on the reflection coefficients of the polynomial transfer function of an autoregressive model of the vibration signals. Faults can be detected online by monitoring the probabilities of the pretrained HMM for the normal case given the features extracted from the vibration signals. The new technique also allows for diagnosis of the type of bearing fault by selecting the HMM with the highest probability. The new scheme was also adapted to diagnose multiple bearing faults. In this adapted scheme, features were based on the selected node energies of a wavelet packet decomposition of the vibration signal. For each fault, a different set of nodes, which correlates with the fault, is chosen. Both schemes were tested with experimental data collected from an accelerometer measuring the vibration from the drive-end ball bearing of an induction motor (Reliance Electric 2 HP IQPreAlert) driven mechanical system and have proven to be very accurate.

111 citations


Journal ArticleDOI
TL;DR: In this paper, two versions of face-gear drive geometry with a helical pinion are considered, one based on a screw involute helicoid and the other based on envelopes of two mismatched parabolic racks of the pinion and the shaper.

110 citations


Proceedings ArticleDOI
TL;DR: In this article, a simple yet accurate model predicting the static and dynamic force characteristics of gas foil bearing is presented, which couples the Reynolds equation for a thin gas film to a simple elastic foundation model for the top foil and bump strip layer.
Abstract: Widespread usage of gas foil bearings (FBs) into microturbomachinery to midsize gas turbine engines requires accurate performance predictions anchored to reliable test data. This paper presents a simple yet accurate model predicting the static and dynamic force characteristics of gas FBs. The analysis couples the Reynolds equation for a thin gas film to a simple elastic foundation model for the top foil and bump strip layer. An exact flow advection model is adopted to solve the partial differential equations for the zeroth- and first-order pressure fields that render the FB load capacity and freguency-dependent force coefficients. As the static load imposed on the foil bearing increases, predictions show that the journal center displaces to eccentricities exceeding the bearing nominal clearance. A nearly constant FB static stiffness, independent of journal speed, is estimated for operation with large loads, and approaching closely the bearing structural stiffness derived from contact operation without rotor spinning. Predicted minimum film thickness and journal attitude angle demonstrate good agreement with archival test data for a first-generation gas FB. The bump-foil-strip structural loss factor, exemplifying a dry-friction dissipation mechanism, aids to largely enhance the bearing direct damping force coefficients. At high loads, the bump-foil structure influences most the stiffness and damping coefficients. The predictions demonstrate that FBs have greatly different static and dynamic force characteristics when operating at journal eccentricities in excess of the bearing clearance from those obtained for operation at low loads, i.e., small journal eccentricity.

106 citations


Journal ArticleDOI
TL;DR: In this article, the performance of a smart sliding base-isolation system, used in a 1:20 scaled bridge model, employing semi-active controllable magneto-rheological (MR) dampers is investigated, analytically and experimentally, under several near-fault earthquakes.
Abstract: Sliding base-isolation systems used in bridges reduce pier drifts, but at the expense of increased bearing displacements under near-source pulse-type earthquakes. It is common practice to incorporate supplemental passive non-linear dampers into the isolation system to counter increased bearing displacements. Non-linear passive dampers can certainly reduce bearing displacements, but only with increased isolation level forces and pier drifts. The semi-active controllable non-linear dampers, which can vary damping in real time, can reduce bearing displacements without further increase in forces and pier drifts; and hence deserve investigation. In this study performance of such a 'smart' sliding isolation System, used in a 1:20 scaled bridge model, employing semi-active controllable magneto-rheological (MR) dampers is investigated, analytically and experimentally, under several near-fault earthquakes. A non-linear analytical model, which incorporates the non-linearities of sliding bearings and the MR damper, is developed. A Lyapunov control algorithm for control of the MR damper is developed and implemented in shake table tests. Analytical and shake table test results are compared. It is shown that the smart MR damper reduces bearing displacements further than the passive low- and high-damping cases, while maintaining isolation level forces less than the passive high-damping case.

Journal ArticleDOI
TL;DR: In this paper, CFX-TASCflow is employed to simulate various fixed geometry fluid-film bearing and damper designs, including hydrodynamic, hydrostatic, and hybrid bearing designs.
Abstract: The traditional method for bearing and damper analysis usually involves a development of rather complicated numerical calculation programs that may just focus on a simplified and specific physical model. The application of the general CFD codes may make this analysis available and effective where complex flow geometries are involved or when more detailed solutions are needed. In this study, CFX-TASCflow is employed to simulate various fixed geometry fluid-film bearing and damper designs. Some of the capabilities in CFX-TASCflow are applied to simulate the pressure field and calculate the static and dynamic characteristics of hydrodynamic, hydrostatic, and hybrid bearings as well as squeeze film dampers. The comparison between the CFD analysis and current computer programs used in industry has been made. The results show reasonable agreement in general. Some of the possible reasons for the differences are discussed. It leaves room for further investigation and improvement on the methods of computation.

Journal ArticleDOI
TL;DR: This paper describes a large-scale evaluation of several different automatic bearing monitoring methods using 103 laboratory and industrial environment test signals and concludes that wavelets are especially well suited for this task.

Journal ArticleDOI
TL;DR: In this article, the authors present results on development of an advanced coating system for use with compliant foil bearings that permits higher operating speeds and temperatures, using a high-temperature, high-speed tribometer.

Journal ArticleDOI
TL;DR: In this article, a detailed theoretical analysis of bearing performance is presented, in which the gas flow within the bearing is initially expressed in the form of simplified dimensionless Navier Stokes equations, and the nonlinear dimensionless Reynolds equation is then derived and subsequently discretized using the Newton method.

Journal ArticleDOI
TL;DR: In this article, a non-linear dynamic analysis of an unbalanced rotor supported by roller bearings has been made and the results show the appearance of instability and chaos in the dynamic response as the speed of the rotor bearing system is changed.
Abstract: In this paper, the non-linear dynamic analysis of an unbalanced rotor supported by roller bearings has been made. The non-linearity in the rotor bearing system is due to Hertzian contact, unbalanced rotor effect and radial internal clearance. The system can excite bi-periodically by the varying compliance frequency and the rotational frequency. The results show the appearance of instability and chaos in the dynamic response as the speed of the rotor-bearing system is changed. Period doubling and mechanism of intermittency have been observed that lead to chaos. Poincare maps, phase plots, time displacement responses and FFT are used to elucidate and illustrate the diversity of the system behavior.

Journal ArticleDOI
TL;DR: In this paper, the effect of an engineered slip/no-slip surface on journal bearing performance is examined, and it is found that judicious application of slip to a journal bearing's surface can lead to improved bearing performance.
Abstract: The no-slip boundary condition is part of the foundation of the traditional lubrication theory. It states that fluid adjacent to a solid boundary has zero velocity relative to the solid surface. For most practical applications, the no-slip boundary condition is a good model for predicting fluid behavior. However, recent experimental research has found that for certain engineered surfaces the no-slip boundary condition is not valid. Measured velocity profiles show that slip occurs at the interface. In the present study, the effect of an engineered slip/no-slip surface on journal bearing performance is examined. A heterogeneous pattern, in which slip occurs in certain regions and is absent in others, is applied to the bearing surface. Fluid slip is assumed to occur according to the Navier relation. Analysis is performed numerically using a mass conserving algorithm for the solution of the Reynolds equation. Load carrying capacity, side leakage rate, and friction force are evaluated. In addition, results are presented in the form of Raimondi and Boyd graphs. It is found that the judicious application of slip to a journal bearing’s surface can lead to improved bearing performance.

Journal ArticleDOI
TL;DR: Polyethylene bearing mobility occurs following mobile-bearing total knee arthroplasty and mobility is maintained during the time interval tested, demonstrating the presence of bearing mobility should result in lower contact stresses reducing the potential for polyethylene wear.
Abstract: In vivo kinematics were determined during a weightbearing deep knee bend in 39 patients implanted with four different designs of mobile-bearing total knee arthroplasty to assess polyethylene bearing mobility patterns and magnitudes. The femoral and tibial components and mobile polyethylene insert (implanted with four tantalum beads) were overlaid onto the fluoroscopic images using a three-dimensional model-fitting technique to determine bearing mobility. Three of the four designs were tested at a single time interval while one was evaluated at two postoperative intervals, (12 months apart) to assess changes in bearing mobility with time. All patients had polyethylene bearing rotation relative to the tibial tray and minimal rotation relative to the femoral component. The average maximum amounts of bearing rotation ranged from 8.4 degrees to 10.3 degrees (range, 3.0 degrees -20.1 degrees). In patients evaluated at two time intervals, the average maximum bearing rotation increased from 8.5 degrees (range, 3.4 degrees -15.5 degrees) at 3 months to 9.8 degrees (range, 48 degrees -14.1 degrees) 15 months postoperatively. The presented data demonstrates polyethylene bearing mobility occurs following mobile-bearing total knee arthroplasty and mobility is maintained during the time interval tested. The presence of bearing mobility should result in lower contact stresses reducing the potential for polyethylene wear.

Journal ArticleDOI
TL;DR: In this article, the axial load effects in lead-rubber bearing response behavior were investigated by extending an existing linear two-spring model to include nonlinear behavior, including an empirical equation for the experimentally observed variation of yield strength, and the bearing forces were found by solving the nonlinear equilibrium and kinematic equations using Newton's method.
Abstract: Existing models for isolation bearings neglect certain aspects of their response behavior. For instance, rubber bearings have been observed to decrease in stiffness with increasing axial load, and soften in the vertical direction at large lateral deformations. The yield strength of lead-rubber bearings has also been observed to vary with axial load, such that a lightly loaded bearing may not achieve its theoretical strength. Models that include these axial-load effects in lead-rubber bearings are developed by extending an existing linear two-spring model to include nonlinear behavior. The nonlinearity includes an empirical equation for the experimentally observed variation of yield strength. For numerical implementation, the bearing forces are found by solving the nonlinear equilibrium and kinematic equations using Newton's method, and the instantaneous bearing stiffness matrix is formed from the differentials of these equations. The response behavior of the models is confirmed by comparison with experimental data.

Journal ArticleDOI
TL;DR: In this article, feedback linearization is employed in combination with robust control techniques for the regulation of a single-axis test rig actuated by a multiple pole magnetic bearing, and an uncertainty framework was proposed for the linearized plant, and a robust controller was designed via /spl mu/ synthesis.
Abstract: Feedback linearization is a promising approach to the nonlinear control problem posed by active magnetic bearing systems. In this paper, feedback linearization is employed in combination with robust control techniques for the regulation of a single axis test rig actuated by a multiple pole magnetic bearing. To this end, a nonlinear polynomial model of the magnetic actuator was developed based on its experimental calibration. The effect of the amplifier and measurement system dynamics on the feedback linearization performance, was also examined, and compensation filters were developed. Finally, an uncertainty framework was proposed for the linearized plant, and a robust controller was designed via /spl mu/ synthesis. Experimental results demonstrate that the feedback-linearized active magnetic bearing system can achieve stability and the specified performance over the entire range of bearing clearance. The introduction of compensation filters is shown to be essential to this result.

Patent
25 Oct 2005
TL;DR: In this paper, a propeller is mounted aft of the rear rotor supporting bearing of a gas turbine, either by the rotor shaft or by the exhaust gases flowing through the exhaust frame of the turbine.
Abstract: A propeller is mounted aft of the rear rotor supporting bearing of a gas turbine. The propeller is driven either by the rotor shaft or by the exhaust gases flowing through the exhaust frame of the turbine. The rotating propeller blows cooling air on the rear bearing. The cooling air can then be circulated through the exhaust frame to cool the exhaust frame as well.

Journal ArticleDOI
TL;DR: This work explores a self-sensing configuration based on the current amplitude modulation that must be robust and relatively low cost and applied to an AMB test rig using reference sensors.
Abstract: The concept of self-sensing active magnetic bearings (AMBs) is to eliminate the position sensors and estimate the position of the levitated object by measuring the bearing coil current The main interest of this approach consists in reducing production costs and hardware complexity Although the idea of self-sensing itself is not new and research has been carried out for years in this topic, it still remains a challenge Many self-sensing methods have been proposed in literature, however they are all very delicate to realize For this reason, there is still no industrial application for self-sensing magnetic bearings This paper investigates the realization of a self-sensing AMB suitable for industrial use The system must be robust and relatively low cost In order to do that, this work explores a self-sensing configuration based on the current amplitude modulation This approach is applied to an AMB test rig using reference sensors

Patent
16 Mar 2005
TL;DR: In this article, a centrifugal air/oil separation system communicates with bearing cavities of the engine and substantially isolates separated oil from contacting the gearbox in order to avoid contact with the gear box.
Abstract: A centrifugal air/oil separation system communicates with bearing cavities of the engine and substantially isolates separated oil from contacting the gearbox.

Patent
08 Nov 2005
TL;DR: In this paper, a thin glass panel is levitated on a porous media air bearing creating a pressurized film of air and preloaded against the air film by negative pressure areas.
Abstract: Thin substrates, such as flat glass panels, are levitated on a porous media air bearing creating a pressurized film of air and preloaded against the air film by negative pressure areas. The pressure can be distributed most uniformly across the pressure areas by defusing the pressure through a porous medium. Such a bearing can be used for glass flattening by holding the glass such that the unevenness is migrated to the side opposite the side to be worked on.

Patent
13 Sep 2005
TL;DR: In this paper, the authors proposed a fluid dynamic bearing system that comprises at least one stationary part that has a shaft and two bearing plates disposed on the shaft at a mutual spacing, and a rotating part that is supported so as to rotate about a rotational axis with respect to the stationary part, and comprises a bearing bush and a sleeve enclosing the bearing bush.
Abstract: The invention relates to a fluid dynamic bearing system that comprises at least one stationary part that has a shaft and two bearing plates disposed on the shaft at a mutual spacing, and at least one rotating part that is supported so as to rotate about a rotational axis with respect to the stationary part, and comprises a bearing bush and a sleeve enclosing the bearing bush. A bearing gap filled with bearing fluid is provided between the parts and at least one sealing gap for sealing the bearing gap that extends concentric to the rotational axis. The bearing comprises at least one fluid dynamic radial bearing and two fluid dynamic axial bearings and at least one recirculation channel that connects the two axial bearing regions to each other. According to the invention, the largest radial diameter of the recirculation channel is greater than or equal to the largest diameter of the sealing gap, and the smallest radial diameter of the recirculation channel is greater than or equal to the largest diameter of an adjacent bearing plate. Moreover, additional and effective deairing of the recirculation channel is effected by a venting device. To realize improved equilibrium of pressure in the bearing gap and improved retention of the bearing fluid, the sealing gaps can be inclined, at least in sections, at an angle α, β with respect to the rotational axis, wherein the angles may have different sizes.

Patent
28 Mar 2005
TL;DR: In this paper, a turbocharger includes a foil bearing assembly mounted in a center housing between a compressor and a turbine of the turbo-charger, and the center housing is a one-piece construction.
Abstract: A turbocharger includes a foil bearing assembly mounted in a center housing between a compressor and a turbine of the turbocharger. The bearing assembly forms a unit installable into the center housing from one end thereof, and the center housing is a one-piece construction. The bearing assembly includes a foil thrust bearing assembly disposed between two foil journal bearings. The journals foils are mounted in annular bearing carriers fixedly mounted in the center housing. A radially inner portion of a thrust disk of the thrust bearing assembly is captured between a shaft and a shaft sleeve of the turbocharger. The center housing defines cooling air passages for supplying cooling air to the foil bearings, and optionally includes a water jacket for circulating engine coolant through the center housing.

Journal ArticleDOI
TL;DR: In this paper, the authors presented an analysis of the pressure development of journal bearing in a various shaft surface texture and velocity variations using a proposed neural network, which can be applied to journal bearings and the model's performance is verified.

Journal ArticleDOI
TL;DR: In this paper, the slip flow effect is considered in order to estimate load-carrying capacity and dynamic coefficients of micro gas-lubricated journal bearings, and the first slip approximation is applied.

Journal ArticleDOI
Sayed A. Nassar1, H. El-Khiamy1, Gary C. Barber1, Qian Zou1, T. S. Sun1 
TL;DR: In this paper, an experimental procedure is proposed for studying the underhead and thread friction in fasteners, and the effective bearing friction radius, underhead friction coefficient, and threads friction coefficient are determined for fasteners with standard hexagonal heads and for flanged head fasteners.
Abstract: An experimental procedure is proposed for studying the underhead and thread friction in fasteners. The effective bearing friction radius, the underhead friction coefficient, and the thread friction coefficient are experimentally determined for fasteners with standard hexagonal heads and for flanged head fasteners. Hence, greater accuracy has been achieved in determining the value of the torque components that are consumed in overcoming friction in threaded fasteners. This would lead to a more reliable torque-tension correlation and would enhance the safety and quality of bolted assemblies. A design of experiment procedure is presented in order to investigate the effect of fastener material class, the thread pitch, and the fastener size on thread friction coefficient. For the underhead bearing friction, an experimental model is presented in order to determine the effect of the radii ratio of the contact area on the bearing friction radius.

Journal ArticleDOI
24 Oct 2005
TL;DR: In this paper, reliable techniques for the measurement of the different parameters of importance for the bearing damage assessment, including their effects on the phenomena and measured quantities, are discussed, and a good understanding of these correlations allows custom-design, cost-effective handling of the matter.
Abstract: Inverter-induced high frequency bearing currents are a parasitic effect that can occur in variable-speed drive systems. While the physical cause-and-effect chains are understood, little has been known on appropriate quantitative assessment of the phenomena. This paper discusses reliable techniques for the measurement of the different parameters of importance for the bearing damage assessment, including their effects on the phenomena and measured quantities. A good understanding of these correlations allows custom-design, cost-effective handling of the matter.