Showing papers on "Bearing (mechanical) published in 2009"

Magnetic bearings : theory, design, and application to rotating machinery

Abstract: and Survey.- Principle of Active Magnetic Suspension.- Hardware Components.- Actuators.- Losses in Magnetic Bearings.- Design Criteria and Limiting Characteristics.- Dynamics of the Rigid Rotor.- Control of the Rigid Rotor in AMBs.- Digital Control.- Dynamics of Flexible Rotors.- Identification.- Control of Flexible Rotors.- Touch-down Bearings.- Dynamics and Control Issues for Fault Tolerance.- Self#x2013 Sensing Magnetic Bearings.- Self#x2013 Bearing Motors.- Micro Magnetic Bearings.- Safety and Reliability Aspects.

Using an electric power cable as the vehicle for communicating an information-bearing signal through a barrier

Abstract: The RF signal generated by a ZigBee radio on the outside of a building structure is conveyed to the interior of the building by guiding it as a surface wave along an electric cable bundle that passes through the building's wall to supply domestic electric power to the interior of the structure. The RF signal is launched by a unique coupler comprising a pair of insulated foil conductors.

A Review on Grease Lubrication in Rolling Bearings

Abstract: Grease lubrication is widely applied to rolling bearings. The consistency of grease prevents it from leaking out of the bearing, makes it easy to use, and will give it good sealing properties. The same consistency prevents an optimal lubrication performance. Most of the grease is pushed out of the bearing during the initial phase of bearing operation and no longer actively participates in the lubrication process, leaving only a limited quantity available, which is stored inside the bearing geometry and on the bearing shoulders (covers or seals). This stored volume strongly determines the remaining lubrication process in the bearing. The distribution of this volume is determined by the grease flow, which is very complex to understand due to the strong nonlinear rheology. There is no consensus on the next phase in the lubrication process. The grease may bleed and provide oil to the raceway; it may be severely sheared in the raceway releasing oil; or small fresh quantities of grease may be sheared off from the volume stored on the shoulder. In addition, the lubrication process may be dynamic. Grease has self-healing properties where fresh grease is supplied in case of film breakdown and self-induced heat development. This article describes the state-of-the-art knowledge on grease lubrication, including grease flow, film formation, film reduction, dynamic behavior, and grease life.

Fault diagnosis of low speed bearing based on relevance vector machine and support vector machine

Abstract: This study concerns with fault diagnosis of low speed bearing using multi-class relevance vector machine (RVM) and support vector machine (SVM). A low speed test rig was developed to simulate various types of bearing defects associated with shaft speeds as low as 10rpm under several loading conditions. The data was acquired from the low speed bearing test rig using acoustic emission (AE) and accelerometer sensors under a constant load with different speeds. The aim of this study is to address the problem of detecting an incipient bearing fault and to find reliable methods for low speed machine fault diagnosis. In this paper, two methods of multi-class classification techniques for fault diagnosis through RVM and SVM are presented and the effectiveness of using AE and vibration signals due to low impact rate for low speed diagnosis. In the present study, component analysis was performed initially to extract the features and to reduce the dimensionality of original data features. The classification for fault diagnosis was also conducted using original data feature and without feature extraction. The result shows that multi-class RVM produces promising results and has the potential for use in fault diagnosis of low speed machine.

Detection of Generalized-Roughness Bearing Fault by Spectral-Kurtosis Energy of Vibration or Current Signals

Abstract: Generalized roughness is the most common damage occurring to rolling bearings. It produces a frequency spreading of the characteristic fault frequencies, thus making it difficult to detect with spectral or envelope analysis. A statistical analysis of typical bearing faults is proposed here in order to identify the spreading bandwidth related to specific conditions, relying on current or vibration measurements only. Then, a diagnostic index based on the computation of the energy in the previously defined bandwidth is used to diagnose bearing faults. The proposed method was validated experimentally with vibration signals, with robust and reliable results. The same procedure can be extended to current signals.

Incipient Bearing Fault Detection via Motor Stator Current Noise Cancellation Using Wiener Filter

Abstract: Current-based monitoring can offer significant economic savings and implementation advantages over traditional vibration monitoring for bearing fault detection. The key issue in current-based bearing fault detection is to extract bearing fault signatures from the motor stator current. Since the bearing fault signature in the stator current is typically very subtle, particularly when the fault is at an incipient stage, it is difficult to detect the fault signature directly. Therefore, in this paper, the bearing fault signature is detected alternatively by estimating and removing nonbearing fault components via a noise cancellation method. In this method, all the components of the stator current that are not related to bearing faults are regarded as noise and are estimated by a Wiener filter. Then, all these noise components are cancelled out by their estimates in a real-time fashion, and a fault indicator is established based on the remaining components which are mainly caused by bearing faults. Machine parameters, bearing dimensions, nameplate values, and the stator current spectrum distribution are not required in the method. The results of online experiments with a 20-hp induction motor under multiple load levels have confirmed the effectiveness of this method.

Epicyclic gear system with superfinished journal bearing

Abstract: An epicyclic gear assembly includes a ring gear, a sun gear, at least one star gear enmeshed between the ring gear and sun gear, a carrier and a journal bearing. The carrier is disposed adjacent the rotatable sun gear and star gear. The journal bearing is disposed in the at least one star gear and connected to the carrier. The journal bearing has an outer radial surface with an amorphous surface finish of less than about 5 micro inches (127 micro mm) measured on an R a scale and the outer surface of the journal bearing interfaces with an inner surface of the star gear.

Strength of circular hollow sections (CHS) tubular beams externally reinforced by carbon FRP sheets in pure bending

Abstract: Particular structural forms such as circular tubular sections when under load may experience premature local buckling of the steel component, attributable to the thin-walled nature of the section. The use of high-strength advanced composite materials tends to accompany the minimum of structural weight, and is hence presently being assessed for effectiveness as supplementary external reinforcing materials. Composite beams of fibre-reinforced polymers (FRP) and steel, formed as tubular steel sections externally reinforced by thin-bonded carbon FRP (CFRP) sheets, exhibit many phenomena not found in conventional structural steel components, and these can have a marked bearing both on the behaviour of members composed of these materials and, by connotation, on the way in which such members are designed. The potential identification of CFRP reinforcement incorporated onto steel circular hollow section (CHS) beams has not been adequately explored, particularly in pure moment regions. This paper provides an experimental study consisting of CHS beams reinforced by CFRP sheets under pure bending. The role of the composite reinforcement is to interact with the enveloped steel component and to restrain the section to deform in a favourable fashion for strength enhancement. It is shown how these sections exploit the best attributes of both reinforcing fibres and steel, conferring greater strength to CHS beams made with thin-walled steel sections. The tests reveal that the strength of composite beams is influenced mainly by the amount of fibre reinforcement and the orientation of fibre skin. Also presented in this paper is an analytical method employing the modular ratio concept and considering the sectional slenderness limits of AS 4100 for evaluation of the strength of CFRP-reinforced CHS beams.

Ceramic materials as bearing surfaces for total hip arthroplasty.

Abstract: During the past decade, advances in total hip arthroplasty component design have produced implants with reliable clinical results in regard to fixation. The foremost unresolved challenge has been the development of bearing surfaces that can withstand the higher demands of younger and more active patients. New alternative bearings with superior wear characteristics that minimize debris include ceramic-on-ceramic, metal-on-metal, and highly cross-linked polyethylenes in combination with ceramic or metal. Alumina-on-alumina ceramic bearings are extremely hard and scratch resistant and provide superior lubrication and wear resistance compared with other bearing surfaces in clinical use. Survivorship revision for any reason for the alumina ceramic bearings at 10 years was significantly higher compared with metal-on-polyethylene. Bearings currently being studied because of their encouraging wear performance in the laboratory are an alumina matrix (82% alumina, 17% zirconia, 0.3% chromium oxide), zirconium oxide, and ceramic-on-cobalt-chromium.

Analytical investigation of a partially textured parallel slider

Abstract: The article presents a one-dimensional isothermal flow model with analytical solution for partially textured surfaces, nominally parallel. The model allows a simple and elegant parametric analysis of slider performance characteristics (load-carrying capacity, friction force, and friction coefficient) in terms of texture dimensions. It is shown that the friction force and load-carrying capacity do not practically depend on the number of cells. Optimum values of design parameters (dimensionless dimple depth and dimensionless textured length), allowing for maximum load-carrying capacity and minimum friction coefficient, are presented in the dimensionless form. The same model is used to give a phenomenologically based solution for the ‘equivalent step bearing’ in terms of load-carrying capacity or friction coefficient. The results show that the concept of equivalent step bearing is questionable, as the equivalent height of the step bearing is not uniquely determined.

Adjustable-Speed Drive Bearing-Fault Detection Via Wavelet Packet Decomposition

Abstract: Adjustable-speed drives perform many vital control functions in the industry, serving in such diverse applications as rolling mills, variable-speed compressors, fans, and pumps. When an adjustable-speed drive fails due to a bearing failure, it is usually catastrophic. Bearing defects introduce vibration anomalies that alter the current characteristic frequencies. This paper addresses the application of motor current signature analysis using wavelet packet decomposition to detect bearing faults in adjustable-speed drives.

An experimental investigation on the bearing failure load of glass fibre/epoxy laminates

Abstract: This paper deals with an experimental investigation on the bearing failure load of glass fibre/epoxy (GFRP) laminates. The effects of fibre-to-load inclination angle and laminate stacking sequence on the bearing load capacity have been determined experimentally on two different type of laminates: unidirectional and bi-directional (cross-ply). Significant reductions in bearing failure load when fibre inclination angle increases are highlighted. Bearing design formulas are also proposed based on the results of the experiments.

Rolling element bearing fault detection using an improved combination of Hilbert and wavelet transforms

Abstract: As a kind of complicated mechanical component, rolling element bearing plays a significant role in rotating machines, and bearing fault detection benefits decision-making of maintenance and avoids undesired downtime cost. However, extraction of fault signatures from a collected signal in a practical working environment is always a great challenge. This paper proposes an improved combination of the Hilbert and wavelet transforms to identify early bearing fault signatures. Real rail vehicle bearing and motor bearing data were used to validate the proposed method. A traditional combination of Hilbert and wavelet transforms was employed for comparison purpose. An indicator to evaluate fault detection capability of methods was developed in this research. Analysis results showed that the extraction capability of bearing fault signatures is greatly enhanced by the proposed method.

2.5D infrared range and bearing system for collective robotics

Abstract: In the growing field of collective robotics, spatial co-ordination between robots is often critical and usually achieved via local relative positioning sensors. We believe that range and bearing sensing, based on infrared technology, has the potential to fulfil the strict requirements of real-world collective robots. These requirements include: small size, light weight, large range, high refresh rate, immunity against tilting and misalignment, immunity against ambient light changes, and good range and bearing accuracy. Currently, there are no range and bearing systems that have been designed to cope with such strict requirements. This paper presents a custom range and bearing system, based on a novel cascaded filtering technology, complemented by hybrid infrared/Radio Frequency (RF) communication, which has been designed specifically to meet all these expectations. The system has been characterised and tested, proving its viability.

Rolling bearing device

Abstract: PROBLEM TO BE SOLVED: To provide a rolling bearing device equipped with a radial bearing 1 and a thrust bearing 11, and capable of reducing manhours of the work of incorporating the rolling bearing device in an apparatus SOLUTION: The radial bearing 1 includes a cylindrical inner ring 2, a cylindrical outer ring 3, a cylindrical roller 4 rolling between the inner and outer rings, and a first cage 6 The thrust bearing 11 includes an annular raceway ring 12 extending to the outside in the radial direction from one-side axial end of the inner ring 2, a needle roller 13 rolling between the raceway ring 12 and the axial end surface 5 of the outer ring 3, and a second cage 14 The raceway ring 12 is formed integrally with the inner ring 2 COPYRIGHT: (C)2009,JPO&INPIT

Thermohydrodynamic Analysis of Bump Type Gas Foil Bearings: A Model Anchored to Test Data

Abstract: The paper introduces a thermohydrodynamic (THD) model for prediction of gas foil bearing (GFB) performance. The model includes thermal energy transport in the gas film region, and with cooling gas streams, inner or outer, as in typical rotor-GFBs systems. The analysis also accounts for material property changes and the bearing components’ expansion due to temperature rises and shaft centrifugal growth due to rotational speed. Gas inlet feed characteristics are thoroughly discussed in bearings whose top foil must detach, i.e., not allowing for subambient pressure. Thermal growths determine the actual bearing clearance needed for accurate prediction of GFB forced performance, static and dynamic. Model predictions are benchmarked against published measurements of (metal) temperatures in a GFB operating without a forced cooling gas flow. The tested foil bearing is proprietary; hence its geometry and material properties are largely unknown. Predictions are obtained for an assumed bearing configuration, with bump-foil geometry and materials taken from prior art and best known practices. The predicted film peak temperature occurs just downstream of the maximum gas pressure. The film temperature is higher at the bearing middle plane than at the foil edges, as the test results also show. The journal speed, rather than the applied static load, influences more the rise in film temperature and with a larger thermal gradient towards the bearing sides. In addition, as in the tests conducted at a constant rotor speed and even for the lowest static load, the gas film temperature increases rapidly due to the absence of a forced cooling air that could carry away the recirculation gas flow and thermal energy drawn by the spinning rotor, Predictions are in good agreement with the test data. A comparison of predicted static load parameters to those obtained from an isothermal condition shows the THD model producing a smaller journal eccentricity (larger minimum film thickness) and larger drag torque. A rise in gas temperature is tantamount to an increase in gas viscosity, hence the noted effect in the foil bearing forced performance.Copyright © 2009 by ASME

Wind Turbine Design Guideline DG03: Yaw and Pitch Rolling Bearing Life

Abstract: This report describes the design criteria, calculation methods, and applicable standards recommended for use in performance and life analyses of ball and roller (rolling) bearings for yaw and pitch motion support in wind turbine applications. The formulae presented here for rolling bearing analytical methods and bearing-life ratings are consistent with methods in current use by wind turbine designers and rolling-bearing manufacturers.

Gas turbine engine with an air cooled bearing

Abstract: A small gas turbine engine with a compressor, a combustor, and a turbine located downstream of the combustor. The compressor and turbine are supported on a rotary shaft, and a main bearing is support on the rotary shaft, the main bearing being located in a hot zone of the combustor. The main bearing includes cooling air passages within the races to provide cooling for the bearing. A cooling air is diverted from the compressor and passed through the bearing cooling passages for cooling the bearing, and then the cooling air is directed into the combustor. The cooling air is also passed through a guide nozzle before being passed through the bearing to cool both the guide nozzle and the bearing. A swirl cup injector is sued to deliver the compressed air from the compressor and the cooling air from the bearing into the combustor, the swirl cup injector also acting to draw the cooling air through the bearing.

Effects of Heating on the Behavior of Lead-Rubber Bearings. I: Theory

Abstract: The energy dissipated per cycle and the characteristic strength of lead-rubber bearings reduce with increasing number of cycles as a result of heating of the lead core. The reduction is substantial depending on the geometric characteristics of the bearing and the speed of motion. This paper presents a theory that is capable of predicting the dependency on time of the characteristic strength and energy dissipated of lead-rubber bearings. The theory is based on predicting the temperature of the lead core and relating the temperature to the strength. A much simpler theory is also presented based on neglect of heat conduction through the steel shim and end plates of the bearing. The theory is useful in predicting the cyclic behavior of lead-rubber bearings for simplified analysis, in extrapolating experimental data from one scale to another and in developing models for dynamic response history analysis of seismically isolated structures that account for the time-dependent mechanical properties of the bearings. A companion paper presents results of eight tests of six lead-rubber bearings that provide verification of the theoretical solution.

Rolling Bearing Fault Classification Based on Envelope Spectrum and Support Vector Machine

Abstract: Based upon Hilbert envelope spectrum and support vector machine (SVM), a method for the fault diagnosis of rolling bearing is proposed in this paper. Targeting the modulation characteristics of rolling bearing fault vibration signals, the Hilbert transform based envelope spectrum analysis is used to extract fault bearing features. In the envelope spectrum, character frequencies are quite clear and can be used as a reliable source of information for bearing diagnosis. Basic SVM is originally designed for two-class classification problem, while bearing fault diagnosis is multi-class case. A new bearing fault diagnosis system based on “one to others” SVM algorithm is presented to solve the multi-class recognition problems. Practical vibration signals measured from rolling bearings with ball fault, inner race fault and outer race fault are analyzed by the proposed method. The results show that the proposed method provides accurate diagnosis and good diagnostic resolution.