Showing papers on "Bearing (mechanical) published in 2010"

Fastening tool with an internal combustion engine with a unique opening and closing chamber abutment

Abstract: The tool is to be used for driving fastening members into a supporting material It comprises a cylinder (3), with a piston (5), a combustion chamber (1, 11), a cylinder head (12) bearing a fuel igniting means (36) in the chamber (1), a pin guide (9), for receiving a fastening member and the piston (5) shaft (7) and a cage (21) Return means are provided for opening the chamber (11), driving the pin guide (9) forwardly, opening and closing abutment means for the chamber (11) There are provided: one single central spring (32) for opening the chamber (11) and, on each side of the tool, one single opening and closing side chamber abutment (18, 55), integral with the chamber (11) and mobile in translation on the corresponding side of the cylinder (3)

Diagnosis of Bearing Faults in Induction Machines by Vibration or Current Signals: A Critical Comparison

Abstract: Mechanical imbalances and bearing faults account for a large majority of the faults in a machine, particularly for small-medium size machines. Therefore, their diagnosis is an intensively investigated field of research. Recently, many research activities were focused on the diagnosis of bearing faults by current signals. This paper compares the bearing fault detection capability obtained with the vibration and current signals. The paper contribution is the use of a simple and effective signal processing technique for both current and vibration signals, and a theoretical analysis of the physical link between faults, modeled as a torque disturbance, and current components. The focus of the paper is on the theoretical development of the correlation between torque disturbances and the amplitude of the current components, together with a review of fault models used in the literature. Another contribution is the re-creation of realistic incipient faults and their experimental validation. Radial effects are visible only in case of large failures that result in air-gap variations. Experiments are reported that confirm the proposed approach.

Application of mother wavelet functions for automatic gear and bearing fault diagnosis

Abstract: This paper introduces an automatic feature extraction system for gear and bearing fault diagnosis using wavelet-based signal processing. Vibration signals recorded from two experimental set-ups were processed for gears and bearing conditions. Four statistical features were selected: standard deviation, variance, kurtosis, and fourth central moment of continuous wavelet coefficients of synchronized vibration signals (CWC-SVS). In this research, the mother wavelet selection is broadly discussed. 324 mother wavelet candidates were studied, and results show that Daubechies 44 (db44) has the most similar shape across both gear and bearing vibration signals. Next, an automatic feature extraction algorithm is introduced for gear and bearing defects. It also shows that the fourth central moment of CWC-SVS is a proper feature for both bearing and gear failure diagnosis. Standard deviation and variance of CWC-SVS demonstrated more appropriate outcome for bearings than gears. Kurtosis of CWC-SVS illustrated the acceptable performance for gears only. Results also show that although db44 is the most similar mother wavelet function across the vibration signals, it is not the proper function for all wavelet-based processing.

Stator Current and Motor Efficiency as Indicators for Different Types of Bearing Faults in Induction Motors

Abstract: This paper proposes a new approach to use stator current and efficiency of induction motors as indicators of rolling-bearing faults. After a presentation of the state of the art about condition monitoring of vibration and motor current for the diagnostics of bearings, this paper illustrates the experimental results on four different types of bearing defects: crack in the outer race, hole in the outer race, deformation of the seal, and corrosion. The first and third faults have not been previously considered in the literature, with the latter being analyzed in other research works, even if obtained in a different way. Another novelty introduced by this paper is the analysis of the decrease in efficiency of the motor with a double purpose: as alarm of incipient faults and as evaluation of the extent of energy waste resulting from the lasting of the fault condition before the breakdown of the machine.

Predicting remaining useful life of rotating machinery based artificial neural network

Abstract: Accurate remaining useful life (RUL) prediction of machines is important for condition based maintenance (CBM) to improve the reliability and cost of maintenance. This paper proposes artificial neural network (ANN) as a method to improve accurate RUL prediction of bearing failure. For this purpose, ANN model uses time and fitted measurements Weibull hazard rates of root mean square (RMS) and kurtosis from its present and previous points as input. Meanwhile, the normalized life percentage is selected as output. By doing that, the noise of a degradation signal from a target bearing can be minimized and the accuracy of prognosis system can be improved. The ANN RUL prediction uses FeedForward Neural Network (FFNN) with Levenberg Marquardt of training algorithm. The results from the proposed method shows that better performance is achieved in order to predict bearing failure.

Machinery Vibration and Rotordynamics

Abstract: PREFACE. 1 Fundamentals of Machine Vibration and Classical Solutions. The Main Sources of Vibration in Machinery. The Single Degree of Freedom (SDOF) Model. Using Simple Models for Analysis and Diagnostics. Six Techniques for Solving Vibration Problems with Forced Excitation. Some Examples with Forced Excitation. Illustrative Example 1. Illustrative Example 2. Illustrative Example 3. Illustrative Example 4. Some Observations about Modeling. Unstable Vibration. References. Exercises. 2 Torsional Vibration. Torsional Vibration Indicators. Objectives of Torsional Vibration Analysis. Simplified Models. Computer Models. Kinetic Energy Expression. Potential Energy. Torsional Vibration Measurement. French s Comparison Experiments. Strain Gages. Carrier Signal Transducers. Frequency-modulated Systems. Amplitude-modulated Systems. Frequency Analysis and the Sideband System. French s Test Procedure and Results. A Special Tape for Optical Transducers. Time-interval Measurement Systems. Results from Toram s Method. Results from the Barrios/Darlow Method. References. Exercises. 3 Introduction to Rotordynamics Analysis. Objectives of Rotordynamics Analysis. The Spring Mass Model. Synchronous and Nonsynchronous Whirl. Analysis of the Jeffcott Rotor. Polar Coordinates. Cartesian Coordinates. Physical Significance of the Solutions. Three Ways to Reduce Synchronous Whirl Amplitudes. Some Damping Definitions. The "Gravity Critical". Critical Speed Definitions. Effect of Flexible (Soft) Supports. Rotordynamic Effects of the Force Coefficients A Summary. The Direct Coefficients. The Cross-coupled Coefficients. Rotordynamic Instability. Effect of Cross-Coupled Stiffness on Unbalance Response. Added Complexities. Gyroscopic Effects. Effect of Support Asymmetry on Synchronous Whirl. False Instabilities. References. Exercises. 4 Computer Simulations of Rotordynamics. Different Types of Models. Bearing and Seal Matrices. Torsional and Axial Models. Different Types of Analyses. Eigenanalysis. Linear Forced Response (LFR). Transient Response. Shaft Modeling Recommendations. How Many Elements. 45-Degree Rule. Interference Fits. Laminations. Trunnions. Impeller Inertias via CAD Software. Stations for Added Weights. Rap Test Verification of Models. Stations for Bearings and Seals. Flexible Couplings. Example Simulations. Damped Natural Frequency Map (NDF). Modal Damping Map. Root Locus Map. Undamped Critical Speed Map. Mode Shapes. Bode/Polar Response Plot. Orbit Response Plot. Bearing Load Response Plot. Operating Deflected Shape (ODS). Housing Vibration (ips and g s). References. 5 Bearings and Their Effect on Rotordynamics. Fluid Film Bearings. Fixed-geometry Sleeve Bearings. Variable-geometry Tilting Pad Bearings. Fluid Film Bearing Dynamic Coefficients and Methods of Obtaining Them. Load Between Pivots Versus Load on Pivot. Influence of Preload on the Dynamic Coefficients in Tilt Pad Bearings. Influence of the Bearing Length or Pad Length. Influence of the Pivot Offset. Influence of the Number of Pads. Ball and Rolling Element Bearings. Case Study: Bearing Support Design for a Rocket Engine Turbopump. Ball Bearing Stiffness Measurements. Wire Mesh Damper Experiments and Computer Simulations. Squeeze Film Dampers. Squeeze Film Damper without a Centering Spring. O-ring Supported Dampers. Squirrel Cage Supported Dampers. Integral Squeeze Film Dampers. Squeeze Film Damper Rotordynamic Force Coefficients. Applications of Squeeze Film Dampers. Optimization for Improving Stability in a Centrifugal Process Compressor. Using Dampers to Improve the Synchronous Response. Using the Damper to Shift a Critical Speed or a Resonance. Insights into the Rotor Bearing Dynamic Interaction with Soft/Stiff Bearing Supports. Influence on Natural Frequencies with Soft/Stiff Bearing Supports. Effects of Mass Distribution on the Critical Speeds with Soft/Stiff Bearing Supports. Influence of Overhung Mass on Natural Frequencies with Soft/Stiff Supports. Influence of Gyroscopic Moments on Natural Frequencies with Soft/Stiff Bearing Supports. References. Exercises. Appendix: Shaft With No Added Weight. 6 Fluid Seals and Their Effect on Rotordynamics. Function and Classification of Seals. Plain Smooth Seals. Floating Ring Seals. Conventional Gas Labyrinth Seals. Pocket Damper Seals. Honeycomb Seals. Hole-pattern Seals. Brush Seals. Understanding and Modeling Damper Seal Force Coefficients. Alford s Hypothesis of Labyrinth Seal Damping. Cross-coupled Stiffness Measurements. Invention of the Pocket Damper Seal. Pocket Damper Seal Theory. Rotordynamic Testing of Pocket Damper Seals. Impedance Measurements of Pocket Damper Seal Force Coefficients (Stiffness and Damping) and Leakage at Low Pressures. The Fully Partitioned PDS Design. Effects of Negative Stiffness. Frequency Dependence of Damper Seals. Laboratory Measurements of Stiffness and Damping from Pocket Damper Seals at High Pressures. The Conventional Design. The Fully Partitioned Design. Field Experience with Pocket Damper Seals. Two Back-to-Back Compressor Applications. Case 1. Case 2. A Fully Partitioned Application. Designing for Desired Force Coefficient Characteristics. The Conventional PDS Design. The Fully Partitioned Pocket Damper Seal. Leakage Considerations. Some Comparisons of Different Types of Annular Gas Seals. References. 7 History of Machinery Rotordynamics. The Foundation Years, 1869 1941. Shaft Dynamics. Bearings. Refining and Expanding the Rotordynamic Model, 1942 1963. Multistage Compressors and Turbines, Rocket Engine Turbopumps, and Damper Seals, 1964 Present. Stability Problems with Multistage Centrifugal Compressors. Kaybob, 1971 72. Ekofisk, 1974 75. Subsequent Developments. New Frontiers of Speed and Power Density with Rocket Engine Turbopumps. The Space Shuttle Main Engine (SSME). High-pressure Fuel Turbopump (HPFTP). Rotordynamic Instability Problem. Noncontacting Damper Seals. Shaft Differential Heating (The Morton Effect). References. INDEX.

An overview of Boeing flywheel energy storage systems with high-temperature superconducting bearings

Abstract: An overview summary of recent Boeing work on high-temperature superconducting (HTS) bearings is presented. A design is presented for a small flywheel energy storage system that is deployable in a field installation. The flywheel is suspended by a HTS bearing whose stator is conduction cooled by connection to a cryocooler. At full speed, the flywheel has 5 kW h of kinetic energy, and it can deliver 3 kW of three-phase 208 V power to an electrical load. The entire system, which includes a containment structure, is compatible with transportation by forklift or crane. Laboratory measurements of the bearing loss are combined with the parasitic loads to estimate the efficiency of the system. Improvements in structural composites are expected to enable the operation of flywheels with very high rim velocities. Small versions of such flywheels will be capable of very high rotational rates and will likely require the low loss inherent in HTS bearings to achieve these speeds. We present results of experiments with small-diameter rotors that use HTS bearings for levitation and rotate in vacuum at kHz rates. Bearing losses are presented as a function of rotor speed.

Detection of Motor Bearing Outer Raceway Defect by Wavelet Packet Transformed Motor Current Signature Analysis

Abstract: Motor current signature analysis (MCSA) is a method of sampling the running current through a data logger at high sampling speed, followed by using mathematical tools such as fast Fourier transform (FFT) to identify relevant motor signature changes in the frequency spectrum for motor fault identification. Although there are numerous types of motor fault, research conducted by Electric Power Research Institute (EPRI) indicated that motor bearing fault accounted for more than 40% of all types of motor fault. The main aim of this paper is to evaluate the use of MCSA for detecting bearing outer raceway defect. Stage-by-stage experimental verification shows that the method of MCSA is effective in detecting bearing fault with the use of wavelet packet transformation (WPT). In addition, a novel linear application of linear regression for wavelet data analysis is applied and presented in this paper.

Dynamic modeling and analysis of a spur planetary gear involving tooth wedging and bearing clearance nonlinearity

Abstract: Tooth wedging, also known as tight mesh, occurs when a gear tooth comes into contact on the drive-side and back-side simultaneously. Tooth wedging risks bearing failures from elevated forces. This work studies the nonlinear tooth wedging behavior and its correlation with planet bearing forces by analyzing the dynamic response of an example planetary gear. This planetary gear is representative of a wind turbine geartrain. A two-dimensional lumped-parameter model is extended to include tooth separation, back-side contact, tooth wedging, and bearing clearances. The results show significant impact of tooth wedging on planet bearing forces for a wide range of operating speeds. To develop a physical understanding of the tooth wedging mechanism, connections between planet bearing forces and tooth forces are studied by investigating physical forces and displacements acting throughout the planetary gear. A method to predict tooth wedging based on geometric interactions is developed and verified. The major causes of tooth wedging relate directly to translational vibrations caused by gravity forces and the presence of clearance-type nonlinearities in the form of backlash and bearing clearance.

Tribological advancements for reliable wind turbine performance.

Abstract: Wind turbines have had various limitations to their mechanical system reliability owing to tribological problems over the past few decades. While several studies show that turbines are becoming more reliable, it is still not at an overall acceptable level to the operators based on their current business models. Data show that the electrical components are the most problematic; however, the parts are small, thus easy and inexpensive to replace in the nacelle, on top of the tower. It is the tribological issues that receive the most attention as they have higher costs associated with repair or replacement. These include the blade pitch systems, nacelle yaw systems, main shaft bearings, gearboxes and generator bearings, which are the focus of this review paper. The major tribological issues in wind turbines and the technological developments to understand and solve them are discussed within. The study starts with an overview of fretting corrosion, rolling contact fatigue, and frictional torque of the blade pitch and nacelle yaw bearings, and references to some of the recent design approaches applied to solve them. Also included is a brief overview into lubricant contamination issues in the gearbox and electric current discharge or arcing damage of the generator bearings. The primary focus of this review is the detailed examination of main shaft spherical roller bearing micropitting and gearbox bearing scuffing, micropitting and the newer phenomenon of white-etch area flaking. The main shaft and gearbox are integrally related and are the most commonly referred to items involving expensive repair costs and downtime. As such, the latest research and developments related to the cause of the wear and damage modes and the technologies used or proposed to solve them are presented.

Bearing apparatuses, systems including same, and related methods

Abstract: In an embodiment, a bearing apparatus comprises a first bearing assembly (202) including a plurality of circumf erentially-spaced first bearing elements (212) each of which includes a first bearing surface (214). The bearing apparatus further includes a second bearing assembly (204) including a plurality of circumf erentially-spaced second bearing elements (224) each of which includes a second bearing surface oriented to engage the first bearing surfaces of the first bearing assembly during operation. At least one of the second bearing elements may be circumf erentially spaced from an adjacent one of the second bearing elements by a lateral spacing greater than a lateral dimension of the at least one of the second bearing elements.

Natural roller bearing fault detection by angular measurement of true instantaneous angular speed

Abstract: The challenge in many production activities involving large mechanical devices like power transmissions consists in reducing the machine downtime, in managing repairs and in improving operating time. Most online monitoring systems are based on conventional vibration measurement devices for gear transmissions or bearings in mechanical components. In this paper, we propose an alternative way of bearing condition monitoring based on the instantaneous angular speed measurement. By the help of a large experimental investigation on two different applications, we prove that localized faults like pitting in bearing generate small angular speed fluctuations which are measurable with optical or magnetic encoders. We also emphasize the benefits of measuring instantaneous angular speed with the pulse timing method through an implicit angular sampling which ensures insensitivity to speed fluctuation. A wide range of operating conditions have been tested for the two applications with varying speed, load, external excitations, gear ratio, etc. The tests performed on an automotive gearbox or on actual operating vehicle wheels also establish the robustness of the proposed methodology. By the means of a conventional Fourier transform, angular frequency channels kinematically related to the fault periodicity show significant magnitude differences related to the damage severity. Sideband effects are evidently seen when the fault is located on rotating parts of the bearing due to load modulation. Additionally, slip effects are also suspected to be at the origin of enlargement of spectrum peaks in the case of double row bearings loaded in a pure radial direction.

Investigation of variable optimum preload for a machine tool spindle

Abstract: Angular contact ball bearings have been widely used in machine tool spindles, and the bearing preload plays an important role on the performance of the spindle. With the development of high speed machining, especially for high speed milling, heavy cutting at a low speed and light cutting at a high speed are often performed on a single machine tool spindle, thus, high stiffness at low speed and low temperature rise at high speed are required. The traditional constant pressure preload method cannot meet the technical requirement of this kind of spindle any more. The variable preload technology is systematically investigated in this paper. At high speed range, FEM method is used to analyze the temperature distribution of the spindle, and the variable spindle preload is determined according to the constraint of temperature rise of bearings. At low speed range, the spindle preload is resolved by the fatigue life of bearings. The dynamic stiffness of the variable preload spindle is analyzed utilizing the Transfer Matrix Method (TMM) and a nonlinear bearing model that includes the centrifugal force and gyroscopic effects. An experimental set-up for the variable preload spindle is developed using hydraulic pressure that can automatically adjust the bearing preload. The proposed method to determine variable preload is verified experimentally by measuring the dynamic stiffness of the spindle and the temperature rise of the test bearing. The results show that the variable preload spindle gives outstanding behavior that the temperature rise at high speed is lower than that of the constant pressure preload spindle, and the dynamic stiffness at low speed range is significantly increased.

Rolling contact fatigue and wear fundamentals for rolling bearing diagnostics - state of the art

Abstract: Rolling bearing operation is affected by friction, wear and lubrication mechanisms, fluid dynamics and lubricant rheology, material properties, and contact mechanics. Changes in rolling surfaces occur due to plastic deformation, rolling contact wear, and rolling contact fatigue. Wear particles can be formed and mixed into the lubricant. Increased levels of vibrations due to surface degradation can be monitored by sensors. Rolling contact wear and rolling contact fatigue during rolling bearing operation can be diagnosed by combining measured and interpreted condition monitoring data with theory, and conclusions drawn thereof can support a continuous prognosis for the remaining bearing life. In the present work, connections between bearing diagnostics and tribological mechanisms are outlined.

Application of Computational Fluid Dynamics and Fluid–Structure Interaction Method to the Lubrication Study of a Rotor–Bearing System

Abstract: Computational methods were used to analyse the elasto-hydrodynamic lubrication of a complex rotor–bearing system. The methodology employed computational fluid dynamics (CFD), based on the Navier–Stokes equation and a fluid–structure interaction (FSI) technique. A series of models representing the system were built using the CFD–FSI methodology to investigate the interaction between the lubrication of the fluid film, and elastic dynamics of the rotor and journal bearing. All models followed an assumption of isothermal behaviour. The FSI methodology was implemented by setting nodal forces and displacements to equilibrium at the fluid–structure interface, therefore allowing the lubrication of the fluid and the elastic deformation of structures to be solved simultaneously. This is significantly different to the more common techniques—such as the Reynolds equation method—that use an iterative solution to balance the imposed load and the force resulting from the pressure of the fluid film to within a set tolerance. Predictions using the CFD–FSI method were compared with the results of an experimental study and the predictions from an ‘in-house’ lubrication code based on the Reynolds equation. The dynamic response of the system was investigated with both rigid and flexible bodies for a range of different bearing materials and dynamic unbalanced loads. Cavitation within the fluid film was represented in the CFD–FSI method using a simplified phase change boundary condition. This allowed the transition between the liquid and vapour phases to be derived from the lubricant’s properties as a function of pressure. The combination of CFD and FSI was shown to be a useful tool for the investigation of the hydrodynamic and elasto-hydrodynamic lubrications of a rotor–bearing system. The elastic deformation of the bearing and dynamic unbalanced loading of the rotor had significant effects on the position of its locus.

Variable speed drive

Abstract: Systems and methods for improved Variable Speed Drives are provided. One embodiment relates to apparatus for common mode and differential mode filtering for motor or compressor bearing protection when operating with Variable Speed Drives, including conducted EMI/RFI input power mains mitigation. Another embodiment relates to a method to extend the synchronous operation of an Active Converter to the AC mains voltage during complete line dropout. Another embodiment relates to an Active Converter-based Variable Speed Drive system with Improved Full Speed Efficiency. Another embodiment relates to a liquid- or refrigerant-cooled inductor. The liquid- or refrigerant-cooled inductor may be used in any application where liquid or refrigerant cooling is available and a reduction in size and weight of a magnetic component is desired.

The Role of Hydrogen on Rolling Contact Fatigue Response of Rolling Element Bearings

Abstract: It is generally accepted that the rolling contact fatigue (RCF) life of bearing components is strongly reduced when the hardened steel matrix contains hydrogen. Although frequently reported in the literature, a physically sound explanation to this phenomenon has not yet been presented. In recent work on building understanding around the nature of the RCF damage process, we have reported on the development of a physically based fatigue damage model. Here we discuss an attempt to interpret the role of hydrogen on the micro-plastic fatigue damage mechanism on the basis of this concept. In this context, the role of hydrogen on the RCF response has been studied in order to find evidence for and to determine its weakening effect on hardened and low-temperature tempered (bearing) steels. In order to perform valid tests, effort was put in controlling the hydrogen content in bearing components before testing using an electrochemical hydrogen charging process. A number of bearing tests were performed clearly showing differences in fatigue response with different amounts of hydrogen present in the microstructure. The results of testing of bearings with hydrogen-containing steel matrices are given. It was found that increased hydrogen content in bearing steel at 5 ppm (by weight) will significantly promote bearing spalling failure and enhance the formation and growth of so-called white-etching crack systems. This experimental information is interpreted in the light of the physically based fatigue damage model.

Modeling strength degradation in lead–rubber bearings under earthquake shaking

Abstract: Lead–rubber bearings are seismic isolators that have been used extensively to protect buildings, bridges and mission-critical infrastructure from the damaging effects of earthquake shaking. Under large-displacement cyclic motion, the strength of a lead–rubber bearing reduces due to energy dissipation and the resultant heating of the lead core. This paper proposes a method to incorporate strength degradation due to lead core heating in modeling the hysteretic behavior of lead–rubber bearings. The validity of the proposed model is investigated through comparing numerical and experimental results. The model is used to examine the effects of lead core heating on the dynamic response of an isolated structure. Copyright © 2010 John Wiley & Sons, Ltd.