Dynamic Behaviors of the Elastohydrodynamic Lubricated Contact for Rolling Bearings

2012 ◽  
Vol 135 (2) ◽  
Author(s):  
Yu-Yan Zhang ◽  
Xiao-Li Wang ◽  
Xiao-Liang Yan
Keyword(s):  
Viscosity Coefficient ◽  
Rolling Bearings ◽  
Transform Method ◽  
Dynamic Behaviors ◽  
Solution Convergence ◽  
Fast Fourier Transform Method ◽  
Vibration Model ◽  
Rolling Element ◽  
Inlet Length ◽  
Stiffness And Damping

The dynamic behaviors of a single elastohydrodynamic lubricated (EHL) contact between a rolling element and raceways under wider load and speed ranges are analyzed numerically based on the transient EHL model and the free vibration model. The discrete convolution and fast fourier transform method is implemented in order to increase the computational efficiency associated with elastic deformations and the semisystem approach is applied to improve the solution convergence under severe conditions. The change of mutual approach is selected as the standard of bearing vibrations and the inlet length and dimensionless natural frequency corresponding to the working load and speed are determined. The numerical results demonstrate that the stiffness increases with the increasing load and decreases with speed. However, the changes of damping are different in various working conditions, especially under heavier load and higher speed. It is also indicated that the stiffness and damping increase with the increase in ambient viscosity and the decrease in pressure-viscosity coefficient.

Stiffness and Damping Analysis of a Single EHL Contact Between the Rolling Element and Raceways Under Wider Load and Speed Ranges

2012 ◽  
Author(s):  
Yuyan Zhang ◽  
Xiaoli Wang
Keyword(s):  
Viscosity Coefficient ◽  
Equivalent Stiffness ◽  
Solution Convergence ◽  
Vibration Model ◽  
Rolling Element ◽  
Inlet Length ◽  
Motion Characteristics ◽  
Stiffness And Damping ◽  
Increasing Load ◽  
Ehl Contact

The numerical analysis for the equivalent stiffness and damping of a single EHL contact between the rolling element and raceways under wider load and speed ranges is presented. The unsteady EHL model and free vibration model are applied to describe the motion characteristics of the rolling element. The inlet length and dimensionless natural frequency are determined according to the corresponding working load and speed. The DC-FFT method is implemented in order to increase the computational efficiency associated with elastic deformations and the semi-system approach is applied to ensure solution convergence under severe conditions which makes the analysis of stiffness and damping in the larger ranges of load and speed possible. The numerical results demonstrate that the stiffness increases with the increasing load and decreases with speed. However, the changes of the damping are complex, which are different in various load and speed ranges, especially under heavier load and higher speed. It is also indicated that the stiffness and damping increases with the increase in ambient viscosity and the decrease in pressure-viscosity coefficient.

Study on Measurement of Thin Film Thickness with Lateral Shearing Interferometry

2013 ◽  
Vol 718-720 ◽  
pp. 848-852
Author(s):  
Jun Hong Su ◽  
Ying Shi ◽  
Jin Man Ge
Keyword(s):  
Film Thickness ◽  
Transform Method ◽  
Shearing Interferometry ◽  
Platform Process ◽  
Fast Fourier Transform Method ◽  
Lateral Shearing ◽  
Phase Unwrap ◽  
Technical Indicator ◽  
Lateral Shearing Interferometry ◽  
Shearing Interference

The film thickness is an important technical indicator of film devices, and its accuracy directly affects various performances of optical components. In fabrication process of film device, fast and accurate measurement of film thickness has positive significance on product quality control. In this paper, measure film thickness with lateral shearing interferometry. Collect interferograms through structured lateral shearing interference platform, process interferogram with Fast Fourier Transform method to extract phase, unwrap the wrapped phase to achieve phase value. Finally, calculate film thickness based on lateral shearing interference principle. The thickness of sample is 119.6800nm measured by this method, basically the same with the result 120.6036nm that measured by ZYGO interferometer. This experiment shows that lateral shearing interferometry not only suit to measurement of film thickness, but also abundant high-precision method of measuring film thickness, and has high practical value.

An Approach to the Use of an External Magnetic Field As a Diagnostic Sign of an Asynchronous Motor Malfunction

2021 ◽  
Vol 64 (3) ◽  
pp. 18-23
Author(s):  
Ildar Yamansarin ◽  
◽  
Mikhail Salikov ◽  
Alexander Padeev ◽  
Dmitry Surkov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Short Circuit ◽  
Asynchronous Motor ◽  
Technical Condition ◽  
Stator Winding ◽  
Electric Motors ◽  
Transform Method ◽  
Fast Fourier Transform Method ◽  
Measurement Location

The article deals with the issues related to the possibility of diagnosing the technical condition of an asyn-chronous electric motor by an external magnetic field. The justification of the problems associated with the di-agnosis of electric motors is given. The difficulties that arise when measuring the external magnetic field of electric motors, as well as the devices with which it is possible to carry out measurements, are described. The re-lationship between the EMF of the sensor and the external magnetic field is shown. The results of processing the EMF waveforms induced by an external magnetic field in an inductive sensor for various electric motors are presented. The processing was carried out by the fast Fourier transform method. The external magnetic field contains the first harmonic and various harmonics that are multiples of the combination of the stator teeth, or the sum of the stator and rotor teeth that fall on one pair of poles. The ratio of the amplitudes of the first and tooth harmonics is affected by the measurement location and the orientation of the sensor. Diagrams showing the ratio of the main and tooth harmonics at different points of the motor body are constructed. The depend-ences of the harmonic amplitudes on the magnitude of the magnetizing current of the stator are given. Changes in the amplitudes and spectrum of harmonics in the presence and absence of an inter-turn short circuit in the stator winding are shown. Diagrams of the circular external magnetic field for the main and higher harmonics are constructed. The study shows the possibility of using an external magnetic field to detect inter-turn short circuits of the stator winding.

Vibration model of rolling element bearings in a rotor-bearing system for fault diagnosis

2013 ◽  
Vol 332 (8) ◽  
pp. 2081-2097 ◽  
Author(s):  
Feiyun Cong ◽  
Jin Chen ◽  
Guangming Dong ◽  
Michael Pecht
Keyword(s):  
Fault Diagnosis ◽  
Rolling Element Bearings ◽  
Vibration Model ◽  
Rolling Element ◽  
Rotor Bearing ◽  
Bearing System

The Effect of Wear Evolution on Vibration-based Fault Detection in Tapered Roller Bearings

2019 ◽  
Vol 9 (1) ◽  
pp. 18-23
Author(s):  
K Rabeyee ◽  
X Tang ◽  
F Gu ◽  
A D Ball
Keyword(s):  
Condition Monitoring ◽  
Rolling Element Bearings ◽  
Rolling Bearings ◽  
Roller Bearings ◽  
Fault Type ◽  
Rolling Element ◽  
Tapered Roller ◽  
Magnitude Variation ◽  
Tapered Roller Bearings ◽  
The Impact

Rolling element bearings (REBs) are typical tribological components used widely in rotating machines. Their failure could cause catastrophic damage. Therefore, condition monitoring of bearings has always had great appeal for researchers. Usually, the detection and diagnostics of incipient bearing faults are achieved by characterising the weak periodic impacts induced by the collision of defective bearing components. However, race wear evolution, which is inevitable in bearing applications, can affect the contact between bearing elements and races, thereby decreasing the impact magnitudes and impeding detection performance. In this paper, the effect of wear evolution on the condition monitoring of rolling bearings is firstly analysed based on internal clearance changes resulting from the wear effect. Then, an experimental study is ingeniously designed to simulate wear evolution and evaluate its influence on wellknown envelope signatures according to measured vibrations from widely used tapered roller bearings. The fault type is diagnosed in terms of two indices: the magnitude variation of characteristic frequencies and the deviation of such frequencies. The experimental results indicate a signature decrease with regard to wear evolution, suggesting that accurate severity diagnosis needs to take into account both the wear conditions of the bearing and the signature magnitudes.

Discussion of Short-Wavelength Laser Beam Focus Using Fast Fourier Transform Method

2011 ◽  
Vol 31 (5) ◽  
pp. 0507001
Author(s):  
杨美霞 Yang Meixia ◽  
钟鸣 Zhong Ming ◽  
任钢 Ren Gang ◽  
何衡湘 He Hengxiang ◽  
刘文兵 Liu Wenbing ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Laser Beam ◽  
Fast Fourier Transform ◽  
Short Wavelength ◽  
Transform Method ◽  
Fourier Transform Method ◽  
Fast Fourier Transform Method
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