Bearing Test System Research Articles

Amorphous Carbon Films In Situ Formed From PTFE Transfer Layer in Solid Lubricated Cryogenic Turbopump Bearings

In order to fully evaluate the service reliability of cryogenic turbopump bearings, a newly developed solid lubricated bearing was tested using a custom ground bearing test system cooled by water. Stains with different color intensity were occasionally exhibited on the surfaces of the bearing balls after ground tests. This may pose a risk for the reliable service of the related bearings in real flight missions. Then the chemical composition and structural information of the stain layers were systematically analyzed by x-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and high-resolution transmission electron microscope (HRTEM). The results manifested that the stain layer had the characteristic of α-C film. The color intensity of stains was not caused by the structural changes, but was due to the difference of stain layers’ thickness. The α-C films in situ formed during bearings operation should result from the defluorination of polytetrafluoroethylene (PTFE) layers, which transferred from retainer to balls in the previous step. Correspondingly, FeF2 was produced on the surfaces of the tested bearing rings as a by-product. Although the tested bearings with α-C films formed on the surfaces of balls did not reach the state of final failure, the affected balls showed high surface roughness, which could be an indicator of an imminent bearing failure.

Stress Analysis and Fatigue Behaviour of PTFE-Bronze Layered Journal Bearing under Real-Time Dynamic Loading

The present paper is based on experimental studies and numerical simulations on the surface fatigue failure of the PTFE-bronze layered journal bearings under real-time loading. ‘Permaglide Plain Bearings P10’ type journal bearings were experimentally tested under different real time dynamic loadings by using real time journal bearing test system in our laboratory. The journal bearing consists of a PTFE-bronze layer approximately 0.32 mm thick on the steel support layer with 2.18 mm thick. Two different approaches have been considered with in experiments: (i) under real- time constant loading with varying bearing widths, (ii) under different real-time loadings at constant bearing widths. Fatigue regions, micro-crack dispersion and stress distributions occurred at the journal bearing were experimentally and theoretically investigated. The relation between fatigue region and pressure distributions were investigated by determining the circumferential pressure distribution under real-time dynamic loadings for the position of every 10° crank angles. In the theoretical part; stress and deformation distributions at the surface of the journal bearing analysed by using finite element methods to determine the relationship between stress and fatigue behaviour. As a result of this study, the maximum oil pressure and fatigue cracks were observed in the most heavily loaded regions of the bearing surface. Experimental results show that PTFE-Bronze layered journal bearings fatigue behaviour is better than the bearings include white metal alloy.

A Hydrostatic Bearing Test System for Measuring Bearing Load Using Magnetic-Fluid Lubricants.

This paper conducts a study on the design of a hydrostatic bearing test system. It involves the determination of viscous properties of magnetic-fluid lubricants. The load of a hydrostatic thrust bearing using a water-based magnetite nanofluid of varying volume flow rate is measured under an applied external induction field via the test system. Results reveal that the presence of nanoparticles in a carrier liquid would cause an enhanced bearing load. Such an effect could be further magnified by increasing the lubricant volume flow rate or the external induction field strength.

Rolling Bearing Fault Diagnosis Based on Wavelet Packet Decomposition and Multi-Scale Permutation Entropy

This paper presents a rolling bearing fault diagnosis approach by integrating wavelet packet decomposition (WPD) with multi-scale permutation entropy (MPE). The approach uses MPE values of the sub-frequency band signals to identify faults appearing in rolling bearings. Specifically, vibration signals measured from a rolling bearing test system with different defect conditions are decomposed into a set of sub-frequency band signals by means of the WPD method. Then, each sub-frequency band signal is divided into a series of subsequences, and MPEs of all subsequences in corresponding sub-frequency band signal are calculated. After that, the average MPE value of all subsequences about each sub-frequency band is calculated, and is considered as the fault feature of the corresponding sub-frequency band. Subsequently, MPE values of all sub-frequency bands are considered as input feature vectors, and the hidden Markov model (HMM) is used to identify the fault pattern of the rolling bearing. Experimental study on a data set from the Case Western Reserve University bearing data center has shown that the presented approach can accurately identify faults in rolling bearings.

Mutual Information-Assisted Wavelet Function Selection for Enhanced Rolling Bearing Fault Diagnosis

This paper presents an enhanced rolling bearing fault diagnosis approach, based on optimized wavelet packet transform (WPT) assisted with quantitative wavelet function selection. Mutual information is utilized as a quantitative measure to select the most suitable wavelet function for the WPT-based vibration analysis. Energy features from coefficients of an optimal set of orthogonal wavelet subspaces which resulted from the WPT-based vibration analysis are input to different classifiers. The fault states of the rolling bearings can then be identified. Experiment studies conducted on a rolling bearing test system have verified the effectiveness of the proposed approach for rolling bearing fault diagnosis.

Research on Magnetic Loading in Reliability Enhancement Testing of Low Viscosity Lubricated Bearings

In order to provide a load environment for the reliability enhancement testing of half-size water-lubricated bearing in the reactor coolant pump, enhanced test principle based on water-lubricated bearing failure mode is researched, and an axial and radial magnetic loading system is developed. Three typical failure modes, including wear, lubrication and vibration, are selected, and their test programs are given to research reliability enhancement testing principle. The qualitative and quantitative relations between load and failure are analyzed. On the basis, the static and dynamic load requirements for the enhanced test of half-size water-lubricated bearing are proposed. A magnetic loading system including structure module and control module is built. The static and dynamic load structures of axial loading component are independent. The radial loading component uses an 8-pole scheme. And the control module supports two kinds of control strategy of open-loop and closed-loop. The performances of loading system are verified by the special experiments. The results show that, the wear loss of tile will increase from 1.0 to 1.2 times, and the start-stop times will reduce by 50% to 54% while the load increases 20% in samples. The axial load module can generate static load, impulse and sinusoidal excitation, and static load can be 100 k N when the gap is 2 mm and the current is 1.2 A. Static load,amplitude of impulse excitation and sinusoidal excitation generated by radial load components are 3.7 k N,500 N and 115 N respectively. The feasibility of magnetic loading technique introduced in reliability enhancement test is initially verified. Open-loop control strategy realized by the artificial adjustment of current is more effective for the multi-field coupling bearing test system with loading device.

Rolling Bearing Fault Diagnosis Based on CEEMD and Time Series Modeling

Accurately identifying faults in rolling bearing systems by analyzing vibration signals, which are often nonstationary, is challenging. To address this issue, a new approach based on complementary ensemble empirical mode decomposition (CEEMD) and time series modeling is proposed in this paper. This approach seeks to identify faults appearing in a rolling bearing system using proper autoregressive (AR) model established from the nonstationary vibration signal. First, vibration signals measured from a rolling bearing test system with different defect conditions are decomposed into a set of intrinsic mode functions (IMFs) by means of the CEEMD method. Second, vibration signals are filtered with calculated filtering parameters. Third, the IMF which is closely correlated to the filtered signal is selected according to the correlation coefficient between the filtered signal and each IMF, and then the AR model of the selected IMF is established. Subsequently, the AR model parameters are considered as the input feature vectors, and the hidden Markov model (HMM) is used to identify the fault pattern of a rolling bearing. Experimental study performed on a bearing test system has shown that the presented approach can accurately identify faults in rolling bearings.

Energy Efficient Multiaxial Resonance Test Systems – New Applications and Testing Methods*

Abstract Modern lightweight design is only feasible exploiting properties of geometry and material. In some applications an uniaxial loading of components is not sufficient and a multiaxial loading of forces or moments becomes necessary. In terms of decreasing development cycles and resultant increasing demands on testing frequencies, multiaxial resonance test systems turn into fast, economically advantageous and energyefficient development tools. Well known problems as interference of actuators were solved by the use of particular decoupling devices. Innovative electronic systems and software applications allow matching or different frequencies for each load directions with variable amplitude ratios. Moreover, the phase between the different loading directions is freely adjustable. This development yielded the two-axial crankshaft test, the multiaxial bearing test system, the four point rotating bending rig with superimposed torsion and the multiaxial resonance actuator.

Non-stationary signal processing for bearing health monitoring

Signals generated by transient vibrations in rolling bearings due to structural defects are non-stationary in nature, and reflect upon the operation condition of the bearing. Consequently, effective processing of non-stationary signals is critical to bearing health monitoring. This paper presents a comparative study of four representative time-frequency analysis techniques commonly employed for non-stationary signal processing. The analytical framework of the short-time Fourier transform, wavelet transform, wavelet packet transform, and Hilbert-Huang transform are first presented. The effectiveness of each technique in detecting transient features from a time-varying signal is then examined, using an analytically formulated test signal. Subsequently, the performance of each technique is experimentally evaluated, using realistic vibration signals measured from a bearing test system. The results demonstrate that selecting appropriate signal processing technique can significantly affect defect identification and consequently, improve the reliability of bearing health monitoring.