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Research Papers: Friction & Wear

# Condition Monitoring of Molybdenum Disulphide Coated Thrust Ball Bearings Using Time-Frequency Signal Analysis

[+] Author and Article Information
Ali Kahirdeh

Department of Mechanical Engineering, Louisiana State University, 2058 Patrick Taylor Hall, Baton Rouge, LA 70803

M. M. Khonsari1

Department of Mechanical Engineering, Louisiana State University, 2058 Patrick Taylor Hall, Baton Rouge, LA 70803khonsari@me.lsu.edu

1

Corresponding author.

J. Tribol 132(4), 041606 (Oct 08, 2010) (11 pages) doi:10.1115/1.4002379 History: Received March 29, 2010; Revised August 08, 2010; Published October 08, 2010; Online October 08, 2010

## Abstract

A method for detection of wear in thrust ball bearings coated with molybdenum disulphide $(MoS2)$ is presented. It employs an energy feature obtained from time-frequency representation of the vibration signal. Extensive experimental studies are conducted to verify the efficacy of the proposed method for fault diagnosis of $MoS2$ coating. These experiments are conducted under both oscillatory and unidirectional motions. The results of vibrations are corroborated with the friction coefficient from the onset of the motion until failure develops. Through monitoring of the energy in time-frequency domain as well as the coefficient of friction, three stages of coating life are identified. They are healthy period, developing damage, and failure. It is shown that the energy feature can detect whenever wear and damage appear and solid lubricant loses its lubrication capabilities.

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## Figures

Figure 9

Case 2: (a) Energy in the time-frequency plane. (b) Plot of the coefficient of friction in oscillatory case. Three stages of the healthy period (I), developing damage (II), and failure (III) are detected.

Figure 10

Time domain vibration signal for the first accelerometer

Figure 11

Case 3: (a) Energy in the time-frequency representation of the signal. (b) Plot of the coefficient of friction, oscillatory (0.5 Hz). Five steps of damage developing and failure occurrences are apparent and labeled using roman numerals. Before these steps, MoS2 is operating in healthy period.

Figure 12

Case 4: (a) Energy in the time-frequency representation of the signal. (b) Plot of the coefficient of friction oscillatory (1 Hz). Healthy period (I) and failure occurrences are labeled using roman numerals.

Figure 13

Reduced thickness of MoS2 coating

Figure 14

Case 5: (a) Energy in the time-frequency representation of the signal. (b) Plot of the coefficient of friction oscillatory (1.5 Hz). Healthy period is labeled (I) in energy plot.

Figure 1

Modular architecture for the fault detection system

Figure 2

MoS2 coated thrust ball bearings

Figure 3

Schematic of the LRI-1A tribometer

Figure 4

Three stages of coating life. (a) Fresh MoS2 coated surface. (b) Coated surface after 360 min while bearing is operating in healthy regime. (c) Failure of the coating. The arrows show the debris ejected from the raceway and accumulated on the sides of the raceway.

Figure 5

Case 1: (a) Energy in the time-frequency plane. (b) Plot of the coefficient of friction unidirectional case. Three stages of healthy period (I), developing damage (II), and failure (III) is apparent.

Figure 6

Case 1: Depleted raceway after the 3000 min

Figure 7

Transfer film on the balls in case 1 after the experiment

Figure 8

Time domain vibration signal

## Errata

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