Observations and Location of Acoustic Emissions for a Naturally Degrading Rolling Element Thrust Bearing

Abstract

Acoustic Emission (AE) technology applied to condition monitoring is gaining acceptance as a useful complimentary tool. This article demonstrates the use of traditional AE parameters, the Enegry Index and Kolmogorov-Smirnov test (KS-test) to detect, locate, and monitor natural defect initiation and propagation in a conventional rolling element thrust bearing. To undertake this task a special purpose test-rig was built to allow for accelerated natural degradation of a bearing race. It is concluded that sub-surface initiation and subsequent crack propagation can be detected using a range of data analysis techniques on AE's generated from natural degrading bearings. The article also investigates the source characterization on AE signals associated with such a bearing while in operation.

Assessment of natural crack initiation and its propagation in slow speed bearings

“…The thrust shaft was driven by a hydraulic cylinder (Hi-Force HYDRAULICS- Under normal conditions of load, rotational speed and good alignment, surface damage begins with small cracks, located between the surface of the flat track and the rolling elements, which gradually propagate to the surface generating detectable AE signals. Elforjani et al [10] employed the following theories to determine the test duration to the onset of surface fatigue: Hertizan theory for determining surface stresses and deformations [11], Thomas and Hoersh theory for sub-surface stress [11], and, the Lundberg and Palmgren theory for fatigue evaluation [12]. For the grooved race the standard procedure for determining dynamic load rating, as described by BS (British Standards Documents) 5512; 1991, was employed.…”

Use of Spectral Kurtosis for Improving Signal to Noise Ratio of Acoustic Emission Signal from Defective Bearings

“…Despite of the success of vibration-based methodologies, over the last decades bearing condition monitoring techniques based on Acoustic Emission (AE) have become very popular [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31]. AE has demonstrated to be a very powerful tool for fault detection and diagnosis particularly in bearings, and some recent studies [13; 32; 33] reported that AE can be more sensitive in detecting incipient faults in bearings over other methodologies based on vibration data.…”

Natural mechanical degradation measurements in slow speed bearings

“…Under normal conditions of load, rotational speed and good alignment, surface damage begins with small cracks, located between the surface of the flat track and the rolling elements, which gradually propagate to the surface generating detectable AE signals. The procedure employed to determine the test duration to the onset of surface fatigue has been previously described by Elforjani et al [10] and involved the Hertizan theory for determining surface stresses and deformations [11], Thomas and Hoersh theory for sub-surface stress [11], and, the Lundberg and Palmgren theory for fatigue evaluation [12].…”