The use of acoustic emission for bearing condition monitoring

Abstract

This paper reports research currently in progress at Swansea University in collaboration with SKF Engineering & Research Centre as part of a continuing investigation into high frequency Acoustic Emission. The primary concerns are experimentally producing subsurface cracks, the type of which would occur in a service failure of a ball bearing, within a steel ball and to closely monitor the properties of this AE from crack initiation to the formation of a ball on the ball surface. It is worth noting that there is evidence that the frequency content of the AE changes during this period, although this has yet to be proved consistent or even fully explained. Conclusive evidence could lead to a system which detects such cracks in a bearing operating in real life conditions, advantageous for many reasons including safety, downtime and maintenance and associated costs. The results from two experimental procedures are presented, one of which loads a single ball held stationary in a test rig to induce subsurface cracks, which are in turn detected by a pair of broadband AE sensors and recorded via a Labview based software system. This approach not only allows detailed analysis of the AE waveforms but also approximate AE source location from the time difference between two sensors. The second experimental procedure details an adaptation of a four-ball lubricant tester in an attempt to produce naturally occurring subsurface cracks from rolling contact whilst minimising the AE arising from surface wear. This thought behind this experiment is reinforced with 3D computational modelling of the rotating system. Nomenclature p 0YYield-inducing contact pressure p 0Maximum contact pressure σ Y Yield stress P Normal load E* Effective Young's modulus between two objects in contact R Effective radius between two objects in contact a Radius of (assumed circular) area formed by two objects in contact IntroductionDetecting a defect within a bearing component before it is causes significant damage to the component, bearing or secondary damage to the associated equipment would be a significant goal for many of those involved in condition monitoring. To achieve this it is necessary to identify the subsurface cracking which occurs before a spall has formed on the surface of a component, and Acoustic Emission (AE) provides evidence that this could become a reality once a greater understanding of the associated phenomena is gained [1]. Several research programs find relationships between statistical analysis of the AE and, for example, defect sizes, but this often involves 'seeding' defects onto a bearing component, producing AE which would only occur once a component was in unacceptable condition [2,3]. The current research programme centres around experimental and computational analysis of the high frequency AE arising from rolling contact test performed with a standard four-ball lubricant tester. This piece of equipment has been used in similar research programs and is justified for the application due to its ability to simulate roll...

Numerical approach to absolute calibration of piezoelectric acoustic emission sensors using multiphysics simulations

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Determination of rolling element bearing condition via acoustic emission

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Perspectives on railway axle bearing condition monitoring

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