The source of Acoustic Emission during meshing of spur gears

Condition monitoring of gears with vibration analysis and Spectrometric Oil Analysis Programs (SOAP) are widely accepted and used in the military aviation industry. Whilst the literature to date has shown the application of the Acoustic Emission (AE) technique to gearbox health monitoring still be in its infancy, there exist opportunities to develop the technique into a complementary diagnostic tool. In developing such a tool, it is imperative that an understanding of the source of AE activity is established. This paper presents experimental results that explore the AE source during a gear mesh and has led to quite unique and significant observations. Keyword: Acoustic Emission, asperity contact, condition monitoring, gear defect diagnosis, machine health monitoring, rolling friction, sliding friction. Literature reviews Application of vibration analysis to gear fault diagnosis and monitoring has been widely investigated and its usage in industry is well established. This is particularly reflected in the aviation industry where helicopter engines, transmission systems, drive trains and rotor systems have adopted vibration analysis for health monitoring. However, research in the application of AE to gear fault detection and monitoring is limited. The most common failures encountered in operational gearboxes include micro-pitting, pitting, scuffing and abrasive wear. Although tooth fracture and bending fatigue are rare, the criticality of such a failure has drawn huge attention from researchers. In examination of the AE technique on these failure modes, most researchers have opted for simulated pit defects. Singh [1, 2], Tandon [3] and Siores [4] performed their experiments using simulated pits, whilst Toutountzakis [5], Sentoku [6] and Miyachika [7] allowed natural defects such as pitting to occur during the tests. The conclusion drawn from all these experiments were encouraging; AE technique was able to detect both seeded and natural defects. Among these researchers, only Toutountzakis and Sentoku employed a slip ring to transmit the AE data from the rotating AE sensor to the acquisition systems, thereby offering a direct transmission path. Others mounted their AE sensors on the bearing or gearbox casing and, claimed successful identification of defective gears. The papers reviewed have illustrated the potential and viability of the AE technique in becoming a useful diagnostic tool in condition monitoring of gears. However, none have DGZfP-Proceedings BB 90-CD Lecture 46 EWGAE 2004 470 investigated the source of AE activity during the gear mesh. An understanding of the fundamental AE source mechanism in meshing gears is of vital importance in developing this technique. Observation of AE bursts during gear mesh AE data was recorded during simulated defect gear tests. An interesting observation was the AE transients associated with the gear mesh. With a sampling rate of 10 MHz and rotational speed of approximately 742 rpm, only 16 meshing teeth signatures were recorded per acquisition window. Figure 1 shows the time domain of an AE signature recorded during the tests under two different load conditions clearly showing the AE transient response associated with gear meshing of 16 teeth. This AE transient response led the authors to investigate the possible source of AE activity due to the meshing gear. The results presented were acquired from the AE sensor mounted on the pinion wheel and AE data was captured with a commercial data acquisition card (PAC) via a slip ring. 0 0.005 0.01 0.015 0.02 0.025 -0.1 -0.05 0 0.05 0.1