In Situ Diagnosis of a Gear-Tooth Surface Damage Using Laser Scattering

We propose herein an in situ method to remotely diagnose gear-tooth damage using scattering of a laser beam. The proposed method provides early and accurate diagnosis of the gear-tooth-surface condition. A tooth surface is first irradiated at oblique incidence by a zone-covering laser beam, and the zone is scanned along the surface of the gear tooth by the rotation of the gear. By analyzing variations in laser scattering between benchmark data and the current data, we can estimate the condition of the gear-tooth surface in terms of abnormal abrasion, pitting, spalling, etc. To test the method, we used it to remotely detect gear-teeth pitting in an experiment during which we simultaneously measured the vibration and sound of the gearbox and pedestal. Our analysis shows that the laser-scattering measurements reveal pitting more clearly and at an earlier stage than does the vibration and noise measurements. Therefore, we conclude that the proposed method estimates the tooth-surface condition with sufficient accuracy to assess the lifetime of the gear. Furthermore, we used the proposed method to diagnose real gear-teeth in situ in practical gearboxes to verify that the method yields an accurate diagnosis of the tooth surface of a lubricated gear. We found that by attaching a cover to the laser receiver; the remote measurements were unaffected by the choice or method of lubrication. For force-feed lubrication, pitting was detected for every speed range under 1800 rpm. These results demonstrate that the proposed method can diagnose the tooth surface of lubricated gears in practical gearboxes. Finally, we developed an automatic damage diagnosis method that is capable of detecting pitting by analyzing the laser-scattering signal from damaged teeth combined with that from the same teeth prior to the damage.