Application of Synchronous Averaging for Detecting Defects of a Gearbox

Condition monitoring of gearboxes in industrial settings is often based on trending vibration levels at gearmesh frequencies and sideband frequencies associated with matting shaft rotational speeds. However, it is debated on the vibration levels for setting different alarms related to the gearbox health. Another issue of controversy is what an indicator of fault severity; is it energy in gearmesh frequencies or the energies in sidebands. In this work, we analyzed vibration signature caused by gear tooth seeded faults of different levels. The data are analyzed in both time and frequency domains. The experimental study is conducted on a Machinery Fault Simulator ™ (MFS). The pinion gear in the gearbox is intentionally faulted with increasing severities, and vibration signal was collected for each case using IEPE accelerometers. Data are also obtained using a high-resolution encoder. Signals are analyzed using time synchronous averaging and traditional spectrum analysis. The results indicate that the vibration signature of a faulted bevel gear tooth is a pulse in time domain. Because of this impulse signal, strong sidebands arise in the spectrum around the mesh frequency. And the energy inside bands are better indicator of tooth defect severity.