Detection and diagnosis of gear-tooth pitting damage by the Average-Log-Ratio ALR algorithm

•Gear tooth pitting detected by Average-Log-Ratio (ALR)•Pit size governs rotational-harmonic amplitudes.•Use of ALR eliminates transmission path effects. Computation of the Average-Log-Ratio (ALR) gear-damage detection algorithm is carried out using accelerometer recordings of the vibration response from a spur-gear-pair pitting test. ALR computed from gear rotational-harmonic amplitudes up to the fifth tooth-meshing harmonic shows monotonically increasing ALR with increasing pitting damage. ALR computations using rotational-harmonic amplitudes between adjacent tooth-meshing harmonics show maximum ALR values moving to lower rotational- harmonic ranges with increasing radial pit size, in agreement with an earlier-derived analytical relationship between radial pit size and transmission-error rotational-harmonic amplitudes. The final rotational-harmonic range with maximum ALR value is in good agreement with that predicted analytically from the observed final pit size, thereby providing additional experimental confirmation of this analytically derived relationship.