Prediction on wear of a spur gearbox by on-line wear debris concentration monitoring

•Debris concentration was modeled considering time-varying wear coefficient.•A full-life gear wear monitoring was performed by on-line visual ferrograph.•Gear wear can be tracked, and early signs of abnormal wear can be captured.•Predicting gear wear by oil debris concentration monitoring was proposed.

The aim of this work is to develop a method for quantifying and predicting gear wear based on on-line wear monitoring. A model of wear debris concentration has been built based on Kragelsky's method with different wear coefficients in corresponding wear stages. A gear test rig with oil-bath lubrication for accelerated wear test was built, and a full-life wear monitoring test was performed by employing an on-line visual ferrograph (OLVF). An index of particle coverage area (IPCA) characterizing wear debris concentration and an OLVF ferrogram were obtained by sampling in-use oil every 2 min. The experiment results indicate that the IPCA curve is consistent with the proposed model, and the early-warning signs of abnormalities can also be observed. Additionally, depositing experiments show that appropriate depositing time (usually not less than 30 s) is crucial for a valid OLVF sampling. Therefore, it is feasible to predict gear wear by on-line wear debris concentration monitoring.