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.