Monitoring and Life Assessment of the Gearbox

This MSc. thesis has been carried out at the university Politecnico di Torino. As, early failure detection has been an integral part of condition monitoring of critical systems, such as wind turbines, helicopter rotor drivetrains etc. On many occasions, driveline components fail catastrophically, leaving no evidence of the root cause of failure and causing extensive damage to test equipment. This can be avoided by detecting failure in early stages. Most of failure detection techniques are based on oil debris monitoring of gears. The objective of this thesis is to find a correlation between oil debris amount, caused by two phenomena wear or pitting and failure mechanism. This task has been divided into two parts. The aim of the first part is to find correlation between debris amount and wear, whereas the aim of the second part is to find correlation between debris amount and pitting, so the mathematical model that has to be developed is the correlation between number of cycles to failure (so the starting events for the production of debris) and the contact stress. As each engagement reduces the life of the teeth, when the damage factor is equal to one, the possibility to have debris is reached. If debris comes earlier than this number of cycles, the debris is surely caused by the wear, if not, it is related principally to the rolling contact fatigue, so pitting. The aim of mathematical model is to compute the number of cycles to failure for pitting and this has been implemented by using Matlab code, where the task is to find the maximum damage factor that a contact path along the mesh cycle generates in a tooth.