Fault Diagnosis of Gear with Multiple Defects in Planetary Gearbox

Continuous and prolonged operation of wind turbine results in fatigue loading on its components and subsequently, the planetary gearbox is one among the most susceptible components subjected to failure. The exposure to continuous loading results in multiple faults in the planetary gearbox, such as pitting, tooth breakage and tooth cracks. A combination of these defects will also occur in the planetary gearbox, which this work has considered. The planetary gearbox dynamic modelling is discussed in this work, which consists of a combination of broken tooth defects and cracked tooth defects occurring on sun gear. The lumped-parameter model consisting of three degrees of freedom for each of the central components, which involve one rotation and two translations in its plane of rotation, is discussed. By considering the Hertzian contact stiffness, tooth pair bending, shearing and axial compression stiffness, the potential energy technique is employed to determine the system's vibration signature from the parametric excitation induced by the variable gear mesh stiffness. The broken tooth and crack cause a fall in a localised region's mean stiffness value. Moreover, a broken tooth can result in the mesh stiffness value to zero during the single tooth contact regime. The vibration spectrum of the faulty system for early fault diagnosis is also discussed in this work.