Simulation of Vibrations Produced by Localised Faults in Rolling Elements of Bearings in Gearboxes

A combined gear/bearing model has been made to study the interaction between gears and bearings in the presence of faults. The thirty-four degree-of-freedom model of the University of New South Wales (UNSW) gearbox test rig is a lumped mass parameter model, which has the capacity to model different fault types (localised inner/outer race faults and extended faults). This is in addition to its original capacity for modelling spalls and cracks in the gears. The gear/bearing model takes into consideration the slippage in the bearings, the Hertzian contact and the nonlinearity of the bearing stiffness (time variant). Results have earlier been published for simulated local faults in the inner and outer races of the bearings as well as for an extended inner race fault. For a complete modelling of localised faults, the simulation model has now been updated to enable simulating faults in the rolling elements. The modelling of the faults in the rolling elements takes into consideration the difference in race curvature and represents a new contribution to the development of the model. The agreement between the processed simulated and measured signals shows the robustness of the developed model and its suitability for testing new diagnostic and prognostic algorithms.