Fault Simulation in a Gearbox Using Finite Element Model Reduction Techniques

Abstract

AbstractA lumped parameter model (LPM) has previously been used to model gear and bearing faults in a gearbox. It was found that simulated signals for localized bearing faults had good correspondence with measured ones in a narrow high frequency band demodulated for envelope analysis. However, for extended faults, there is more interaction with the gearbox structure, as the fault modulates the gear meshing, and the correspondence was poorer. Forces at the bearings from the LPM model were applied to a finite element (FE) model of the casing, and the results improved but were still deficient. This paper has benefited from CMS (component mode synthesis) based FE model reduction techniques to reduce the FE model of a gearbox casing into manageable and well representative degrees of freedom of the casing. The reduced model of the casing was embedded with the LPM of the internals, which was previously obtained with the aid of Simulink® and has the capability of capturing time-varying stiffness nonlinearities arising from gears and bearings and has also the capability of simulating geometrical faults (spalls) for both gears and bearings. In order to extend the validity of the combined /reduced model, the forces are extracted from combined/reduced model and convolved with the impulse responses corresponding to the FRFs of the whole gearbox. The results show the improvements obtained through combining the reduced model of the casing with the LPM model giving a much better correspondence with measured signals. This has been verified for both the fault free and faulty cases.KeywordsImpulse ResponseLump Parameter ModelFault SimulationGear MeshingBearing FaultThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.