Modelling roller bearing dynamics inducing instantaneous angular speed variations

Abstract

Modelling the dynamics of roller element bearings has been used to explain the interactions between localized faults and their impact on the measurable quantities representing the dynamic behavior of the system e.g. acceleration. Most part of the models describes the non-linear contact of roller bearing normal forces by means of Hertz Theory. Recently, analysis of the Instantaneous Angular Speed (IAS) has been proven to effectively detect bearing mechanical faults and it has shown to be an advantageous tool for non-stationary machinery surveillance. Mechanical analysis implies that rotating speed variations are due to torque variations. However, the phenomena describing how dynamic interaction of bearing components induces tangential forces generating angular periodic disturbances to the shaft speed, have not been discussed at all. In this work an original formulation to induce tangential forces to the shaft due to the bearing components dynamics is presented. The roller bearing model is based on Hertzian contact, localized faults can be added and the analysis is suitable for simulation of non-stationary conditions.