Low speed bearings’ instantaneous angular speed behavior

Abstract

This work describes shaft’s Instantaneous Angular Speed (IAS) behavior in the presence of a spall on bearing’s race at low speeds. It is shown that fault signature becomes more apparent in IAS signal when speed decreases and load increases. EEMD processing of the signal is implemented to overcome the shortcoming of IAS sensitivity at low loading conditions. IAS behaviour while passing through the spall perform three different variation stages: Speed increase (entrance moment) caused by the instantaneous loss of contact pressure, a speed sharp decrease when the rolling element hits the spall edge and finally speed recuperation phase (exit moment) and system’s dynamical response to impact. It is considered that the number of angular samples between the entrance and exit moments defines the fault size. Different fault sizes at different speeds (<60 rpm) were tested and its estimation was satisfactory which is the first step for a successful bearing prognosis.