Vibration model of rolling element bearings with inner race faults considering impact force

Bearing dynamic modeling is an important mean to understand its fault mechanism, it is the theoretical foundation and the key link of fault diagnosis of rolling element bearings. In order to predict rolling bearings' vibration characteristics correctly, based on Hertz contact theory, a 3-DOF dynamic model for rolling element bearings with inner race faults considering impact force was developed, and the contact between inner race and shaft and the contact between outer race and housing were simplified as spring-damper connections. The contacts between rolling elements and races were simplified as springs. The impact force related to rotating speed was in troduced into the dynamic model as a motion parameter. The formula for impact force containing the parameter rotating speed was derived. The numerical solution to the non-linear vibration equation was obtained using Runge-Kutta method. The numerical results for 6204 deep groove type ball bearings with inner race faults were obtained with the proposed model and compared with test results. The results showed that the proposed dynamic model considering impact force can be used to effectively predict fault frequencies and amplitudes for rolling element bearings' fault vibration signals.