Dynamics modelling for deep groove ball bearings with local faults based on coupled and segmented displacement excitation

As the important load-carrying components, rolling bearings are prone to failure, it is necessary to reveal their fault mechanism. According to the Hertz contact theory and Newton's second law, a novel dynamic model of faulty deep groove ball bearing is proposed by considering the integrated effects (coupling and segmentation effects) based on the half-sine displacement impact excitation function. The proposed dynamic model provides more accurate description of the generated displacement impact excitation when the bearing suffers from a local surface fault. The contact force response at the failure position and its bilateral positions can generate obvious impacts simultaneously when the coupled effect of rolling elements has been taken into account, which make the peak value of optimized acceleration response increase to near three times of that computed by the traditional half-sin fault bearing dynamic model. There are prominent and symmetric impulses repetitively occurring in the Y-direction acceleration response when the coupled and segmented effects of rolling elements have been simultaneously considered in the dynamic model. The acceleration response of the proposed model more accords with the actual situation and has more obvious impulsive feature than traditional model, especially when the bearing has a minor damage. The influences of rotational speed and fault size of bearing have been described as two optimized parameters a and b. Finally, the proposed dynamic model is validated by the experimental data and Harris's method, and compared with the traditional model. The simulated and experimental results indicate that the proposed model would achieve more appropriate and accurate dynamic simulation analysis of the faulty bearings.