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Ball bearings, one of the most widely used components in rotating machinery, play a critical role in system performance. Localized defects such as pit and spall may develop in ball bearings during service. The vibration waveform of the impulse generated by a ball passing over a defect on the races is determined by the shape and size of the localized defect. Hence, it is important to study the relationship between the localized defect shape and its pulse waveform characteristics in order to diagnose the types of defect in bearings. This study examines the effects of the defect shape, radial load and shaft speed on the pulse waveform characteristics generated by localized defects using the method of explicit dynamic finite element analysis. To validate the proposed model, the results obtained from the experiments have also been provided, and the waveform and the duration of the pulse generated by the defect on the outer race are in good agreement with the simulation results, which shows validation of the proposed model. Both the experimental results and the simulation results have confirmed that the impulse shape generated by the defect on the raceway will be influenced by the contact deformations at the edges of the defect. The results obtained also demonstrate that the explicit dynamic finite element analysis approach can be used to analyze the pulse waveform characteristic generated by localized defects in ball bearings.

Vibration characteristics of a deep groove ball bearing caused by a localized surface defect are greatly affected by defect sizes, such as the length, width, and depth. However, effects of the defect depth, the time-varying contact stiffness between the ball and defect, and the relationship between the time-varying contact stiffness and defect sizes have not been considered in previous defect models. In this work, a new defect model considering a new force–deflection relationship is presented to replace the Hertzian force–deflection relationship to describe the ball-line contact between the ball and defect edge. Both the time-varying displacement impulse and time-varying contact stiffness are considered. The relationship between the time-varying contact stiffness and defect sizes is obtained. Effects of defect sizes on the vibrations of the deep groove ball bearing, especially the defect depth that cannot be described by previous defect models, are investigated. The simulation results are compared with those from the previous defect models. The results show that the model developed can predict a more realistic impulse caused by a localized surface defect for dynamic simulation of the deep groove ball bearing. An experimental investigation is also presented to validate the proposed model.