A Numerical Analysis of Internal Radial Clearances on Affecting Vibration of Rolling Element Bearings with Local Defects

Rolling element bearing is an essential component in rotating machines and its condition monitoring has attracted much concern in past decades. Bearing vibration response analysis will provide theoretical basis for fault diagnosis and maintenance of the machinery. In view of bearing usually go through various wear during operating process, resulting in increase of clearance, this paper presents a nonlinear bearing vibration model of deep groove ball bearings to explore the vibration responses affected by bearing internal radial clearance, rotational speed and external load, as well as the diagnosis features for condition monitoring. A nonlinear dynamic model with six degrees of freedom was established at first. Then, numerical simulation was implemented. Lastly, a comprehensive analysis from time domain and frequency domain were carried out based on statistical indicators and spectra. Numerical results show that information from frequency domain outperforms statistical indicators from time domain for bearing clearance monitoring. To bearings with local defects on outer and inner races, the ball pass frequency of outer race (BPFO) and ball pass frequency of inner race (BPFI) shows uptrends with the increase of bearing clearances in general, respectively. However, there are fluctuates in BPFI for inner race fault, which needs special care in fault detection. Besides, spectral centroid has better performance on monitoring clearances of bearing with local defects. All these findings provide theory and data support for bearing fault diagnosis at an early stage.