Online Vibration Monitoring Of Ball Bearing DamageUsing an Experimental Test Rig

Abstract

Rolling element bearings in rotating machinery are vulnerable mechanical components that are prone to premature failure with dire consequences. Early warning of impending bearing failures is vital to the safety and reliability of high-speed turbomachinery. At present, vibration monitoring is one of the most common procedures used to detect online damage and early failure of rolling element bearings. This paper presents results from an experimental rotor-bearing test rig with known induced damage in the supporting ball bearings. Two types of damages are examined, namely, that of 1) the ball rolling element and 2) the inner race of the bearing. Four online vibration signature analyzing schemes are used: 1) time averaging, 2) frequency domain analysis, 3) joint time-frequency analysis (Wigner-Ville and wavelet transforms), and 4) chaotic vibration analysis (modified Poincare diagrams). The results from the various procedures are compared for efficiency in early pinpointing of damage and reliability in the detection. Based on this study, it was found that, in the case of race damage in which interactions with the damage area take place in a periodic manner during shaft rotation, vibration signals resulting from contacts with the damage location can generally be found within a typical window of data sampling, and damage can be identified using all four selected online procedures. For the case of ball-element damage, the vibration signals are chaotic in nature due to the unpredictable rotational patterns of the ball elements. Under such conditions, interactions with the ball-element damage area may not occur within the particular data sampling period, and as a result, damage cannot be detected by the traditional time-frequency procedures. It is also demonstrated that, in this study, the modified Poincare map approach using a relatively large amount of sampling data can be effective in identifying damage in the ball rolling element.