Effects of machine speed on the development and detection of rolling element bearing faults

This research investigates the effects of a variable machine speed on machine vibration and the implications for bearing fault detection. These effects are important to understand because when ignored they can significantly hinder the ability to detect bearing faults. Experimental results verify that a variable machine speed can directly and nonlinearly alter the level of machine vibration. This is due to differences in mechanical damping and resonance at various machine speeds. While this effect is difficult to notice in healthy machines, it can become significant as bearing health degrades. An additional effect that speed can exert is on the rate of development of a bearing fault. Variations in speed can actually retard or temporarily mask the increase in machine vibration due to a bearing fault. This phenomenon is observed in experimental trials as the bearing fault enters an advanced and more deteriorated stage. This can inadvertently make a machine appear healthy even though a bearing failure is imminent. However, by understanding these effects, a more skillful application of the available condition monitoring tools in variable speed applications is achieved.