If a defect is present in the balls (or rollers) of a bearing, what pattern would you see in the vibration data?

When there is a defect in the balls or rollers of a bearing, the vibration data will typically display a non-synchronous peak along with cage rate sidebands. This is indicative of a fault condition where the rolling elements impact the inner or outer race in a periodic manner.

The principal frequency associated with such defects is tied to the ball pass frequency, which is influenced by the speed of the shaft and the geometry of the bearing. This non-synchronous peak reflects the irregularities created by the defect. Additionally, the presence of sidebands at the cage frequency indicates that the cage is also contributing to the vibration patterns due to its motion around the bearing.

This relationship highlights the complex dynamics within the bearing where any flaw leads to measurable changes in vibrational characteristics. Monitoring these vibrations allows for early detection and maintenance actions, preventing further damage.