What type of peak is typically observed with a defect on the outer race of a bearing?

In vibration analysis, defects in rolling element bearings, such as those located on the outer race, typically produce non-synchronous peaks in the frequency spectrum. This is due to the nature of how these defects interact with the moving components of the bearing.

When a defect exists on the outer race, the rolling elements (such as balls or rollers) strike the damaged area of the raceway as they rotate. This causes an impact that generates vibration. Since these impacts occur at irregular intervals and are not directly tied to the rotation of the shaft, the resulting peak is classified as non-synchronous.

In this specific scenario, the absence of sidebands accompanying the non-synchronous peak suggests that the defect is not significantly modulating the frequency component of the signal. Sidebands typically arise when there is some form of modulation or influence on the rotation frequency, often seen when there is a defect that consistently interrupts the normal rhythm of the component's operation. Therefore, the clean non-synchronous peak without sidebands indicates a relatively straightforward impact response to the defect, characteristic of an outer race failure.