Which of the following indicates a problem with the inner race when analyzing vibration spectra?

The presence of a peak in the vibration spectrum accompanied by shaft rate sidebands is indicative of an issue with the inner race of a bearing. This specific pattern occurs due to the way vibrations are transmitted through the bearing components. When there is a fault in the inner race, it affects the load distribution and the contact between the rolling elements and the raceway, leading to repetitive impacts as each rolling element passes over the defect.

This interaction creates vibrations that are modulated by the rotational speed of the shaft, which is reflected in the spectrum as a peak at the fault frequency with sidebands spaced at the shaft speed. The sidebands represent the modulation of the vibration signal due to this repetitive impact, helping to confirm that the root cause of the vibrations is indeed a problem with the inner race.

In contrast, a flat peak may indicate general noise or less specific issues, while a peak without sidebands could suggest a steady-state condition that is not characteristic of bearing faults. Harmonic sidebands might suggest different types of faults or resonances, which are not specific to inner race problems. Understanding how the spectrum is affected by different failure modes is key in accurately diagnosing bearing issues.