An investigation of diagnostic techniques for rolling element bearings under conditions of poor signal to noise ratio and multiple element faults

This thesis proposes two techniques for the diagnosis of faults in rolling elementbearings. One of these techniques is based on the autocorrelation analysis and the otheris based on the time synchronous averaging analysis. These techniques are developed totackle some common problems encountered in the use of the traditional envelope spectraltechnique for the analysis of bearing faults. The autocorrelation techniques areproposed for cases in which the defect harmonics and their associated modulation sidebandsare intertwined. Such cases may occur when diagnosing inner race and rollingelement faults, especially under poor signal to noise ratio conditions. The sync-periodfrequency analysis technique is aimed at cases where multiple faults coexist in differentelements of a bearing under conditions of poor signal to noise ratio. Theoretical aspectsof these two techniques are addressed in detail. Using these techniques, experimentalinvestigations with both synthetically generated data and rig-test data are performed.Comparisons between proposed methods and the traditional envelope spectral methodare presented throughout all chapters of this thesis.The investigation has demonstrated that the autocorrelation analysis techniquesare effective tools for the diagnosis of inner race and rolling element faults and aresuperior to the envelope spectral technique for low signal to noise ratio conditions. Thesync-period frequency analysis technique has proven to be a powerful diagnostic methodfor cases where multiple element faults coexist in rolling element bearings