Diagnosis of bearings by novel non-linear non-stationary higher order spectra

A study was conducted to implement and experimentally validate the non-linear non-stationary wavelet bicoherence (WB) technology for the detection of local fatigue defects in rolling bearings by vibration measurements. The SKF bearing test-rig had a coupled variable speed drive (VSD) motor driving a shaft supported on three identical bearings. Tests were carried out at 60 Hz frequency and 196 N radial load for the investigations under the study. Vibration signals were captured from two unidirectional accelerometers placed along the horizontal and vertical directions on the test bearing housing. The captured vibration signals for no-defect and inner race (IR) defect cases were first re-sampled in the angular domain using a speed reference signal. The re-sampled signal was segmented into periods, and training and testing sequence signals were formed.