A Fiber Bragg Grating-Based Measurement Method for Outer-Ring Fault Detection in Rolling Bearings

A fiber Bragg grating (FBG)-based measurement method is proposed for outer-ring fault detection in rolling bearings. To acquire fault-related responses in a near-source manner, a circumferential groove was machined on the bearing outer ring, and an FBG sensor was embedded and bonded to directly measure the dynamic strain of the outer ring. The acquired strain signal was first decomposed using local mean decomposition (LMD), and the product function components were selected for reconstruction according to a correlation coefficient-kurtosis weighted criterion. Maximum correlated kurtosis deconvolution (MCKD) was then applied to enhance the weak periodic impulsive components associated with the outer-ring fault. Experiments were conducted on an NJ205EM cylindrical roller bearing with an artificial outer-ring defect at a rotational speed of 600 r/min and a sampling frequency of 8 kHz. The results show that the raw FBG signal contains the outer-ring fault characteristic frequency, but the fault-related component is weak and easily affected by surrounding spectral components. After LMD-MCKD processing, the fault characteristic frequency and its harmonics become more distinguishable in the envelope spectrum. A comparison with the conventional minimum entropy deconvolution (MED) method further confirms the effectiveness of the proposed method. The fault feature amplitude ratio and the corresponding local signal-to-noise ratio increase from 12.257 and 21.767 dB for MED to 16.985 and 24.555 dB for the proposed LMD-MCKD method, respectively. These results demonstrate that the proposed FBG-based near-source strain measurement combined with LMD-MCKD processing provides an effective approach for weak outer-ring fault detection in rolling bearings.