Crack Localization in Operating Rotors Based on Multivariate Higher Order Dynamic Mode Decomposition

Abstract

A novel output-only crack localization method is proposed for operating rotors based on an enhanced higher-order dynamic mode decomposition (HODMD), in which the nonlinear breathing crack-induced super-harmonic characteristic components from multiple vibration measurement points are simultaneously extracted to compose the corresponding super-harmonic transmissibility damage indexes. Firstly, the theoretical background of the HODMD is briefly reviewed. Secondly, the proposed crack localization method is dedicated which improving the HODMD for multivariate signals by casting the total least square method into standard HODMD and adaptively selecting the order parameter of Koopman approximation by optimizing the super-harmonic frequency vector. In addition, the super-harmonic characteristic components are evaluated and harnessed to derive the damage index based on super-harmonic transmissibility and fractal dimension. Finally, the proposed method is investigated and demonstrated by numerical simulations and experiments. Both numerical and experimental results show that the proposed method is powerful in realizing multi-crack localization for running rotors accurately and robustly in the case of no baseline information on intact rotors. Moreover, the interferences from commonly existing steps and misalignment can also be eliminated.

An algorithm for localization of fatigue crack in spinning rotor based on proof by negation

“…Identification of cracks in structural and spinning members attracts consistent research, and newer algorithms and methods keep appearing in the literature. For the identification and localization of cracks in rotors, multivariate higher-order dynamic mode decomposition has been successfully attempted by Lu et al [18]. The proposed methodology is quite signal-noise-aware.…”