Damage Inspection of Structures by Space-Wavenumber and TimeFrequency Analyses

Abstract

This paper presents dynamics characterization and damage inspection of structures by using a boundary-effect evaluation method (BEEM) to perform spacewavenumber analysis of operational deflection shapes (ODSs) and a conjugate-pair decomposition (CPD) method to perform time-frequency analysis of dynamic responses of some structural points to a harmonic excitation. BEEM is for locating and estimating small structural damage by processing ODSs measured by a fullfield measurement system (e.g., a scanning laser vibrometer or a camera-based motion measurement system). BEEM is a nondestructive spatial-domain method based on area-by-area processing of ODSs and it works without using any structural model or historical data for comparison. CPD uses adaptive windowed regular harmonics and function orthogonality to perform time-frequency analysis of time traces by extracting time-localized regular and/or distorted harmonics. Both BEEM and CPD are methods for local spectral analysis based on local, adaptive curve fitting. Numerical simulations and experimental results show that the combination of BEEM and CPD for space-wavenumber and time-frequency analyses provides an accurate tool for damage inspection of thin-walled structures.