Baseline subtraction technique in the frequency-wavenumber domain for high sensitivity damage detection

Abstract

This paper suggests a method for high-sensitivity damage detection. The method is based on pitch-catch measurements of Lamb waves combined with a baseline subtraction technique in the frequency-wavenumber domain. Small amplitude converted modes, generated during the interaction of propagating waves with damage, can thus be detected with minimal a priori information regarding their expected location in the frequency-wavenumber plane. This method is applied in the present paper to a case of notches with varied depth. Finite element simulations are carried out in the temporal domain to mimic results obtainable in real-world experiments. Two cases are studied, namely when each of the two pure fundamental modes are incident on a notch. The advantages of the method are detailed. The procedure to implement this method is described in the context of Structural Health Monitoring (SHM) or Non-Destructive Testing (NDT).

Keywords: Baseline subtraction; Damage; Frequency–wavenumber domain; Lamb waves; Mode conversion; Spectral leakage.