Guided circumferential waves and their applications in characterizing cracks in annular components

This paper presents a review of recent advances in the study of guided circumferential waves and their applications in characterizing radial cracks in annuluses. The main focus of this research is to develop methodologies that can determine the crack location and size. To locate the crack, a time frequency representation technique (the energy density of the short time Fourier transform or spectrogram) is used to discern the arrival time of a given mode at a given frequency for both the incident and backscattered waves. By calculating the time delay of a specific mode in the spectrogram, the distance between the receiver and the crack can be determined. Thus, the crack is located. For sizing the crack, a time domain counterpart of Auld's formula is derived. By using the time domain Auld's formula, the backscattering energy coefficient can be obtained directly from experimental measurements, as well as calculated from the synthetic, numerical data. By comparing the experimentally obtained and numerically calculated backscattering energy coefficients, the size of the crack can be determined.