Global Crack Detection using Bispectral Analysis

C R P Courtney, Bruce Drinkwater, Simon Neild, Paul Wilcox

Research output: Contribution to conferencePaperpeer-review

92 Citations (SciVal)


A global non-destructive testing technique for detecting cracks in engineering parts has been developed. The technique uses the bispectrum to analyse the mixing of two ultrasonic sinusoidal waves in a sample. The bispectrum’s insensitivity to noise allows more sensitive detection of mixing signals than the power spectrum. Two sinusoidal signals are generated by signal generators, amplified and applied to a piezo-ceramic disk bonded to a sample. The sample is excited at very-high-order modes of vibration. The response of the sample is measured by a second piezoceramic disk and the received signal analysed using the bispectrum signalprocessing technique. Frequency mixing occurs as a result of the non-linear behaviour of cracks in the structure. Experiments with fatigue-cracked steel beams demonstrate that fatigue cracks produce a strong mixing effect and that the bispectrum signal relating to the frequency mixing is sensitive to the length of the crack; allowing the quantification of the crack length. Progress is being made in applying the technique to more practical situations: the sensitivity of the technique to transducer position and the input signal parameters (frequency and amplitude) is quantified experimentally.
Original languageEnglish
Publication statusPublished - 2006
Event9th European Conference on NDT - Berlin, Germany
Duration: 25 Sept 200629 Sept 2006


Conference9th European Conference on NDT


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