Crack detection of beam-structures based on transient waves

A method for crack detection in beam-structures is developed based on the transient waves under arbitrary external forces. Massless rotational springs are introduced for modeling cracked sections in a Timoshenko beam, and the wave responses of the perfect and cracked beams are calculated accurately by the reverberation-ray matrix method. Since it is hard to identify cracks from the wave responses directly, the Hilbert-Huang transform is employed to analyze the dynamic results. Numerical examples show that extra wavecrests can be observed from the Hilbert spectrum of the cracked beam when compared with the perfect one. These extra wavecrests are found to be generated by waves scattered from the cracked cross-sections. The location of the crack can then be determined according to the wave speed and possible propagation path.