Damage Identification in Thick Steel Beam Based on Guided Ultrasonic Waves

Most current studies of guided-wave-based damage detection have been conducted on thin plate-like structures. This article presents a study of damage identification based on activated ultrasonic waves in a thick steel beam. The diagnosis procedure, with key parameters such as excitation frequency and cycle number of the diagnostic waveform, is elaborated in relation to beam dimension as well as pulse-echo/pitch-catch configurations of PZT active sensors attached to the beam. Finite element simulation was conducted to characterize wave propagation in the beam, and the signals of wave propagation were experimentally measured; the results show good agreement with outcomes of the simulation. To aid damage identification, the group velocity of the guided wave was calculated using the envelope of the signal, which was obtained by Hilbert transform. The results for damage location and severity assessment demonstrate that the guided-wave-based damage identification approach can also be applied to certain thick structures for the purpose of structural health monitoring.