This paper presents damage detection in thick steel plates by using guided ultrasonic waves and non-contact laser vibrometry. Guided waves are generated by piezoelectric transducers (PZT). A scanning laser Doppler vibrometer is used to measure the full velocity wavefield of guided waves in the plate, based on the Doppler Effect. The measured full wavefield in terms of time and space contains a wealth of information regarding guided wave propagation in the plate as well as guided wave interaction with damage. Through wavefield analysis, the cumulative energy map of damage induced waves is derived for damage detection and quantification. For the proof of concept, an experiment is performed on a 1/4 inch steel plate with three surface defects of different sizes and shapes. The detection result shows that the locations and sizes of high energy areas in the cumulative energy map agree well with those of the actual defects. Overall the method presented in this paper using guided waves and non-contact laser vibrometry is effective to detect and quantify location, size and shape of damage in thick steel plates.
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