Damage visualization of pipeline structures using laser-induced ultrasonic waves

In this study, a noncontact non-destructive testing method is implemented to visualize damages of a pipeline structure. An ND:YAG pulsed laser system was used to generate guided waves and a galvanometer-based laser scanner scans a specific area to find damage location. The wave responses were measured using a piezoelectric sensor attached to the pipeline. The measured time and spatial responses were transformed to data in frequency and wavenumber domains through three-dimensional Fourier transform. Damage-sensitive features could be obtained using wavenumber filter to extract standing wave energy. A flaw imaging technique of the pipeline structure was conducted by calculating root mean square. Notches and thickness reduction at a pipeline structure were investigated to verify the effectiveness and the robustness of the proposed non-destructive testing approach. Additionally, a series of experiments were repeated under heating condition to consider the real-world pipeline structures.