Lamb wave generation using nanosecond laser ablation to detect damage

This paper proposes a non-contact damage detection method based on Lamb waves generated by laser ablation (LA). Previously, Lamb waves generated by contact-type sensors such as acoustic emission or piezoelectric zirconate titanate devices have been studied to detect damage. Lamb wave generation systems with embedded contact-type excitation devices to objective structures to be inspected may quickly realize large-area damage detection on a huge object such as an aircraft. However, replacing contact-type devices with non-contact devices in Lamb wave generation systems, the systems will have sufficient potential to excite under the specific conditions such as submerged target structures in liquid and high-temperature substances. The LA-generated Lamb waves that have amplitudes several hundred times larger than those generated by conventional laser-thermoelastically generated Lamb waves are of advantage from the viewpoint of the signal-to-noise ratio in the measurements. When the laser fluence reaches 1012–10...