Experimental Velocity Measurements of the Low-Order Anti-symmetric Lamb Wave Generated-Detected in Metallic Plates Using Air-Coupled Concave Array Transducers

This paper experimentally demonstrates the viability of Lamb waves generation and detection in metallic plates using ultrasonic air-coupled concave array transducers. For this purpose, a self-developed air-coupled Lamb wave NDT system has been used in three different metallic plates, such as stainless steel, copper and brass. First, pure copper plates were used to calibrate the measuring system and then other tests were performed in 304 stainless steel and CW508L brass. The obtained Lamb waves confirm the theoretical values, both in the phase velocity and in the group velocity measurements. In addition, a complete study of the errors in the measurements is also provided.