Air-coupled ultrasonic NDE of bonded aluminum lap joints

Theoretical and Experimental Investigations of Transmission Coefficients of Longitudinal Waves through Metal Plates Immersed in Air for Uses of Air Coupled Ultrasounds

“…So many applications for the Lamb wave transductions using the airborne ultrasounds were reported. Acoustic anisotropy measurements of various kinds of thin plates, 11) lap-joint qualities of adhesive aluminum plates, 12) plate thickness measurements using the Lamb wave dispersion-relations, 13) moisture-content estimations in polymer materials using the attenuation factors of the A 0 -mode Lamb waves, 14) thickness measurements of Al plates 15) and delamination detections in CFRP plates 16) were, respectively, carried out. Very interesting way to use the zero group velocity (but finite phase velocity) region of the S 1 -mode Lamb wave was proposed for efficient defect detection in plates.…”

Air-coupled ultrasonic through-transmission thickness measurements of steel plates

“…Some examples of materials studied by air-coupled ultrasound include plant leaves [15], wood products [16], Plexiglass [17], drug tablets [18], stacked cylindrical spaghetti rods [19], textile materials [20,21], composite laminates [22], fibre reinforced plastics [23], polymers [23,24,25], paper [26,27], food products [28,29], and aluminium [30,31]. Most of the materials listed here can be described as soft, having much lower characteristic acoustic impedance than steel.…”

“…In addition to being used on a wide variety of materials, air-coupled ultrasound has also been used for miscellaneous applications, such as imaging, defect detection [30], and disbonding detection in multilayer materials [31]. The transmitting and receiving of the ultrasonic waves have also been done using a variety of transduction methods, e.g.…”

<title>Air-coupled ultrasonic measurements in composites</title>

“…Recent improvements in instrumentation and also in air-coupled transducer design have been made, thus allowing electrostatic transducers to be used for the generation and detection of waves in solid plates [18]. Applications of these transducers have been seen in ultrasonic testing of metals [19], adhesively bonded multilayered structures [20] and bonded aluminum lap joints [21] and in through transmission using broadband pulses. Applications in NDE of green-state ceramic structures [22] at elevated temparatures and the classification of fluids in steel vessels [23], have also been reported.…”