Air-coupled, focused ultrasonic dispersion spectrum reconstruction in plates

Air-coupled Ultrasonic Testing of Materials

NDE Applications of Air-Coupled Ultrasonic Transducers

Abslract In recent years, several new NDE applications of air-coupled, as opposed to liquid-coupled, ultrasonics have been seriously pursued. The applications range from throughtransmission testing of aerospace laminates and various honeycomb or foam filled materials, and solar cells, to pulseecho flaw detection in plastic electronic packaging materials and in-line inspection of large-diameter ...

Air-coupled microphone measurements of guided waves in concrete plates

Quality control and quality assurance of pavements is today primarily based on core samples. Air void content and pavement thickness are parameters that are evaluated. However, no parameter connected to the stiffness is evaluated. There is a need for fast and reliable test methods that are truly non-destructive in order to achieve an effective quality control and quality assurance of pavements....

Reconstruction of Rayleigh-Lamb dispersion spectrum based on noise obtained from an air-jet forcing.

The time-domain cross correlation of incoherent and random noise recorded by a series of passive sensors contains the impulse response of the medium between these sensors. By using noise generated by a can of compressed air sprayed on the surface of a plexiglass plate, we are able to reconstruct not only the time of flight but the whole wave forms between the sensors. From the reconstruction of...

Air coupled ultrasonic detection of surface defects in food cans

In this paper we describe an ultrasonic inspection system used for detection of surface defects in food cans. The system operates in pulse-echo mode and analyzes the 220 kHz ultrasonic signal backscattered by the object. The classification of samples into valid or defective is achieved with χ statistics and the k-nearest neighbour method, applied to features computed from the envelope of the ul...