< Terug naar vorige pagina


The Quasi-Harmonic Ultrasonic Polar Scan for Material Characterization: Experiment and Numerical Modeling

Tijdschriftbijdrage - Tijdschriftartikel

Conventionally, the ultrasonic polar scan (UPS) records the amplitude or time of flight in reflection or transmission using short ultrasonic pulses for a wide range of incidence angles, resulting in a unique fingerprint of the critical bulk wave angles of the material at the insonified spot. Here, we investigate the use of quasi-harmonic ultrasound (bursts) in a polar scan experiment, experimentally as well as numerically. It is shown that the nature of the fingerprint drastically changes, and reveals the positions of the leaky Lamb angles. To compare with experiments, both plane wave and bounded beam simulations have been performed based on the recursive stiffness matrix method. Whereas the plane wave computations yield a pure Lamb wave angle fingerprint, this is no longer valid for the more realistic case of a bounded beam. The experimental recordings are fully supported by the bounded beam simulations. To complement the traditional amplitude measurement, experimental and numerical investigations have been performed to record, predict and analyze the phase of the transmitted ultrasonic beam. This results in the conceptual introduction of the 'phase polar scan', exposing even more intriguing and detailed patterns. In fact, the combination of the amplitude and the phase polar scan provides the complete knowledge about the complex transmission coefficient for every possible angle of incidence. This comprehensive information will be very valuable for inverse modeling of the local elasticity tensor based on a single polar scan experiment. Finally, the polar scan method has been applied for the detection of an artificial delamination. Contrary to the pulsed UPS, the quasi-harmonic UPS (both the amplitude and phase recording) shows a superior sensitivity to the presence of the delamination.
Tijdschrift: Ultrasonics
ISSN: 0041-624X
Volume: 58
Pagina's: 111-122