The quasi-harmonic ultrasonic polar scan for material characterization: experiment and numerical modeling

Mathias Kersemans; Arvid Martens; Koen Van Den Abeele; Joris Degrieck; Lincy Pyl; Filip Zastavnik; Hugo Sol; Wim Van Paepegem

doi:10.1016/j.ultras.2015.01.002

The quasi-harmonic ultrasonic polar scan for material characterization: experiment and numerical modeling

Ultrasonics. 2015 Apr:58:111-22. doi: 10.1016/j.ultras.2015.01.002. Epub 2015 Jan 14.

Authors

Mathias Kersemans¹, Arvid Martens², Koen Van Den Abeele², Joris Degrieck³, Lincy Pyl⁴, Filip Zastavnik⁴, Hugo Sol⁴, Wim Van Paepegem³

Affiliations

¹ Department of Materials Science and Engineering, Ghent University, Technologiepark-Zwijnaarde 903, 9052 Zwijnaarde, Belgium. Electronic address: Mathias.Kersemans@UGent.be.
² Department of Physics, Catholic University of Leuven - KULAK, Etienne-Sabbelaan 52, 8500 Kortrijk, Belgium.
³ Department of Materials Science and Engineering, Ghent University, Technologiepark-Zwijnaarde 903, 9052 Zwijnaarde, Belgium.
⁴ Department Mechanics of Materials and Constructions, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium.

PMID: 25620710
DOI: 10.1016/j.ultras.2015.01.002

Abstract

Conventionally, the ultrasonic polar scan (UPS) records the amplitude or time-of-flight in transmission using short ultrasonic pulses for a wide range of incidence angles, resulting in a 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, both experimentally and 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 Whereas the plane wave computations yield a pure Lamb wave angle fingerprint, this is no longer valid for the more realistic case of a bounded beam.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 UPS experiment. Finally, the UPS method has been applied for the detection of an artificial delamination. Compared to the pulsed UPS, the quasi-harmonic UPS (both the amplitude and phase recording) shows a superior sensitivity to the presence of a delamination.

Keywords: Amplitude and phase; Delamination; NDT; Quasi-harmonic waves; Ultrasonic polar scan.