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Designing and evaluating transducers for narrowband ultrasonic spectroscopy
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signalbehandling.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signalbehandling.
2007 (engelsk)Inngår i: NDT & E international, ISSN 0963-8695, E-ISSN 1879-1174, Vol. 40, nr 1, s. 49-56Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Introduction of new composite materials in aerospace applications has created a demand for an efficient NDE technique. Ultrasonic resonance inspection is especially suitable for the inspection of multilayered structures. In our previous work we have described the principle of narrowband ultrasonic spectroscopy (NBUS), where the surface of an inspected structure is scanned with a resonant transducer whose frequency response is monitored in a narrow frequency band. This paper is concerned with optimizing the NBUS setup consisting of a piezoelectric transducer coupled to a multi-layered structure. Differences in the electrical impedance of a piezoelectric transducer caused by variations of parameters of the inspected structure are estimated using an equivalent circuit model and a finite element analysis. The theoretical analysis presented in the paper results in design guidelines for NBUS transducers.

sted, utgiver, år, opplag, sider
2007. Vol. 40, nr 1, s. 49-56
Emneord [en]
Narrowband ultrasonic spectroscopy, Transducer design, Layered materials
HSV kategori
Identifikatorer
URN: urn:nbn:se:uu:diva-13355DOI: 10.1016/j.ndteint.2006.07.006ISI: 000242411700007OAI: oai:DiVA.org:uu-13355DiVA, id: diva2:41125
Tilgjengelig fra: 2008-01-22 Laget: 2008-01-22 Sist oppdatert: 2018-01-12bibliografisk kontrollert
Inngår i avhandling
1. Ultrasonic Arrays for Sensing and Beamforming of Lamb Waves
Åpne denne publikasjonen i ny fane eller vindu >>Ultrasonic Arrays for Sensing and Beamforming of Lamb Waves
2010 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

Non-destructive testing (NDT) techniques are critical to ensure integrity and safety of engineered structures. Structural health monitoring (SHM) is considered as the next step in the field enabling continuous monitoring of structures.

The first part of the thesis concerns NDT and SHM using guided waves in plates, or Lamb waves, to perform imaging of plate structures. The imaging is performed using a fixed active array setup covering a larger area of a plate. Current methods are based on conventional beamforming techniques that do not efficiently exploit the available data from the small arrays used for the purpose. In this thesis an adaptive signal processing approach based on the minimum variance distortionless response (MVDR) method is proposed to mitigate issues related to guided waves, such as dispersion and the presence of multiple propagating modes. Other benefits of the method include a significant increase in resolution. Simulation and experimental results show that the method outperforms current standard processing techniques.

The second part of the thesis addresses transducer design issues for resonant ultrasound inspections. Resonant ultrasound methods utilize the shape and frequency of the object's natural modes of vibration to detect anomalies. The method considered in the thesis uses transducers that are acoustically coupled to the inspected structures. Changes in the transducer's electrical impedance are used to detect defects. The sensitivity that can be expected from such a setup is shown to highly depend on the transducer resonance frequency, as well as the working frequency of the instrument. Through simulations and a theoretical argumentation, optimal conditions to achieve high sensitivity are given.

sted, utgiver, år, opplag, sider
Uppsala: Acta Universitatis Upsaliensis, 2010. s. 83
Serie
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 732
Emneord
imaging, array processing, guided waves, Lamb waves, dispersive waves, multi-modal waves, spatial filtering, mode suppression, resonant ultrasound, transducer design, direction of arrival estimation, adaptive beamforming
HSV kategori
Identifikatorer
urn:nbn:se:uu:diva-122189 (URN)978-91-554-7785-1 (ISBN)
Disputas
2010-05-21, Siegbahnsalen, Lägerhyddsvägen 1, Uppsala, 13:15 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2010-04-28 Laget: 2010-04-07 Sist oppdatert: 2018-05-28bibliografisk kontrollert

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