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Proceedings Paper

Non-linear material characterisation using the noncollinear method
Author(s): Anthony J. Croxford; Paul D. Wilcox; Bruce W. Drinkwater
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Paper Abstract

Conventional ultrasonic NDT techniques are limited in their ability to detect small defects by the diffraction limit, that is there is much reduced sensitivity to defects smaller than the wavelength of the interrogating ultrasonic wave. While not a major issue for most inspection, this problem becomes particularly significant for the detection of fatigue damage prior to crack formation. In this regime conventional NDT has proven to be inadequate. For this reason significant effort has been expended on the development of non-linear techniques. These techniques rely on deviations of the material from linear stress strain behaviour which create harmonics in the resulting frequency response. Evidence suggests that changes to a materials condition, such as fatigue damage, change this non-linear response. This paper presents a non-linear inspection method using a non-collinear interaction. This technique has several advantages over other harmonic approaches in that there is spatial separation, modal separation and frequency separation of the non-linear signal. This allows the origin of the non-linear signal and underlying noise levels to be well defined. The capability of the technique is demonstrated using plastically strained material and samples subjected to low cycle fatigue.

Paper Details

Date Published: 9 April 2010
PDF: 6 pages
Proc. SPIE 7649, Nondestructive Characterization for Composite Materials, Aerospace Engineering, Civil Infrastructure, and Homeland Security 2010, 76491X (9 April 2010); doi: 10.1117/12.847233
Show Author Affiliations
Anthony J. Croxford, Univ. of Bristol (United Kingdom)
Paul D. Wilcox, Univ. of Bristol (United Kingdom)
Bruce W. Drinkwater, Univ. of Bristol (United Kingdom)


Published in SPIE Proceedings Vol. 7649:
Nondestructive Characterization for Composite Materials, Aerospace Engineering, Civil Infrastructure, and Homeland Security 2010
Peter J. Shull; Aaron A. Diaz; H. Felix Wu, Editor(s)

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