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Proceedings Paper

Onward and inward: extending the limits of thermographic NDE
Author(s): Steven M. Shepard; James R. Lhota; Bruce A. Rubadeux; Tasdiq Ahmed
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Paper Abstract

In current thermographic NDE practice, the detection limits of various methods are typically undefined, beyond citing the deepest flat bottom hole that has been successfully detected in a particular material. Little distinction is made between the ability of a thermographic system to detect the presence of a subsurface defect, to measure its physical properties, or to resolve adjacent defects. Although many practitioners rely on a `rule of thumb', which states that the aspect ratio (diameter/depth) of a detectable defect must be greater than 1, it has been shown to be unreliable as a basis for determining the feasibility of a particular inspection. It is possible to characterize the performance of a thermographic system using a simple procedure, so that the ability of the system to detect, resolve, or measure defects in a particular material or sample type can be successfully modeled. The intrinsic detection limits derived from this approach effectively defines a thermal point spread function that defines the minimum detectable defect size at a particular depth. This information can be used to remove blurring due to lateral heat flow, and extend the depth at which resolution is possible.

Paper Details

Date Published: 30 March 2000
PDF: 5 pages
Proc. SPIE 4020, Thermosense XXII, (30 March 2000); doi: 10.1117/12.381551
Show Author Affiliations
Steven M. Shepard, Thermal Wave Imaging, Inc. (United States)
James R. Lhota, Thermal Wave Imaging, Inc. (United States)
Bruce A. Rubadeux, Thermal Wave Imaging, Inc. (United States)
Tasdiq Ahmed, Thermal Wave Imaging, Inc. (United States)

Published in SPIE Proceedings Vol. 4020:
Thermosense XXII
Ralph B. Dinwiddie; Dennis H. LeMieux, Editor(s)

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