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Proceedings Paper

Application Of Thermal Pulses And Infrared Thermal Imagers For Observing Sub-Surface Structures In Metals And Composites
Author(s): J. M. Milne; W. N. Reynolds
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Paper Abstract

The introduction, over the past few years, of thermal imagers with Sprite detectors and optical scanning systems compatible with TV video standards has opened up many new fields of application. A particular example which this paper describes is a thermal pulse technique pioneered by Harwell for the non-destructive inspection of different materials for sub-surface defects and other structural features(1)(2). The method is now commonly referred to as Pulse Video Thermography or PVT. Its success depends on the differing thermal properties of materials as defined by their thermal diffusivities. When a short pulse of heat incident at time to is absorbed by a surface it diffuses through the material until a new equilibrium is regained. During this time any obstructions to the diffusion or any local differences in the thermal properties of the material, will at certain times after time to give rise to detectable temperature differences or contrasts on the external surfaces. These transient thermal events can be monitored by a thermal imager and recorded on a video cassette recorder for a subsequent field-by-field interpretation and analysis. In this paper the basic principles are described and some examples are given on how PVT has been successfully applied to materials of widely different thermal properties. The use of Pulse Video Thermography as a non-destructive method of inspection is now well established. But its wider adoption is at present inhibited by the comparatively high costs of thermal imagers and their supporting logistics. If cheaper pyro-electric Vidicons can achieve comparable performance to the optical scanners then PVT would soon be recognised as a complementary technique to those traditionally used for industrial nondestructive testing.

Paper Details

Date Published: 1 May 1986
PDF: 10 pages
Proc. SPIE 0590, Infrared Technology and Applications, (1 May 1986); doi: 10.1117/12.951997
Show Author Affiliations
J. M. Milne, National NDT Centre (England)
W. N. Reynolds, National NDT Centre (England)

Published in SPIE Proceedings Vol. 0590:
Infrared Technology and Applications
Lionel R. Baker; Andre Masson, Editor(s)

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