Pulsed thermography defect detection limits

D. Almond, S. Pickering

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Remarkably, there has been no analytic consideration of the origin of the widely accepted limitation on pulsed thermography defect detection performance that defect aspect ratio (diameter/depth) must exceed two. A simple modification of the one-dimensional expression for the contrast of a layer has been developed that provides an accurate prediction of peak contrast and contrast peak time for defects of all aspect ratios. The modification is based on the assumption that defect image contrast is limited by the diffusion of trapped heat from above the defect to the defect edge. The analytic model results have been shown to agree with numerical modelling for a range of materials, including composites which have anisotropic thermal conductivity. Both peak defect image contrast and occurrence time are found to be systematic functions of defect aspect ratio but, in addition, contrast falls with defect depth. The rule-of -thumb is only true for a limited range of defect depths and it depends critically on absorbed excitation/flash energy. The analytic impulse excitation model can be developed for other forms of excitation (long pulse or periodic) or used to model time derivative processing of thermography data. The possibility of developing a thermographic NDE expert system will be discussed.

Original languageEnglish
Title of host publication50th Annual Conference of the British Institute of Non-Destructive Testing 2011, NDT 2011 Held in conjunction with the Materials Testing Exhibition, MT 2011
PublisherBritish Institute of Non-Destructive Testing
Number of pages1
ISBN (Print)9781618393432
Publication statusPublished - 1 Jan 2011
Event50th Annual Conference of the British Institute of Non-Destructive Testing 2011, BINDT 2011 - Telford, UK United Kingdom
Duration: 13 Sep 201115 Sep 2011

Publication series

Name50th Annual Conference of the British Institute of Non-Destructive Testing 2011, NDT 2011 Held in conjunction with the Materials Testing Exhibition, MT 2011

Conference

Conference50th Annual Conference of the British Institute of Non-Destructive Testing 2011, BINDT 2011
CountryUK United Kingdom
CityTelford
Period13/09/1115/09/11

ASJC Scopus subject areas

  • Computational Mechanics
  • Mechanics of Materials
  • Safety, Risk, Reliability and Quality
  • Materials Science (miscellaneous)

Cite this

Almond, D., & Pickering, S. (2011). Pulsed thermography defect detection limits. In 50th Annual Conference of the British Institute of Non-Destructive Testing 2011, NDT 2011 Held in conjunction with the Materials Testing Exhibition, MT 2011 (50th Annual Conference of the British Institute of Non-Destructive Testing 2011, NDT 2011 Held in conjunction with the Materials Testing Exhibition, MT 2011). British Institute of Non-Destructive Testing.