A comparison of the pulsed, lock-in and frequency modulated thermography nondestructive evaluation techniques

Krishnendu Chatterjee, Suneet Tuli, Simon G Pickering, Darryl P Almond

Research output: Contribution to journalArticle

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Abstract

Pulsed, lock-in and frequency modulated thermography are three alternative nondestructive evaluation techniques. The defect imaging performance of these techniques are compared using: matched excitation energy; the same carbon fiber composite test piece and infrared camera system. The lock-in technique suffers from blind frequencies at which phase images for some defects disappear. It is shown that this problem can be overcome by using frequency modulated (chirp) excitation and an image fusion algorithm is presented that enhance phase imaging of defects. The signal-to-noise ratios (SNRs) of defect images obtained by the three techniques are presented. For the shallowest defects (depths 0.25 and 0.5 mm, 6 mm diameter), the pulsed technique exhibits the highest SNRs. For deeper defects the SNRs of the three techniques are similar in magnitude under matched excitation energy condition.
Original languageEnglish
Pages (from-to)655-667
Number of pages13
JournalNDT and E International
Volume44
Issue number7
DOIs
Publication statusPublished - Nov 2011

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Defects
evaluation
defects
Signal to noise ratio
signal to noise ratios
Excitation energy
excitation
Imaging techniques
Image fusion
fiber composites
carbon fibers
chirp
Carbon fibers
fusion
Cameras
cameras
Infrared radiation
energy
Composite materials

Cite this

A comparison of the pulsed, lock-in and frequency modulated thermography nondestructive evaluation techniques. / Chatterjee, Krishnendu; Tuli, Suneet; Pickering, Simon G; Almond, Darryl P.

In: NDT and E International, Vol. 44, No. 7, 11.2011, p. 655-667.

Research output: Contribution to journalArticle

Chatterjee, Krishnendu ; Tuli, Suneet ; Pickering, Simon G ; Almond, Darryl P. / A comparison of the pulsed, lock-in and frequency modulated thermography nondestructive evaluation techniques. In: NDT and E International. 2011 ; Vol. 44, No. 7. pp. 655-667.
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