Defect depth quantification using lock-in thermography

Publication Type:

Journal Articles


Quantitative InfraRed Thermography Journal, Volume 12, Number 1, p.37–52 (2015)



In this paper we explore the defect evaluation in austenitic stainless steel (SS) using Lock-in technique and the effect of modulation frequency on defect detectability. A review of international literature indicates that while such studies have been attempted on materials like Perspex and composites, studies on austenitic SS like AISI 316, which are widely used in nuclear and other process industries, have been limited. For depth quantification, blind frequency method and phase contrast method have been discussed. The one dimensional analytical modeling proposed by Bennett and Patty has been adopted in blind frequency method. The investigation on the effect of defect size and shape on blind frequency and phase contrast has been carried out. The phase contrast method for depth quantification was found to be appropriate.


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