Journal ArticleDOI
Image Enhancement in Transient Lock-In Thermography Through Time Series Reconstruction and Spatial Slope Correction
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TLDR
An image reconstruction algorithm that enables LI thermography tests in the transient regime and removes temperature gradients due to nonuniform heating and surface emissivity variation is proposed.Abstract:
Lock-in (LI) thermography is a popular thermal-nondestructive-testing technique which, like other active thermographic techniques, requires an external heating stimulus, preferably on a blackened surface. It is not, however, immune to nonideal situations like nonuniform heating and surface emissivity variation. The phase image, to some extent, helps to reduce the effect of these artifacts but is inadequate if the variations are large. For example, a poorly blackened metallic sample with reflecting patches on its surface is very difficult to actively thermograph because of direct reflection from the surface. This paper proposes an image reconstruction algorithm for offline removal of such artifacts. In addition, the proposed algorithm enables LI thermography tests in the transient regime and removes temperature gradients due to nonuniform heating. The algorithm was tested with a mild-steel sample having 20-mm-diameter back-drilled holes at various depths ranging from 0.2 to 7.7 mm, stimulated at 20-, 40-, 50-, 60-, and 80-mHz excitation frequencies. The effect of the total number of heating cycles is also presented.read more
Citations
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Journal ArticleDOI
Automatic detection of CFRP subsurface defects via thermal signals in long pulse and lock-in thermography
TL;DR: Wang et al. as discussed by the authors proposed a model to detect defects automatically by extracting the thermal signal characteristics of carbon fiber reinforced plastics (CFRP), which can detect defects with minimum aspect ratio (ratio of short side to depth).
Proceedings ArticleDOI
Single channel blind source separation for defect identification using Eddy Current Pulsed Thermography
TL;DR: In this paper, a single channel blind source separation is proposed to process the Eddy Current Pulsed Thermography (ECPT) image sequences, which enables the detection automatically extract valuable spatial and time patterns according to the whole transient response behavior without any training knowledge.
Journal ArticleDOI
Two-stage convolutional neural network for joint removal of sensor noise and background interference in lock-in thermography
Journal ArticleDOI
Feature Detection of GFRP Subsurface Defects Using Fast Randomized Sparse Principal Component Thermography
Proceedings ArticleDOI
An optimization method for evaluating variations in paint coating thickness by infrared thermography
TL;DR: In this article, a new treatment approach is proposed to overcome the harmful effects of non-uniform heating in active infrared thermography test, based on a linear decomposition of the thermographic surface response evolution using a PLSR algorithm based on the SVD decomposition.
References
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Book
Theory and Practice of Infrared Technology for Nondestructive Testing
TL;DR: In this paper, the authors present an active and passive approach to active thermography for nondestructive testing of infrared sensors and Optic Fundamentals using Matlab M-Scripts.
Journal ArticleDOI
Pulse phase infrared thermography
Xavier Maldague,Sergio Marinetti +1 more
TL;DR: In this article, an approach combining both of pulse (PT) and modulated infrared thermography is proposed which combines simultaneously advantages both of PT and MODI, and the results are presented and the theory is discussed as well.
Journal ArticleDOI
Thermal wave imaging with phase sensitive modulated thermography
TL;DR: In this paper, the authors combined thermal wave and thermography to provide a short-time low-frequency phase angle image where non-thermal features can be suppressed using lock-in data analysis.
Journal ArticleDOI
Reconstruction and enhancement of active thermographic image sequences
TL;DR: In this paper, the authors proposed a deterministic active thermographic response is deterministic, to the extent that the postexcitation time evolution for a defect-free sample can be accurately predicted using a simple one-dimensional model.
Journal ArticleDOI
Lock-in thermography for nondestructive evaluation of materials
Datong Wu,Gerd Busse +1 more
TL;DR: In this paper, the phase sensitive modulation thermography (or "lock-in thermography") combines the advantages of photothermal radiometry with the fast technique of infrared imaging thereby revealing hidden defects in a short time.