Constrained Autoencoder-Based Pulse Compressed Thermal Wave Imaging for Sub-Surface Defect Detection

Non-destructive testing & evaluation techniques play an essential role in ensuring safety of materials in operation at various industry sectors. Pulse compressed favourable thermal wave imaging is one of the widely used non-destructive testing techniques due to its excellent noise rejection capa...

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Bibliographic Details
Published in:IEEE sensors journal Vol. 22; no. 18; pp. 17335 - 17342
Main Authors: Kaur, Kirandeep, Mulaveesala, Ravibabu, Mishra, Priyanka
Format: Journal Article
Language:English
Published: New York IEEE 15.09.2022
The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subjects:
Autoencoder
Constraints
Cost function
Deep learning
frequency modulated thermal wave imaging (FMTWI)
Frequency modulation
Imaging
Low carbon steels
non-destructive testing & evaluation (NDT&E)
Nondestructive testing
Orthogonality
Photothermal effects
Principal component analysis
Sensors
Signal to noise ratio
Surface defects
Thermal imaging
Thermal wave imaging
Thermography
Training
ISSN:1530-437X, 1558-1748
Online Access:Get full text
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Summary:Non-destructive testing & evaluation techniques play an essential role in ensuring safety of materials in operation at various industry sectors. Pulse compressed favourable thermal wave imaging is one of the widely used non-destructive testing techniques due to its excellent noise rejection capabilities. However, the high dimensional thermal imaging data needs to be encoded into lossless compressed form to highlight the hidden defects inside the materials. This paper proposes a novel constrained and regularized autoencoder based thermography approach for sub-surface defect detection in a mild steel specimen. Certain properties such as non-correlation of encoded data, weight orthogonality, and weights with unit norm length have been highlighted which are non-existent in linear autoencoders but are responsible for better defect detection inside the materials inspected by frequency modulated thermal wave imaging. Novel constraints are formulated for autoencoder cost function to incorporate these significant properties. The proposed approach is able to provide better defect detection, in terms of signal to noise ratio of defects, than linear autoencoder as well as traditional principal component thermography approach. Also, non-correlation of encoded data is found to be the most significant factor in achieving better defect detection followed by properties ensuring weight orthogonality and weights with unit norm length.
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ISSN:1530-437X
1558-1748
DOI:10.1109/JSEN.2021.3056394