What is it about?
Of various active thermal non-destructive techniques, pulse and lock-in thermography gained wide acceptance in thermal non-destructive testing community due to their fast and easy implementation respectively. However, these techniques have limited applications due to high peak power (pulse based thermographic techniques) and long experimentation time (lock- in thermography) requirements. In order to address limitations of these widely used techniques, FMTWI is introduced to enhance the defect detection sensitivity and resolution, with the usage of low peak power heat sources in a moderate experimentation time. Further, FMTWI enhances its defect detection capabilities with the usage of pulse compression favourable post-processing schemes.
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Why is it important?
This letter highlights computationally inexpensive and efficient noise reduction post-processing approach to study noise immune defect detection capabilities of FMTWI for sub-surface anomaly detection. Results obtained from the PCA based post-processing scheme on pulse compressed data proves the noise rejection capabilities of the main lobe having higher correlation coefficient (temperature) with the imposed heat flux over that of the low correlation coefficient noise sensitive side lobes. Further, the proposed approach proved to be an efficient method for reduction in data and computation.
Perspectives
Among the various non-destructive testing and evaluation methods, infrared thermography gained its importance due to its fast, whole-field, remote and quantitative evaluation capabilities for inspection of various materials. Being an optimum technique in terms of usage of low peak power heat sources in a moderate experimentation time, frequency modulated thermal wave imaging (FMTWI) plays a vital role in the infrared thermographic community. This letter highlights the noise rejection capabilities of the proposed pulse compression favourable FMTWI by using Principal Component Analysis (PCA) as a post-processing technique. The proposed scheme has been tested on a mild steel sample having sub-surface flat bottom hole defects located inside the test specimen at various depths. It is clear from the obtained results that the reconstructed pulse (main lobe) concentrates much of the imposed energy into a narrow duration, which enhances the defect detection sensitivity and resolution in order to visualize the sub-surface defects with higher signal to noise ratio.
Prof. Ravibabu Mulaveesala
Indian Institute of Technology Delhi
Read the Original
This page is a summary of: Experimental Investigation on Noise Rejection Capabilities of Pulse Compression Favourable Frequency Modulated Thermal Wave Imaging, Electronics Letters, January 2019, the Institution of Engineering and Technology (the IET),
DOI: 10.1049/el.2018.8047.
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