Feature extraction using normalized cross-correlation for pulsed eddy current thermographic images

Abstract

Pulsed eddy current (PEC) thermography is an emerging method in the field of non-destructive testing and evaluation (NDT&E). Defects can be characterized by tracking the diffusion of heat in a sample through the analysis of a sequence of PEC thermographic images. This study takes advantage of the capabilities of PEC thermography to gain quantitative information about complex geometrical defects, i.e. angular defect characterization through the analysis of the surface thermal distribution. To conduct the analysis, a new approach using a normalized cross-correlation technique is proposed. The strength of the proposed approach lies in its ability to track the heat diffusion through sequential PEC thermographic images in a metallic sample. The results of the analysis are used to determine the dimensions of defects in the sample under test. These results have shown the effectiveness of the proposed technique in providing features which have good agreement with defect detection and evaluation.

Threat Target Classification Using Ann and SVM Based on a New Sensor Array System

“…This system uses cross correlation between coherence polarisation and cross polarisation to distinguish between different handguns objects [31]. Cross correlation has also been applied on EM transient response signals obtained from a series of EM signals for defect characterization [25].…”

“…The first is based on the shape features of an object using invariant moments [19,20], while the second is based on the material features of an object, which are inferred from both the amplitude range [21] and principal component analysis (PCA) [22] of the EM signal. The third category applies cross correlation [23][24][25] upon the reconstructed EM transient response signal. These features, individually and in combination, will be anticipated as the object's signature and are fed to an ANN and SVM classifier.…”

A Review of Optical NDT Technologies

“…As laser-based modalities optical NDT methods have poor penetration, recent development of pulsed eddy current thermography can overcome this limitation [ 100 ]. The normal laser-based speckle interferometery optical technique is good at observing surface defects.…”

Defect characterisation using pulsed eddy current thermography under transmission mode and NDT applications

“…The external stimulus can be hot air jet, laser or flash lights, ultrasonic waves, hot water, eddy current etc [3,4]. Pulsed eddy current (PEC) thermography, combining PEC [5] and thermography, has its own advantages [6,7]. Several applications have been reported in the literature for crack [8] and corrosion [9] detection in metallic alloy and crack detection in carbon fibre reinforced plastic (CFRP) [10].…”