Issue << content << On-the-Fly Weld Defects Pattern Analysis whilst Performing S-Scan Material Coverage Using PA UT Modality


DOI: 10.12737/article_58e64083937cd2.29391145

2017. Vol.20. 1, pp. 43-47

On-the-Fly Weld Defects Pattern Analysis whilst Performing S-Scan Material Coverage Using PA UT Modality

G. Passi, S. R. Tsomuk

Introduction. Sometime it may occur that the dangerous defects do not return the echoes exceeding the threshold level and may not be rejected based on the echo-amplitude evaluation. On the other hand the shape of the inhomogeneity on the cross-sectional image obtained through S-scan coverage and the echo dynamic analysis may lead to suspecting a crack and rejecting the defect. To back or decline the suspect on-the-fly there is a number of approaches and implementations available; one of them has been presented in the article.
The method. The technique presented in the article utilizes the effect of diffraction occurring due to interaction of the shear wave with the inhomogeneity in the material followed by the mode conversion and evaluating both the shear wave echo and the diffracted (scattered) mode converted longitudinal (compression) wave signals returned to the probe (so called Ktl technique). In 80th the Ktl technique was developed fundamentally and its implementation was based on the use of the specially designed twin crystal angle beam probes, in which the first crystal is used for the regular shear wave pulse echo inspection and the second one — just for the receiving of the diffracted mode converted compression wave signals. The new state-of-the-art solution is based on the use of the regular PA probes utilizing the ability of Sonotron NDT‘s portable ultrasonic PA instruments ISONIC 3510, ISONIC 2010, and ISONIC 2009 to perform on-the-fly embedding of the additional focal laws into the running sequence used of the routine inspection and implementing them with the purpose of receiving and analysis of the complimentary mode converted longitudinal wave signals, which carry the additional data required for identifying the defect under evaluation.
The results. The comparison experiments were performed on the same reflectors with the use of conventional modality and the above said specially designed twin crystal angle beam probe and PA modality; the matching of the results has been demonstrated. The results obtained on the real defects were confirmed through macro-slicing.
Conclusion. The embodiment for the PA-based on-the-fly defect pattern analysis utilizing the classic Ktl technique has been found practically useful and recommended to the users of Sontron NDT’s PA instruments.
Keywords: phased array ultrasonic testing (PA UT), defect pattern analysis, diffraction, mode conversion, on-the-fly dynamic control of focal laws.
 
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