Showing papers by "Anish Kumar published in 2022"

High resolution in non-destructive testing: A review

Abstract: Since the beginning of the applications of non-destructive testing/evaluation (NDT/NDE) techniques, efforts have been made consistently to improve their detection sensitivity and resolution. In the present paper, factors governing lateral resolution in three major NDT techniques, viz., ultrasonic testing (UT), x-ray radiographic testing (XRT), and eddy current testing (ECT) are presented. Furthermore, a review of recent advances in these NDT techniques to reach the theoretically achievable resolution limit or even surpassing the same using alternate approaches is also discussed. For example, resolution in UT is theoretically limited to half the wavelength by the Rayleigh limit; however, subwavelength resolutions have been achieved through the applications of near field methods by capturing the evanescent field. On the other hand, the resolution achieved in XRT is primarily limited to half the source/focal spot size, which is many orders of magnitude larger than the wavelength. Over the years, the reduction in the focal spot from macro-focus to micro-focus and now to nano-focus has led to improvement in the resolution to a few nanometers, of course, in combination with suitable magnification required due to detectors with limited pixel size (a few μm to a few 10 s of μm). Similarly, innovations in electromagnetic/magnetic sensors have significantly improved the resolution achieved in ECT. Atomic force microscopy, metamaterials, and artificial neural network-based methods have been employed for obtaining high-resolution NDE images. At the end, authors' perspective toward possible directions for high-resolution NDT is presented.

Effect of flaw orientation on magnetic flux leakage and remote field eddy current inspection of small diameter steel tubes

Abstract: ABSTRACT This paper presents effect of flaw orientation on magnetic flux leakage (MFL) and remote field eddy current (RFEC) inspection of small diameter (19.05-mm outer diameter, OD and 2.77-mm wall thickness, WT) seamless low carbon steel tubes. Artificial electro-discharge machined (EDM) notches in three carbon steel Tubes A (orientations from 0° to 90° in steps of 10° and 50% WT depth), B (70° orientation and depths from 10% WT to 100% WT in steps of 10% WT) and C (50° orientation and depths from 10% WT to 60% WT in steps of 10% WT) were used to investigate the detectability of notches with different orientations and depths. Studies on different notch orientations reveal that RFEC technique detected all the notches with good signal-to-noise ratio (SNR), while MFL technique detected the notches with orientations from 40° to 90°. The effect of notch orientation is observed more in MFL technique as compared to RFEC technique. Further, the effects of scanning speed and notch depth for the detection of oriented notches were studied. Studies reveal that the effect of scanning speed is also more (40 times) dominant in MFL technique as compared to RFEC technique. Studies also reveal that the scanning effect is again dependent upon the notch depth. For 70° oriented notches, MFL technique is found to be more sensitive to notch depth as compared to RFEC technique. For 50° oriented notches, RFEC technique is found to be more sensitive to notch depth as compared to MFL technique.