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The attenuation of ultrasound beams in coarse-grained austenitic stainless steels due to grain boundary scattering influences flaw detection and sizing. This paper presents an approach for processing ultrasonic B-scan images of thick coarse-grained austenitic stainless steel parts using a discrete wavelet transform (DWT) technique. In this approach, DWT processing of A-scan signals obtained during B-scan imaging is performed to reduce the noise caused by grain boundary scattering. The Daubechies (db8) mother wavelet with decomposition level 5 is found to be optimum for this purpose. Experimental studies are carried out on coarse-grained stainless steel specimens having flaws machined at different depths. These studies reveal that the proposed approach results in an improvement of more than 13 dB in signalto-noise ratio, as compared to two-dimensional DWT processing of the original B-scan image using the same wavelet and decomposition level. Furthermore, the proposed approach produces a smaller number of artefacts than the twodimensional DWT technique. The studies reveal that by using the proposed approach it is possible to detect flat-bottomed holes located at 40 mm below the surface of a 50 mm-thick stainless steel part with a grain size of 200 µm at normal incidence. The proposed approach is fast and attractive for online implementation. [ABSTRACT FROM AUTHOR]

The study aims at investigating the imaging and sizing capabilities of ultrasonic phased arrays and the synthetic aperture focusing technique (SAFT) of surface-breaking defects in a carbon steel plate. The defects were imaged using a phased array transducer and the relative arrival time technique (RATT) was used to size the defects. Studies were carried out to size near-through-wall defects so as to estimate the largest size of defect that can be accurately sized in accordance with the leak before break (LBB) criterion in critical applications. Additionally, the study also aims at sizing the smallest defect that can be sized accurately using the two techniques. The study also shows a direction for improved sizing accuracy of certain defects by means of the hybrid-based genetic algorithm (GA) approach which otherwise was limited by the two imaging techniques. [ABSTRACT FROM AUTHOR]

‘Shaligram’ is a special kind of stone. In India it has significant importance in the religious context. Shaligrams occur in nature in various colours and shapes. Some of them have a liquid entrapped in them. Since their occurrence is rare, it is observed that some artificial shaligrams are being traded. Presently there exists no means to ascertain the genuineness of such a shaligram. In this study, it is demonstrated that a fake shaligram containing liquid can be identified by two different non-destructive evaluation methods, ie ultrasonics and radiography, by detecting the presence of capping material. [ABSTRACT FROM AUTHOR]