New publications about algorithms

Geometrical and acoustic properties of the seam

The TOFD method, widely used in ultrasonic flaw detection, allows to distinguish a crack from a volumetric reflector by the phase of the echo signals and to determine its height with high accuracy. However, the TOFD method without scanning with piezoelectric converters across the welded joint does not allow to determine the displacement of the reflector from the center of the seam, which is very important when evaluating the control results. The scanning devices used for this purpose have a complex design, their price is higher than that of one—dimensional sanitizing devices, and, most importantly, the control time increases significantly. If we use echo signals reflected from the bottom of the object of control, taking into account the change in the type of wave, then a combined image of the reflector can be obtained from a set of partial images recovered by the digital focusing antenna (CFA) method. If the echo signals measured in the combined mode for each piezoelectric transducer are used, it is possible to estimate the displacement of the reflector across the welded joint with an accuracy of ± 1.5 mm. Numerical and model experiments have confirmed the operability of the proposed approach.
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PWI in ultrasonic non-destructive testing

Image restoration of reflectors by digital focusing antenna (CFA), along with such advantages as high resolution over the entire area of image restoration of reflectors, the ability to obtain images taking into account the reflection and transformation of the wave type from the boundaries of the object of control, has several disadvantages: a large volume of measured echo signals, a long image recovery time and insufficiently high energy of ultrasonic waves, entered into the object of control. The Plane Wave Imaging (PWI) method allows you to combine the advantages of phased array antenna technology (FAR) and CFA technology. In PWI mode, when a plane wave is emitted, all elements of the antenna array (AR) work (as in the HEADLIGHT mode), which allows you to increase the energy entered into the control object, and echo signals are recorded by all elements of the AR (as in the CFA mode). The images of the reflectors are restored by the combination SAFT method. To obtain an image, the number of emitted plane waves can be used less than the number of antenna array elements, which reduces the volume of measured echo signals. The transfer of calculations to the area of spatial sectors allows to increase the speed of recovery of the presentation of reflectors. Model experiments have shown the positive and negative sides of obtaining images of reflectors by PWI compared with the CFA method both for the case of using a prism and without a prism.

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Determining the type of reflector (LL, LT, TT)

Ultrasonic flaw detection has developed methods for recording and analyzing echo signals to determine the type of reflector and its dimensions. The method of digital focusing with an antenna (CFA) allows you to restore the image of the entire discontinuity boundary using echo signals reflected from the bottom of the control object, taking into account the transformation of the wave type. However, this approach is not always applicable in practice, since the shape of the bottom of the object of control may be unknown. Using the features of the behavior of the reflection coefficient for different types of waves, it is possible to draw a conclusion about the type of reflector from images only on a direct beam. Numerical and model experiments have confirmed the operability of the proposed approach.