No 5 (2024)

The widespread introduction of antenna arrays into the practice of ultrasonic testing has made it possible to obtain images of reflectors using either phased array technology or digital aperture focusing (DFA) technology. However, many current regulatory documents regulating the rules for conducting ultrasonic non-destructive testing in the nuclear power industry, petrochemistry, gas industry, etc., require determining the equivalent dimensions of reflectors. The article proposes a method for calculating the DAF—DAC array to determine the diameter of an equivalent flat-bottomed hole (FBH) when analyzing an image. It was shown that it is more efficient to work not with the amplitude of the image, but with the integral amplitude. Numerical experiments have shown the accuracy of determining the diameter of the FBH of the order of ± 0.1 mm. In model experiments, the accuracy of determining the diameter of the FBH turned out to be modulo less than 0.2 mm.

The problem of random oscillations generated by inner defect within the neighborhood of the boundary of the elastic massive body under the pre-failure stage is considered. The investigation is based on results of the invariants’ method in acoustic emission (AE) theory consisting in the stability conditions of the mean of statistic distribution parameters of signal characteristics under the same pre-failure stage. The mathematical model of arising wave process of displacement oscillations in the massive body is constructed and the correctness of its using is studied. The problem in question is reduced to the investigation of a boundary integral equation in special stochastic process classes. The task of reconstructing from AE signals and describing the nature of the random process of defect radiation at the free boundary of the body is set. Some numerical are presented.

A mathematical model of radiation transparency in the computational implementation of the dual energy method based on analog discrimination of the original signals is given. The generalized mathematical model of radiation transparency in the analyzed implementation of the dual energy method is based on the analog separation of the initial electrical signals from the X-ray detector by amplitude into low-energy and high-energy signals with subsequent counting of these signals. Analog separation of the output signals of the X-ray detector by amplitude is carried out using a two-channel amplitude analyzer. The proposed model takes into account the maximum energy of X-ray photons, the energy threshold for separating signals into low-energy and high-energy signals, materials and sizes of radiation-sensitive detector elements, and parameters of control objects. The model can be used to conduct research on the influence of noise caused by the quantum nature of X-ray radiation on the quality of identification of the attenuating material, for example, by effective atomic number, in relation to the considered implementation of the dual energy method, as well as for a reasonable choice of parameters of the corresponding dual-energy digital radiography systems and X-ray computed tomography.

The results of nondestructive testing (NDT) of a turbine blade made of a heat resistant alloy with a ceramic coating were obtained by using ultrasonic infrared (IR) thermography. The purpose of the study was to determine possibilities of this NDT technique in detecting cracks in the blade and the coating. Image processing was performed by using principal component analysis, which allows to underline defect indications in IR images. The obtained test results were in a good accordance with the results obtained by means of penetrants with a considerably shorter inspection time. Potentials of IR ultrasonic thermography in the detection of “kissing: cracks and cracks located in difficult to reach sites was demonstrated.