№ 3 (2024)

When interpreting acoustic emission (AE) observation data, a model of a crack in the form of a cavity in the shape of an oblate ellipsoid of revolution was used. When the length of its semi-minor axis tends to zero, the ellipsoid models a circular disc-shaped crack. Using data from two amplitude-frequency spectra of AE recorded during the destruction of a concrete sample, distributions of the power of acoustic radiation along the lengths of the semi-axes of the ellipsoidal cavities were constructed. It is shown that by the time the second spectrum is recorded, a redistribution of acoustic radiation occurs in favor of a discrete set of growing main cracks with high semi-major axis lengths and a small opening value.

In the model of the infinite cylinder the formulas and the corresponding algorithm for finding the magnetic field strength inside and outside the homogeneous cylinder placed in the external magnetic field of arbitrary configuration are deduced. Testing the results of calculations on these formulas for their correspondence with known physical laws, as well as on their coincidence with well-known analytical answers in the limiting private cases of the forms of magnetics were carried out. A computer program in Fortran language has been compiled and debugged to implement calculations using the proposed algorithm.

Moisture of high voltage distribution network cables will cause major safety hazard, but there is no effective means to detect and analyze the internal humidity state of the cables. Therefore, it is urgent to develop a new non-destructive detection method to evaluate the waterproof performance of distribution network cables and their connectors. The internal structure of the cable is a multi-layer structure composed of wires, cross-linked polyethylene insulation layer, and silicone rubber insulation sheath. We used the reflective terahertz pulse signal to detect the internal states of the cable, and judge whether it contains water stains according to the echo characteristics. In addition, three-dimensional data was obtained through cylindrical coordinate scanning and terahertz images were reconstructed based on feature information, which were consistent with the distribution of water stains between the cable insulation sheath and cross-linked polyethylene insulation layer. The results show that the terahertz technology can realize the high sensitivity detection of cable moisture state, which is of great significance in the power and transmission industry.

This study was devoted to the development of data fusion techniques obtained by one or several nondestructive testing (NDT) methods. Experimental results were obtained by applying laser vibrometry and optical infrared thermography to evaluation of impact damage in carbon fiber composite. These NDT techniques are different by their physical nature and supply specific testing results. The proposed data fusion method allows increasing reliability of inspection results and enables estimating defect parameters. It involves both averaging data of each single NDT technique and merging the results obtained by two methods. Vibrograms obtained by laser vibrometry were used to analyze acoustic response of the test sample toward stimulation at different frequencies. In its turn, infrared thermographic NDT supplies the sample response toward thermal stimulation. It has been shown that the fusion of these two techniques supplies a comprehensive information on defect size and location. Also, the automation of the fusion procedure increases NDT productivity and reduces subjectivity of testing results.