Russian Journal of Nondestructive Testing最新文献

Dissimilar metal welds (DMWs), widely used in many components of nuclear power plants, may cause catastrophic failures because of damages (such as corrosion). Pulsed eddy current testing (PECT) could be used for DMW detection for its advantages of broadband property and high lift-off immunity. However, the research on PECT for DMW detection has seldom been studied because its structure and material are complicated. In this paper, the detection and evaluation of flaws in DMWs are studied based on the transmitter-receiver (Tx-Rx) PECT probe. Simulation and experiment studies show that, for better detection accuracy, the Tx coil of the probe should be located above the pressure vessel, the Rx coil should be located above the weld, and the minimum distance between the Tx and Rx coils is suggested. Moreover, the peak value of the differential signal and the coefficient a₁ of the fitted differential signals with a second-order Gaussian function can be used for defect evaluation. The research in this paper is beneficial for DMW detection by using PECT Tx-Rx probes.

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

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 nondestructive detection method to evaluate the waterproof performance of distribution network cables and their connectors. The internal structure of the cable is a multilayer 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.

The image quality of reflectors reconstructed using digital focusing antenna technology or a phased array antenna depends on the accuracy of determining such wedge parameters as X-value, path, longitudinal wave speed, and angle of probe. These parameters do not always correspond to their rated values both due to the imprecision of manufacturing wedges and placing antenna array elements in the housing and due to the wear of wedges during operation. The present paper discusses two types of calibration of a wedge-mounted antenna array, viz., variational and simplified. The principle of variational calibration is to minimize the objective function that describes the difference between the echo signals measured by the antenna array from side drilled holes, for example, in  an ISO 19675 PAUT (phased array ultrasonic testing) calibration block, and the calculated echo signals. Simplified calibration is based on analyzing the arrival time of echo signals from the wedge base; this makes it possible to estimate the path and angle of the wedge knowing the velocity of a longitudinal wave in it. The operation of variational calibration is tested on echo signals calculated in CIVA software to demonstrate the multiravine structure of the objective function. An assessment is made of the required accuracy in determining all four wedge parameters. The results of calibrating an antenna array on four wedges are presented and the results of variational and simplified calibrations are verified. The accuracy of determining wedge parameters using variational calibration is more than twice as good as the results obtained with simplified calibration. However, the time required to carry out calculations for variational calibration is more than three orders of magnitude longer than for simplified calibration.

Formulas and the corresponding algorithm for finding the magnetic field strength inside and outside a homogeneous cylinder placed in an external magnetic field of arbitrary configuration are deduced in the model of an infinite cylinder. The results of calculations based on these formulas are tested for their correspondence with known physical laws as well as for their coincidence with the well-known analytical answers in the limit particular cases of the forms of magnetics. A computer program in Fortran language implementing calculations using the proposed algorithm has been compiled and debugged.

Lamb wave detection is increasingly being utilized in the industry due to its extensive coverage area, high signal detection efficiency, and ease of operation. This paper offers a quantitative review of eight signal transformation methods utilized for de-noising and time-frequency analysis of Lamb waves, which include Fourier transform (FT), singular value decomposition (SVD), short-time Fourier transform (STFT), Wigner–Ville distribution (WVD), wavelet transform (WT), S-transform, Hilbert–Huang transform (HHT), as well as empirical mode decomposition (EMD) and its improved algorithms. The performances of signal transformations on denoising and defect location are assessed quantitatively using the signal-to-noise ratio (SNR) and time-of-flight (ToF). The results demonstrate that the complete ensemble EMD with adaptive noise (CEEMDAN) is able to suppress noise effectively while maintaining the primary features of the signal in an adaptive manner. Additionally, the continuous WT can obtain a more accurate time-frequency distribution, thereby providing the superior analytical ability for dispersive lamb wave signals with respect to positioning on the time axis.

This article analyzes the results of personal certification for eddy current testing of railway facilities. The influences of education level, the work experience, the candidate age on the qualifying examinations results are considered. The conformity between test task difficulties and certification candidate training is analyzed with Rasch method. The characteristic curves of test task difficulties and the characteristic curves of candidate training levels are constructed. The results general and special examinations of  2020 and 2021 are analyzed to identify extreme test questions. The research results enable to assess the candidate training and the test task difficulties through latent parameters measured as logit unit. The analysis identified test tasks with overstated and understated task difficulty logits compared with the logits of the candidate training, assessed the correspondence between test difficulties and training candidate level, and assessed a distribution uniformity of the tasks difficulty. The required training logit of candidates for the certification is calculated for successful passing general and special exam tests. The getting results give a basis for further analysis of the tasks complexity, identification the reasons for the insufficiency of the auditory material familiarization for the tasks with low rate of response, for making adjustments to the consulting sessions, as well as the content and form of the test.

This work reports an ultrasonic long waveguide sensor for measuring the fluid level utilizing longitudinal L(0, 1), torsional T(0, 1), and flexural F(1, 1) wave modes. These wave modes were transmitted and received simultaneously using stainless-steel wire. A long waveguide (>12 m) covers a broader region of interest and is suitable in the process industry’s hostile environment applications, “fluid levels and temperature measurements.” In this work, we used fluids “diesel, water, and glycerin” for measuring fluid levels based on the sensor’s reflection factors from time domain and frequency domain signals. We examined the impact of wave mode attenuation effects for long waveguide sensor design while changing the waveguide lengths. Initially, we obtained the L(0, 1) and T(0, 1) modes reflections from the 12.6 m waveguide length when one end of the long waveguide was fixed with a shear transducer at 45° orientation. Subsequently, we want to study and identify all wave modes (especially F mode) travel distances. Hence, we would like to investigate the guided wave propagation characteristics (attenuation, ultrasonic velocity, and frequency of all wave modes) in the long waveguide while cutting systematically at intervals of 1 m, starting from its original length of the waveguide 12.6 m by analyzing the A-scan signals of various lengths of a single waveguide. This simple and cost-effective technique can monitor the high fluid depths and temperature in power plants, oil, and petrochemical industries while designing a long waveguide sensor with appropriate ultrasonic parameters.

In this study, a gas discharge electroacoustic transducer (GDEAT) based on a pulsed electric discharge in the air under atmospheric pressure has been investigated. The acoustic characteristic of GDEATs have been determined in the frequency range from 40 Hz to 4 MHz by evaluating acoustic pressure and recording amplitude–frequency characteristics of membranes. The electrothermoacoustic processes have been studied in open type gas discharge systems where the electrode space is in a direct contact with the environment. Some features of using the above-mentioned GDEATs in material nondestructive testing (NDT) have been demonstrated. It has been shown that, on the one hand, the wear of both electrodes and insulation limits the work life of transducer’s electrode system; however, on the other hand, this may lead to deposition of microparticles on the test object surface. The wear of the electrode system was evaluated quantitatively. The results of the chemical analysis of the deposited microparticles are presented. The possibility of using GDEATs for noncontact stimulation of local resonant vibrations in subsurface defects and visualizing vibrations by means of laser Doppler vibrometry is shown in the case of NDT of a glass fiber composite.

The paper provides an overview of the main directions of using the thermoelectric testing method in various spheres of the national economy. The thermoelectric method is most widely used in industry. There are publications on the application of the thermoelectric method to quality control of turning and friction stir welding. It is shown that the thermoelectric method makes it possible to increase the reliability of testing and, based on testing data, ensure optimal modes of the technological process of metalworking and welding. A number of papers are devoted to the application of the thermoelectric method to plastic deformation testing; the dependence of thermal EMF on the degree of plastic deformation is revealed. Recently, publications have appeared on the application of the thermoelectric method to testing the thermal resistance of the “power semiconductor device housing–thermal interface–cooling radiator” structure. This design is very common in electronic technology. In addition, there are papers on the use of the thermoelectric method to test the transient resistance of contacts in the power supply network. It is shown that with an increase in contact resistance, the value of thermal EMF increases proportionally; this can be used to prevent emergencies in power supply networks. The thermoelectric method has also been successfully applied to diagnosing the degree of titanium hydrogen saturation. The dependence of the thermal EMF on the degree of hydrogenation has been revealed. The use of the thermoelectric method is not limited to the field of industrial production. The thermoelectric method is successfully used in medicine for the label-free detection of nucleic acid sequences, for the temperature diagnosis of human teeth, as well as for the diagnosis of inflammatory processes in the human body.