编号 2 (2024)

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

Aiming at the problem that signals collected from local electromagnetic loading operations are usually mixed with background noises (especially white noise), this paper proposed an electromagnetic acoustic emission signal denoising technology based on cross recurrence quantification analysis (CRQA). Firstly, the decomposition layer and penalty factor of variational mode decomposition (VMD) are set by experience or optimization algorithm, and then the original signal is decomposed. Secondly, the main components are selected by the CRQA algorithm, and the electromagnetic acoustic emission signal after denoising is obtained by superposition reconstruction. The simulation and experimental results show that when 5dB noise is added, CRQA can effectively remove the background noises in electromagnetic acoustic emission signals compared to the correlation coefficient algorithm, and it can assist in realizing the high-precision non-destructive testing of alloy materials.

Reference blocks for penetrant testing have been developed, allowing measurements using an optical microscope of both the opening width of surface defects and their depth. In this case, the condition that defect cavities do not extend onto the side faces of the blocks is met. Experimental data on the dependence of the defect’s indications area after development on their width (0.5—8.5 µm) and depth (40—860 mm) are presented. Using correlation analysis, the statistical significance of the above parameters is shown.

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.