Russian Journal of Nondestructive Testing最新文献

Additive manufacturing has been playing a significant role in the manufacturing of components with complex geometries for aerospace applications recently. Comprehensive nondestructive testing techniques (NDT) are vital for the successful quality evaluation of critical components in this domain. Appropriate selection of the NDT scheme is essential for the qualification of such components. Major NDT techniques are designed based on the interaction of electromagnetic radiation and the response of the sound or heat energy transmission or reflection from the test object. The common defects noticed in the components made through additive manufacturing (AM) routes are pores, clusters of porosities, micro-cracks, lack of fusion and layer delamination. Considering the morphology and the complications in the geometry of aerospace components, many conventional NDT techniques are unsuitable for the inspection of AM components. Detection of unfused powder in the AM components by conventional radiography is difficult due to the low radiation attenuation coefficient gradient between the unfused and fused metallic regions. Also, the detection of defects in the radiography technique depends entirely on the beam path. Multiple radiography images with different beam angles and film combinations are essential to get the maximum information on the defects by conventional radiography techniques. In this aspect, computed tomography, a noncontact NDT technique provides a better solution for determining embedded defects such as lack of fusion and layer separation due to presence of unfused powder in the AM components. The present study compares the capability of computed tomography and 2D digital radiography for the identification of lack of fusion defects in stainless steel SS316L specimens fabricated through the Laser powder bed fusion AM route.

The first section of this study is devoted to characterizing the lateral wave generated by a laser along the air-aluminum interface. This includes determining its propagation velocity, analyzing its spectrum, and evaluating the variation of its amplitude in relation to the generation/detection distance (d). The obtained results have shown that the lateral wave propagates at the speed of the longitudinal volume wave, following the d^–n law, where n equals 2.46. Its spectrum exhibits a wide bandwidth, with a cutoff frequency of fc = 3 MHz. The second part of the paper focuses on utilizing these waves for surface defect detection, with a comparative analysis of results obtained with Rayleigh waves. Various tests were conducted to analyze the impact of defects on the lateral wave on transmitted or reflected modes. The outcomes illustrate modifications in the temporal signals and frequency spectra of the lateral wave in the presence of defects.

Capturing the spatio temporal radiation in the infrared portion of the spectrum from any object renders the temperature evolution of it and culminates in presenting the information about the hidden subsurface anomalies within the object. However deeper depth scanning and higher depth resolution with enhanced subsurface visualization are the significant challenges generally encountered in these studies that demands various stimulation and processing mechanism to explore these details. This manuscript introduces a novel log frequency modulation-based stimulation along with various post-processing approaches that caters to these requirements. This modality facilitates a band of low frequencies with increased energy in the stimulus for deeper depth scanning and spectral processing approaches to provide enhanced depth resolution in a single experimentation cycle. The hypothesis is validated through the experimentation carried out over a carbon fiber-reinforced plastic specimen with embedded flat bottom holes. A qualitative comparison between various signal processing approaches using thermographic metrics like the sizing of the defects and signal-to-noise ratio recommends the superiority of proposed stimulation and processing techniques for enhanced defect detection.

Layered materials incorporating hydrogen were obtained using Nb/Zr films with varying numbers of layers from 50 to 100. The films were deposited on a silicon substrate using a vacuum magnetron sputtering method on a dedicated setup. The film thickness varied from 10 to 50 nm. The resulting material was hydrogenated with protons on a TPU electrostatic generator with an energy of up to 1.2 MeV. The deposition modes for nanoscale metallic multilayer Zr/Nb systems were determined: for a Zr target the specific power of the sputtering system was 37.9 W/cm², and for a Nb target it was 26.4 W/cm². A coating with clear boundaries between individual layers of zirconium and niobium was obtained. It was shown that the optimal conditions for studying nanoscale Zr/Nb layers are a pressure of 700 Pa, a power of 40 W, a frequency of 2 kHz, and a plasma filling factor of 12.5% for coatings with individual layer thicknesses of 100 nm. For coatings with layer thicknesses from 10 to 50 nm, the optimal conditions are a pressure of 650 Pa, a power of 40 W, and a frequency of 1 kHz. The thermo EMF method (GOST (State Standard) 25315–82) was used for testing. It was found out that after proton irradiation, an intensive accumulation of hydrogen atoms occurs near the interfaces; it reduces the structure defectiveness and entails a change in the thermo EMF up to the inversion of its sign. The hydrogen distribution is predominantly bimodal, with local maxima in hydrogen concentration observed at the Nb/Zr interfaces, while accumulation at the Zr/Nb interface is considerably lower. Hydrogen localization near interfaces primarily occurs around zirconium.

Enhancing imaging performance is one of long-term goals pursued by ultrasonic phased array in the field of nondestructive testing. However, the computational complexity will grow when the imaging methods are improved. In this work, delay-multiply-and-sum (DMAS) is combined with sparse array technique to achieve better imaging performance and maintain the almost same computational cost as sparse total focus method (TFM) needs. Comparison analysis is conducted on the beam pattern and imaging metrics, and the result indicates that sparse DMAS works better over sparse TFM at the same level of imaging time.

The strength of cast-in-place concrete is obtained using the innovative pendulum hammering test method (PHTM) to reduce structural damage to concrete. A specially developed PHTM device is used to apply a fixed impact force to nails and determine the relationship between the penetration depth of nails and the compressive strength of the concrete. Adverse factors such as aggregate type and concrete moisture content on concrete strength were eliminated and their impact on PHTM test results was avoided. The compressive strength of the tested concrete cube samples ranges from 20 to 50 MPa. The reliability and repeatability of PHTM are superior to the Schmidt hammer (SRH) and pull-out testing methods used in on-site testing. Research has confirmed that PHTM is suitable for in situ testing of prefabricated buildings, beam column joints, and other densely reinforced areas, and unsuitable for coring. Compared with other testing methods, PHTM testing has high accuracy and minimal damage to concrete structures.

This article is dedicated to improving the method of backward calculation of elastic moduli for road pavement layers in a dynamic setting, which involves analyzing deformation characteristics in the time domain. To address this issue, a mathematical model of a layered half-space has been adapted to compute amplitude–time characteristics of deformation on the surface of the layered medium and to construct corresponding maxima of vertical displacements. Adjustments have been made to the design values of vertical displacements relative to recorded experimental displacements in field conditions. The correspondence between the final values of maximum vertical displacements, amplitude–time characteristics on the surface of the layered medium, and the shapes and areas of dynamic hysteresis loops on the surface of the investigated medium has been demonstrated, achieved by adjusting the design characteristics relative to the experimental data. For the first time in solving the problem of determining the mechanical parameters of layered media, dynamic hysteresis loops and the comparison of their design and experimental areas have been proposed as a criterion for the adequacy of the result achieved.

Frequency response analysis (FRA) is the widely used technique for diagnosis of power transformer winding. Previous works in the field of FRA have steer to the standardization of its measurements procedure. To date, there is no reliable standard code for the interpretation of FRA results. In this context, this paper proposes a new parametric method to synthesis the High frequency electrical ladder network circuit (HF-ELNC) of the transformer winding. Initially, a nondestructive process is applied to extract three main winding parameters. Mainly, the shunt-series capacitances and the total equivalent inductance basing on the frequency response data from the winding terminal. To this end, the proposed continuous-time state–space model is converted into a gain-numerator-denominator form. After that, the derived matrix equations are iteratively estimated by population-based algorithm using enhanced logistic choatic marine predator algorithm (ELCMPA), from where, three objective functions are considered in the model of identification including the capacitances, the inductances and the resistances. As well, classical methods such as finite elements or analytical formulas require design winding specifications. In this study, instead of winding geometry knowledge, the proposed method certifies a unique, physically and mutually coupled HF-ELNC. The accuracy of the proposed method is validated through case study of a real transformer winding.

The paper is devoted to the development of a finite element model of an eddy current probe designed to test the degree of soldering in lap-joint soldered connections of conductive busbars. A methodology for developing a finite element model has been devised that includes a geometric parameter that, when altered, leads to the remeshing of the finite element grid without affecting the test parameters of nondestructive testing. This allows for a series of signal measurements of the finite element model of the eddy current probe, followed by averaging, thereby ensuring acceptable accuracy. The test results confirm the functionality of the eddy current probe, with a defect size measurement range in the soldered joint from 0 to 100% and a guaranteed main absolute error in measuring the degree of soldering of 5%.

A new method for detecting subsurface solid objects buried in farmlands, such as plastic bottles, wasted cans, etc., has been proposed by applying the technique of infrared (IR) thermography to monitor the temperature of soil surface subjected to solar irradiation. Through both experimentation and simulation, this study parameterizes the influence of environmental factors on IR images and validates the detection capabilities of the method. To verify the feasibility of IR thermography testing, the experimental section of the work is devoted to monitoring aluminum and polyethylene terephthalate cans buried in sand with varying grades of moisture. The dependencies between the efficiency of foreign object detection and their depth are derived. A restoring pseudothermal flux algorithm was used to reduce the impact of lateral diffusion on IR thermographic detection of foreign objects buried in soil. Variations of soil temperature caused by varying solar radiation during multiple day-night cycles are used to improve the detectable diameter-depth ratio. The described technique is efficient and provides no harm to human beings.