Russian Journal of Nondestructive Testing最新文献

In this paper, the influence factors on the dynamic response of a lined tunnel embedded in an inhomogeneous half-space under incident SH waves are investigated. An analytical solution for the scattering of plane SH waves by a lined tunnel embedded in an inhomogeneous half-space is derived through the complex function method and the conformal mapping technique. The analysis focuses on the treatment of straight and circular boundaries by proper coordinate transformation converting the physical plane to the corresponding image plane. The unknown coefficients for the scattered wave functions are calculated by solving a series of infinite algebraic equations. Then, the influence factors on the dynamic response of a lined tunnel in an inhomogeneous half-space are investigated through the calculation example.

The concept of “thermal equivalents” of impact damage in composites, created by iteratively fitting the parameters of flat bottom hole defects, has been elaborated. In thin-walled composites, impact damage tends to be located near the surface opposite to the impact, so thermal inspection on the rear surface of the product is most effective for their detection. Detection of defects on the front surface is associated with small signal amplitudes in the region of temperature indications and requires the use of the thermal equivalent of impact damage in the form of a combination of flat bottom hole defects. On the rear surface, temperature indications of impact damage are often butterfly-shaped and characterized by a large area of defect “footprints.” Single flat-bottom flaws can serve as thermal equivalents of such defects. The proposed concept of thermal equivalents of real defects in composites is verified experimentally on a carbon fiber-reinforced plastic specimen with impact damage of 62 J energy.

The effect of annealing temperature of nickel plastically deformed according to various schemes on the change of its microstructure and level of magnetic characteristics was investigated. The processes of recovery and recrystallization in the nickel structure are reflected quite informatively both in the change of such magnetic characteristics as coercive force and maximum magnetic permeability and in the change of the field dependence of differential magnetic permeability. In different structural states (deformed and recrystallized structures), the position of the peak of differential magnetic permeability changes, as does its height. Thus, the established patterns can be used to analyze the processes of nickel recrystallization and assess the change in its structural state during manufacturing or operation.

Elastic half-space models are widely used in geophysics and road science. In road science, these models are most often used to study the stress-strain state of pavements, which are artificially created layered media on the surface of the soil and geological massif, the main task of which is to distribute and transfer the load from a moving vehicle and ensure the comfort and safety of the user, as well as the durability of the road. Taking into account the common properties of road pavement and geological environment, methods close to geophysical methods are becoming more and more widespread when assessing the condition of road pavements. In the article the method of harmonic analysis is applied, which is realized to calculate the main characteristics of the response of layered media to test shock loading. Calculations of the amplitude–frequency characteristic of displacements at the point of shock loading were performed, and the change of its shape depending on the elastic moduli of the half-space layers was analyzed. It was found that a decrease in the elastic modulus of intermediate layers forms a pronounced ‘plateau’ in the low-frequency response of displacements. Decrease in the elastic modulus of the upper layer of the medium leads to an increase in the amplitude of displacements as the frequency increases. An increase in the elastic modulus of the underlying half-space leads to the appearance of an inflection point localized in the region of 500 rad/s, separating the amplitude–frequency response of displacements into two sections. The obtained results can be used in the development of nondestructive testing methods for layered media, oriented on the recording and analysis of the displacement amplitude–frequency response.

The rapid growth of filament winding techniques for fabricating plastic composite structures has not been matched by advancements in testing and evaluation methods. The Naval Ordnance Laboratory (NOL) ring test has emerged as a valuable technique for assessing filament wound composites, proving useful for material comparison in research and development, as well as quality control. Internal pressure is applied to ring-shaped specimens in a manner similar to burst testing used for pressure vessels. This method allows direct observation of fracture behavior within FRP layers, which is not possible with actual pressure vessels. This paper standardizes ring fabrication and testing methods for determining ring tensile strength and demonstrates the benefits of ring burst tests. Fracture analysis of carbon/epoxy NOL rings, under both defect-free and adverse conditions, was conducted using acoustic emission (AE) measurements to understand strength degradation. A mathematical method was also created to predict the failure load of carbon/epoxy NOL rings with a reasonable margin of error. The simplicity and cost-effectiveness of this method make it a practical alternative to burst tests of pressure vessels.

In air-coupled ultrasonic nondestructive testing of a number of products (biological objects, products made of chemically active or explosive materials), the amplitude of the electrical signal applied to the transmitting piezoelectric transducer is limited and, in some cases, cannot exceed a value of the order of U ~ 10–15 V. In this case, the sensitivity of testing is considerably reduced and therefore all possible ways should be used to increase it. First of all, piezoelectric transducers with the highest possible electroacoustic conversion coefficient should be used. In addition, it is necessary to select such an air gap length ({{d}_{{{text{air}}}}}) between the transmitting transducer and the test object that ensures the maximum amplitude of the ultrasonic emission signal “at the input” of the product. Since the maximum amplitude of the ultrasonic signal emitted by the transducer is located in the near field of the transducer, it is necessary to select the value ({{d}_{{{text{air}}}}}) corresponding to the length of the near field of the transmitting transducer in air, provided that in this case there is no re-reflections of the emission signals in the air gap. In turn, this requires the use of short (broadband) ultrasonic signals and, consequently, the use of ultrasonic broadband piezoelectric transducers. The article shows that the parameters of the matching layers of the air-coupled ultrasonic piezoelectric transducer affect both the bandwidth of the transducer and the spatial characteristics of the transducer, including the position of the acoustic field maximum. It is shown that it is possible to determine the maximum of the ultrasonic broadband signal in air in order to determine the optimal length of the air gap, at which the ultrasonic signal with maximum amplitude is emitted into the product, by analyzing the correlation distribution of the field of an air-coupled broadband transducer. The results of the experiments are presented, confirming the necessity of providing the optimum length of the air gap between the air-coupled ultrasonic transmitting transducer and the test object to increase the sensitivity of through-transmission testing of simulators of products made of explosive materials.

X-ray computed tomography (XCT) is one of the most informative methods of nondestructive testing of polymer composite materials (PCMs) and products made of them. One of the important stages of the XCT of PCM products is segmentation, the automation of which is of research interest. In the segmentation process, it is important to identify isotexture zones containing local X-ray density variations. In this paper we investigate the possibilities of three-dimensional texture filtering (Gaussian filter, Gabor filters) in clustering of X-ray computed tomography data by simple linear iterative clustering (SLIC) algorithm and evaluated their efficiency in terms of parameters: the share of mismatch between the boundaries of clusters and the boundaries of segmented areas and sphericity of clusters, as well as the performance in terms of the time to partition the dataset into the required number of clusters. The results of the study show that the application of three-dimensional texture filters improves the clustering accuracy and sphericity of isotexture clusters of PCM product XCT data without any considerable increase in clustering time compared to the raw data. The maximum increase in clustering accuracy was observed when using a combination of Gaussian and Gabor filters, while clustering time increased.

During the picking, storage, and transportation processes, collisions between fruits can cause mechanical damage and reduce the overall quality of the fruit. In order to ensure the quality of fruits, it is necessary to carry out nondestructive testing on fruits. This paper investigates a method for nondestructive evaluation (NDE) of early mechanical damage in apples using pulsed infrared thermography (PIRT). Thermal excitation was applied to apples, and temperature differences were captured with an infrared camera. Fast Fourier transform, principal component analysis, and morphological algorithms were used to process and analyze the images. The experimental results show that the morphological algorithm performs better than other algorithms in defect edge detection, enabling clear identification of defect features and reducing noise interference. We provide an efficient and accurate NDE solution for mechanical damage in apples, which is significant for improving the quality of agricultural products and extending their shelf life.

Carbon fiber reinforced polymer has been widely used in the repair and reinforcement of steel structures due to its excellent structural performance. The CFRP-reinforced steel structures are widely used in various industries. However, due to the effect of various unexpected loads, hybrid structures are prone to generate defects, which will harm structure safety. Hidden corrosion defect on the interface of CFRP and steel substrate is a typical defect type and proposes an urgent need for non-destructive testing (NDT) methods. This study investigates the possibilities of corrosion defect detection using eddy current pulsed thermography (ECPT) and proposes an improved excitation coil configuration, ferrite-yoke-Helmholtz-coil, to improve the effectiveness and generality of the ECPT technology. Experiments were conducted on the CFRP-reinforced steel structure with prefabricated corrosion defects, and the results demonstrate the effectiveness of the proposed excitation configuration. The influence factors of the detection effect were also studied, including the defect size, excitation current, and excitation duration. The findings demonstrate that the proposed excitation coil configuration is efficient for hidden corrosion defect detection.

The influence of varying annealing temperature on magnetic and magnetoacoustic properties of cold-deformed alloy 97% Ni, 3% Fe has been investigated. The study of the microstructure of the nickel–iron alloy showed the presence of rolling texture up to annealing temperatures of approximately 500°C. With further increase of annealing temperature of the investigated alloy, as a result of recrystallization, the texture disappears and anisotropy of its magnetic and magnetoacoustic parameters decreases considerably. The sensitivities of magnetic and magnetoacoustic parameters to the rolling-induced anisotropy of the nickel–iron alloy are compared. It is shown that the differential magnetic permeability measured with the DIUS-1.21M hardware and software system is a parameter most sensitive to anisotropy.