Problems Of Nondestructive Testing Research Articles

Quantitative guided wave imaging with shear horizontal waves and deep convolutional descent full waveform inversion

Effectively determining the size and thickness distributions of corrosion damages is a vital problem in nondestructive testing (NDT). In this article, a new approach is introduced that employs magnetostrictive transducers (MST) to excite the first dispersive shear horizontal mode (SH1), and utilizes the DCD-FWI (deep convolutional descent full waveform inversion) to provide comprehensive thickness mapping in just 1 s. Compared with traditional imaging techniques, DCD-FWI network is an intrinsically full waveform inversion (FWI) based method, which yields reliable imaging results in large scale finite element simulations. Moreover, the shorter wavelength and resistance to water loading of SH guided waves bring about reliable imaging results. Combined with these advantages, the high energy transfer efficiency of the MST enhances the proposed method's robustness, as demonstrated by guided wave tomography experiments on aluminum plates.

Mathematical modeling of diagnostics of thermoelastic layered medium

The article discusses the problems of non-destructive testing of multilayer composite materials. Technological influences during manufacturing and the influence of external factors during the operation of composite structures can lead to the occurrence of material defects, which manifests itself as heterogeneity and anisotropy of individual layers and, as such, affects thermomechanical processes in multilayer composites. In the work as a model of non-destructive testing, the mathematical problem of determining the thermomechanical characteristics of weakly inhomogeneous and weakly anisotropic layers of a multilayer half-space is formulated. The tests include measurements on the outer surface of the half-space of temperature and displacements arising as a result of thermoelastic processes initiated in a special way in the layered medium under study. An approach to solving the formulated problem, based on the linearization of the original nonlinear equations and the application of the method of stationary basic processes, is proposed.

Old but not obsolete: Dimensional analysis in nondestructive testing and evaluation

This paper proposes dimensional analysis for solving Non-Destructive Testing & Evaluation (NDT&E) problems. This is the first time that this approach has been adopted in the framework of NDT&E, and the paper ushers in the development of probes and methods for simultaneously estimating several parameters with a simple approach. The most important theorem of dimensional analysis is Buckingham’s π theorem, based on the concept that the laws of the physics do not depend on the particular set of units chosen. At the core of this theorem is a systematic reduction in the number of variables describing a physical problem. This reduction is equal to k, the number of fundamental dimensions required to describe the variables of the physical problem in its original setting. This makes the approach ideal when the number of variables in the physical problem is not much greater than k. In this paper, we demonstrate the approach’s effectiveness in the simple problem of simultaneously estimating the thickness and electrical conductivity of a conducting plate, via Eddy Current Testing. The approach is original, effective, efficient, and currently patent-pending. All the aspects, from theory to experimental validation, are provided, and it is proved that the proposed method achieves a very good degree of accuracy over a wide range of thicknesses and electrical conductivities. Moreover, the proposed method is compatible with the in-line and real-time estimation of thickness and electrical conductivity in an industrial environment.

Concrete Non-destructive Testing Technology and Its Application

Nondestructive testing of concrete has a very important position in the construction industry, this paper explains the nondestructive testing, introduces the necessity of nondestructive testing in a number of aspects, classifies the nondestructive testing technology of concrete, introduces the characteristics of several types of nondestructive testing, explains the current application of nondestructive testing in various fields of construction, the problems of nondestructive testing.

Grid Convergence Analysis of Grid-Characteristic Method on Chimera Meshes in Ultrasonic Nondestructive Testing of Railroad Rail

A three-dimensional direct problem of ultrasonic nondestructive testing of a railroad rail treated as a linear elastic medium is solved by applying a grid-characteristic method on curved structured Chimera and Cartesian background meshes. The algorithm involves mutual interpolation between Chimera and Cartesian meshes that takes into account the features of the transition from curved to Cartesian meshes in three-dimensional space. An analytical algorithm for generating Chimera meshes is proposed. The convergence of the developed numerical algorithms under mesh refinement in space is analyzed. A comparative analysis of the full-wave fields of the velocity modulus representing the propagation of a perturbation from its source is presented.

Mathematical modeling of diagnostics of residual stresses in a layered medium

The work is devoted to the use of mathematical modeling in the framework of the problems of non-destructive testing of structural materials. A mathematical formulation of a three-dimensional problem of diagnostics for elastic layered medium is constructed, which makes it possible to determine the spatial distribution of residual stresses from the values of displacements measured on the surface of a layered half-space, which arose as a result of a specially initiated wave process. Under the assumption of weak inhomogeneity and anisotropy of the layers, a transition is made to a linearized (which is ill-posed) problem, the procedure for solving which is constructed using the method of stationary basic processes. As an example, the case of diagnosing a one-dimensional (depending only on the distance to the surface) distribution of residual stresses is considered.

Estimating complex dielectric permittivity of materials by the frequency dependences of reflection and transmission coefficient magnitudes in the microwave range

Electromagnetic waves of the microwave range are an effective tool for solving problems of non-destructive testing and diagnostics as applied to dielectric, semiconductor, and composite materials, ferrite products. An algorithm is suggested for estimating the complex permittivity of non-magnetic materials by the frequency dependences of reflection and transmission coefficient magnitudes during the interaction of electromagnetic waves in the microwave range with a sample in the form of a plate located in the cross section of a closed rectangular waveguide. Statistical analysis methods are applied to evaluating the errors arising during the application of this algorithm due to imperfect matching of the waveguide measurement path with the receivers and generator of the scalar circuit analyzer. It is shown that the proposed algorithm using the results of measuring reflection and transmission coefficients in a wide frequency range can significantly reduce the influence of frequency-dependent measurement errors on the accuracy of complex permittivity estimation. An additional advantage of the algorithm is that its implementation does not require vector network analyzers, which are very expensive.

Non-destructive estimation of conductive network constructed by 1D fillers in polymer composites via small angel X-ray scattering

Efficient and non-destructive estimation of conductive network in conductive polymer composites is now becoming an urgent issue than ever owing to the rapid rise of modern electronic industry. Nevertheless, traditional observation and estimation method inevitably cause damage and distortion to sample, demanding urgent development of a non-destructive fidelity detection methodology. In this study, the degree of network formation of carbon nano-fibers in polymer matrix was calculated based on small-angle X-ray diffraction (SAXS). The degree of fiber network construction based on the power law coefficient (A) has been proved to be valid and effective in comparison with other testing methods. Moreover, a mathematical model was established to predict the electrical conductivity of the conductive polymer composite. This study not only solves the problem of non-destructive testing of fiber network construction, but also provides theoretical guidance for the design of conductive polymer composites.

Enhanced phase method of signal detection for ultrasonic magnetostriction defectoscopy of power equipment

The magnetostrictive method of ultrasonic flaw detection has certain advantages, in particular, the ability to control objects with complex geometry, at their high temperature, the ability to control dry contact between the transducer and the object, difficult access to the controlled area, etc. The peculiarities of the generation of ultrasonic waves by magnetostrictive transducers and their distribution in control objects determine the low level of the signal/noise ratio, which limits the possibilities of practical application of this method. The aim of the paper is to improve the phase method for detecting signals of magnetostrictive receivers with a low signal/noise ratio and to check the effectiveness of the proposed technical solution for solving problems of non-destructive testing of energy equipment elements using magnetostrictive defectoscopes. The paper discusses the phase method of detecting radio pulse signals of magnetostrictive converters against the background of additive noise, which is based on a combination of the capabilities of the discrete Hilbert transformation, which makes it possible to determine the envelope and phase of signals, and methods of statistical processing of the results of phase measurements. The proposed signal processing algorithm was studied both in a model experiment and when processing real magnetostrictive defectoscope signals. The proposed method makes it possible to detect radio pulse signals with a signal/noise ratio close to 1. The reliability of the obtained data is confirmed by the results of computer simulation. The considered method of detecting signals can be used in ultrasonic magnetostrictive defectoscopes and other diagnostic systems operating in conditions of reduced signal/noise ratio. Keywords: magnetostrictive defectoscope, ultrasonic defectoscopy, phase methods of signal processing, Hilbert transform, envelope, phase, sample resulting length of the vector.

Modification of the Grid-Characteristic Method on Chimera Meshes for 3D Problems of Railway Non-destructive Testing

Modification of the Grid-Characteristic Method on Chimera Meshes for 3D Problems of Railway Non-destructive Testing

IX INTERNATIONAL INDUSTRIAL FORUM "TERRITORY NDT – 2022"

A brief overview of the events of the IX International Industrial Forum “NDT Territory. Non-destructive testing. Tests. Diagnostics” Within the framework of the forum, round tables were held on topical problems of non-destructive testing and technical diagnostics, a youth scientific and technical conference, the All-Russian competition of final qualification works “New Generation – 2022”, the final of the All-Russian competition on non-destructive testing “Defectoscopist 2022” and a National Prize in the field non-destructive testing and technical diagnostics. At the exhibition of instruments and equipment, modern means of NDT and TD were presented. The review briefly discusses the main achievements of companies in the field of creation and application of technical means intended for testing, measuring and non-destructive testing of modern structures and materials for various purposes. These are means of vibration diagnostics and non-destructive testing based on the use of various physical methods for the interaction of radiation and fields with the substance and the object of control. Brief information about the companies involved in solving these problems is given.

Method of the Mechanical Properties Evaluation of Polyethylene Gas Pipelines with Portable Hardness Testers

This article is devoted to the study of means and methods for non-destructive testing mechanical properties of polyethylene gas pipelines that have been in operation for 25–55 years. In order to assess mechanical properties, stress at yield was chosen as a key parameter. Stress at yield is determined from the results of tensile tests and is associated with the limiting circumferential (hoop) stress, determined from the results of tests for short-term pressure. Tensile tests require sample cutting and the shutdown of pipelines’ service. To solve this problem of nondestructive testing of pipelines, tests were carried out using the methods of Shore, Leeb and dynamic instrumental indentation. According to the test results, it was revealed that the correlation coefficient between the values of stress at yield and hardness, obtained by the method of dynamic instrumental indentation, is 0.98 which confirms the possibility of the evaluation of the mechanical properties of pipelines by the method of dynamic instrumental indentation.

Evaluation of Pipe Cracks Based on Cloud Contour of Three-Dimensional Induced Eddy Current Field

Considering the problem of non-destructive testing and quantitative evaluation of metal materials, an electromagnetic method for visual and quantitative evaluation of surface defects on metal pipe is proposed in this paper. The dual-excitation probe with the combination of arc-shaped and rectangular coils is constructed. The eddy current magnetic field on the outer cylindrical surface of metal pipe is calculated and analyzed by COMSOL Multiphysics finite-element software, and then the influences of crack location and geometric parameters on three-dimensional magnetic field characteristics are studied. The results show that the cloud contours constructed by the magnetic induction intensity norm can accurately evaluate the information such as the location, size, depth, and orientation of the surface crack. In addition, the cloud contours constructed separately by the magnetic induction intensity in three directions can be used for auxiliary judgment to further determine the relevant important parameters of the surface crack to be tested.

Investigation of Spectral and Temporal Characteristics of Free Vibrations of Bearing Rings Press Joints for Solving Problems of Non-Destructive Testing

To determine the possibility of controll the fit tightness of the press joints of the inner rings of the bearings with the journals of the wheelset axles by the method of free vibrations, experimental studies of the frequency and time patterns of bearing free rings natural vibrations, tuning samples, which are press joints of rings and shafts with interferences from 20 to 90 microns and joints of bearing rings with real axles of wheelsets, received from operation to the mid-life repair in car repair depots. The influence of various boundary conditions on the natural oscillation parameters of the free ring of the bearing has been studied. The natural frequencies of bearing rings in a free state and samples of rings and shafts press joints were experimentally determined. A comparative analysis of theharmonic spectra of their own oscillations was carried out, on the basis of which a criterion for the fit leakeage of the ring to the axle neck of the wheelset was found. The finite element method is used to calculate natural frequencies and the corresponding modes of ring vibrations in a free state and interference samples. A comparative analysis with the experimentally obtained frequencies was carried out. To analyze the patterns of free oscillation damping, the Fourier signal transformation was performed. Their amplitude-frequency-time characteristics were obtained. The spectra of free vibrations were calculated for bearing rings put on the axle journal manually, without interference with the gap between the contact surfaces of the axle and the ring filled with industrial oil and without it, for a press connection with a tight fit and for a weak press fit. A comparative analysis of the obtained spectra was carried out, on the basis of which a method for determining the fit leakeage of the ring to the axle neck was developed.

3D modeling of pulsed thermal NDT: Back to basic features and subtle phenomena

By using advanced 3D modeling of thermal nondestructive testing (TNDT) problems, most of basic TNDT features are shortly described, but the emphasis is put on the analysis of some subtle physical phenomena which may be observed in TNDT experiments, and most of them have not been properly reflected in the earlier studies. These are: 1) the “smashing” of 2D defect surface “footprints” because of 3D heat diffusion, 2) practical approaches to determining defect lateral size by their surface temperature indications, 3) clarification of a limiting defect size/depth ratio providing reliable detection of subsurface defects; 4) inversion of “classical” temperature signals at longer times, 5) defect shading, 6) influence of composite anisotropy on defect detectability, and 7) combined heating/cooling allowing to govern behavior of surface temperature profiles.

Nonlinear interaction of Rayleigh waves in isotropic materials: Numerical and experimental investigation

Surface treatment intensity monitoring is still an open and challenging nondestructive testing problem. For the estimation of residual stress with ultrasonic measurements, local linear and nonlinear elastic constants are needed as input. In this paper, nonlinear elastic-wave interactions (also called wave mixing or scattering) — namely, the generation of secondary ultrasonic waves in a nonlinear medium — are considered as a prospective means for near-surface nonlinear elastic parameter evaluation. The allowed interactions between bulk and surface waves, as well as the dependence of the scattering efficiency on the frequency and angle between source waves, were investigated through an analytical model, then compared with FEM simulations and experimental results. Finally, possible future steps for the development of the applied methods for the determination of near-surface higher-order elastic constants are discussed. In addition, several problem-relevant data processing procedures are presented.

Characterization of nonlinear ultrasonic waves behavior while interacting with poor interlayer bonds in large-scale additive manufactured materials

Over the past decades, researchers have developed several nonlinear ultrasonic techniques for quality control of materials commonly used in different applications. Owing to the superior sensitivity of nonlinear ultrasound waves to small defects such as micro-cracks, their applicability in different nondestructive testing (NDT) problems has been investigated in numerous studies. These studies utilize frequency domain analysis to detect the generation of higher harmonics because of the formation of defects in the inspected medium. Frequency domain analysis based on the Fourier transform is a significant approach used in linear systems; however, it may not perform adequately on nonlinear systems. Hence, studies on nonlinear dynamics and physics consider analyzing systems' behavior in the phase-space domain. In contrast to the frequency domain analysis, which can result in information loss, analysis in the phase-space domain retains all the information regarding a system's states. In this study, the nonlinearities induced by poor interlayer bonding in polymer-based additive manufactured parts in the phase-space domain are investigated. It is convenient to characterize the nonlinearity in the phase-space domain because it provides a geometrical representation of a system's states. Two types of low quality interlayer bond are considered. The first type is simulated artificially while the second type is manufactured by reducing the bond quality during the printing process. The analysis verified that the received ultrasonic signals exhibit classical nonlinear behavior in the phase-space domain while interacting with simulated poor interlayer bonds. In addition, the results showed that the behavior of ultrasonic waves is amplitude-dependent and evolves into models that have not been previously reported. Furthermore, Largest Lyapunov Exponent (LLE) is used to quantify the behavior of nonlinear ultrasonic waves while interacting with poor interlayer bonds. Using LLE, it was observed that the divergence rate of the phase-space trajectories depends on the amplitude of the excitation. This observation quantitatively proves that nonlinear behavior of ultrasound while interacting with poor interlayer bonds can be amplitude-dependent. The results of both simulated and inherent poor interlayer bond cases showed that LLE can be used as a reliable quantitative damage-sensitive feature to detect and potentially characterize weak bonds, which are difficult to detect using conventional approaches. In addition, the reported results in the phase-space domain provide a basis for proposing a new mathematical model for ultrasonic waves interacting with poor interlayer bonds.

Ultrasonic signal noise reduction based on convolutional autoencoders for NDT applications

One of the most challenging problems of ultrasonic non-destructive testing is the signal distortion caused by the presence of noise, yielding the sound wave corruption and thus degrading the ultrasonic imaging technology performance due to Time of flight methods’ loss of precision. Deep learning algorithms have proven their effectiveness in reducing noise on several types of signals in different domains. In this paper, we propose a one-dimensional convolutional autoencoder for ultrasonic signal denoising. The efficiency of the proposed architecture is compared to the wavelet decomposition method, collating the peak signal-to-noise ratio values on the denoised signals. Our method proved its potential for NDT applications in recovering temporal information even on very noisy signals, and improving the PSNR by about 30 dB.

VIII INTERNATIONAL INDUSTRIAL FORUM "TERRITORY NDT – 2021"

A brief overview of the events of the VIII International Industrial Forum “NDT Territory. Non-destructive testing. Tests. Diagnostics” The exhibition of NDT and TD instruments and tools was accompanied by a business program. Within the framework of the forum, round tables were held on topical problems of non-destructive testing and technical diagnostics, a youth scientific and technical conference, the All-Russian competition of final qualification works “New Generation – 2021”, the final of the All-Russian competition on non-destructive testing “Defectoscopist 2021” and a national prize in the field non-destructive testing and technical diagnostics.

Transformation of the rotating eddy current testing signal at the desired eddy current orientation

The results of rotating eddy current testing can be regarded as the results superposed by uniform eddy current testing in orthogonal directions. However, in the case of directional nondestructive testing problems, such as weld detection, only the results from the induced current that is perpendicular to the crack have the greatest sensitivity. In contrast, the results from other induced current orientations may experience substantial noise generated by welds. In this work, a brief method is proposed to transform the results of rotating eddy current testing into the results of uniform eddy current testing at the desired eddy current orientation. The experiments indicated a good match between the signal distribution and amplitude of the transformed results and the results of the uniform eddy current testing. Moreover, the proposed method was applied for weld detection. The results revealed that the weld noise significantly decreased and that the locations of slits could be clearly identified. The results validated that the proposed method can improve the detection ability and expand the application of the rotating eddy current testing technique.