Nondestructive Testing Applications Research Articles

Identification of Materials Using a Microwave Sensor Array and Machine Learning

Material identification has many applications in non-destructive testing, chemistry, infrastructure maintenance, etc. Here, for this purpose, we propose a technique based on the use of a microwave sensor array with the elements of the array resonating at various frequencies within a wide range and applying machine learning algorithms on the collected data. Compared to the widely use single resonating sensors, the proposed methodology allows for material characterization over a wide frequency range which, in turn, improves the accuracy of the material identification procedure. The performance of the proposed methodology is tested via the use of easily available materials such as woods, cardboards, and plastics.

Characterization of Microstructure Variations by Laser-Ultrasound during and after the Heat Treatment of Metals

We demonstrate the potential of laser ultrasound for non-destructive testing applications in steel production and processing in two use cases: (1) Imaging of the grain structure transition between the thermally hardened surface and the unaffected core material with a comparison to sectional views by an optical microscope. We found very good correlation between the laser ultrasonic image and the microscopic view at the cross section. (2) In situ monitoring of Poisson’s ratio of steel sheets during thermal processes by evaluation of resonant frequencies of Lamb waves. In our ongoing research the results will be correlated to metallurgical properties of interest.

Transparent memory testing based on dual address sequences

An effectiveness of the application of classical non-destructive tests for testing storage devices and their main disadvantages, among which there are great time complexity and low diagnostic ability, are analysed. The concept of double address sequence 2A is defined and the examples of their formation based on counter address sequences and Gray code are provided. The basic element of non-destructive tests with the use of double address sequences is synthesized and its detecting and diagnostic abilities for different storage devices defects are explored. There are two new non-destructive tests of memory devices March_2A_1 and March_2A_2 and an estimation of their time complexity and efficiency of failure detection are given. A significantly lower time complexity of the proposed tests and their high diagnostic ability in comparison with classical non-destructive tests are shown.

Thermal waves emitted by moving sources and the Doppler effect

This paper theoretically studies the Doppler effect for thermal waves, finding an expression of the frequency shift for the two cases of moving source, and moving observer. Differences and analogies with the Doppler effect for electromagnetic and acoustic waves are highlighted. Thermal shock waves are introduced and simulated numerically. An application for nondestructive evaluation and testing of materials is also discussed.

Terahertz subwavelength edge detection based on dispersion-induced plasmons.

Terahertz imaging has recently attracted great attention owing to the abilities of high penetration and low ionizing damages. However, the low resolution and low contrast resulting from the diffraction limit and unwanted background illumination significantly hinder the extensive usage. In this Letter, we propose and numerically demonstrate a terahertz subwavelength imaging method capable of extracting only the edges and fine features of the targets. The underlying physics is the efficient transmission of the scattering evanescent waves related to key geometric information while blocking the propagating components. By exploiting the structurally induced plasmons in a bounded metallic waveguide, the transmission channel for evanescent waves is realized by hyperbolic metamaterials through periodically stacking dielectric layers. On this basis, high-contrast edge detection with a resolution up to ${0.1}\lambda$ is demonstrated at terahertz wavelengths. The proposed terahertz imaging method may find important applications in non-destructive testing, weak scattering object detection, and high-contrast microscopy.

Design of a new type of omnidirectional shear-horizontal EMAT by the use of half-ring magnets and PCB technology

In this paper, an electromagnetic acoustic transducer (EMAT) for generating and receiving omnidirectional shear-horizontal (OSH) wave in aluminum plate is developed. The proposed OSH-EMAT consists of a specially designed printed circuit board (PCB) coil and a pair of half-ring magnets. Vertical oriented static magnetic field and the radial alternative eddy current are applied to excite the Lorentz force along the circumferential direction. A three-dimensional finite element model has been established to simulate the distributions of the static magnetic flux, the eddy current, and the exciting process of SH wave. Further experimental results show that the proposed electromagnetic ultrasonic transducer has good consistency in the performance of omnidirectional excitation and reception. The new OSH-EMAT design has the potential for many non-destructive testing applications owing to its low cost, acceptable accuracy and convenient processing and fabrication.

A hybrid spectral/finite element method for accurate and efficient modelling of crack-induced contact acoustic nonlinearity

We propose a 2D hybrid spectral/finite element scheme for numerically resolving crack-induced contact acoustic nonlinearity in solid structures. While the high-order spectral element method (SEM) is much more efficient than the classical low-order finite element method (FEM), the fact that spectral elements are relatively large renders the SEM ineffective in discretizing microscopic cracks. The classical FEM, on the other hand, is good at modelling complex geometries. However, the computation of large-scale structures by the classical FEM can be extremely expensive. In this work, the coupling between high-order spectral elements and low-order finite elements is formulated by the Lagrange multipliers method. The nonlinear contact between crack surfaces is modelled using a penalty method. The aim of the proposed hybrid method is to simultaneously reduce the degrees of freedom (DOFs) in systems and ensure high numerical accuracy. A comprehensive mesh convergence study has been conducted to demonstrate the high convergence rate of the proposed method in modelling ultrasonic wave propagation, and its capability to converge for weak crack-induced contact acoustic nonlinearity. Through a series of numerical experiments on generation and propagation of nonlinear ultrasonic wave modes, the proposed method has been shown to possess a high accuracy and geometric flexibility, and require significantly less computational resources than the classical FEM. The proposed hybrid method will provide an efficient, accurate and robust numerical approach for studying crack-induced contact acoustic nonlinearity which nowadays is being widely exploited by non-destructive testing applications.

Non-contact harmonic magnetic field detection for parallel steel pipeline localization and defects recognition

A novel detection method and targets signal extraction algorithm for parallel steel pipeline localization and defects recognition based on harmonic magnetic field are proposed. An orthogonal vector differential focusing array detector was designed, which radiates high-frequency (HF) and ultra-low-frequency (ULF) electromagnetic waves to pipeline based on the principle of Frequency Modulated Continuous Wave (FMCW), and records the signals in parallel using high-sensitivity Tunnel Magneto Resistance (TMR) array sensors. The joint signal pre-processing algorithm of Combination Morphological Pulse Elimination (CMPE) and Quantum Genetic Gaussian Potential Stochastic Resonance (QGGPSR) is proposed to improve signal quality by adaptively eliminating random pulse and noise. The time–frequency analysis algorithm Complementary Ensemble Local Mean Decomposition (CELMD) is used to decompose the pipeline defects signal in detail, and the appropriate components are selected and fused into a correlation array signal cluster. Finally, the targets signal are separated by Limited-memory BFGS Independent Component Analysis (L-BFGS-ICA) based on machine learning optimization to enhance their legibility. The magnetic dipole harmonic simulation model and the 20# steel parallel pipeline experimental platform are established, and compared with the passive detection method to verify the effectiveness and practicality of the proposed method. The results show that this method can accurately locate parallel pipelines and detect different kinds of defects in noisy environment, which is of great significance for the application of non-contact Non-Destructive Testing (NDT) in practical engineering.

Advances in applications of non-destructive testing (NDT): a review

Manufacturing defects and discontinuities in a product are anomalies which can lead to severe damages which may sometimes involve loss of life. These defects must be examined and corrected before the product goes into service. There are two methods of testing a product for defects and discontinuities viz. Destructive Testing and Non-Destructive Testing. Destructive Testing entails subjecting the product to conditions that leads to failure of the product whereas Non-Destructive Testing (NDT) is the process of examining the products for defects in a way in which it retains its usefulness for future service. This paper discusses various methods involved in NDT such as Visual Testing, Magnetic Particle Inspection, Penetrant Testing, Ultrasonic Testing, Radiographic Testing, Acoustic Emission and Eddy Current Testing with a major focus on advances in the applications of NDT.

The alternative Kirchhoff approximation in elastodynamics with applications in ultrasonic nondestructive testing

The Kirchhoff approximation is widely used to describe the scatter of elastodynamic waves. It simulates the scattered field as the convolution of the free-space Green’s tensor with the geometrical elastodynamics approximation to the total field on the scatterer surface and, therefore, cannot be used to describe nongeometrical phenomena, such as head waves. The aim of this paper is to demonstrate that an alternative approximation, the convolution of the far-field asymptotics of the Lamb’s Green’s tensor with incident surface tractions, has no such limitation. This is done by simulating the scatter of a critical Gaussian beam of transverse motions from an infinite plane. The results are of interest in ultrasonic nondestructive testing. doi:10.1017/S1446181120000036

Excitation and manipulation of guided shear-horizontal plane wave using elastic metasurfaces

The lowest order shear horizontal wave (SH0 wave) is of great importance in structural health monitoring (SHM) and nondestructive testing (NDT), since it is the only non-dispersive guided wave mode in elastic plates. However, SH0 wave is less used than Lamb waves in the past decades, which is mainly attributed to the fact that controllable excitation of pure mode SH0 wave and manipulation of its propagation are more difficult than Lamb waves. In this work, inspired by the unique feature of SH0 wave that it can propagate around curved surfaces with negligible reflection, metasurfaces based on multiple arch-shaped strips are proposed for generating plane SH0 wave from a cylindrical wave source and realizing anomalous refraction of SH0 wave. Firstly, after analyzing the wave modes in finite-width arch-shaped strips, the strips’ capability of covering full 2π phase shift with high transmittances is demonstrated. Then three types of metasurfaces, i.e. the device for converting cylindrical SH0 wave to plane wave, the metasurface for directional refraction and the one for delivering the wave energy along a circular path are designed and validated by simulations. After that, experiments are conducted to investigate the designed metasurfaces’ performances and the obtained results are in good agreement with the design expectations. The proposed metasurfaces provide a cheap way to generate plane SH0 wave and manipulate its propagation, which will have great potential applications in NDT and SHM.

Advances in applications of Non-Destructive Testing (NDT): A review

ABSTRACT Manufacturing processes such as casting, rolling, forging, extrusion, material removal processes, etc. are some of the common techniques used today in manufacturing industries. However, these processes must be carried out with utmost precision and precaution. Even the slightest negligence can give rise to anomalies which can be classified as defects or discontinuities depending upon their repairability. Non-Destructive Testing or NDT is amode of testing which has been adopted by industries for decades to test mass manufactured products for anomalies. This paper discusses various NDT methods, such as Visual Testing, Magnetic Particle Inspection, Penetrant Testing, Ultrasonic Testing, Radiographic Testing, Acoustic Emission and Eddy Current Testing. The paper also discusses how technical advancements have broadened the scope of NDT even in industries that may not be manufacturing oriented, indicating that NDT is not limited to detection of anomalies. Even though these developments have made NDT more favourable, this paper highlights the fact that these techniques are mostly manual and heavily dependent upon inspectors’ knowledge and experience, leaving room for errors. This paper also discusses the key challenges and future scope in the field of NDT.

SOME ASPECTS OF NON-DESTRUCTIVE TESTING OF EQUIPMENT AND PIPELINES OF NUCLEAR POWER PLANTS

Topical aspects of non-destructive testing (NDT) of equipment and pipelines of power units of nuclear power plants (NPP) are considered. Non-destructive testing is an integral part of the entire life cycle of a nuclear power plant. Briefly analyzed documentation and types of non-destructive testing at the stage of manufacturing equipment and pipelines. Power of ultrasonic testing of welded joints of pipelines with a thickness of 2 to 6 mm. The main points of drawing up technological maps of non-destructive testing are noted. A brief analysis of the application of non-destructive testing in accordance with the requirements of the regulatory documents of the Russian Federation and the safety standards of the International Atomic Energy Agency is provided. It is shown that in recent years there has been a tendency to expand the role of NDTs from the classical approach of detecting and assessing defects to the use of NDTs in the study of metal degradation and ageing processes during the operation of NPP equipment and pipelines.

Recent Advancements in Non-Destructive Testing Techniques for Structural Health Monitoring

Structural health monitoring (SHM) is an important aspect of the assessment of various structures and infrastructure, which involves inspection, monitoring, and maintenance to support economics, quality of life and sustainability in civil engineering. Currently, research has been conducted in order to develop non-destructive techniques for SHM to extend the lifespan of monitored structures. This paper will review and summarize the recent advancements in non-destructive testing techniques, namely, sweep frequency approach, ground penetrating radar, infrared technique, fiber optics sensors, camera-based methods, laser scanner techniques, acoustic emission and ultrasonic techniques. Although some of the techniques are widely and successfully utilized in civil engineering, there are still challenges that researchers are addressing. One of the common challenges within the techniques is interpretation, analysis and automation of obtained data, which requires highly skilled and specialized experts. Therefore, researchers are investigating and applying artificial intelligence, namely machine learning algorithms to address the challenges. In addition, researchers have combined multiple techniques in order to improve accuracy and acquire additional parameters to enhance the measurement processes. This study mainly focuses on the scope and recent advancements of the Non-destructive Testing (NDT) application for SHM of concrete, masonry, timber and steel structures.

Non-destructive inspection and quantification of defects in plywood using a portable digital holographic camera

The demand for plywood products for the interior and exterior construction has grown significantly over the years. Therefore, detection of defects present in the plywood is of prime importance to maintain good quality of construction. In this study, qualitative and quantitative analyses of defects in plywood using digital holographic interferometric technique are presented. In this process, thermal and mechanical loads are applied to the test sample of plywood to generate interferometric fringes by comparing the normal and stressed states of the test sample. A portable digital holographic camera developed for non-destructive testing applications is employed for detection of cracks, delamination, edge defects, and layer opening in the plywood. The defects in the plywood sample are identified by observing discontinuities in the interferometric fringes. Quantitative analysis of defects is performed by plotting their 2-D and 3-D phase profiles from the digital holographic interferometric results. The obtained results of defects on plywood are validated by a mechanical profiler.

Wave propagation in glass fibre-reinforced polymer (GFRP) bars subjected to progressive damage—Experimental and numerical results

Glass fibre reinforced polymer (GFRP) is a material of increasing interest in civil engineering applications. It is used as internal reinforcement for concrete structures (especially in extremely corrosive environments), as well as structural profiles, plates, and gratings. However, estimating the life of GFRP structures represents a challenge for the construction industry. To address this challenge, a numerical model of elastic wave propagation in GFRP bars is presented in this paper so that it can be used to reduce the number of physical testing required to estimate the degradation of GFRP bars in the field.The proposed numerical model is designed to assist the application of ultrasonic non-destructive testing (NDT) techniques and develop a framework for the evaluation of progressive damage of GFRP bars due to a highly alkaline environment. The proposed methodology consists of: (i) development and calibration of a numerical model of elastic wave propagation in GFRP bars in Abaqus, (ii) simulation of deterioration of the bars, and (iii) comparison of experimental, large and low strain tests (shear test and ultrasonic evaluation) with results of numerical simulations.The results show that the model (low strain properties) correctly captures the deterioration rates seen in the shear strength test (large strains). The model is used to study ultrasonic features and demonstrates that low strain measurements (e.g. wave dispersion, wave amplitude) can be used to estimate the effect of progressive damage on large strain properties in GFRP bars, which can result in a decreased number of required destructive tests.

Real-time dual-channel speckle interferometry based on an improved dual-observation configuration with spatial phase-shifting

This paper develops a real-time dual-channel speckle interferometry system based on an improved dual-observation configuration to address the issue of simultaneous measurement of the out-of-plane displacement and slope. A dual-observation configuration combined with an additional light path is used to provide the possibility to create two measurement channels corresponding to the out-of-plane displacement and slope, respectively. In the system, two symmetric observation light paths are slightly displaced from each other by a deliberate tilt of the plane mirror to introduce an adjustable lateral shear. One of the two observation beams is shared by both measurement channels to improve the system’s stability. Besides, using the spatial carrier phase-shifting technique induced by multi-aperture, the real-time phase retrieval is achieved for simultaneous measurement of the dynamic out-of-plane displacement and slope. Both the experimental investigation and the non-destructive testing (NDT) application are finally presented to demonstrate the feasibility and effectiveness of the proposed system.

Linear and nonlinear resonant ultrasonic techniques applied to assess delayed ettringite formation on concrete samples

This study investigates the application of different ultrasonic Non-Destructive tests to assess Delayed Ettringite Formation, in concrete samples exhibiting low kinetic expansions (and up to 0.21%). Linear and nonlinear Resonant Ultrasonic Spectroscopy and Acoustic Emission tests were used. Scanning Electron Microscopy and optical microscopy observations were conducted at the end of the monitoring tests. The results showed a slight increase of the dynamic modulus and Quality factor while nonlinear hysteretic parameters remained constant over the test duration. Acoustic Emission tests attested the occurrence of events. However, the microscopic observations did not reveal meaningful differences in microcracking extent between the samples.

Multidirectional total variation-based method for fringe pattern despeckling: application to the phase retrieval in digital speckle pattern interferometry

Digital speckle pattern interferometry (DSPI) is a widely used technique in various high-precision nondestructive testing applications. However, a coherence multiplicative noise, called speckle noise, is produced. Speckle noise degrades the quality and the resolution of the fringes, leading to difficulties in fringe analysis and phase retrieval. We aim to restore the DSPI correlation fringes and reduce the speckle noise through a multidirectional total variation method. In this method, the local fringe orientation, computed through Riesz transform, is used to increase the sensitivity of the variational regularization to the spatially varying directional intensity changes. The proposed algorithm is applied to the directional wavelet phase retrieval technique. The performance of the proposed method is evaluated with both simulated and experimental DSPI fringe patterns, obtaining satisfactory results.

Resonant properties of a multilayer strip-slot transition and its application for microwave measurements of dielectric properties of materials

Statement of the problem: One of the actual problems of applying radio materials at high and ultrahigh frequency ranges is the problem of increased requirements for the accuracy of assessing their dielectric properties. Currently, non-resonant and resonant methods are applied to assess the dielectric properties of radio materials at the frequency ranges indicated above. Non-resonant methods are expedient for application in non-destructive testing of large-area sheet materials. Their implementation requires the application of an expensive vector network analyzer. Resonant methods are applied with a limited amount of the test material or in its powder state. In the implementation of resonant methods the main investigated parameter is the displacement of the frequency of the electrical resonance. As a consequence, only the amplitude values of the transmission and reflection coefficients need to be known. This feature makes it possible to carry out microwave measurements for the resonant method applying a scalar network analyzer which has a lower cost compared to a vector network analyzer. That feature is an advantage in some cases. One of the promising directions in the development of the resonant measurement method is its implementation based on applying of a volumetric-modular technology. In particular its implementation that based on application of a multilayer strip-slot transition. The problem with this approach is the lack of researches in terms of the effectiveness of the application of the multilayer strip-slot transition as a device with a tunable frequency of electrical resonance. Aim: The aim of this article is to present a resonant method based on the application of the multilayer strip-slot transition as a basic measuring device. Such a design solution for the implementation of resonant microwave measurements has no analogues. This determined the conduction of current research. The task of which is to theoretically and experimentally substantiate the effectiveness of applying a multilayer strip-slot transition to implement the resonant method for measuring the dielectric properties of materials. Results: The results of theoretical and experimental studies of the resonance properties of the multilayer strip-slot transition are presented. Its application makes it possible to realize an original volume-modular device for the resonant method of measuring the dielectric parameters of materials in the microwave range of wavelengths. The theoretical research is based on the development of an equivalent circuit, which is presented in the form of a cascade connection of four-port networks. The results of mathematical simulation of the multilayer strip-slot transition prove the possibility of implementing on its basis the resonance method for measuring the dielectric parameters of materials in the microwave range of wavelengths. Experimental studies were carried out on a sample of a volume-modular device with the multilayer strip-slot transition. The test material was a powder representing barium hexaferrite BaFe10Ti2O19 partially substituted by titanium. The coincidence of the results of mathematical simulation and experimental studies of the frequency-selective properties of a multilayer strip-slot transition is more than 95%. The error in assessing the permittivity of the used powder material based on the results of theoretical and experimental studies does not exceed 4.5%. Practical significance: The results of the research showed the possibility of applying of the multilayer strip-slot transition as a basic element for the implementation of the resonance method for measuring the dielectric properties of materials. The advantages of the proposed design are compactness and the ability to measure the dielectric properties of powder materials using scalar network analyzers.