Electromagnetic Nondestructive Evaluation Research Articles

A Dual Mode Nondestructive Evaluation Sensor With Simultaneous Inductive and Capacitive Outputs

Conventional electromagnetic Non-Destructive Evaluation (NDE) techniques are usually sensitive to either conductors or insulators. The emerging non-destructive assessment of "insulator-conductor" composite structures is thus faced with cost and efficiency problems due to this limitation. In this paper, a novel detection technique that combines inductive and capacitive methods is proposed for the inspection of "insulator-conductor" composite structures. A new structure of a planar inductive-capacitive dual-mode sensor in which the inductive and capacitive modes can be excited simultaneously with a single excitation signal without the need for mode switching is developed. The output signal of this sensor is analyzed in relation to the spatial electromagnetic field using equivalent circuit analysis and finite element (FE) simulation. A signal conditioning module for the proposed sensor is designed and a dual-mode test system that simultaneously detects signals from both modes is built. Experimental results from the test system show that the proposed detection method is sensitive to defects in both the insulating and conducting layers of the "insulator-conductor" composite structure and thus can detect corrosion under the insulation, surface cracks on the conductor and interface debonding with the detected signals able to reflect the size of the defects. The detection information of the two modes is complementary, proving that the method is able to comprehensively evaluate "insulator-conductor" composite structures.

Miniaturized multi-modality field-ready sensing system for defect detection of CFRP materials

As infrastructure decays rapidly due to structural and material aging and failures, the development of new improved, and efficient nondestructive evaluation (NDE) techniques is vital for system health monitoring and preventive maintenance. Composite material, such as carbon fiber reinforced polymer (CFRP) plays a significant role in energy and transportation infrastructure due to the advantages of corrosion resistance, durability, and lightweight, which contributes to minimal maintenance and long service life. However, due to their unique anisotropic dielectric and mechanical characteristics, detecting composite material defects by NDE techniques is still challenging. This paper presents a novel, low-cost miniaturized multi-modality imaging system combining low-frequency capacitive shortwave and high-frequency microwave NDE technologies to detect various types of defects in CFRP materials. Based on the governing electromagnetic theory behind multi-modality electromagnetic NDE methods, the merit of combining low-frequency shortwave and near-field microwave imaging for dielectric characterization of composite materials is thoroughly investigated and demonstrated. Then, a miniaturized imaging system is developed to operate at ultra-wide bands: 10 kHz to 200 MHz for the capacitive shortwave probes and 1 GHz to 9 GHz for the microwave probes. Customized multi-material joining samples of CFRP and steel with different defect types, locations, depths, and sizes are tested by the developed imaging system, and the experimental results of the miniaturized system are compared with the existing table-top systems, which demonstrates comparatively accurate results for the developed multi-modality imaging system. The compact and practical nature of the presented imaging system makes it an optimal tool that can be utilized in field conditions with constrained operational spaces and NDE uncertainties.

Multi-Point Interaction of Partially Conductive Cracks with Sweep Frequency Eddy Currents in Electromagnetic Non-Destructive Evaluation

An investigation of real corrosion cracks that can be partially conductive in electromagnetic non-destructive evaluation using sweep-frequency eddy-current frequency-response analysis is carried out in this study. A new approach incorporating innovative solutions is proposed. The goal was to increase the probability of detection of real corrosion cracks in contrast to the conventional sweep-frequency method that is based on single-point signal detection. The proposed procedure was tested on real material specimens where differential responses were gained from real corrosion cracks. Seven austenitic steel plate specimens having corrosion cracks were inspected. Eddy-current responses due to the material cracks were sensed, while a multi-point approach was used for this purpose. The presented unique results clearly showed that the detection ability of a fixed probe driven with sweep-frequency excitation signal could be increased when the multi-point detection is used, and the gained signals are further mathematically processed.

Research on the fatigue magnetization of ferromagnetic materials under low cycle fatigue based on the magneto-mechanical effect

Fatigue damage that caused by low cycle fatigue may lead to many seriously industrial accidents and economic losses, which can be effectively evaluated by magnetic signal based on the magneto-mechanical model. However, the prevailing theoretical model have some limitations (e.g. inaccurate quantification, many unknown coefficients that difficult to obtain, etc.) in describing fatigue magnetization. A new nonlinear magneto-mechanical model based on J-A model proposed in this paper has superior prediction capability for the magnetization under elasto-plastic deformation. In addition, the evolution of the magnetic signal of ferromagnetic materials during the fatigue process is obtained by combining the viscoplastic model and magneto-mechanical model, the fitting equation of magnetic signal and fatigue damage in material fatigue process are proposed, and the determination coefficients are all greater than 0.99. The results of this paper can provide a basis for the electromagnetic nondestructive evaluation of fatigue damage of ferromagnetic materials in engineering.

Lift-off suppression based on combination of bridge and transformer signal conditionings of eddy current testing

Lift-off is a challenging issue in electromagnetic non-destructive testing and evaluation, especially in eddy current testing. It seriously affects the detection sensitivity and quantification accuracy. This paper proposes a combined signal conditionings of differential eddy current structure based on bridge and transformer for lift-off suppression. It provides both amplitude and phase information via two signal conditionings for multiple parameter measurement. Specifically, a multiple parameters fusion response model is established according to equivalent circuits between the electromagnetic sensing coupling and lift-off. This model enables to greatly reduces the lift-off ambiguities from mixed signal since lift-off parameter can be eliminated and defect information is increased. In particular, it is suitable for irregular lift-off variation suppression with non-parameters adjusting. Different defect samples have been conducted to validate the proposed method.

Influence of Varying Tensile Stress on Domain Motion.

Magnetic domain motion has been widely studied in the fields of spintronics, nanowires, and thin films. However, there is a lack of such studies on industrial steels, especially for domain motion under the action of varying stress. Understanding domain motion under stress is helpful for the improvement of evaluation accuracy and the establishment of theoretical models of passive, nondestructive testing technology. This paper presents the influence of varying tensile stresses on the magnetic domain motion of silicon steel sheets. Magnetic domain rotation and domain wall displacement were characterized using magnetic domain images, and their motion mechanisms under elastic and plastic stresses are presented. The results show that the domain rotation under stress involves reversible and irreversible changes. The effect of material rearrangement on domain rotation and domain wall displacement after plastic deformation is discussed. Based on the motion mechanism, a threshold stress value (TSV) required for the complete disappearance of the supplementary domains in the elastic range is proposed, enabling the classification of the elastic stress ranges in which the reversible and irreversible domain rotations occur. In addition, the effect of microstructure on TSV is also discussed, and the results show that the regions far away from the grain boundary need larger stresses to complete an irreversible domain rotation. Additionally, the domain width and orientation also affect the TSV. These findings regarding the domain motion mechanism and TSV can help to explain the sequence of domain rotation under stress and modify the stress assessment under dynamic loads in electromagnetic nondestructive evaluation, especially in the magnetic memory method.

Diagnosis of Artificial Flaws from Eddy Current Testing Signals Based on Sweep Frequency Non-Destructive Evaluation

An investigation of artificial flaws in electromagnetic non-destructive evaluation using eddy-current frequency-response analysis is carried out in this study. A new approach incorporating innovative solution is proposed. The goal was to increase the resolution of gained signals in contrast to the conventional sweep-frequency method. The proposed procedure was tested on real material specimens where differential responses were gained from artificial electro-discharge machined flaws. Two plate specimens having EDM flaws of various dimensions were inspected. Eddy-current responses due to the material flaws were sensed and compared to a dataset that was obtained by numerical modelling. The presented unique results clearly show that the resolution of a fixed probe driven with sweep-frequency excitation signal can be increased when the appropriate probe instrumentation is used and the characteristics are further mathematically processed.

Detection of Decarburising Depth in Hadfield Steels Using a Multi-magnetic NDE Method

ABSTRACT This paper reports the capability of a range of electromagnetic non-destructive evaluation (NDE) methods to characterise the decarburising phenomena in Hadfield steels. Four Hadfield steel samples were austenitised at 1050 °C for 1, 2, 3 and, 4 hours in an air furnace followed by water quenching to produce various decarburising depths. The decarburisation depth was characterised using hardness profile measurements, optical and scanning electron microscopy, and X-ray diffraction analysis. The results confirmed the occurrence of decarburising and presence of a surface martensite layer of 35 to 110 µm depending on austenitisation time. The microstructural change at the surface affects the magnetic properties of the sample and enables electromagnetic NDE methods to detect the transformed layers quantitatively. In the non-destructive characterisation step, the relationships between the austenitising time and the outputs from magnetic flux leakage (MFL), initial magnetisation curve (BH) and eddy current (EC) methods are reported. Comparing the results obtained from the three magnetic NDE methods, it can be concluded that MFL and EC (phase angle output) have the potential to quantify the surface microstructural changes occurring as a result of the decarburising process in Hadfield steels.

Pulse-Modulation Eddy Current Imaging for 3D Profile Reconstruction of Subsurface Corrosion in Metallic Structures of Aviation

Metallic structures of non-ferromagnetic materials such as aluminum alloy, titanium alloy, etc., are widely used in the engineering field of aviation. Owing to harsh and hostile environments, subsurface corrosion manifests itself in the in-service Metallic Structures of Aviation (MSA), and is usually hidden within the structure body, leaving it barely detected. Such defect has been found to be one of the most critical defects posing a severe threat to structural integrity and safety of MSA. Therefore, it is imperative to conduct imaging and quantitative assessment of the subsurface corrosion with effective Non-destructive Evaluation (NDE) techniques. Pulse-modulation Eddy Current technique (PMEC) has been identified to be superior to other electromagnetic NDE techniques in evaluation of corrosion in conductors. In light of this, in this paper PMEC for imaging and 3D profile reconstruction of subsurface corrosion in MSA is investigated. Novel features extracted from testing signals are proposed in a bid to enhance the sensitivity of the PMEC response. An image processing technique based on the modified Theta Map is proposed and utilized for recognition of corrosion opening profile. An efficient inversion method, which is focused on the corrosion-profile reconstruction right within the corrosion region and based on a sectional scanning strategy, is investigated along with the establishment of the database conceiving PMEC responses to regular-shaped corrosion. It has been found from the experimental results that the proposed inversion scheme is feasible and applicable for 3D profiling of subsurface corrosion in MSA with the averaged evaluation accuracy of 95.4%.

Application of Closed Magnetic Circuit Method for Evaluating the Stress Distribution along Depth Direction

Electromagnetic nondestructive evaluation method is feasible in assessing stress or residual stress levels in ferromagnetic structures, for there is a strong inherent correlation between the permeability and the stress. This study is based on the closed magnetic circuit method for testing stress distribution along depth. Firstly, a theory is proposed for describing the propagation of electromagnetic energy inside ferromagnetic materials. A layered model is established considering the electromagnetic field experienced different attenuation at different depths. And each layer is assumed to have the identical physical state. Then, multi-frequency eddy current method is proposed to testing the in-depth permeability variation and consequently the stress-depth profile. For simply using the convolution integral, a novel inversion algorithm is given to resolve the convolution integral. To apply the proposed method for testing the stress-depth profile, multi-frequency eddy current experiments are conducted through a four-point bending device; with the specimen material employed is 45# steel. Finally, map the experimental data fitting curve to the theoretical calculation curve, and hence can verify the proposed theory and the inversion algorithm.

Novel Time-Domain Parameters for Detection and Classification of Flaws Using Pulsed Eddy Current Technique

Pulsed eddy current (PEC) testing is an electromagnetic nondestructive evaluation (NDE) technique which is used for detection and classification of flaws. This paper presents an approach for the extraction of novel timedomain flaw parameters viz. amplitude ratio (V₁/VSUB0/SUB) and time constant (τ) for detection and classification of different flaws. Experiments are carried out on stainless steel (SS-316) plate with artificial EDM notches whose width (1.0 mm & 3.0 mm) and depth (1.0 mm to 6.0 mm) varied. The proposed approach can classify both surface and sub-surface flaws in an 8.0 mm thick SS plate. The advantage of the proposed approach is that it doesn’t require a reference signal subtraction or signal processing methodologies for the detection and classification of flaws.

Analysis of electromagnetic non-destructive evaluation modelling using Stratton-Chu formulation-based fast algorithm.

The eddy current non-destructive evaluation (NDE) modelling using Stratton-Chu formulation-based fast algorithm is analysed. Stratton-Chu formulations, which have no low frequency breakdown issue, are selected for modelling electromagnetic NDE problems with low frequency and high conductivity approximations. As the main contribution of this article, the robustness and efficiency of the approximations, which result in big savings in both memory and CPU time, are validated and analysed using examples from practical EC testing. The boundary element method (BEM) is used to discretize the integral equations into a linear system of equations: the first order Rao-Wilton-Glisson (RWG) vector basis functions with the flat triangle meshes of the object and pulse basis functions are selected to expand the equivalent surface currents and the normal component of magnetic fields, respectively. Then the multilevel adaptive cross approximation (MLACA) algorithm is applied to accelerate the iterative solution process. The performance and efficiency of adaptively applying a multi-stage (level) algorithm based on the criteria concluded for the operators are shown. This article is part of the theme issue 'Advanced electromagnetic non-destructive evaluation and smart monitoring'.

Capacitive imaging for adhesive bonds and quality evaluation.

Defective adhesive bonds pose significant threats towards structural integrity due to reduced joint strength. The nature of the adhesion of two solids remains poorly understood since the adhesion phenomenon is relevant to so many scientific and technological areas. A concept that has been gaining our attention from the perspective of non-destructive testing is the properties discontinuity of the adhesion. Discontinued properties depend significantly on the quality of the interface that is formed between adhesive and substrate. In this research, discontinued electrical properties at the interface are considered. The simplified model is free from multidisciplinary knowledge of chemistry, fracture mechanics, mechanics of materials, rheology and other subjects. From a practical standpoint, this emphasizes the need to establish a good relationship between electrical properties of adhesive bonds and corresponding measurements. Capacitive imaging (CI) is a technique where the dielectric property of an object is determined from external capacitance measurements. Thus, it is potentially promising since adhesive and substrate differ in terms of dielectric property. At the interface between adhesive and substrate, discontinuity of the dielectric properties causes abrupt changes in electric field spatial distribution and thus alters capacitance measurement by simulating defects in adhesive joints regarding permittivity uncertainties. Further understanding of the cause of degraded adhesion quality can be obtained. This article is part of the theme issue 'Advanced electromagnetic non-destructive evaluation and smart monitoring'.

Wireless power transfer-based eddy current non-destructive testing using a flexible printed coil array.

Eddy current testing (ECT) has been employed as a traditional non-destructive testing and evaluation (NDT&E) tool for many years. It has developed from single frequency to multiple frequencies, and eventually to pulsed and swept-frequency excitation. Recent progression of wireless power transfer (WPT) and flexible printed devices open opportunities to address challenges of defect detection and reconstruction under complex geometric situations. In this paper, a transmitter–receiver (Tx–Rx) flexible printed coil (FPC) array that uses the WPT approach featuring dual resonance responses for the first time has been proposed. The dual resonance responses can provide multiple parameters of samples, such as defect characteristics, lift-offs and material properties, while the flexible coil array allows area mapping of complex structures. To validate the proposed approach, experimental investigations of a single excitation coil with multiple receiving coils using the WPT principle were conducted on a curved pipe surface with a natural dent defect. The FPC array has one single excitation coil and 16 receiving (Rx) coils, which are used to measure the dent by using 21 C-scan points on the dedicated dent sample. The experimental data were then used for training and evaluation of dual resonance responses in terms of multiple feature extraction, selection and fusion for quantitative NDE. Four features, which include resonant magnitudes and principal components of the two resonant areas, were investigated for mapping and reconstructing the defective dent through correlation analysis for feature selection and feature fusion by deep learning. It shows that deep learning-based multiple feature fusion has outstanding performance for 3D defect reconstruction of WPT-based FPC-ECT.This article is part of the theme issue ‘Advanced electromagnetic non-destructive evaluation and smart monitoring’.

Terahertz smart dynamic and active functional electromagnetic metasurfaces and their applications.

The demand for smart and multi-functional applications in the terahertz (THz) frequency band, such as for communication, imaging, spectroscopy, sensing and THz integrated circuits, motivates the development of novel active, controllable and informational devices for manipulating and controlling THz waves. Metasurfaces are planar artificial structures composed of thousands of unit cells or metallic structures, whose size is either comparable to or smaller than the wavelength of the illuminated wave, which can efficiently interact with the THz wave and exhibit additional degrees of freedom to modulate the THz wave. In the past decades, active metasurfaces have been developed by combining diode arrays, two-dimensional active materials, two-dimensional electron gases, phase transition material films and other such elements, which can overcome the limitations of conventional bulk materials and structures for applications in compact THz multi-functional antennas, diffractive devices, high-speed data transmission and high-resolution imaging. In this paper, we provide a brief overview of the development of dynamic and active functional electromagnetic metasurfaces and their applications in the THz band in recent years. Different kinds of active metasurfaces are cited and introduced. We believe that, in the future, active metasurfaces will be combined with digitalization and coding to yield more intelligent metasurfaces, which can be used to realize smart THz wave beam scanning, automatic target recognition imaging, self-adaptive directional high-speed data transmission network, biological intelligent detection and other such applications. This article is part of the theme issue 'Advanced electromagnetic non-destructive evaluation and smart monitoring'.

Physic perspective fusion of electromagnetic acoustic transducer and pulsed eddy current testing in non-destructive testing system.

Comprehensive non-destructive testing (NDT) for pipelines is a critical and challenging task. This paper proposes a novel physic perspective fusion NDT method of electromagnetic acoustic transducer (EMAT) and pulsed Eddy current testing (PECT) for detecting hybrid defects. This transceiver-integrated fusion sensor structure can simultaneously excite ultrasound and pulsed eddy current. Therefore, the generated ultrasound is applied to detect deep defects, while the eddy current detects surface defects. The theoretical derivation of EMAT and PECT fusion mechanism has been developed for analysis and interpretation of the results. In addition, numerical simulation on the detection of hybrid defects including surface defects with different width, depth and multiple bottom-thinning defects has been conducted. Experiments on both ferromagnetic and non-ferromagnetic material verify the feasibility of composite detection. Finally, tests have been validated on pipeline with weld defects, and the results show that the composite inspection method is capable of monitoring thickness variations and inspecting surface defects. This article is part of the theme issue 'Advanced electromagnetic non-destructive evaluation and smart monitoring'.

Efficient calculation of transient eddy current response from multi-layer cylindrical conductive media.

The transient response from a transmitter-receiver coil system inside a multi-layer cylindrical conductive configuration is obtained. The particular set-up applies to well logging as well as to eddy current tube testing. In this work, a number of improvements are presented to existing models for an efficient calculation of the induced voltage. These include: domain truncation, novel treatment of arbitrary number of layers in order to avoid computational overflows and efficient time response calculation. The latter is based on a combination of Laplace inversion techniques for short- and long-time transient responses. This article is part of the theme issue 'Advanced electromagnetic non-destructive evaluation and smart monitoring'.

Correction to 'Octane isomer dynamics in H-ZSM-5 as a function of Si/Al ratio: a quasi-elastic neutron scattering study'.

You have accessMoreSectionsView PDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmail Cite this article O'Malley Alexander J., Sakai Victoria García, Dimitratos Nikolaos, Jones Wilm, Richard C., Catlow A. and Parker Stewart F. 2020Correction to ‘Octane isomer dynamics in H-ZSM-5 as a function of Si/Al ratio: a quasi-elastic neutron scattering study’Phil. Trans. R. Soc. A.3782020028220200282http://doi.org/10.1098/rsta.2020.0282SectionYou have accessCorrectionsCorrection to ‘Octane isomer dynamics in H-ZSM-5 as a function of Si/Al ratio: a quasi-elastic neutron scattering study’ Alexander J. O'Malley Alexander J. O'Malley Google Scholar Find this author on PubMed Search for more papers by this author , Victoria García Sakai Victoria García Sakai Google Scholar Find this author on PubMed Search for more papers by this author , Nikolaos Dimitratos Nikolaos Dimitratos Google Scholar Find this author on PubMed Search for more papers by this author , Wilm Jones Wilm Jones Google Scholar Find this author on PubMed Search for more papers by this author , C. Richard C. Richard Google Scholar Find this author on PubMed Search for more papers by this author , A. Catlow A. Catlow Google Scholar Find this author on PubMed Search for more papers by this author and Stewart F. Parker Stewart F. Parker Google Scholar Find this author on PubMed Search for more papers by this author Alexander J. O'Malley Alexander J. O'Malley Google Scholar Find this author on PubMed Search for more papers by this author , Victoria García Sakai Victoria García Sakai Google Scholar Find this author on PubMed Search for more papers by this author , Nikolaos Dimitratos Nikolaos Dimitratos Google Scholar Find this author on PubMed Search for more papers by this author , Wilm Jones Wilm Jones Google Scholar Find this author on PubMed Search for more papers by this author , C. Richard C. Richard Google Scholar Find this author on PubMed Search for more papers by this author , A. Catlow A. Catlow Google Scholar Find this author on PubMed Search for more papers by this author and Stewart F. Parker Stewart F. Parker Google Scholar Find this author on PubMed Search for more papers by this author Published:14 September 2020https://doi.org/10.1098/rsta.2020.0282This article corrects the followingResearch ArticleOctane isomer dynamics in H-ZSM-5 as a function of Si/Al ratio: a quasi-elastic neutron scattering studyhttps://doi.org/10.1098/rsta.2020.0063 Alexander J. O'Malley, Victoria García Sakai, Nikolaos Dimitratos, Wilm Jones, C. Richard A. Catlow and Stewart F. Parker volume 378issue 2176Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences06 July 2020Phil. Trans. R. Soc. A378, 20200063 (Published online 6 July 2020) (doi:10.1098/rsta.2020.0063)This correction concerns figure 6. The y-axis values given were of an order of magnitude larger than the true values, the corrected figure appears below. The paper has now been updated. Figure 6. Q-dependence of the HWHM (Γ) of the quasi-elastic components of QENS spectra of n-octane in each H-ZSM-5 sample from 300 to 400 K. (Online version in colour.)Download figureOpen in new tabDownload PowerPoint Previous Article VIEW FULL TEXT DOWNLOAD PDF FiguresRelatedReferencesDetailsRelated articlesOctane isomer dynamics in H-ZSM-5 as a function of Si/Al ratio: a quasi-elastic neutron scattering study06 July 2020Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences This Issue16 October 2020Volume 378Issue 2182Theme issue ‘Advanced electromagnetic non-destructive evaluation and smart monitoring’ compiled and edited by GuiYun Tian and Theodoros Theodoulidis Article InformationDOI:https://doi.org/10.1098/rsta.2020.0282PubMed:32921239Published by:Royal SocietyPrint ISSN:1364-503XOnline ISSN:1471-2962History: Published online14/09/2020Published in print16/10/2020 License:© 2020 The Author(s)Published by the Royal Society. All rights reserved. Citations and impact Subjectsinorganic chemistrymaterials sciencephysical chemistry

Quantitative evaluation of electrical conductivity inside stress corrosion crack with electromagnetic NDE methods.

This paper presents a comparison of studies on the local distributed electrical conductivity in stress corrosion crack (SCC) from signals of eddy current testing (ECT) and direct current potential drop (DCPD) aiming to improve SCC sizing accuracy when using electromagnetic non-destructive testing (NDT) methods. Experimental setups of ECT and DCPD were established, respectively, to collect measurement signals due to artificial SCCs in a plate of austenitic stainless steel. The local conductivity in the SCC region was reconstructed from the feature parameters extracted from the measured ECT and DCPD signals through inverse analyses. The inversion strategies for ECT and DCPD, each including an efficient forward simulation and an optimization scheme, were introduced from the viewpoint of conductivity reconstruction. Inversion results obtained from the measured ECT and DCPD signals showed the consistent trend which proved the validity of the predicted electrical conductivity indirectly. It is clarified that the electrical conductivity in a SCC is relatively high at the crack tip area and may become as high as 17% of that of the base material. These results provide a good reference to enhance the sizing accuracy of SCC with an electromagnetic NDT method such as ECT by updating the conductive crack model based on the results of this work. This article is part of the theme issue 'Advanced electromagnetic non-destructive evaluation and smart monitoring'.

Preface: advanced electromagnetic non-destructive evaluation and smart monitoring.

Preface: advanced electromagnetic non-destructive evaluation and smart monitoring.