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The accuracy in evaluating conductive layer coating thicknesses over conductive materials has recently been advanced with the potential application of apparent eddy current conductivity (AECC) spectroscopy. This approach minimises the sensitivity to variation in lift-off distance between the used eddy current coils and tested samples while capturing the actual conductivity profile with accuracy. This investigation further explores the potential integration of AECC spectroscopy with emerging machine learning (ML) capabilities in a theoretical-based supervised learning approach using artificial neural networks (ANNs). The complex spatial integral transform of the eddy current signal effectively filters out the information related to abrupt changes in the conductivity profile of step-like multi-layer structures, which renders the application of ANNs unfeasible for such structures. However, in the case of rectangular conductivity profiles covered in this study, it not only demonstrates the accuracy in estimating AECC spectrums over a range of different coating and substrate conductivity combinations and their associated coating thicknesses but also the retrieval of these unknown input parameters from measured AECC spectrums. The implementation of the ANN inverse model to experimentally measured AECC spectrums resulted in a maximum uncertainty of 3.37% in the conductive layer thickness estimation within a practical lift-off range. [ABSTRACT FROM AUTHOR]

This research explored the impact of air gap on torque and eddy current behavior of a magnet-north-pole rotating axial disk-type magnetic coupler using the magnetic equivalent circuit method. A magnetic equivalent circuit (MEC) model was developed to analyze the torque and induced eddy current behavior for the magnetic N-pole rotation angle 0° to 30° axial disk type magnetic coupler (MC). Torque equations were derived by combining Kirchhoff's law and the integral method, whereas induced eddy current equations were derived using Ampere's law. Flux leakage reluctance equations were obtained using an integral method. Furthermore, the study conducted 2D finite element simulations, and the results were validated against experimental data to ensure the accuracy and reliability of the proposed MEC model. Finally, the research findings suggested that an air gap length of 4 mm was an optimum length to obtain maximum torque and minimum magnetic saturation effects for a proposed MEC model of N-pole rotating axial disk type MC. [ABSTRACT FROM AUTHOR]

Distributed point source method (DPSM) has been gradually applied to the field of nondestructive testing (NDT). As a semi-analytical modelling technique, DPSM is extremely powerful and straightforward for solving various engineering problems, such as ultrasonic fields and electromagnetic field. In this paper, the technique is extended to model the eddy current field including sweep frequency measurement and scanning defect. The configuration of eddy current sensors consists of excitation coil and solid-state magnetic field measurement sensors such as Hall device and giant magnetoresistive sensor. Besides that, the wave propagation has been described and magnetic field created by eddy current has been calculated. The results obtained by DPSM is compared with that calculated by finite element method (FEM) in terms of accuracy and computation time, which indicates DPSM can improve calculation speed while ensuring calculation accuracy. [ABSTRACT FROM AUTHOR]

Despite improvements in nondestructive testing (NDT) technologies, the quality assurance of concrete reinforcing bar placement is still primarily conducted with conventional methodologies, which can be time-consuming, ineffective, and damaging to the concrete components. This study investigated the performance of two commercially available cover meters and one groundpenetrating radar (GPR) device. A cover meter was found to have the greatest accuracy for depths smaller than 3.19 in. (81.0 mm), while the GPR performed better for greater depths. The effect of reinforcing bar depth, diameter, and type; neighboring reinforcing bars; and concrete conditioning on the performance of the devices was quantified. The use of epoxy-coated reinforcing bar, galvanized reinforcing bar, and stainless-steel reinforcing bar were found to have a negligible effect on cover meter accuracy. A model was developed to predict the precision of the GPR post-measurement analysis given a depth and concrete dielectric constant. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We present a new method for accurately measuring the aperture of a fluid-driven fracture. This method uses an eddy current probe located within a completion tool specifically designed to obtain the fracture aperture in the wellbore at the location where the fluid is injected into the fracture. The probe induces an eddy current in a target object, producing a magnetic field that affects the overall magnetic field. It does not have any limitations with respect to fluid pressure and temperature within a large range, making it unlike other methods. We demonstrate the accuracy and performance of the sensor under laboratory conditions. A hydraulic fracture experiment in a porous sandstone is conducted and discussed. The obtained measurement of the evolution of the fracture inlet aperture by the eddy current probe during the multiple injection cycles performed provided robust information. The residual fracture aperture (after the test) measured by the probe is in line with estimations from image processing of X-ray CT scan images as well as a thin-section analysis of sub-parts of the fractured specimen. The robustness and accuracy of this electromagnetic induction probe demonstrated herein under laboratory conditions indicate an interesting potential for field deployment. [ABSTRACT FROM AUTHOR]

C45, a ferromagnetic material, can be strengthened by heat treatment such as quenching and is widely used as a material for general mechanical parts such as springs in automobiles. However, the presence of defects or flaws can cause cracking during the quenching stage, and a high-speed inspection method for detecting defects is required. In this study, we proposed and examined an inspection method for detecting defects using only a DC magnetic field by moving a round steel bar material at a high speed of 1 m/s inside a ring-shaped permanent magnet and generating eddy currents due to the velocity effect. [ABSTRACT FROM AUTHOR]

The degaussing process is crucial for ensuring magnetic protection in ships. It involves the application of oscillating and attenuating magnetic fields to eliminate residual magnetism in the ship's structure. However, this process can lead to the generation of distorted magnetic fields within the ship's cabin, posing a potential threat to electronic equipment performance. Therefore, it is essential to have a comprehensive understanding of the dynamic magnetic field response in ship structures to develop effective degaussing systems. To address this need, this paper proposes an eddy current model for analyzing the dynamic magnetic field response in ferromagnetic metal structures. This model focuses on the role of eddy currents in shaping the magnetic field response and provides valuable insights into the underlying mechanisms. Using the proposed eddy current model, the effects of key system parameters such as thickness, conductivity, and the length-scale of the ship structure can be analytically investigated. This analysis helps in understanding how these parameters influence the dynamic magnetic field response and aids in the design and optimization of degaussing systems. The effectiveness and applicability of the proposed eddy current model are demonstrated through comprehensive investigations involving two simulation cases of varying complexity. The model accurately predicts the changing trends of the dynamic magnetic field response, as confirmed through finite element simulations. This validation highlights the model's ability to reproduce simulation results accurately and its potential as a powerful tool for analyzing and optimizing dynamic magnetic field responses. In summary, the proposed eddy current model represents a significant advancement in the field. It provides a valuable theoretical framework for understanding and analyzing the dynamic magnetic field response in ferromagnetic metal structures. By offering insights into the underlying mechanisms and the influence of key parameters, this research contributes to the development of improved degaussing systems and enhances the overall magnetic protection capabilities of ships. [ABSTRACT FROM AUTHOR]

Aluminum alloys (AAs) are pivotal materials in modern aircraft due to their superior mechanical properties and low weight. The structural integrity of these alloys, crucial for aircraft safety, heavily depends on heat treatment processes that alter their mechanical characteristics. Nondestructive evaluation (NDE) techniques, such as eddy current (EC) conductivity measurements, play a vital role in assessing these alloys throughout their lifecycle. EC methods enable the measurement of electrical conductivity, a structure-sensitive parameter that correlates with mechanical properties affected by heat treatments and operational stresses. This paper reviews the application of EC conductivity measurements in the aerospace industry, focusing on their role in assessing AA structural integrity. It discusses how EC methods can penetrate non-conductive coatings, crucial for in-service measurements without surface removal. Recent developments include a novel small-size EC probe and signal processing algorithms aimed at enhancing sensitivity to conductivity changes through dielectric coatings, up to 0.5 mm thick, commonly found in aircraft structures. Key findings include analyses of specific electrical conductivity (SEC) changes in AAs due to heat treatment deviations and long-term operational stresses, crucial for predicting residual life and maintaining safety standards. Case studies on aircraft wing skins and helicopter rotor blades demonstrate the practical application of EC conductivity meters in identifying critical damage zones. The methodology proves effective in evaluating localized degradation based on SEC distributions, thereby enhancing maintenance efficiency and aircraft safety. Overall, this research underscores the significance of EC conductivity measurements in advancing NDE practices for AAs in aircraft applications. The methodologies and findings presented aim to improve safety, durability assessment, and maintenance efficiency in the aerospace industry. [ABSTRACT FROM AUTHOR]

In magnetic pulse welding, the deformation phenomenon of a moving sheet is divided into the deformation and continuous collision processes, then, the deformation analysis of the sheet is performed by using a magnetic pressure delivered to the sheet. When applying the pressure provided by neglecting an electric field generated during the deformation of the sheet, the calculated values accord only with one point for many measured values of both deformation height and deformation velocity, and errors greatly increase as the calculated values deviate from the point according. The new magnetic pressure corrected using a pressure drop coefficient is introduced because the deforming sheet leads to a drop in the pressure. If a successive approximation is applied to the deformation analysis, many calculated values approach the standard measured values. The calculated values are within a small error range for the measured values at 17 out of 18 points. It has been clarified that the deformation of the moving sheet is estimated fairly accurately by using the successive approximation. [ABSTRACT FROM AUTHOR]

Pore and crack formation in parts produced by additive manufacturing (AM) processes, such as laser powder bed fusion, is one of the issues associated with AM technology. Surface and subsurface cracks and pores are induced during the printing process, undermining the printed part durability. In-situ detection of defects will enable the real-time or intermittent control of the process, resulting in higher product quality. In this paper, a new eddy current-based probe design is proposed to detect these defects in parts with various defects that mimic pores and cracks in additively manufactured parts. Electromagnetic finite element analyses were carried out to optimize the probe geometry, followed by fabricating a prototype. Artificial defects were seeded in stainless steel plates to assess the feasibility of detecting various flaws with different widths and lengths. The smallest defect detected had a 0.17 mm radius for blind holes and a 0.43 mm notch with a 5 mm length. All the defects were 0.5 mm from the surface, and the probe was placed on the back surface of the defects. The surface roughness of the tested samples was less than 2 µm. The results show promise for detecting defects, indicating a potential application in AM. [ABSTRACT FROM AUTHOR]

The purpose of the current study was to investigate the effects of B0 and linear eddy currents on ultrashort echo time double echo steady state (UTE-DESS) imaging and to determine whether eddy current correction (ECC) effectively resolves imaging artifacts caused by eddy currents. 3D UTE-DESS sequences based on either projection radial or spiral cones trajectories were implemented on a 3-T clinical MR scanner. An off-isocentered thin-slice excitation approach was used to measure eddy currents. The measurements were repeated four times using two sets of tested gradient waveforms with opposite polarities and two different slice locations to measure B0 and linear eddy currents simultaneously. Computer simulation was performed to investigate the eddy current effect. Finally, a phantom experiment, an ex vivo experiment with human synovium and ankle samples, and an in vivo experiment with human knee joints, were performed to demonstrate the effects of eddy currents and ECC in UTE-DESS imaging. In a computer simulation, the two echoes (S+ and S-) in UTE-DESS imaging exhibited strong distortion at different orientations in the presence of B0 and linear eddy currents, resulting in both image degradation as well as misalignment of pixel location between the two echoes. The same phenomenon was observed in the phantom, ex vivo, and in vivo experiments, where the presence of eddy currents degraded S+, S-, echo subtraction images, and T2 maps. The implementation of ECC dramatically improved both the image quality and image registration between the S+ and S- echoes. It was concluded that ECC is crucial for reliable morphological and quantitative UTE-DESS imaging.

PurposeCompared to conventional arterial spin labeling (ASL) methods, velocity-selective ASL (VSASL) is more sensitive to artifacts from eddy currents, diffusion attenuation, and motion. Background suppression is typically suboptimal in VSASL, especially of CSF. As a result, the temporal SNR and quantification accuracy of VSASL are compromised, hindering its application despite its advantage of being delay-insensitive.MethodsA novel dual-module VSASL (dm-VSASL) strategy is developed to improve the SNR efficiency and the temporal SNR with a more balanced gradient configuration in the label/control image acquisition. This strategy applies for both VS saturation (VSS) and VS inversion (VSI) labeling. The dm-VSASL schemes were compared with single-module labeling and a previously developed multi-module schemes for the SNR performance, background suppression efficacy, and sensitivity to artifacts in simulation and in vivo experiments, using pulsed ASL as the reference.ResultsDm-VSASL enabled more robust labeling and efficient backgroud suppre across brain tissues, especially of CSF, resulting in significantly reduced artifacts and improved temporal SNR. Compared to single-module labeling, dm-VSASL significantly improved the temporal SNR in gray (by 90.8% and 94.9% for dm-VSS and dm-VSI, respectively; P

The detection of defects in aluminium alloys using eddy current testing (ECT) can be restricted by higher electrical conductivity. Considering the occurrence of discontinuities during the selective laser melting (SLM) process, checking the ability of the ECT method for the mentioned purpose could bring simple and fast material identification. The research described here is focused on the application of three ECT probes with different frequency ranges (0.3–100 kHz overall) for the identification of artificial defects in SLM aluminium alloy AlSi10Mg. Standard penetration depth for the mentioned frequency range and identification abilities of used probes expressed through lift-off diagrams precede the main part of the research. Experimental specimens were designed in four groups to check the signal sensitivity to variations in the size and depth of cavities. The signal behavior was evaluated according to notch-type and hole-type artificial defects' presence on the surface of the material and spherical cavities in subsurface layers, filled and unfilled by unmolten powder. The maximal penetration depth of the identified defect, the smallest detectable notch-type and hole-type artificial defect, the main characteristics of signal curves based on defect properties and circumstances for distinguishing between the application of measurement regime were stated. These conclusions represent baselines for the creation of ECT methodology for the defectoscopy of evaluated material. [ABSTRACT FROM AUTHOR]

This paper introduces an LC resonator-based single-frequency eddy current (EC) sensor designed for corrosion detection in reinforcing bars (rebars) embedded within concrete structures. The work addresses the challenges of the limited detection ranges and reduced sensitivity over longer distances, prevalent in current EC sensor applications. The sensor development process involved a systematic experimental approach to carefully selecting each parameter in the LC resonator. The sensor design aimed to assess the condition of the rebar from a distance of up to 5–6 cm outside the concrete and provide insights into different corrosion levels. By examining the characteristics of the inductors, the parallel resistance R p of the eddy current coil was identified as a key parameter reflecting the corrosion conditions in the rebar. The relationship between the R p fluctuations and temperature variations was investigated, with the data indicating that an approximately 155 Ω variation can be expected per 1 °C change within the temperature range of 20–25 °C, allowing for temperature compensation if necessary. Subsequently, the sensor's performance was evaluated by placing a rebar within a concrete block, where controlled mechanical degradation cycles were applied to simulate uniform corrosion in the rebar. The experimental results show that our EC sensor can detect material loss around the rebar with accuracy of approximately 0.17 mm. [ABSTRACT FROM AUTHOR]

The in-process detection of grinding burns has earned considerable interest from both researchers and industries in recent years. Various Non-destructive testing (NDT) technologies, including Eddy Current (EC), Barkhausen Noise (BN), and Acoustic Emission sensors (AE), have been employed to address this issue, yielding successful results for specific applications. However, a comprehensive understanding of burn generation and its prevention in grinding operations remains an area of interest that has not yet been fully resolved. This paper focuses on investigating the electromagnetic response of a custom-made EC sensor applied to UNE F-522 (AISI 01) steel during in-process inspections. Experimental grinding tests have been performed using a special EC inspection head installed in the grinding machine. The impedance change of the material during grinding is discussed in terms of the machine out-puts (Power consumption) and other grinding variables, such as number of passes, the roughing stock removal, and the finishing strategy. The experimental results demonstrate that the proposed EC technology not only enables the detection of burns, but also enhances comprehension of the surface integrity changes occurring during the grinding process. [ABSTRACT FROM AUTHOR]

Eddy current array (ECA) technology is increasingly being used in the aerospace industry for non-destructive testing of aircraft components. This study evaluates the performance of ECA in detecting defects in aircraft components, focusing on its effectiveness, reliability, and sensitivity. The study evaluates the effectiveness of ECA technology in eddy current defectoscopy by introducing a dimensionless efficiency coefficient, then seeks to validate this coefficient through experimental testing of aircraft component materials with artificially induced defects of various sizes, types, and orientations to simulate real-world scenarios. ECA's sensitivity in detecting small and subsurface defects is analyzed, along with precise defect sizing and positional information. Reliability and repeatability are investigated through repeated measurements. Furthermore, the article analyses the impact of various factors on the performance of ECA, including surface conditions, probe configurations, and inspection parameters. Comparative analysis is performed to assess the advantages and limitations of ECA in comparison to other conventional inspection methods. The findings of this study will contribute to a better understanding of the capabilities and limitations of ECA in detecting aircraft component defects. The results will aid in optimizing inspection strategies, enhancing the reliability of defect detection, and improving the overall maintenance practices in the aerospace industry. [ABSTRACT FROM AUTHOR]

The R&D of Central Solenoid Model Coil is a preparatory stage towards the final fabrication of China Fusion Engineering Test Reactor Central Solenoid. In view of the risk of being tear down or destroyed of the CSMC insulation components and current lead caused by the electromagnetic force, the preload system is designed and mounted around the circumferential direction of the cylindrical coil modules. In order to check the joint resistance, peak magnetic field, AC loss, mechanical performance of preload components under eddy current, CSMC will be tested under several typical current waves. For the sake of safety, a comprehensive mechanical analyses on the preload components need to be carried out before the final commissioning of CSMC. In this paper the magnetic density and eddy current on the preload components are calculated first. Then the electromagnetic force on the preload components under the testing current is analyzed. Finally, the mechanical analysis and stress evaluation are performed. The study presented in the paper will provide reference for the operation of CSMC under the testing current. [ABSTRACT FROM AUTHOR]

The service life and structural safety of components are affected by the thermal ageing of materials; therefore, a non-destructive evaluation of materials is extremely essential and crucial. In this work, heat-resistant steel Cr12MoV was selected as a specimen, and the embrittlement period of heat-resistant steel Cr12MoV was obtained by accelerated thermal ageing experiments. The effects of service temperature and service time on the mechanical properties of heat-resistant steel were analysed. The non-destructive testing of heat-resistant steel was carried out by using magneto-acoustic compound detection techniques based on electromagnetic acoustic transducers. In the process, magneto-acoustic compound detection signals were decoupled. The electromagnetic characteristic parameters and ultrasonic characteristic parameters of the detection signals were extracted to evaluate the mechanical properties and thermal ageing of heat-resistant steel. The quantitative evaluation ability of thermal ageing brittleness of heat-resistant steel was improved by using the magneto-acoustic compound detection techniques compared with single eddy current detection method or single ultrasonic detection method. [ABSTRACT FROM AUTHOR]

In modern industry, accurately assessing metal coupling by welding is critical. Given its reliability and other advantages, the eddy current test (ECT) is essential and commonly used in metal processing, especially welding. The classical ECT assesses the presence of discontinuities in the structure by monitoring the change in the probe's impedance. According to the wireless power transfer (WPT) theory, ECT members will exchange power wirelessly through mutual induction determined by inductance, capacitance, and resistance (LCR). The cracks will affect the mutual induction in the ECT's power exchange. Since LCRs are impedance components, the crack in the target will affect the system's mutual induction, as it did to the impedance in the classical ECT. This study applies the WPT model of ECT, implements system response analysis to assess cracks, and compares the results with classical ECT. The test piece is a metal arc-welded joint on SS 316 with an implanted notch on the welded joint to simulate the crack. A series of initial tests were performed to ensure the test piece was defects-free. Simulation and a frequency scan were performed to acquire a safe measurement. The result was that both the classical ECT and the system's response analysis successfully assessed the presence of cracks with excellent agreement. The system's response analysis yields a more rapid result than classical ECT. [ABSTRACT FROM AUTHOR]

Being able to characterise objects at low frequencies, but in situations where the modelling error in the eddy current approximation of the Maxwell system becomes large, is important for improving current metal detection technologies. Importantly, the modelling error becomes large as the frequency increases, but the accuracy of the eddy current model also depends on the object topology and on its materials, with the error being much larger for certain geometries compared to others of the same size and materials. Additionally, the eddy current model breaks down at much smaller frequencies for highly magnetic conducting materials compared to non-permeable objects (with similar conductivities, sizes and shapes) and, hence, characterising small magnetic objects made of permeable materials using the eddy current at typical frequencies of operation for a metal detector is not always possible. To address this, we derive a new asymptotic expansion for permeable highly conducting objects that is valid for small objects and holds not only for frequencies where the eddy current model is valid but also for situations where the eddy current modelling error becomes large and applying the eddy approximation would be invalid. The leading-order term we derive leads to new forms of object characterisations in terms of polarizability tensor object descriptions where the coefficients can be obtained from solving vectorial transmission problems. We expect these new characterisations to be important when considering objects at greater stand-off distance from the coils, which is important for safety critical applications, such as the identification of landmines, unexploded ordnance and concealed weapons. We also expect our results to be important when characterising artefacts of archaeological and forensic significance at greater depths than the eddy current model allows and to have further applications parking sensors and improving the detection of hidden, out-of-sight, metallic objects. [ABSTRACT FROM AUTHOR]

Currently, most commercial measuring instruments for electrical conductivity are primarily used to measure the conductivity of thick specimens. However, measuring the conductivity of thin films with these instruments can be challenging due to the limitation of skin depth. To address this issue, a conductivity measurement method for metal films has been proposed based on the transformer model of an eddy current sensor. It can be found that the phase of impedance change is related to the thickness and conductivity of the specimen when the thickness of the specimen is less than the skin depth. To validate the method, a finite element model is employed to simulate it, and the relative errors of conductivity measurements are analysed. The experimental results are then compensated using the estimated errors, and the influence of excitation frequency is evaluated. Finally, specimens with different conductivities and thicknesses are prepared to verify the method. The results indicate that the relative errors fall within 7.36% before compensation and within 5.25% after compensation, which demonstrates the feasibility of the proposed method for conductivity measurement of metal films. [ABSTRACT FROM AUTHOR]

Copyright of e & i Elektrotechnik und Informationstechnik is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Twisted wires made of insulated strands, known as stranded conductors or litz wires, are used in various areas where the eddy current loss within the wire needs to be reduced. These areas include induction heating, resonance-based wireless energy transfer, and certain radio frequency devices. Some litz wires consist of thousands of individual conductor strands that are twisted together in multiple stages, creating a hierarchical bundle structure. Computer simulations (typically using finite element analysis) are used in the optimal design of the bundle structure. However, detailed three-dimensional models are computationally demanding. In this work, a two-dimensional finite element model was presented for simulating the eddy current loss in cables made of twisted wires. The key element of the model is considering the bundle structure (generally referred to as 3D configuration conditions) within the cross-sectional model domain. The accuracy of the proposed model is tested against 3D finite element simulations. The new method is shown to be accurate, and its computational cost is by orders of magnitude lower than that of 3D models. [ABSTRACT FROM AUTHOR]

The cylinder linear induction motor (CLIM) is a variation of the rotary induction motor. Its structure is simple, it has a low manufacturing cost, and it can generate linear thrust without the need for a conversion mechanism. It is particularly suitable for electromagnetic catapults, magnetic levitation transport, and industrial production fields, due to its strong environmental adaptability. Designing a high-thrust and high-efficiency CLIM is a great challenge due to its inherent drawbacks, such as the low thrust density and power density of induction motors. In this article, two CLIMs with different topologies are proposed to meet the demand for control-rod drives in high-temperature and high-pressure environments. The article elucidates the topologies of the two CLIMs and proposes an analytical computational approach for the CLIM. Modern optimization algorithms were utilized to optimize the design of the structural parameters of both CLIMs. A 3D-FEA simulation was used to compare and analyze the air-gap magnetism and thrust characteristics of two CLIMs. The results indicate that the copper-ring secondary CLIM has a higher thrust density and is more suitable for use in control-rod drive mechanism (CRDM) systems. [ABSTRACT FROM AUTHOR]

Cold spray (CS) is a solid-state process for depositing thick layers of material via the successive high-velocity impact of powder particles onto a solid surface, which leads to high rates of deformation, interparticle bonding, and coating build-up. Although CS is finding commercial utilization in non-load-bearing repair and coating applications, clear nondestructive characterization procedures are necessary to realize its potential in load-bearing structural applications. In this study, the viability of electrical conductivity and through thickness ultrasound wave velocity measurement methods was studied to serve as a means for nondestructive quantitative measurement for quality control in CS and potentially other additive manufacturing (AM) methods. Eddy current, ultrasound, porosity, hardness, and uniaxial tensile strength tests were conducted on CS deposited layers of aluminum alloy 6061 and copper on aluminum alloy 6061 and commercially pure copper substrates, respectively. CS gas dynamic parameters were intentionally and systematically varied to result in corresponding discrete differences in mechanical properties of deposits. Ultrasound measurements of longitudinal wave velocity and eddy current electrical conductivity measurements showed good correlation with process conditions, microstructural characterization results, and destructive mechanical tests (hardness, tensile). The results of this work show that ultrasound wave velocity and electrical conductivity correlate well with increased particle impact velocity in CS deposited aluminum and copper blocks, which evidently show an incremental decrease in porosity, increase in hardness, and increase in tensile strength. The outlined ultrasound and eddy current nondestructive testing methods present effective means for quantitative assessment of cold spray deposited structures while intact with the substrate. [ABSTRACT FROM AUTHOR]

This research paper represents the estimation and reduction of eddy current loss in a Magnetic Fault Current Limiter (MFCL). The nonlinear model of the device is established using electromagnetic coupled circuit supported by Finite Element Model. The current limiting performance of the MFCL is investigated by simulation study as well as laboratory testing. It is further observed that a significant amount of eddy current loss takes place inside the core and permanent magnet of the device. Different methods (shorting ring, lamination of permanent magnet and variation of magnet length) are proposed to reduce the eddy current. The advantages and disadvantages of these methods are discussed. Some design modifications are also proposed to minimize the temperature rise caused by the eddy current. [ABSTRACT FROM AUTHOR]

Corrosion detection (CD) has become a high priority in chemical industries, defense and transportation sectors to extend the life of existing or new systems while ensuring the safety of the existing components and reducing downtime to minimise economic losses. Here, this article is aimed to review and discuss non-destructive techniques used widely in the industry to detect, monitor and repair corrosion problems early on. The comprehensive review provides a detailed discussion, a functional mechanism, advantages and disadvantages of crucial non-destructive CD techniques widely used in the industry, helping the reader choose the type of corrosion monitoring methods effectively. An extensive literature review of visual and optical testing techniques, acoustic emissions, eddy current, guided wave and equipment, infrared thermography, radiographic, microwave and millimeter wave, and terahertz imaging is discussed. The underlying mechanism, its merits and limitations, along with the usage scenario, is explained that can be related across different areas making it interdisciplinary research for corrosion monitoring techniques. [ABSTRACT FROM AUTHOR]

This paper deals with the study of organic coatings (patinas) on historical bronzes, specifically those applied on small-size statues in Renaissance workshops. These coatings, often transparent and translucent, contain a mixture of organic and inorganic components and may be still preserved in hidden parts of statues in indoor displays. However, the complexity of the original varnishes, their degradation and alteration over time, and the coexistence of materials added for conservation and maintenance purposes are challenging for their characterization. The often well-preserved surface of varnished bronzes and their small size make it mandatory to make the most of using noninvasive techniques for their investigation. To this end, to simulate the actual historical coatings, we prepared a set of mock-ups following ancient recipes and using materials that were available in the Renaissance. We used the samples to assess to what extent it is possible to disclose the formulation (binders, colourants, and other additives) and the thickness of a Renaissance patina with noninvasive methods. Microprofilometry (MP), optical coherence tomography (OCT), and eddy current (EC) gauge were tested on the samples and the results were combined with reflectance Fourier transform infrared (FT-IR) spectroscopy. The analyses performed on the mock-ups set the ground for investigating a Renaissance bronze featuring reddish semi-transparent varnish layers. The achievements are discussed in this paper, along with the limitations of the use of a noninvasive approach. [ABSTRACT FROM AUTHOR]

In industrial practice, no sensors capable of obtaining microstructural information in situ during thermo-mechanical processing of Al alloys are commonly employed. Inductive electrical conductivity measurement is safe, inexpensive, and capable of acquiring valuable information about precipitation and dissolution processes. However, commercial eddy current sensors work only at low temperatures near room temperature and are thus not suitable for in situ conductometry during heat treatments of Al alloys. We designed a high-temperature eddy current sensor and performed in situ conductometry during the homogenization of six Al-Mg-Si wrought alloys, three of which are experimental recycling-friendly alloys with increased Fe content. The results are interpreted with regard to microstructural investigations, and the advantages and limitations of our approach are discussed. As a proof-of-concept, we show how the conductivity curves and extrusion process parameters can be combined to predict final extrudate grain structures using machine learning. To achieve this, we employed finite element simulation of extrusion coupled with microstructural simulation over a wide parameter range, validated by extrusion experiments and metallography, and trained a feedforward neural network. We believe our interdisciplinary approach can lead to improvements in the industrial processing of Al wrought alloys.

In order to study the air gap magnetic field distribution and torque of axial-flux solid magnetic couplers with 9 pairs of permanent magnets, a layer model is firstly introduced, which divides the couplers into conductive and non-conductive areas. The two-dimensional magnetic scalar potential method is derived to solve the magnetic field strength in conductive areas and the magnetic scalar potential in non-conductive areas. Carter coefficient is introduced to correct the 3D end effects, and the formula of air gap flux density and torque is derived. Then， the distribution of 3D air gap magnetic field, eddy current and the influence of different working parameters on the characteristics of the torque are obtained by the finite element simulation software. Finally, a measure system of three-dimensional magnetic field and the magnetic drive experimental platform are built to measure the 3D air gap magnetic field and the torque. The experimental results are in good agreement with the results of theoretical calculation and the simulation analysis, which shows that the formula of the air gap flux density and the torque have high accuracy and can be used as a reference for further research on the transmission characteristics of eddy-current magnetic couplers.

The open-loop current transducer comprises a magnetic core made of soft magnet material and includes a Hall sensor. Traction motors in applications such as electric vehicles tend to be driven at high speeds. It pushes the inverters to increase the fundamental frequency of the output current above 1 kHz. However, this high frequency current generates eddy currents in the magnetic core of the current transducers. They deteriorate the measurement data thereby resulting the amplitude error and phase shift error, which is applied open-loop current transducer with the lamination magnetic core. In this study, the errors of an open-loop current transducer due to eddy currents were analyzed through mathematical modeling and finite element method (FEM). Furthermore, the impact of the error on permanent magnet synchronous motor current control was studied. The phase shift error of the current transducer used in this study reaches 3.6 degree when the frequency of current was 1.5 kHz, resulting in about a 20% torque reduction during field-weakening operation at 200 kW, 22500 rpm. On the other hand, the amplitude error of the current transducer is only 0.18% in the same condition. In order to correct the error, an online compensation method is proposed based on FEM simulation results. The phase shift error was verified through the experiments with a $300~\mu H$ , 3-phase inductive load. The proposed method was also validated through the experimental results conducted for variable frequencies from 500 Hz to 1.5 kHz.