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Impurities resulting from the erosion of plasma-facing components (PFCs) in the plasma chamber disrupt the normal operation of tokamaks. Additionally, continuous erosion leads to the premature aging of these components, affecting their long-term performance and reliability. To quantify erosion and redeposition directly within the machine between operational phases, non-destructive testing methods are crucial. This study evaluates the 4-point and eddy current (EC) methods for measuring the erosion of PFCs and the design of dedicated erosion markers composed of tungsten and alumina multilayers. The 4-point method, sensitive to thickness loss, necessitates electrically insulating layer. Conversely, the EC method requires a conductivity difference between materials but eliminates the need for interlayers. These non-destructive techniques can be effectively integrated into the tokamak to monitor erosion without requiring component removal. Both methods demonstrate potential for accurate thickness measurements. Our results demonstrate that tungsten erosion of less than 2 μm can be assessed using both the four-point probe and EC methods.

Inspection of components with surface discontinuities is an area that volumetric Non-Destructive Testing (NDT) methods, such as ultrasonic and radiographic, struggle in detection and characterisation. This coupled with the industrial desire to detect surface-breaking defects of components at the point of manufacture and/or maintenance, to increase design lifetime and further embed sustainability in their business models, is driving the increased adoption of Eddy Current Testing (ECT). Moreover, as businesses move toward Industry 4.0, demand for robotic delivery of NDT has grown. In this work, the authors present the novel implementation and use of a flexible robotic cell to deliver an eddy current array to inspect stress corrosion cracking on a nuclear canister made from 1.4404 stainless steel. Three 180-degree scans at different heights on one side of the canister were performed, and the acquired impedance data were vertically stitched together to show the full extent of the cracking. Axial and transversal datasets, corresponding to the transmit/receive coil configurations of the array elements, were simultaneously acquired at transmission frequencies 250, 300, 400, and 450 kHz and allowed for the generation of several impedance C-scan images. The variation in the lift-off of the eddy current array was innovatively minimised through the use of a force–torque sensor, a padded flexible ECT array and a PI control system. Through the use of bespoke software, the impedance data were logged in real-time (≤7 ms), displayed to the user, saved to a binary file, and flexibly post-processed via phase-rotation and mixing of the impedance data of different frequency and coil configuration channels. Phase rotation alone demonstrated an average increase in Signal to Noise Ratio (SNR) of 4.53 decibels across all datasets acquired, while a selective sum and average mixing technique was shown to increase the SNR by an average of 1.19 decibels. The results show how robotic delivery of eddy current arrays, and innovative post-processing, can allow for repeatable and flexible surface inspection, suitable for the challenges faced in many quality-focused industries.

This paper presents the results of experiments using the eddy current system designated for nondestructive inspection of carbon fiber-reinforced composites. For this purpose, the eddy current testing system with a differential transducer with two pairs of excitation coils oriented perpendicularly and a central pick-up coil was utilized. The transducer measures the magnetic flux difference flowing through the pick-up coil. The transducer of this design has already been successfully utilized to inspect isotropic metal structures. However, the anisotropy of the composites and their lower conductivity compared to metal components made the transducer parameters adjustment essential. Thus, various excitation frequencies were considered and investigated. The system was evaluated using a sample made of orthogonally woven carbon fiber-reinforced composites with two artificial flaws (the notches with a maximum relative depth of 30% and 70%, respectively, thickness of 0.4 mm, and a length of 5 mm). The main goal was to find a configuration suitable for detecting hidden flaws in such materials.

Nowadays, electromagnetic pollution originated from artificial intelligence devices, fifth-generation (5G) cellular networks, as well as ever-increasing electronic devices applying and/or producing electromagnetic waves has excited the global concern. Evidently, the novel threats are springing up as a sleeping giant awaiting to irrupt; thus, the immediate counteraction is inescapable against the augmenting harmful electromagnetic waves. Till date, based on the permeability and permittivity of the materials in the microwave region, diverse microwave absorbing structures have been fabricated to overcome the aforementioned problem. It is worth noting that nanostructures are under the spotlight as a hot spot generated from their incomparable surface area-to-volume ratio tuning polarizability, magnetic features, electrical conductivity, eddy current loss, and other absorbing mechanisms. It should be noted that the secondary pollution produced at the threshold of the absorbing structures is tunable by the impedance matching. Hitherto, the size, shape, and morphology of nanostructures have been manipulated to improve microwave attenuation. The more surface area-to-volume ratio brings the more defect, dipole, and interfacial polarization as well as enhances the interfacial interactions at heterogeneous interfaces providing more multiple reflections and scattering. On the other hand, the intrinsic properties of the absorbing media and their unique interactions at grain boundaries can promote microwave attenuation which have recently attracted a great deal of attention. The obtained results manifest that the morphology and medium influence on microwave absorbing characteristics are the tip of the iceberg investigated by diverse approaches. In this study, a comprehensive prospect is presented using recent researches related to the size, shape, defect, morphology, and medium effect on the microwave absorbing mechanisms paving the way for microwave attenuation. The achieved works have attested that the mentioned parameters are the vital factors influencing the microwave absorbing properties. Graphical abstract

The present study proposes a novel eddy-current-based tuned inerter damper (EC-TID) that integrates the tuned inerter damper (TID) with nonlinear eddy current damping. The inclusion of nonlinear eddy current damping is expected to improve the control performance of optimal TID. In particular, the mechanical model and configuration of proposed EC-TID are introduced in detail. A closed-form solution for EC-TID optimal design in both undamped and damped structures is established based on effective damping ratio enhancement (EDRE) effect. This closed-form solution ensures equivalence of nonlinear eddy current damping through employment of statistical linearization techniques (SLT) with both force-based and energy-based equivalent criteria. The EC-TID control effectiveness obtained through Monte Carlo simulation under white noise excitation, which include effective damping ratio and EDRE effect, verifies the accuracy of the closed-form solution established via SLT, and highlights the importance of a large critical velocity of EC-TID in achieving higher accuracy. Moreover, it has been found that the closed-form solution for EC-TID and eddy-current-based tuned viscous mass damper (EC-TVMD) optimal design exhibit significant similarities when their equivalent damping ratios are identical. Several numerical studies have been conducted to investigate the control performance of EC-TID under real seismic excitations. The results demonstrate that both TID and EC-TID exhibit superior EDRE effects in mitigating the seismic response of structures compared to viscous and eddy current dampers with the same damping parameters. Additionally, EC-TID offers improved performance over TID, including slightly higher effectiveness, pre-designed maximum damping force, and reduced deformation. Noted that EC-TID is more effective than EC-TVMD in reducing structural seismic responses when their equivalent damping ratio is set at 0.03. This finding contrasts with a recent study where TID and tuned viscous mass damper (TVMD) exhibited comparable effectiveness under the same conditions.

This paper presents a new method for nondestructive testing—a pulsed multifrequency excitation and spectrogram eddy current testing (PMFES-ECT), which is an extension of the multifrequency excitation and spectrogram eddy current testing. The new method uses excitation in the form of pulses repeated at a specified time, containing several periods of a waveform consisting of the sum of sinusoids with a selected frequency, amplitude and phase. This solution allows the maintenance of the advantages of multifrequency excitation and, at the same time, generates high energy pulses similar to those used in pulse eddy current testing (PECT). The effectiveness of the new method was confirmed by numerical simulations and the measurement of thin Inconel plates, consisting of notches manufactured by the electric-discharge method.

Summary Two kinds of methods have been primarily used to improve the vibration performance of high‐rise buildings. One approach is to enhance the structural lateral stiffness, which may increase the component size and inefficiently use material. The other approach is to employ vibration control devices, such as tuned mass dampers (TMDs), tuned liquid dampers (TLD) and other supplemental damping devices. This latter approach has proved to be quite economical and efficient, and as such, increasingly used in practice. The Shanghai Center Tower (SHC) is a super high‐rise landmark building in China, with a height of 632 m. In order to mitigate its vibration during wind storms, a new eddy‐current TMD was installed at the 125th floor. Special protective mechanisms were incorporated to prevent excessively large amplitude motion of the TMD under extreme wind or earthquake scenarios. Results of reduced‐scale laboratory tests and field tests are presented in this paper to characterize the dynamic properties of the damping device and validate the fidelity of the numerical results. Results of structural analyses indicate that for SHC the eddy‐current TMD was able to reduce wind‐induced structural acceleration by 45%–60% and earthquake‐induced structural displacement by 5%–15%. The installation of the TMD was completed in December 2014, and the performance observed to date is judged to be good. Copyright © 2016 John Wiley & Sons, Ltd.

In this study, an eddy current (EC) detector is integrated in an additive/subtractive hybrid manufacturing (ASHM) process. The detector facilitates in-process inspection and repair operations through material deposition, defect detection, and removal processes layer by layer. A feasibility test is carried out on eddy current detection of subsurface defects in additively manufactured parts by using an EC detector. The study compares the results obtained from the EC detection with those by the X-ray computed tomography and the destructive methods. Experiments and simulations are conducted to investigate the effect of excitation frequency on intensity of the eddy current signal. The effects of residual heat of an additively manufactured specimen and lift-off distance of an EC probe on impedance changes are also investigated. In addition, the effect of defect width on EC signal is analyzed. The study shows that the EC method is capable of detecting subsurface defects in the ASHM parts. It is promising to integrate the EC detection and subtractive manufacturing into additive manufacturing to produce parts with improved quality and better performances.

Permanent magnet eddy current couplers (PMECCs) have the characteristics of contactless torque transmission, removal of torque ripple, smooth dynamic process, and adjustable speed, and can be used as couplings, dampers, brakes, and speed governors. Their applications in industry, vehicles, and energy fields are gradually expanding. At the same time, the requirements for the torque density and dynamic performance of PMECCs are increasing. Therefore, a large amount of research work has focused on the fast and accurate modeling, design, and optimization of PMECCs. This paper provides a survey on the development of PMECCs technology. The main topics include the structure and classification of PMECCs, modeling methods, loss and heat transfer analysis modeling, and optimization design. In addition, this paper shows the future trends of PMECCs research. All the highlighted insights and suggestions of this review will hopefully lead to increasing efforts toward the model’s construction and the optimal design of PMECCs for future applications.

Ultra-high-pressure tubular reactors are crucial pieces of equipment for polyethylene production. Long-term operation under high temperature, high pressure, and other extremely harsh conditions can lead to various defects, with circumferential cracks posing a major safety risk. Detecting cracks is challenging, particularly when they are under a protective layer of a certain thickness. This study designed a pulsed eddy current differential probe to detect circumferential cracks in ultra-high-pressure tubular reactors, with the lift-off distance acting as a protective layer. Detection models for traditional cylindrical and semi-circular excitation differential probes were established using finite element simulations. Corresponding experiments under different lift-off conditions were carried out, and the model’s accuracy was verified by the consistency between the simulation results and experimental data. The distribution of the eddy current field under different conditions and the disturbances caused by cracks at various positions to the detection signal were then calculated in the simulations. The simulation results showed that the cracks significantly disturbed the eddy current field of the semi-circular excitation differential probe compared with that of the traditional cylindrical probe. The designed differential probe effectively detected circumferential cracks of specific lengths and depths using the difference in the voltage signals. The experimental results were in agreement with the simulation results, showing that the designed probe could effectively detect 20 mm-long circumferential cracks at a lift-off of 60 mm. The experimental results also show that the probe’s detection coverage area in the axial direction varied with the lift-off height. The probe design and findings are valuable for detecting cracks in ultra-high-pressure tubular reactors with protective layers.