International Journal of Applied Electromagnetics and Mechanics - Volume 57, issue 1

Authors: Wang, Shen | Huang, Songling | Wang, Zhe | Zhao, Wei

Article Type: Research Article

Abstract: Electromagnetic acoustic transducers (EMATs) are non-contact ultrasonic transducers used to generate ultrasonic waves directly in the tested metal samples, suitable for special situations like testing moving or hot metal solids. EMATs rely on electromagnetic coupling, and the transduction efficiency of EMATs is relatively low, so it’s crucial to improve their performance through building accurate models and implementing structural optimisations. Modern evolutionary optimization algorithms involve a number of evaluations of the objective function of the optimization problem, so it’s necessary to explore surrogate models to reduce the time consumption during evaluation of the computationally expensive objective function, especially when the function …corresponds to complex numerical models, like the EMAT model. We focused on the application of Kriging surrogate model (DACE) in EMAT modeling in this work. The formulations of the DACE model were reviewed, then the model of an omnidirectional EMAT was introduced. Three methods to calculate the amplitudes of the displacement components were discussed and compared, including the time-domain method, the multifrequency method (with FFT/IFFT processing), and the single frequency method applying directly the phasors. The DACE model of the EMAT was then built to predict outputs on a discrete grid of the design variables. Finally the obtained DACE model was used as the surrogate model in the optimization of the EMAT driven by the simulated annealing algorithm. With the DACE model, the total time consumption of optimization of the EMAT was reduced greatly. Show more

Keywords: Kriging, surrogate model, DACE, omni-directional electromagnetic acoustic transducer, EMAT, Lamb waves, optimization, simulated annealing

DOI: 10.3233/JAE-170030

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 57, no. 1, pp. 1-18, 2018

Authors: Stojanović, Goran M. | Lečić, Nikola | Kojić, Sanja | Vasiljević, Dragana

Article Type: Research Article

Abstract: Demands for circuits with higher density in modern electronics have imposed the necessity for electronic components with compact size, high frequency operational range, high efficiency and cost-effectiveness. This requires the new design of electronic components, such as multi-phase coupled inductor with ferrite Ni-Zn core which is studied in this paper. Printed circuit board (PCB) technology was used to develop six symmetrical conductive copper coils, while specially designed innovative ferrite core has been mounted through the PCB, to create a compact component. For ferrite core, two Ni-Zn materials denoted with C2025 and CN20 were used. Testing of the component has been …performed using the following characterization methods: (a) structural characterization using scanning electron microscope; (b) electrical characterization using Impedance analyzer; and (c) mechanical characterization using Nanoindenter. It can be concluded from tests carried out (load-displacement curves and hardness module) that designed and manufactured component can be exposed to mechanical stress and vibrations and can be used in applications such as DC/DC convertors. Show more

Keywords: Ferrite, inductor, SEM, nanoindentation, hardness test

DOI: 10.3233/JAE-170031

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 57, no. 1, pp. 19-27, 2018

Authors: Qiu, Li | Yu, Yijie | Yang, Yuqi | Nie, Xiaopeng | Xiao, Yao | Ning, Yan | Wang, Fazhi | Cao, Cheng

Article Type: Research Article

Abstract: Electromagnetic forming (EMF) is a processing technology using pulsed electromagnetic force to achieve a high forming speed. It draws wide attention because it significantly improves metal material formability. At present, the electromagnetic force is ordinarily generated in the whole workpiece area during the EMF process, which results in a conical contour of formed workpiece with poor forming performance. Therefore, this paper proposes a method named Electromagnetic Forming with Local Loading (EMFLL), in which the electromagnetic force is mainly generated in the specific area of the workpiece. By using ANSYS Software, it gives the simulations for the analysis of the magnetic …flux density distribution and the electromagnetic force distribution in the EMFLL process with the new type of coil. The obtained results show that the electromagnetic force generated by the new type of coil is more concentrated. Finally, a series of experiments on the traditional EMF and EMFLL of AA5052 with a diameter of 160 mm and a thickness of 2 mm has been carried out, the experimental results show that a well-proportioned deformation at the bottom of the workpiece is achieved by EMFLL, which verifies that EMFLL has some certain potential in lightweight alloy processing. Show more

Keywords: Electromagnetic forming with local loading (EMFLL), electromagnetic force, magnetic flux density, finite element model

DOI: 10.3233/JAE-170038

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 57, no. 1, pp. 29-37, 2018

Authors: Zhao, Ruijie | Li, Huiwen | Zhang, Desheng | Huang, Jun | Shi, Weidong

Article Type: Research Article

Abstract: Annular linear induction pump (ALIP) is considered as an ideal type of coolant pump in liquid metal cooled reactors. However, the low pump efficiency and the flow instability have yet been solved, especially for large-scale pump design. In this work, a two-dimensionally symmetrical ALIP model is developed and both single-sided (SS) and double-sided (DS) windings in stators are simulated in the designed ALIP model. The pump performance characteristics (H-Q curve) are obtained by calculating the differential pressure between inlet and outlet at varying flow rate conditions. The simulated results are validated with the previously published experiment. The results show that …the differential pressure of the DS-type pumps is slightly lower than that of SS pump with the same input energy while the radial velocity profile in the channel of the DS pumps with the winding number of outer stator twice that of inner stator shows the best uniform velocity distribution. By peeking into the Lorentz force and induced magnetic field, the DS pump with equal winding numbers at inner and outer stators actually deteriorates the induced magnetic field, resulting in a highly non-uniform Lorentz force in the channel radial direction, particularly at high flow rate. The results demonstrate the importance of finding an appropriate ratio of winding numbers in the DS-type pump design in order to improve the pump performance. Show more

Keywords: ALIP, CFD, MHD, winding scheme, pump performance

DOI: 10.3233/JAE-170086

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 57, no. 1, pp. 39-51, 2018

Authors: Liu, Yapi

Article Type: Research Article

Abstract: With the development of modern industry, more and more permanent magnetic materials are used at elevated temperatures. Thus it has become more and more important to measure their magnetic properties accurately both at room temperature and elevated temperatures. In this paper, for a better understanding of temperature coefficients, measuring of the magnetic properties at elevated temperatures and related problems are reviewed and discussed qualitatively. Advices on magnetizing permanent magnets at elevated temperatures are also given. In addition, principal problems and new advances involved in measuring techniques at elevated temperatures are also discussed. Furthermore, problems associated with testing magnets at elevated …temperatures using a vibrating sample magnetometer (VSM) are also presented. Show more

Keywords: Permanent magnetic materials, magnetic measurement, temperature coefficient, magnetic properties at elevated temperatures

DOI: 10.3233/JAE-170119

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 57, no. 1, pp. 53-67, 2018

Authors: Tang, Enling | Liu, Mei | Han, Yafei | Wang, Ruizhi | He, Liping | Liu, Shuhua | Wang, Meng | Xiang, Shenghai | Xia, Jin | Guo, Kai | Ma, Jianjun

Article Type: Research Article

Abstract: In order to better describe the spatial distributions of characteristic parameters for plasma generated by hypervelocity impact, a large number of experiments have been performed by using two-stage light gas gun loading system and measurement system of plasma characteristic parameters. Based on experimental results determining the splash process, the expanding process of the plasma cloud ejected is obtained near the impact point. For physical process of oblique collision, the expansion of plasma cloud is approximately ellipsoidal distribution. Based on expanding characteristics of plasma cloud determine the space layout of triple Langmuir probe, characteristic parameters of plasma generated by hypervelocity impact …are acquired at the incidence angles of 45 ∘ and 60 ∘ and the impact velocities of about 3 km/s. In the paper, the ellipsoidal equations of the plasma cloud generated by collisions are determined in the three-dimensional space, and the spatial distributions of the plasma characteristic parameters are established. According to the geometric distribution established by hypervelocity impact on 2A12 aluminum plate, the rules and average expanding velocity of the plasma cloud are obtained. Furthermore, the average expanding velocity of plasma cloud increase with the decreasing of the distance from the measured point to impact point at the impact velocities of about 3 km/s and the incidence angles of 45 ∘ and 60 ∘ , respectively. Meanwhile, the linear relationships about impact velocities and distances from the measured point to the impact point are more stronger at the incidence angle of 60 ∘ than that at the incidence angle of 45 ∘ . It is of great significant to further reveal the physical process of the plasma generated by hypervelocity impact. Show more

Keywords: Hypervelocity impact, plasma, characteristic parameters, spatial distribution, expanding velocity of the plasma cloud

DOI: 10.3233/JAE-170120

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 57, no. 1, pp. 69-81, 2018

Authors: Peng, Lisha | Huang, Songling | Wang, Shen | Zhao, Wei

Article Type: Research Article

Abstract: Magnetic flux leakage (MFL) testing is a commonly used nondestructive testing (NDT) technique for signal analysis and defect detection. MFL signal prediction is essential to build forward model and solve defect inverse problem. This paper innovatively proposed an element-scaling-revising method (ESRM) for MFL signal analysis. A forward model for predicting MFL signal is established by ESRM. It doesn’t need to solve the forward finite element method (FEM) model in the calculation process; thus can greatly reduce computation cost, while maintaining a high precision. In this method, the MFL signals of element defects is obtained from FEM model in advance. Then …detection plane of defect is scaled and the lift-off value is revised according to scaling factor k . This method is verified both numerically and experimentally to demonstrate its feasibility. Show more

Keywords: Element-scaling-revising method (ESRM), forward model, magnetic flux leakage (MFL) testing, lift-off value

DOI: 10.3233/JAE-170128

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 57, no. 1, pp. 83-92, 2018

Authors: Li, Xiangchao | Xu, Xiaopei | Cai, Lujin

Article Type: Research Article

Abstract: For the problem of twisted pair coupling lightning electromagnetic impulse, using a combination of test and theory, established a experimental model of twisted pair coupled lightning electromagnetic impulse, get the twisted pair coupling lightning electromagnetic impulse voltage and spectrum characteristics, test results: (1) The situation of twisted pair link matching resistance (100 Ω ): the coupling voltage increases with the addition of the impulse current; Meanwhile, there is not much impact when increase the height of the coupling voltage. (2) The situation of twisted pair link ground electric resistance: the coupling voltage was positively correlated with the ground …electric resistance value in the same height; The coupling voltage increases with increasing height when the resistance value remains the same. (3) Spectral characteristics of the coupling voltage: The frequencies are mainly concentrated around the two frequencies of 8 kHz and 2.3 MHz and the magnitude of the coupling voltage is proportional to the ground electric resistance and the impulse current. The experimental results are in good agreement with the theoretical analysis. The results have some guiding significance. Show more

Keywords: Twisted pair, coupling, lightning electromagnetic impulse, frequency spectrum

DOI: 10.3233/JAE-170135

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 57, no. 1, pp. 93-105, 2018

Authors: Wang, Hujun | Li, Decai | He, Xinzhi | Li, Zhenkun

Article Type: Research Article

Abstract: When applied in the field of sealing liquids, sealing performance of ferrofluids degrades due to the surface instability induced by direct contact and relative motion between ferrofluids and the sealed liquids. Consequently, it can not be widely applied. In order to improve the performance of ferrofluid seal for liquid medium, an improved ferrofluid seal adding gas isolation device was developed to prevent direct contact between ferrofluids and the sealed liquids. The critical pressure of the improved ferrofluid seal was derived theoretically. Magnetic field intensity in the seal gap and fluid dynamics of the sealed liquids and compressed gas were simulated. …A special designed experiment platform was built on which the critical pressure and seal life of the original structure and improved structure were measured and compared. From the theory and experiment results, it can be seen that sealing performance has been significantly improved with the adoption of the improved ferrofluid seal and the sealing problem has been solved by converting sealing liquids to sealing gas. The results of this study give a guidance for solution of sealing liquids with ferrofluids. Show more

Keywords: Ferrofluid seal, critical pressure, seal life, gas isolation

DOI: 10.3233/JAE-170141

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 57, no. 1, pp. 107-122, 2018

Authors: Yu, Qiang | Tian, Lisi | Wang, Xuesong | Cheng, Yuhu

Article Type: Research Article

Abstract: In this paper, a novel magnetic circuit network model is proposed for flux calculation on switched reluctance machines (SRM) of double saliency. Specifically, the airgap reluctance is modeled by a topology of paralleled magnetic paths that only depends on geometry and rotor position, while magnetic saturation on poles is modeled by a simple lookup approach. Such network is featured by allowing magnetic coupling effect from multiple phases. The flux linkage and torque generation considering the coupling can be calculated in a fast and accurate way without limit of power density or rotating speed.

Keywords: Switched reluctance machine, magnetic equivalent circuit, phase coupling, magnetic saturation

DOI: 10.3233/JAE-170167

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 57, no. 1, pp. 123-132, 2018