Magnetic Field Intensity Distribution Research Articles

Investigation of a newly developed shear built-in valve type MR damper with high damping: Theories and experiments

Magnetorheological (MR) dampers are widely used as semi-active energy-dissipation devices in structural vibration control. Traditional MR dampers, particularly their working mode, often struggle to achieve a high damping force output and sometimes fail to meet the needs of practical engineering. Therefore, it is necessary to study MR dampers that can provide a high damping force. This study proposes an MR damper that combines a built-in shear valve with various working modes of shear extrusion. The damper generates a higher damping force by applying a current to the coils at different positions and altering its working mode. First, the ANSYS Maxwell software simulates the internal magnetic circuit of the damper to assess whether the magnetic field intensity distribution and circuit direction meet the design requirements. Analysis revealed that the internal magnetic circuit distribution was reasonable and satisfied the operating requirements of the damper. Furthermore, the mechanical models of the two working modes were derived based on the Bingham and double-viscous models. Finally, the accuracies of the mechanical models were verified experimentally. The experimental results showed that the simulation values closely matched the experimental values under all the working conditions. Therefore, the proposed mechanical models are reasonable, and can provide significant reference values for practical engineering applications.

ОСНОВНІ РЕЖИМИ РОБОТИ І ГРАФІЧНИЙ ІНТЕРФЕЙС КОРИСТУВАЧА КОМПЛЕКСУ ДЛЯ ЕКСПЕРИМЕНТАЛЬНИХ ДОСЛІДЖЕНЬ МАГНІТНИХ ПОЛІВ І ДІАГНОСТУВАННЯ ЕЛЕКТРОЕНЕРГЕТИЧНОГО ОБЛАДНАННЯ

Hardware and software monitoring complex is designed to study the relationship between changes in the patterns of the magnetic field intensity distribution with power equipment failures. In experimental studies with predetermined techni-cal faults artificially introduced into the object the complex will provide useful and reliable results by registering changes in the magnetic field induction in the spatial, temporal and frequency domains. The choice and flexible adjust-ment of data collection tools by the researcher will ensure the use of the most appropriate method for measuring, con-verting and displaying information about the investigated faults. The article presents the main operating modes and graphical user interfaces of a personal computer and a mobile data acquisition system that jointly convert, store, ana-lyze and display measurement information received from various magnetic sensors. The generalized functional specifi-cation of the complex software, the design of the graphical user interface (GUI) as parts of the real-time operating sys-tem (RTOS) of the mobile data acquisition system (DAQ) and PC software will also be used in the development of prob-lem-oriented computer diagnostic systems for electric power equipment. Ref. 12, fig. 3.

Application of bioinspired geomagnetic sensor measurements and geomagnetic map modeling based on neural networks in simulated navigation

A geomagnetic field is a vector field in which the strength and direction are related to geographical location. Geomagnetic navigation technology, which uses collected geomagnetic field information to achieve positioning and navigation, has the advantages of reliability, stability, accuracy, and concealment. With the deepening research on geomagnetic navigation, bioinspired geomagnetic navigation technology has also been developed, which mainly studies and imitates the magnetic sensing mechanism and navigation behavior of animals, providing new research ideas for geomagnetic navigation technology. The magnetic particle hypothesis and free radical pair hypothesis are two mainstream mechanisms of biological sensing using the geomagnetic field, and studies have shown that these two mechanisms may be coupled within organisms. In this study, we propose a bioinspired weak magnetic vector (BWMV) sensor based on the joint sensing mechanism of magnetic particles and free radicals. It consists of a magnetic rod made of soft magnetic material and a tunnel magnetoresistance (TMR) sensor array. A magnetic rod was used to simulate magnetic particles to convert magnetic field angle information into magnetic field intensity distribution information, and the TMR sensor array was used to simulate the perception of the magnetic field distribution by free radicals. In addition, artificial neural networks (ANNs) were used for BWMV sensors to obtain the mapping relationship between the magnetic field distribution and parameters, which can be used for geomagnetic navigation. To verify the navigation effect of the BWMV sensor in the laboratory, a simulated geomagnetic navigation device was built, and the high-precision mapping relationship from geomagnetic parameters to latitude and longitude information of the selected navigation area was obtained through another ANN. Finally, the effectiveness of the BWMV sensor based on ANNs for geomagnetic navigation is verified using simulated navigation experiments.

Analytical calculation method of a liquid-cooling eddy current brake considering magnetic saturation and skin effect

In this article, a clear and concise analytical method for predicting the performance of a Liquid-cooling eddy current brake (LC-ECB) is proposed. The LC-ECB has a coolant channel in the rotor to allow direct cooling of the inner surface of the stator. The static air-gap magnetic field distribution is obtained by the dynamic magnetic equivalent circuit (MEC) method, and the magnetic flux leakage and global magnetic saturation effects are fully considered. The magnetic field intensity distribution function of the eddy current reaction magnetic field is derived for the first time based on Ampere circuital theorem. Considering the local magnetic saturation and skin effect, a novel double-iteration algorithm based on the conservation principle of magnetic pressure drop is applied to obtain the transient air-gap flux density distribution, and then the brake torque expression is obtained. The finite element method (FEM) and experimental results show that the proposed method is feasible and effective. The new model is easy to program and can be easily used in the initial design and optimization of LC-ECB.

Research on the influence of temperature about the measureing performance of lead–bismuth-eutectic electromagnetic flowmeter

Lead-bismuth-eutectic (LBE) is one of the preferred transmutation targets and coolants for the fourth-generation nuclear reactors. There are complex and interactive factors affecting the flow control of LBE in high temperature operation, which makes it difficult to trace the quantity-value of a lead–bismuth-eutectic electromagnetic flowmeter (LBE-EMFM). In this paper, the measuring characteristics of LBE-EMFM at high temperature are analyzed and studied. The results show that the magnetic field intensity and flow field distribution are the main factors affecting the performance of the flowmeter. With the increase of temperature, the magnetic field intensity and the flow velocity gradient near the measuring tube wall increase, the linearity of LBE-EMFM decreases, and the sensitivity decreases non-linearly. The research of this paper provides an important reference for detecting the flow parameters of LBE and optimizing the performance of LBE-EMFM in the control process of the nuclear industry.

Magnetic-responsive Fe3O4@PDMS@SiO2 omniphobic microciliary arrays for dynamic manipulation of droplets and spheres

Many biological organ surfaces exhibit unique micro/nano structures, which may be adopted for directional transportation of droplets and spheres for applications in microfluidics, biomedical analysis, chemical reactions and materials research. However, realizing efficient and dynamic manipulation of multi-form substances in different media remains a great challenge. In this study, magnetic-responsive Fe3O4@PDMS@SiO2 omniphobic microciliary arrays (MMAs) are fabricated by combining nanosecond laser machining of PTFE template and transfer replication process. Due to the modification by omniphobic SiO2, the optimized MMAs possess 40 wt% iron oxide content with water contact angle > 140°, rolling angle < 3°, and oil contact angle of 129°. Therefore, the MMAs can dynamically manipulate water, oil, air bubble, and solid. Under the stimulation of a moving magnet, microcilia pillars bend and deform sequentially in a wave-like manner, which generates the directional driving force and rapidly transports water and oil droplets, solid spheres and air bubbles in both water and oil media. A droplet up to 25 μL and a solid sphere up to 2 g can be continuously transported at a maximum velocity of 2.4 mm/s. The magnetic field intensity distribution is simulated by COMSOL Multiphysics software, and the force distributions are theoretically calculated. The multi-substances transportation strategy has potential applications in biomedical processes, targeted drug delivery and microfluidics.

A non-uniform magnetic field coupled lattice Boltzmann model and its application on the wetting dynamics of a ferrofluid droplet under gravity effects

To extend the mesoscopic model for simulating the wetting dynamics of ferrofluid droplets, an improved multicomponent multiphase pseudopotential lattice Boltzmann (LB) model coupled with the magnetic field solver is constructed in this work. Through a series of validation studies, the accuracy and reliability of the proposed coupled model are ensured. The ferrofluid droplet is subjected to the effects of non-uniform magnetic field and gravity. The influences of various magnetic Bond numbers (Bom) and gravitational Bond numbers (Bo) on the wetting dynamics of a ferrofluid droplet on a hydrophobic surface are discussed, and the mechanism behind the morphological evolution of the ferrofluid droplet is unveiled. The results show that the curvature of the phase interface is a key factor influencing both the magnetic field intensity distribution around the phase interface and the pressure distribution inside the ferrofluid droplet, thus changing the evolution of the droplet morphology. The variation of Bom has a monotonic impact on the morphological evolution of the ferrofluid droplet and its equilibrium state, while the effect of the Bo depends on the magnitude of Bom. At Bom=49.98 and Bo=4.1, the ferrofluid droplet splits from the central position and into three parts in the end. The amplitude and duration time of the oscillation of the ferrofluid droplet increase with Bom. This study can provide a model reference and some key theoretical understandings for the numerical study of the wetting dynamics of ferrofluid droplets.

Experiment and numerical simulation of stress detection for oil and gas pipelines based on magnetic stress coupling of pipeline steel

In this study, a stress detection method is proposed to address the challenge of developing a nondestructive stress testing technique for oil and gas pipelines in real-time and online due to the complexity of the service environment and particularity of the transportation medium. The method is based on the magnetic mechanical properties of pipeline steel materials and the magnetic induction intensity stress coupling relationship. To evaluate the proposed method, six commonly used pipeline steels (X52, X56, X60, X65, X70, and X80) were selected as research objects, and their hysteresis curves were tested. The local magnetization key parameters of oil and gas pipelines were determined based on their magnetic properties. In addition, a finite element simulation model was established for oil and gas pipelines with coupling of magnetic field and stress field. This study appraise the distribution of magnetic field and magnetic induction intensity along the length and cross section height of the oil and gas pipelines simulation model after local magnetization, without being pressurized. Moreover, it examines the mechanism of magnetic induction intensity and stress variation of the simulation model under different internal pressures of the oil and gas pipelines. To this end, a coupling relationship of axial stress, circumferential stress, and magnetic induction intensity was separately established. Moreover, stress–strain test and magnetic induction intensity test systems were integrated to test the X80 pipeline steel. Through analyzing the test data and finite element simulation data, the validity of magnetic coupling simulation of oil and gas pipelines and the reliability of stress detection were verified. The results provide a theoretical basis for the key technologies of nondestructive online stress detection of oil and gas pipelines.

Carbide twist drill surface polishing and cutting edge passivating based on magnetic field-assisted shear thickening

The multi-field compound polishing method based on the shear thickening has been applied to the processing of various hard materials due to its characteristics of low damage and adaptability to complex surface shapes. The surface defects on the carbide twist drill are usually produced during the grinding. This paper proposes a magnetic field-assisted shear thickening polishing (MASTP) method based on shear thickening and pumping effect, aiming to enhance surface quality of twist drill and passivate cutting edges to improve its cutting performance. The microscopic material removal mechanism of the twist drill and the rheological properties of magnetic shear thickening fluid were analyzed. The magnetic field intensity distribution in the polishing area for two types of magnetic pole arrangements is simulated. A numerical simulation was used to investigate the effect regularity of the polishing gap and spindle speed on the flow field shear stress. Experimental validation was carried out based on the processing platform. The results show the effects of processing parameters on twist drill surface roughness improvement rate and edge radius correspond to the simulated shear stress. After 60 min of polishing, the surface roughness improvement rate reached 94.7% and 80.4% at the body clearance and margin of the twist drill, respectively. The passivating radius of the major cutting edge can reach 12.92 μm, while the passivating radius of the minor cutting edge can reach 15.73 μm. At the same time, the edge defects caused by the grinding are also removed.

Strong nonreciprocal radiation for extreme small incident angle

The perfect nonreciprocal radiation effect for extreme small incident angle is studied. The proposed scheme consists of a patterned magneto-optical (MO) material on a continuous MO film backed with a metallic mirror and coated with a metallic film. Perfect emission and extreme small absorption are achieved at resonance, which results in the realization of near-complete nonreciprocal radiation for an incident angle of only 1o. Such phenomenon is attributed to the excitation of guided mode resonance (GMR) in the MO material, which is revealed by investing the magnetic field intensity distribution and confirmed by the impedance matching theory. In addition, the near-complete nonreciprocal radiation performance remains excellent in a wide range of structure parameters, which lowers the costs of production. Last, the scheme is also employed to investigate the possibility for realizing enhanced nonreciprocity with small applied magnetic field and dual-band nonreciprocal radiation. It is believed the proposed scheme is promising in improving the energy conversion in solar cells, thermophotovoltaics as well as thermal routers and thermal diodes.

Dynamic characteristics of large permanent magnet direct‐drive generators considering electromagnetic–structural coupling effects

AbstractDynamic characteristics of large permanent magnet direct‐drive generators (PMDGs) considering electromagnetic–structural coupling effects are analyzed in this study. Using the conformal mapping method, the scalar magnetic potential of the air gap magnetic field considering the slot effect is calculated. On the basis of the discrete current element and magnetic equivalent circuit model, the local magnetic saturation effect of the stator and rotor is quantitatively simulated and the air gap magnetic field intensity distribution is obtained via numerical simulation. A series of uniformly distributed equivalent electromagnetic springs are introduced to develop an electromagnetic–structural coupling finite element PMDG model. The proposed air gap field analysis method is verified by the finite element analysis results. On the basis of the test platform for the Goldwind 1.5 MW PMDG, both modal and dynamic response tests for the stator/rotor coupling system are conducted, and the results are compared with the natural frequencies, mode shapes, and vibration responses obtained using the numerical model. The effects of the air gap length and rotor speed on the natural frequencies of the coupling system are analyzed. The proposed model has the potential to accurately evaluate the PMDG vibration energy, avoiding resonance points, and maintaining stable operations of the unit.

Development and substantiation of the electrodynamic parameters of a continuous operation radio wave installation for the heat treatment of eggs

Introduction. The existing methods of cooking eggs in water and with steam have a high energy intensity. Currently, the problem of continuity of the technological process is still not solved. That is why, in order to reduce energy consumption, reduce water consumption and intensify the process of heat treatment of eggs, we consider it relevant to use the energy of the electromagnetic field of super high frequency (SHFEMF) in a special temperature regime without using water.Methodology. Three-dimensional modeling of the installation was carried out in the Compass 18.0 program, the justification of the heat treatment modes was carried out by analytical methods, to identify the optimal parameters (energy consumption and temperature regime) of the proposed installation, second-degree least squares polynomials were used, in particular, a rotatable second-order planning matrix, statistical analysis of the matrix was carried out in a software package for statistical analysis Statistica 12, confirmation of analytical data with empirical data was carried out in the CST Microwave Studio program for three-dimensional modeling of electromagnetic field propagation processes in the Eigenmode calculation module, where patterns of electric and magnetic field intensity distribution in a spherical resonator were studied.Results. The structural design of the conveyortype radio wave installation allows for heat treatment of eggs when moving in dielectric cups through slotted spherial resonators. The borehole of the process is less than 0.5 due to the location of the cups in the resonators and between them in relation 4:9. The value of the resonator's own Q-factor reaches 8800. The visualization in the program shows a uniform distribution of the electric field in the resonator, with a voltage of 1.5–3 kV/cm, which ensures high sterility of the product. From the regression models compiled on the basis of the matrix of rotatable planning of the second-order experiment, it follows that the effective duration of exposure to EMF is 154 s, the specific energy costs are equal to 143 Wh/kg. The speed of rotation of the conveyor gear motor is 0.4 rpm.

The enhanced nonreciprocal radiation with topological interface states

The enhanced nonreciprocal radiation effect based on topological interface states is studied, which is realized by inserting a Weyl semimetal film between two asymmetric topological photonic crystals. It is found that near-perfect nonreciprocal radiation is realized for the wavelength of 10 μm under the incident angle of 60°, which is attributed to the topological interface state excited at the boundary between two asymmetric topological photonic crystals, and it is revealed by investigating the magnetic field intensity distribution. Besides, it is shown that the designed structure can also be expanded to achieve strong tri-band nonreciprocal radiation and sing-band nonreciprocal radiation with larger nonreciprocity. The concepts proposed in this work should be attractive for the design of novel energy harvesting devices and infrared stealth.

Investigation of the optimum design of magnetic field arrangement to enhance heat transfer performance of Fe3O4-water magnetic nanofluid

In this study, numerical simulations were conducted to explore the best possible magnetic field arrangement that can maximize the heat exchange performance of Fe3O4-water magnetic nanofluid. Orientation of magnets poles, number of magnets, and the distribution of magnetic field intensity over the flow path are studied to obtain the optimum design which is then tested at various values of magnetic nanoparticles volume fraction, magnetic flux density, and Reynolds number. Results indicated that the optimum design is achieved by placing magnets with N–N orientation and adjusting the magnetic flux density to increase by a rate of 100% between each two successive magnets along the path of the flow. Results also revealed that the average Nusselt number and pressure drop increase when the magnetic flux density is increased. Furthermore, it was found that the effect of increasing magnetic nanoparticles volume fraction on the heat transfer performance is higher at low Reynolds number. An increase of the average Nusselt number in the range of 16.44%–24.46% compared to the design without magnetic field was achieved when using the optimum design with an average magnetic flux density of 1000 Gauss, and magnetic nanoparticles volume fraction of 4%.

Strong nonreciprocal radiation with topological photonic crystal heterostructure

A nonreciprocal thermal emitter, which consists of a magnetic Weyl semimetal embedded in a topological photonic crystal, is proposed and investigated. An emitter exhibits strong nonreciprocal radiation, which results from the exaction of a topological photonic state between two photonic crystals (PhCs). The underlying physical mechanism of such behaviors is disclosed by illustrating magnetic field intensity distributions at resonances and is further confirmed by investigating the band diagram and the Zak phases of the two PhCs. Aside from that, radiation properties of the proposed emitter remain excellent within wide geometric dimension ranges, which should be interesting for practical fabrication. Finally, considering the actual manufacture and the more intense interest of multi-channel nonreciprocal radiation, the extension of the designed scheme to the multi-channel scheme with more practical structure is also investigated. The results should provide possibility for the development of energy devices and thermal emitters with more engineered function.

Diffusion behavior and coercivity enhancement of Tb-containing NdFeB magnet by dip-coating TbH3

There is a growing demand for high coercivity of NdFeB magnets with low heavy rare earth in the emerging applications. In this work, dip-coating 0.02 g and 0.09 g TbH3 on the Tb-containing NdFeB magnet enhance coercivity at room temperature，respectively. The highest coercivity achieve about 30 kOe at room temperature after diffusion, which can apply to traction motors of electric vehicles. The magnetic field intensity distribution of magnet was analyzed by finite element method. Microstructures show TbH3 coat contents and original composition of NdFeB magnet influences the formation of Tb-rich shell and grain boundary phase, and determine finally diffusion depth and Tb concentration. The Tb atoms diffuse into the interior of the magnet, forming a network Tb-rich shell existed around Nd2Fe14B grains, resulting in the coercivity enhancement.

Magnetically tunable dual-band terahertz absorption based on guided-mode resonance.

We propose a magnetically tunable dual-band terahertz (THz) absorber by using an InAs substrate with a subwavelength zero-contrast germanium grating. The results demonstrate that the absorption peaks in this absorber can be dynamically tuned by changing the intensity and the rotation angle of the applied transverse magnetic field, which is achievable at a moderate order of magnitude of 0.1 Tesla. In addition, we investigate the distribution of magnetic field intensity and find that the magnetically tunable absorption originates from the combination of the magneto-optical effect and the guided-mode resonance effect, where the absorption peaks shift in different directions at normal incidence and oblique incidence. Furthermore, the absorption intensity of the proposed structure could reach 99% with an ultra-high Q-factor of 258. This work paves the way for actively adjustable high-resolution THz absorption or a nonreciprocal thermal emitter.

Simulation and experimental study of remote field current testing for hidden defects of aluminum alloy plate with damping coating

PurposeDetection of hidden defects of aluminum alloy plate with damping coating is a challenging problem. At present, only a few non-destructive testing methods exist to address this engineering problem. Without the restriction of skin effect, remote field eddy current (RFEC) overcomes the interference caused by the damping coating. The RFEC, which has potential advantages for detecting the hidden defects of aluminum plate with damping coating, can penetrate the metal plate to detect buried depth defects. This study aims to test how thick the RFEC sensor can penetrate the metal plate to detect the buried defects.Design/methodology/approachThe magnetic field distribution characteristics are analyzed, the magnetic field intensity distribution is calculated, and the structure and parameters of the coil, magnetic circuit and shielding damping are determined through the two- and three-dimensional finite element simulation methods. Optimal excitation frequency is obtained, and the distance between the excitation coil and detection coil is determined by analyzing the relationship between excitation frequency and remote field points.FindingsSimulation and experimental results verify the feasibility of applying the RFEC detection technology in detecting the hidden defects of aluminum alloy plate with damping coating.Originality/valueIn this paper, the RFEC testing model of hidden defects in aluminum plate sample with damping coating is established by using the finite element method.

A Monitoring Equipment Charging System for HVTL Based on Domino-Resonator WPT With Constant Current or Constant Voltage Output

The domino-resonator wireless power transfer system is designed in this work to harvest energy from the magnetic field around a 110-kV high voltage transmission line and supply power to the online monitoring device continuously over 1.1 meters insulation distance. Each domino resonator is evenly spaced and is embedded inside sealed insulation discs. The theoretical analysis shows that the constant voltage (CV) mode and the constant current (CC) mode can be realized by adjusting the receiver's switch state, which can meet the battery's CV and CC charging requirements. Such a method cancels the communication between the transmitter and the receiver. The finite-element simulation results show that the influence on the electric and magnetic field intensity distribution near the insulator can be negligible. Finally, a 30 W prototype with an output voltage of 7 V is built. The experimental results show that the fluctuation of output voltage (CV mode) and output current (CC mode) is less than 6% and 7%, respectively. The maximum efficiency is higher than 40% when the transmission distance is 1.1 m, and the number of coils is 12.

Theoretical and experimental investigations of magnetic field assisted ultra-precision machining of titanium alloys

Although titanium (Ti) alloys possess unique properties that allow them to compete with many other materials in advanced industries such as aerospace, marine and biomedical, they have poor machining performances. The primary objective of this study is to investigate the distribution of magnetic field intensity at the cutting environment in single-point diamond turning (SPDT) of Ti–6Al–4 V alloy and its influence on the machining performances, with the goal of achieving the desired machining conditions of magnetic field assisted ultra-precision machining, especially magnetic field intensity and the corresponding machining parameters, and to enhance the machinability of Ti–6Al–4 V alloy. In this study, magnetic field-assisted machining (MFAM) system was designed and coupled with ultra-precision machining (UPM) using single-point diamond turning for increasing the machinability and improving the surface quality of Ti6Al4V alloy machined parts. The finite element method (FEM) was developed to demonstrate the influences of the generated magnetic field on the machining processes. The Experimental results showed the capability of magnetic field assistance to enhance the machining performance of Ti–6Al–4 V alloy. These findings provided strong evidence that a magnetic field has the ability to extend cutting tool life, additionally, MFAM achieved the lowest value of surface roughness, representing a 33 percent improvement in surface roughness. This research contributes to the support of the optimum MFAM by FEM and the achievement of high-quality machined Ti alloys in UPM for similar research works, as demonstrated by the experimental results.