Magnetic Interaction Force Research Articles

Study of self-assembly between two magnetic particle chains in magnetorheological fluids

The self-assembly behavior of individual magnetic particles in magnetorheological liquids has been extensively analyzed in previous studies, but the self-assembly behavior between chains of magnetic particles has rarely been investigated. In this paper, the self-assembly mechanism between chains of magnetic particles is investigated using simulation and experimental methods. Firstly, a two-dimensional coupling simulation numerical model of particle-magnetic field-flow field is constructed by analyzing the magnetic force, fluid force and contact interaction force between magnetic particles. The accuracy of the simulation model was verified through experiments. Then the attraction and repulsion dividing line of two magnetic particle chains are analytically calculated by simulation combined with parametric scanning. And analyze the law of the influence of the number of magnetic particles between magnetic particle chains on the attraction and repulsion dividing line. Finally, the different self-assembly behaviors that occur when magnetic particle chains are in different regions of attraction and repulsion between them are experimentally verified. Thus, this study provides new insights into the self-assembly mechanism between chains of magnetic particles in magnetorheological fluids in terms of the effect of the number of magnetic particles on the attraction–repulsion dividing line.

IoT-Based Heartbeat Rate-Monitoring Device Powered by Harvested Kinetic Energy.

Remote patient-monitoring systems are helpful since they can provide timely and effective healthcare facilities. Such online telemedicine is usually achieved with the help of sophisticated and advanced wearable sensor technologies. The modern type of wearable connected devices enable the monitoring of vital sign parameters such as: heart rate variability (HRV) also known as electrocardiogram (ECG), blood pressure (BLP), Respiratory rate and body temperature, blood pressure (BLP), respiratory rate, and body temperature. The ubiquitous problem of wearable devices is their power demand for signal transmission; such devices require frequent battery charging, which causes serious limitations to the continuous monitoring of vital data. To overcome this, the current study provides a primary report on collecting kinetic energy from daily human activities for monitoring vital human signs. The harvested energy is used to sustain the battery autonomy of wearable devices, which allows for a longer monitoring time of vital data. This study proposes a novel type of stress- or exercise-monitoring ECG device based on a microcontroller (PIC18F4550) and a Wi-Fi device (ESP8266), which is cost-effective and enables real-time monitoring of heart rate in the cloud during normal daily activities. In order to achieve both portability and maximum power, the harvester has a small structure and low friction. Neodymium magnets were chosen for their high magnetic strength, versatility, and compact size. Due to the non-linear magnetic force interaction of the magnets, the non-linear part of the dynamic equation has an inverse quadratic form. Electromechanical damping is considered in this study, and the quadratic non-linearity is approximated using MacLaurin expansion, which enables us to find the law of motion for general case studies using classical methods for dynamic equations and the suitable parameters for the harvester. The oscillations are enabled by applying an initial force, and there is a loss of energy due to the electromechanical damping. A typical numerical application is computed with Matlab 2015 software, and an ODE45 solver is used to verify the accuracy of the method.

Powering piezoelectric frequency up-converter with rotary magnetic forces for torque-sensing application

A piezoelectric frequency up-energy harvester (PFU-EH) utilizing an SECE circuit (synchronized electric charge extraction) is developed for torque-sensing application in rotating machinery. Development of an explicit theoretical model for the system with the PFU-EH, considering phase angle shifts and magnetic impulsive forces is proposed to formulate the frequency response equations for voltage and power outputs using Fourier analysis. In this study, harvesting electrical energy can be achieved through the magnetic force interaction between the cantilevered piezoelectric beam, which carries two attached magnets, and the compound rotating disk structure, also carrying two attached magnets. The compound rotating disk structure, composed of a metal ring (outer disk) and a flywheel (inner disk) connected by a spring system, can create a phase angle caused by an applied load. As a result, mechanical torque is formed for inducing magnetic excitation to the PFU-EH and subsequently generating an AC voltage signal. The functionality of the AC voltage harvested by the PFU-EH can be further leveraged for two primary benefits. First, it can be converted into DC voltage output using the SECE circuit, enhancing the effectiveness of the electric signal without requiring load matching under different modal vibrations. Second, the SECE harvesting voltage can simultaneously function as a sensing signal for detecting mechanical torque itself. The sensing signal detection process is further analyzed by applying feature extraction from the spectrogram and utilizing a 2D-CNN for auxiliary segment identification. Finally, the experimental results demonstrate reasonable agreement with the predicted outcomes.

Shear stiffening and magneto-induced properties of magnetorheological elastomer based on self-healing poly(urethane-urea) matrix

A novel multifunctional composite material, defined as self-healing magnetorheological elastomer (SH-MRE), which exhibits both shear stiffening and magnetorheological effects as well as self-healing ability, is obtained by dispersing carbonyl iron particles in a poly(urethane-urea) matrix. The dynamic shear properties are tested through oscillation frequency and magnetic field sweeps. When shear stress is applied with an excitation frequency of 0.1 Hz to 100 Hz, the storage modulus of the poly(urethane-urea) matrix increases sharply, showing a good shear stiffening effect. In addition to the magnetically dependent mechanical properties with a magnetic flux density of 0–0.894 T, the self-healing efficiency of the isotropic SH-MREs with destructive shear damage after healing can be influenced by the mass fraction of the carbonyl iron particles, the applied magnetic field strength and the support of trace solvents. Based on the experimental results, it is believed that the hydrogen bonds in the dynamic hard domains and the magnetic interaction forces between the carbonyl iron particles induced by the magnetic field are the cause of the good multifunctional properties.

Path-Dependent Anisotropic Colloidal Assembly of Magnetic Nanocomposite-Protein Complexes.

Anisotropic self-assembly of nanoparticles (NPs) stems from the fine-tuning of their surface functionality and NP interaction. Strategies involving ligand interaction, protein interaction, and external stimulus have been developed. However, robust construction of monodispersed magnetic NPs to tens of microns of anisotropically aligned colloidal assembly triggered by adsorbed protein intermolecular interaction is yet to be elucidated. Here, we present the NP-protein interaction, magnetic force, and protein corona intermolecular interaction serially but independently induced path-dependent self-assembly of 100 nm Fe3O4@SiO2 nanocomposites. Dynamic formation of the micron-sized anisotropic magnetic assembly was reproducibly realized in a continuous medium in a controllable manner. Formation of the primary globular clusters upon the unique NP-protein complexes with the help of ions acts as the prerequisite for the anisotropic colloidal assembly, followed by the magnetic force-driven pre-organization and protein intermolecular electrostatic interaction-mediated elongation. The protein concentration rather than the protein original structure plays a more pivotal role in the NP-protein interaction and subsequent colloidal assembly process. Two typical serum proteins fibrinogen and bovine serum albumin enable formation of the anisotropic colloidal assembly but with a different subtle morphology. Furthermore, the obtained micron-sized magnetic colloidal assembly can be dissociated rapidly by adding a negative electrolyte in the medium due to the interference in the NP-protein interaction. However, the self-assembly process can be recycled based on the dissociated colloidal assembly.

Study on the trajectory of magnetic particles in the process of magnetorheological elastomer pre-structure

Magnetorheological elastomers (MREs) is made by embedding micro/nano-sized magnetic particles in a polymer matrix. Among them, the distribution and arrangement of internal magnetic particles have an important influence on the performance of magnetorheological elastomers. Therefore, the current research mainly focuses on the influence of the distribution and arrangement of magnetic particles inside MREs on its performance. However, there are few studies on the trajectory of magnetic particles in the prefabrication process of magnetorheological elastomers. In order to solve the above problems, this paper firstly calculated the magnetic interaction force and fluid force of the magnetic particles through numerical simulation. Then, the equation of motion of the magnetic particles is obtained through the coupling of the magnetic interaction force and the fluid force. Finally, the numerical simulation is verified through experiments. In addition, it is found through numerical simulation that the trajectory of magnetic particles is determined by the direction of the magnetic interaction force, instead of its magnitude. After that, the relationship between the direction of the magnetic interaction force and the motion trajectory is analyzed and summarized. The findings of this study have a directive function in explaining the mechanism of magnetic particle arrangement.

Piezomagnetic cantilever stator energy harvester using Savonius wind rotor

This paper proposes the piezomagnetic cantilever beam energy harvester connected to the Savonius vertical axis wind turbine for micro-power generation. The system consists of a rotor plate that is driven by the vertical shaft of the turbine and a stator with a vertically installed piezoelectric cantilever beam. Several magnets are mounted on the rotor and one magnet is attached at the free end of the cantilever as a tip mass. The alternating magnetic interaction force between magnets on the stator and the rotor induces deflection and strain on the piezoelectric layer that generates power. The arrangement of the magnets, wind speed, and resistive loads are some parameters that play important roles in the output power that are relatively investigated by experiments with the same conditions. Based on experimental results, by increasing resistive load, output power increases and then decreases. The same trend was observed for the gap distance between magnets mounted on the rotor and the stator. The 11 mm gap, 60 mm distance from the center, and 33 kΩ were obtained for the arrangement of the magnets on the rotor and also resistive load which leads to the highest power density of 0.85 μWcm-2 at 9.5 m/s wind speed using the standard circuit. Adding a second piezoelectric cantilever causes 37% (1.17 μWcm-2) and 80% (1.54 μWcm-2) improvement in the output power compared to single piezoelectric for series and parallel electrical connection respectively.

Influence of a High Static Magnetic Field on the Morphology of Primary Al3Fe Phase in Al-3%Fe Alloy

It had been done the experiments of the solidification on Al-Fe alloy under a high static magnetic field (10T). The effect of high magnetic field on the morphology of primary Al3Fe phase in Al-3%Fe alloy solidification structure has been investigated by analyzing the microstructures. The experimental results shew that the variation of the morphology of Al3Fe phase was obvious under a high static magnetic field, and them changed to particle-likes and short needles from needle-likes, and they were arranged in chains along the direction of magnetic field to form oriented layered structure. The critical nucleation work reduced and the nucleation rate increased under the applied field, and the magnetic interaction caused by the field can suppress the growth of needle-like Al3Fe phase, both of them resulted in the particle-likes and short needles grains of primary Al3Fe phase to nucleate and grow preferentially. Under the action of magnetic moment and the magnetic interaction force a high static magnetic field, the grains of Al3Fe rotated and then polymerized, and finally formed chain arrangements and layer structures.

Deflection of a bubble pair induced by negative magnetophoresis in a Hele-Shaw cell

To explore how a magnetic field act on the motion of a bubble pair suspended in a ferrofluid, we introduce an “effective magnetic dipole” to represent the air bubble and further solve the two-dimensional Laplace's equation to obtain the distribution of magnetic potential. The derived magnetic interaction force has two components. The tangential one allows the bubble pair to deflect to be parallel to the magnetic field, where the deflection is clockwise at an angle less than 90°. Inversely, it is counterclockwise. The radial component appears as attraction or repulsion depending on the relative position, which switches from attraction to repulsion at critical angles θc = 55° and 125°. Meanwhile, we performed a simple verification experiment in a Hele–Shaw cell to evaluate the deflection angle and spacing of the bubble pair, and the results are in good agreement with the model. This technique has promise in bubble manipulation for microfluidics.

Data – Driven modelling of the interaction force between permanent magnets

Understanding the magnetic interaction force between permanent magnets is important for the design and optimization of the system where they are implemented. However, the methods that are utilized in the literature to compute this force are either time-consuming or approximated with a low degree of generalization. This article presents a surrogate model developed based on a data-driven approach using a deep learning method which addresses this problem. Firstly, a charge model is applied to derive a semi-analytical model (SAM) of the interaction forces between permanent magnets. Using this SAM, the features of the deep learning model (DLM) have been selected, and the training, validation and test datasets that are used to train the DLM have been generated. The DLM training process took 2 h and 30 mins to complete. The difference between the SAM and deep learning model is less than 4.2%, and there are 99.2% and 96.05% of the cases over 885 random tested samples where the errors are less than 2% and 1%, respectively; this indicates that the selected deep learning model is feasible and can provide accurate results compared to the original SAM. Moreover, the permutation feature importance (PFI) analysis shows that the most predictive feature is the separation distance between the magnets, and the heights of the magnets have less predictive power than their radii; the generality of the deep learning model is also demonstrated based on the PFI criteria. Furthermore, compared with Finite Element Analysis (FEA) and the SAM, the surrogate model yields a high accuracy of prediction (the minimum, average and maximum differences between the surrogate and FEA models are 0.06%, 0.42% and 1.74%, respectively) while it required a computational time less than 10-4 s, which is multiple orders of magnitude lower than its FEA and SAM counterparts. The developed data-driven surrogate model can facilitate the design, optimization processes of permanent magnet systems and online computation of the magnetic force through a dynamic study. In addition, using the superposition principle, the magnetic forces between cross-shaped permanent magnets can be computed using the surrogate model. The authors have further designed a user-friendly software interface to compute the magnetic force using the recently developed surrogate model; the software is publicly available under the CC BY 4.0 license, and can be found at: https://github.com/vantainguyen/Force-between-magnets-machine-learning.

Investigation on transient dynamics of rotor system in air turbine starter based on magnetic reduction gear

As an auxiliary mechanical device, Air Turbine Starter (ATS) uses compressed air as power source to start and drive the engine. It withstands the impact of high-pressure airflow during operation, which may cause collision between key components. For this reason, it is necessary to investigate the transient dynamics of ATS rotor system. However, different from the traditional dual rotor structure, ATS uses magnetic reduction gear (MRG) as a reduction unit, which involves multiple physical fields such as magnetic field and stress field, bringing challenges to transient dynamics analysis. In this paper, the magnetic interaction forces between various rotors are innovatively simplified into the form of springs, and added to the solution model to achieve the decoupling of multiple physical fields. On this basis, the transient displacement response of MRG-ATS has been analyzed using transient dynamics theory. The results indicate that the transient displacement of the rotor system has obvious characteristics of oscillation attenuation. The study reveals the feasibility of MRG-ATS application under transient shock.

Structure of a two-dimensional superparamagnetic system in a quadratic trap.

Ground-state structures of a two-dimensional (2D) system composed of superparamagnetic charged particles are investigated by means of molecular dynamics simulation. The charged particles trapped in a quadratic potential interact with each other via the repulsive, attractive, and magnetic dipole-dipole forces. Simulations are performed within two regimes: a one-component system and a two-component system where the charged particles have the identical charge-to-mass ratio. The effects of magnetic dipole-dipole interaction, mixing ratio of the two species and confinement frequency on the ground-state structures are discussed. It is found that as the strength of the magnetic dipole increases, the charged particles tend to self-organize into chainlike structures. The two species particles exhibit different structural features, depending on the competition of electrostatic repulsive interaction, magnetic dipole-dipole interaction and confinement force. The potential lanes are observed through analyzing the global potential of the magnetic particles, which guide the unmagnetic particles aligning themselves in the direction of the potential lanes.

Influence of interparticle friction on the magneto-rheological effect for magnetic fluid: a simulation investigation

This work studied the effect of interparticle friction force on the magnetorheological properties for magnetic fluid using particle-level dynamic simulations. A novel numerical model considering the friction force and elastic normal force between coarse microspheres was developed. The analysis revealed the relationship between magnetic fluid microstructure and friction coefficient (μ) of particles for the first time. Under steady shear flow, plate-like aggregations were formed under a moderate friction coefficient (μ≈ 0.2), while thick chains with large inclinations were observed under strong friction forces (μ > 1.5). When 0.2 ≤ μ ≤ 1.5, the friction forces hardly affected the rheological properties. If μ > 1.5, friction forces could enhance the shear stress by 102%. Friction force hampered the relative movement of magnetic particles in the thick chains and enlarged the average dip angle of microstructures. The magnetic dipolar force between microspheres generated stronger shear stress in such particle aggregations. The optimal friction coefficient was determined as 2 ≤ μ ≤ 2.75 in simulations by considering the saturation magnetizations, external fields, shear rates, and particle concentrations. The enhancement of shear stress was relevant to the relative strength between magnetic force and friction interaction. Simulated shear stress in magnetic field sweep matched well with experiments in the literature. This work will open a promising avenue in the development of high-performance magnetic fluid.

ORTHODONTIC TREATMENT WITH Nd-Fe-B MAGNETS

The aim. The development of methodology for experimental and theoretical assessment of interaction forces between magnets in an orthodontic apparatus, the test of corrosion resistance of protective oxide and nitride coatings deposited on Nd-Fe-B magnets surface. Materials and methods. The Nd-Fe-B permanent magnets with saturation magnetization Ms≈1100 G and bilayer ZrN / ZrO2 coatings were used. To experimental measure of interaction forces between magnets the device was assembled on the base of analytical balance. The distance between the magnets was varied using non-magnetic plates. The ZrO2 and ZrN coatings have been analyzed for their corrosion properties in 0.9 % NaCl quasi-physiological solution. Results. An original method was proposed for calculating of magnetic interaction forces for materials with high magnetic anisotropy, which has good agreement with experimental measurement of forces. The theoretical model takes into account the size of the magnets and the mutual influence of their opposite faces. An increase of corrosion resistance of magnetic materials can be provided by zirconium oxide or nitride compounds, which contribute to inhibition of electrochemical corrosion of Nd-Fe-B magnets. Conclusions. A method for calculating of interaction forces between permanent magnets, which are used for correction of malocclusion in orthodontic, has been developed. The passivation of the Nd-Fe-B permanent magnets surface can be achieved by applying of bilayer ZrN / ZrO2 coating.

Transient Response of Inductrack Systems for Maglev Transport: Part I—A New Transient Model

AbstractAs a new strategy for magnetic levitation, Inductrack systems with Halbach arrays of permanent magnets have been applied to Maglev trains and intensively researched in various projects. In an Inductrack system, the magnetic interaction forces are coupled with the motion of a moving vehicle carrying Halbach arrays, which in many situations results in complicated transient behaviors of the system. In this two-part paper, a new transient model of two degrees-of-freedom for Inductrack systems is proposed. The highlight of this work is that the transient model is developed based on the fundamental principle of physics, without the assumption of steady-state quantities and averaged magnetic forces and with the finite dimensions of Halbach arrays in consideration. In Part I, the transient model is derived through the establishment of a set of nonlinear integro-differential governing equations, and the magnetic interaction forces in the Inductrack system are determined in analytical form. In Part II, the solution of the governing equations, model validation with the previous results in the literature, and transient response analysis via numerical simulation is presented. Although only two degrees-of-freedom have been considered, the approach of modeling and analysis presented in this paper can be extended to general cases of multi-degrees-of-freedom.

Buckling and vibration of FG graphene platelets/aluminum sandwich curved nanobeams considering the thickness stretching effect and exposed to a magnetic field

This paper studies the buckling and vibration analyses of a new model composed of a homogeneous ceramic curved nanobeam sandwiched between two reinforced composite layers. The face layers are made of an aluminum matrix reinforced with functionally graded (FG) graphene nanosheets (nanoplatelets) (GNShs). The present model is assumed to be embedded in an elastic substrate, exposed to an axial magnetic field and axial compressive external loads. Moreover, various boundary conditions are considered. The faces contain multi-composite nanolayres. Each nanolayer is composed of an aluminum matrix reinforced with uniformly distributed GNShs. The material properties of each face layer as a whole are graded through the thickness according to a piecewise micromechanical model. A refined higher-order curved beam theory is introduced in the polar coordinates considering the thickness stretching effect. Based on the proposed theory, four motion equations are presented containing Lorentz magnetic force and beam-foundation interaction. These equations are analytically solved to obtain the mechanical buckling load as well as the natural frequencies of the sandwich curved nanobeam. Since the general form of the strain-displacement relations is considered in the polar coordinates, the present formulation gives precise results for both shallow and deep curved beams. The effects of the different parameters such as arc angle, magnetic field parameter, elastic substrate parameters, boundary conditions, graphene wight fraction and core thickness on the buckling load and free vibration of the sandwich curved composite beams are investigated.

A Novel Three-Axial Magnetic-Piezoelectric MEMS AC Magnetic Field Sensor.

We report a novel three-axial magnetic-piezoelectric microelectromechanical systems (MEMS) magnetic field sensor. The sensor mainly consists of two sensing elements. Each of the sensing elements consists of a magnetic Ni thick film, a Pt/Ti top electrode, a piezoelectric lead zirconate titanate (PZT) thin film, a Pt/Ti bottom electrode, a SiO2 insulation layer, and a moveable Si MEMS diaphragm. When the sensor is subjected to an AC magnetic field oscillating at 7.5 kHz, a magnetic force interaction between the magnetic field and Ni thick film is produced. Subsequently, the force deforms and deflects the diaphragms as well as the PZT thin film deposited on the diaphragms. The deformation and deflection produce corresponding voltage outputs due to the piezoelectric effect. By analyzing the voltage outputs through our criterion, we can obtain details of the unknown magnetic fields to which the sensor is subjected. This achieves sensing of three-axial magnetic fields. The experimental results show that the sensor is able to sense three-axial magnetic fields ranging from 1 to 20 Oe, with X-axial, Y-axial, and Z-axial sensitivities of 0.156 mVrms/Oe, 0.156 mVrms/Oe, and 0.035 mVrms/Oe, respectively, for sensing element A and 0.033 mVrms/Oe, 0.044 mVrms/Oe, and 0.130 mVrms/Oe, respectively, for sensing element B.

Improving efficiency of piezoelectric based energy harvesting from human motions using double pendulum system

Harvesting electrical energy from various human motions using piezoelectric energy harvesters (PEH) is gaining research attention in recent years. The energy harvested could potentially power hand held electronic devices and medical devices without the need of external power source for recharging batteries. In this study, an attempt is made to improve the efficiency of PEH to harvest energy from human motions by adopting a double pendulum system coupled with magnetic force interactions. For the purpose of comparison, three configurations of PEH which includes the conventional PEH with cantilever beam (PEHCB), the PEH with single pendulum system (PEHSP) and the PEH with double pendulum system (PEHDP) are experimentally studied. Excitations by both mechanical shaker and major human body parts during walking and jogging motions are investigated. The performance of each configuration, in terms of voltage and power produced as well as the idle time between each cycle, are analysed, compared and discussed. ANSYS© software is used to analyse the proposed model and MATLAB© software is used to calculate the output power. The results demonstrate that, with the use of the proposed double pendulum system, multiple impacts in each motion cycle is generated, thus producing higher voltage and power as compared to the conventional PEHCB. The idle time between each motion cycle is also effectively reduced. The efficiency of the PEH is thus significantly increased.

Investigation on the self-assembly of magnetic core-shell nanoparticles under soft-magnet element by using discrete element method

Abstract The self-assembly of magnetic core-shell nanoparticles in the presence of a magnetic template, which consists of an array of soft-magnetic elements embedded in non-magnetic substrate, is analyzed by using discrete element method. An external bias magnetic field is used to magnetize the soft-magnetic elements to saturate state. The high-gradient field produced by elements combined with biased uniform magnetic field provides a flexible way to control the behavior of particles. An equivalent source method is adopted to obtain the closed-form magnetic field analysis, which not only improves the calculation efficiency but also enables accurate prediction of the Kelvin force. In the presence of magnetic field, the behavior of the magnetic nanoparticles is dependent on the magnetic and hydrodynamic forces. Therefore, the assembled structures of magnetic nanoparticles are firstly investigated without considering the magnetic dipole interaction force, in which an unordered nanostructure is formed. As a contrast, the self-assembly of particles is also simulated by taking all forces into account. In this case, the magnetic nanoparticles assemble into an ordered 3D structure, which presents a hexagonal close packed structure. A comparison between the results of the mentioned two cases denotes that the magnetic dipole interaction force plays an important role in controlling the self-assembly of magnetic nanoparticles.

Design and analysis of switchable magnetic polarity bistable energy harvester

Multistable vibration harvesters that involve repelling magnet force result in improved efficiency over a wider bandwidth in comparison to the conventional resonant devices. However, the dynamic performance of the vibration harvester can be further improved by switching the magnetic force polarity to ensure pull force on the mass as it moves towards the mean position. In the presented work, the design and analysis of a switching polarity bistable harvester has been presented, which changes the magnetic interaction polarity in order to improve power output as well as efficient operational bandwidth. An innovative mechanism has been developed to operate the harvester with switching polarity for higher base acceleration amplitude. The proposed design has integrated switchable polarity magnetic interaction and rotary electric generator which is driven by a compound gear train in the conventional spring-mass harvester. Analytical and numerical simulations have been formulated to illustrate efficient operational characteristics over the operating frequency band and to determine the optimum electrical damping coefficient. Effects of magnetic interaction force, the inertia of the switching mechanism and gears have been considered in the numerical analysis. A prototype delivered the peak power of 1.49 W at the resonance frequency and exhibited 50% increase in power in comparison to fixed polarity design.