Magnetic Loading Research Articles

Response characteristic of the magnetorheological plastomer under different varying magnetic fields

As a kind of novel magneto-sensitive smart soft material, magnetorheological plastomers (MPPs) have great application potential in the areas of absorber, damper and sensor. In this work, the mechanical behaviors of MRPs under several different varying magnetic fields were studied. The viscoelastic characteristic of the MRPs was seriously depended on the type of external magnetic field. A linearly changed magnetic field would cause the increase of zero field storage modulus ΔG0′ of MPRs for about 1 MPa, which would severely reduce the magnetorheological effect of MRPs (from 500% to 50%). The direction of the external magnetic field had no influence on the variation of G0′. While under the square wave magnetic field, no variation of the magnetic storage modulus was found when the external magnetic field was removed. A particle-level dynamics simulation was performed to observe the microstructure evolution of the MRP sample under different magnetic loading model. And a possible mechanism was proposed to explain the different residual storage modulus of the MRPs sample under different magnetic loading mode. The discovery would contribute to enhance the regulatory capacity of the MRP material in the application of the smart device.

Impact of Manufacturing Tolerances on a Low-Reactance Slotless PM Synchronous Machine

This paper presents the impacts of manufacturing tolerances on a 1 MW slotless permanent magnet synchronous motor used in an aircraft propulsion system. The motor was designed using multiphysics analysis of electromagnetics, mechanical structure and thermal analysis to obtain a high torque density. It has several governing characteristics, including a Halbach permanent magnet arrangement, slotless stator windings, an outer rotor, lower reactance and a high current density. Since the current density of this design is high, the existence of circulating currents should be considered for safe operation under different levels of manufacturing tolerances. In particular, the low reactance of the motor and the slotless structure greatly contribute to increase the circulating current. Therefore, this paper analyzes various factors affecting the circulating current such as eccentricity and imbalanced windings. Finally, an analytical model is used to calculate magnetic and electric loading, and non-linear finite element analysis are applied and compared to obtain the machine performance.

Elliptical crack problem in magneto-electro-thermo-elasticity of transversely isotropic materials: 3D analytical and numerical solutions

Crack problems are of high research value for multi-ferroic composite media, which have great potential in developing multi-functional devices. In account of the magneto-electro-thermo-elastic coupling effect, this paper investigates an elliptical crack contained in an infinite body of transversely isotropic multi-ferroic composite medium. The two crack surfaces are symmetrically loaded by the combinations of uniform mechanical, electric, magnetic and temperature loadings. The electric and magnetic permeabilities of the crack are idealized to be completely permeable (or impermeable), and thus four combinations of boundary conditions are considered. The field variables in the 3D space, as well as some parameters with great significance in fracture mechanics, are derived analytically, with the generalized method of potential theory. A unified solution of the field variables appropriate for all the four cases is proposed. By the principle of virtual displacement, the finite element formulation is also presented. Numerical results obtained from analytical method and simulations are presented for validating the present analytical solutions, and discussing the effect of magneto-electro-thermo-elastic properties.

Effect of nano-additives blended diesel-biodiesel on performance and emissions of CI engine in the presence of magnetic field

ABSTRACTIn the present study, biodiesel produced from waste cooking oil was added to the diesel fuel at various volume percentages. Nanoparticles of cobalt oxide and cerium oxide were also used as additive to diesel-biodiesel blends. The fuel was magnetized by two neodymium magnets with grade of 42. The effect of six parameters including the magnetic field, biodiesel percent, nano-additives concentration, nano-additives ratio (CeO2 to Co3O4), engine speed, and engine load were evaluated using the Box-Behnken experiment design and RSM method. Optimization of performance parameters and engine emissions showed that the best conditions involved the magnetic field of 1,561.66 Gauss, nano-additives concentration of 12.26 ppm, nano-additives ratio of 56.37%, biodiesel volume fraction of 4.98 vol%, engine speed of 1,962 rpm and engine load of 66.14%. Under these conditions, the engine performance and emissions were as follows: maximum engine torque of 14.67 ± 0.73 Nm, maximum engine power of 3.36 ± 0.14 kW, minimum brake special fuel consumption (BSFC) of 272.50 ± 140.77 gr/kW.h, minimum carbon monoxide (CO) emission of 0.136 ± 0.086 vol%, minimum carbon dioxide (CO2) emission of 0.027 ± 0.28 vol%, minimum-unburned hydrocarbons (UHC) of 0.032 ± 48.12 ppm and minimum nitrogen oxide (NOx) of 4 ± 13.78 ppm with the desirability of 0.89.

Devising a procedure to choose optimal parameters for the electromechanical shock absorber for a subway car

A procedure for determining basic estimation parameters has been devised for the proposed structure of the electromechanical shock absorber. The procedure is based on a simplified mathematical model for determining the electromagnetic and electromotive force for the electromechanical shock absorber. Feature of the model is taking into consideration the operational modes of permanent magnet based on the calculation of a magnetic circle. The model devised makes it possible to perform approximate calculation of the shock absorber operational modes and could be used for solving the problem on the optimization of parameters for an electric shock absorber. We have verified adequacy of the constructed simplified mathematical model by comparing the results from calculating the mechanical characteristic for a shock absorber based on the simplified procedure and those obtained using a finite element method in the axial-symmetrical statement of the problem. There is a good match between the results from calculations based on the simplified procedure and from modeling a magnetic field using the method of finite elements. We have determined the geometric relationships between the elements of the structure that ensure the optimal uniform magnetic load on the elements of the magnetic circuit. The problem on the conditional two-criteria optimization of parameters for the electromechanical shock absorber has been stated. We have chosen constraints that are divided into the three following categories. Constraints for a permanent magnet demagnetization that make it possible to maintain operability of the permanent magnet. Constraints for a current density, which ensures the thermal modes in the shock absorber operation. Constraints for assembly and constraints for the parameters of an optimization problem, which enable the arrangement of a structure within the running part of a carriage. It has been proposed to choose the reduced volume of a shock absorber as a criterion, which predetermines the cost of constructing a shock absorber, and its efficiency as a criterion, which predetermines the recuperated energy of oscillations. The parameters were convoluted to a single objective cost function; the weights were defined. We have chosen, as an optimization method, the combined method that includes a genetic algorithm at the preliminary stage of the search. At the final stage of an optimization procedure an optimum is refined by using the Nelder-Mead method. The result from solving the optimization problem on the shock absorber's parameters is the defined optimal geometric dimensions and the number of turns in the winding of the electromechanical shock absorber.

Characterization of giant magnetostrictive materials under static stress: influence of loading boundary conditions

Giant magnetostrictive materials (GMM) can be integrated in actuator or sensor applications. The design of these systems is optimized based on a good knowledge of the material properties and conditions of use. Terfenol-D exhibits the greatest room temperature strain among commercially available GMM, however, its magneto-elastic behavior is very sensitive to pre-stress level. In this work, the design of an experimental setup dedicated to the characterization of GMM magneto-mechanical behavior under constant stress is described. A major difficulty is to master the mechanical boundary conditions while the sample is subjected to dynamic magnetic loading. The dynamic stress experienced by the sample is connected to the magnitude of the magnetostriction strain, the stiffness of the sample and the stiffness of the characterization setup. Results show that an appropriate setup is able to reduce the dynamic stress variations induced by magnetic excitation variations below 0.1 MPa, while this dynamic stress can reach up to 20 times the magnitude of the applied stress when the control system is not used. With the boundary conditions being controlled, magnetic and magnetostrictive behavior of Terfenol-D are characterized under various uniaxial compressive stress levels, from the stress-free conditions to 90 MPa. By comparing the results obtained under controlled and non-controlled stress conditions, it is shown that uncontrolled boundary conditions can be responsible for errors of several percent on the magnetic induction measurement. The measurement of strain is even more sensitive to the boundary conditions, with errors up to 40% and 30% on the longitudinal and transverse strains, respectively. This work highlights the utmost importance to control the boundary conditions in order to characterize the magneto-mechanical behavior of GMM.

Design and Characteristic Analysis of a 1 MW Superconducting Motor for Ship Propulsions

Electric motors tend to be large in size because they have low speed and high torque characteristics. A superconducting motor (SCM) can be a key technology used to solve these problems. Using the characteristics of a superconductor, the SCM can reduce the volume and weight. This paper deals with the design and characteristic analysis of a 1 MW SCM for ship propulsion. An effective design of the SCM was suggested considering the electromagnetic, thermal, and mechanical properties of the motor. The SCM was designed using Y-Ba-Cu-O (YBCO) wires focusing on size, operating filed current, magnetic flux density, heat load, and mechanical stress. The current leads were also designed to minimize the heat loss in the motor, and the thermal contraction and mechanical force were calculated to design the torque tube. Electromagnetic, mechanical, and thermal characteristics were analyzed using a 3D finite element method program. As a result, the size of SCM was minimized, and the heat loss was also reduced by an effective current lead design. The designed torque tube was structurally stable with a 70% stress margin. These results will help to expand the electric propulsion motor capacity and improve the efficiency of the ship propulsion system.

Architecture and Optimization of a Low-Frequency Maglev Energy Harvester

Low-frequency harvesters are attractive due to their availability in the ambient environment. The paper presents the design, analysis and optimization of the magnetic levitation harvester. A new nonlinear model of the electromechanical coupling, depending on the magnet position versus coil is proposed. Additionally, the influence of magnetic suspension (stiffness), load resistance and magnet-coil configuration on the foldover effect is shown.

Magneto-visco-hyperelasticity for hard-magnetic soft materials: theory and numerical applications

Soft materials that can deform under external stimuli offer great opportunities for the development of new structural applications such as sensor-actuator systems, soft robots or biomedical devices. Among these materials, soft polymers filled with magnetic particles are experiencing an increasing interest from the scientific community. Apart from magnetorheological elastomers and ferrogels, a new magneto-sensitive material type has been developed recently. These so-called hard-magnetic materials allow for shape-programmability by the addition of magnetically-hard particles within a polymeric matrix. In this regard, constitutive and computational frameworks describing the magneto-mechanics of such materials are needed to provide new avenues in the development of novel applications based on hard-magnetic soft polymers. To this end, this work focuses on the mathematical modelling of the magneto-mechanics of hard-magnetic soft materials and their implementation in finite element (FE) frameworks. The proposed continuum model is formulated for large deformations and within a thermodynamically consistent framework. In addition, the model incorporates viscous contributions to account for relaxation and dissipation effects in the deformation process of these materials when subjected to external magnetic fields and/or mechanical loading. To illustrate the theory, the magneto-mechanical model is implemented within an implicit static FE framework and three numerical examples are provided to explore potential applications as well as to evaluate the influence of the external magnetic field application on the viscoelastic response of the material. Finally, the framework is implemented in an implicit dynamic FE framework to evaluate the role of inertial terms on the dynamic response of these materials.

Sizing, Analysis, and Verification of Axial Flux-Switching Permanent Magnet Machine

This paper proposes the analytical design methods of axial flux-switching permanent magnet (AxFSPM) machines. The analytical design methods take the influences of electric and magnetic loadings into account to calculate the specific sizing and scalability of the AxFSPM machine. In addition, the winding functions are implemented to derive the self-, mutual-, d-axis, and q-axis inductances. The results of analytical design methods indicate that the magnetic loading has bigger impact on the stator dimensions of AxFSPM machines than the electrical loading. The d- and q-axis inductances of the all-pole-wound AxFSPM machines are similar under the same number of slots and turns. A prototype is manufactured using analytical design methods. The experimental results show that the prototype machine achieves target specification and the usefulness of the proposed design method is verified.

Pulsed laser heating of a thermoelastic micro-stretch medium under the effect of a magnetic field in the context of a dual-phase-lag model

This investigation is to study the effect of magnetic field and thermal loading due to pulsed laser heating on a rotating micro-stretch thermoelastic medium. The bounding plane surface is heated by a non-Gaussian laser beam. The problem is studied in the context of the dual-phase-lag model, Lord and Shulman theory and Green–Naghdi theory of type II. The normal mode analysis is used to solve the problem to obtain the exact expressions for the displacement components, the micro-rotation, normal force stress, tangential couple stress and temperature distribution. All quantities in the presence and the absence of magnetic field and two values of time in the presence rotation are shown graphically.

Study on axial resonance magneto-electric (ME) effects of layered magneto-electric composites

An experimental investigation has been carried out to capture the magneto-mechanical behavior and material parameters of magnetostrictive material. Further, the experimental study is extended to capture the magnetoelectric (ME) coupling response of trilayered composites by applying both alternating and static magnetic fields. From the experiments, it is observed that the magnetostrictive material has a nonlinear hysteretic behavior. Hence, a three dimensional (3-D) nonlinear constitutive model has been proposed based on a thermodynamic framework and multisurface plasticity. In ME composites, it is also observed that a large ME coupling response can be obtained while operating near resonance frequencies. To capture the resonant ME effects, a theoretical formulation has been proposed based on axial vibrations theory and the proposed constitutive model has been incorporated in the formulation. The simulated resonant ME coupling response based on the proposed formulation is compared with the experimental data and found to be in agreement with each other. Further, a parametric study has been performed to address the variation of the resonant ME response as a function of various parameters such as axial compliance ratio, volume fraction of constituents, temperature, direction of magnetic loading and aspect ratio. This study reveals that the coupling response can be optimized by choosing the suitable parameters based on design requirement.

Demagnetization research on PMs in the Halbach magnetized pulsed alternator

Demagnetization behavior of Halbach magnetized compensated pulsed alternator (CPA) is studied by using finite element method (FEM) under the different demagnetization factors in this paper. The effect of armature reaction magnetic field and thermal rise on demagnetization of PMs is analyzed. This paper investigates the effect of different demagnetization factors on magnetic field distribution, load current, and no-load phase voltage. A series of dynamic demagnetization points in Halbach array permanent magnet (PM) are evaluated to search the worst working point. Partial demagnetization risk can be represented by the worst working point, and the global demagnetization of the PM is represented by the no-load phase voltage characteristics after discharge. The research results demonstrated that the compensation shield with a certain thickness can increase the discharge current and weaken the demagnetization influence of armature reaction. The demagnetization effect of armature reaction on PMs at high temperatures will be strengthened.

Energizing behaviors of a no-insulation and layer-wound REBCO coil in high magnetic field

REBCO coated conductor has been regarded as one of the most viable high-temperature superconductor (HTS) options for next-generation high field magnets, mainly owing to its large in-field current carrying capacity and higher mechanical strength. To explore REBCO coil technology, a small-scale REBCO coil was designed, fabricated and tested. The REBCO coil has a winding inner diameter of 15 mm, outer diameter of 29 mm and length of 38 mm using layer-wound and no-insulation technology. The REBCO coil was tested in a 31.5 T background field, leading to a high field of 32.5 T. The no-insulation behaviors of the REBCO coil, including the charging delay and magnet constant, were investigated at 77 K and 4.2 K respectively. With the magnetic load from the high fields, we found the REBCO coil was mechanically damaged after the experiments, being two major patterns: peeling and bucking.

Microprocessor based prototype design of a PMDC motor with its system identification and PI controller design

This paper describes the development process of a permanent magnetic direct current (PMDC) motor prototype in details. The designed prototype is used for speed control purposes. The developed model is intended to have two types of inputs: one is analog input which accepts variable direct voltage for system identification purpose, and the other is the pulse width modulation input, which can be used to interface with the outside world such as microcontrollers or programmable logic controllers. A microprocessor (with 8 bit resolution and a high performance RISC CPU) acts as a core of the module as it accepts the inputs and accordingly provides the output. An IR sensor acts as feedback sensor and provides pulses to the microprocessor which performs frequency to voltage (F/V) converting function and gives a variable output direct voltage as the speed of the motor varies. The actuator is a permanent magnetic direct current motor driven using metal oxide semiconductor field effect transistor based driving circuit. A four stages magnetic load mechanism is attached to the motor shaft. For test experiment, an ARDUINO MEGA MATLAB SIMULINK support package-based module is developed to provide the inputs and measure the outputs, then open loop test, system identification and PI controller design are carried out and satisfying results are obtained. Illustrating the detailed procedure and the step by step work of the design process of the PMDC motor prototype is the main contribution of current work.

Experimental Evaluation of Structural and Temporal Characteristics of Material Fracture Based on Magnetic Pulse Loading of Ring Samples

The study of fracture of thin aluminum rings due to shock loading generated by magnetic-pulse method was performed. This method provides experimental results on dynamic fracture under conditions of pure tension for a wide range of loading conditions. To simulate rapture of the ring samples a structural-temporal fracture criterion was applied. This criterion allows for analysis of the effects which are characteristic for the dynamic experiments. The fracture incubation time value and ultimate stresses are calculated for the aluminum rings subjected to pulse loading. An analytical relationship between the critical stress and the fracture time are obtained and this relation is in good agreement with the experimental data.

High Torque Density and Low Torque Ripple Shaped-Magnet Machines Using Sinusoidal Plus Third Harmonic Shaped Magnets

This paper proposes a novel shaped-magnet surface permanent magnet machine design concept featuring magnets shaped according to a sinusoid plus a third harmonic along the axial direction, and full-pole-pitched distributed stator windings with a unity winding factor to provide high torque density with essentially zero torque ripple for high-performance motor applications. The magnet thickness is uniform along the radial direction so as not to impair the magnet's ability to handle the demagnetization force. The proposed design was compared against a full-pole-pitched magnet design with maximum magnetic loading and a conventional bread-loaf magnet design. The results demonstrate that the proposed shaped-magnet design uses the magnet materials efficiently to achieve torque density comparable to that of the full-pole-pitched magnet design, and essentially zero torque ripple without compromising its resistivity against a demagnetization force, which conventional bread-loaf magnets cannot offer.

Analysis of Stator Slots and Rotor Pole Pairs Combinations of Rotor-Permanent Magnet Flux-Switching Machines

This paper investigates the influence of stator slots and rotor pole pairs combinations on torque performances in rotor permanent magnet flux switching (RPM-FS) machines. Based on a magnetomotive force (MMF) permeance model, the candidates of stator slots and rotor pole pairs combinations with higher torque capability can be determined by analyzing the PM-MMF and winding factor. Meanwhile, the candidates with a lower torque ripple can be obtained by referring to the cogging torque, which is related to the greatest common divisor of stator slots and rotor pole pairs. In addition, from the field modulation principle, the RPM-FS machines with the same fundamental magnetic loadings and winding factors exhibit identical fundamental harmonic torque, but different modulation harmonic components. Finally, four candidates with attractive torque performance are chosen, and the characteristics are verified by finite-element analysis and experiments.

Surface effect on a nano‐elliptical hole or nano‐crack in magnetoelectroelastic materials under antiplane shear

AbstractBased on the Gurtin‐Murdoch surface/interface model, an antiplane shear problem of a magnetically and electrically impermeable nano‐elliptical hole in magnetoelectroelastic (MEE) materials with surface effect is presented subjected to far‐field anti‐plane mechanical and in‐plane electrical and magnetic loadings. By using the complex function method and conformal mapping technique, exact closed‐form solutions of the stress, electric displacement and magnetic induction intensity factors near the crack tip are obtained when the nano‐elliptical hole is reduced to a nano‐crack. Numerical examples are provided to show the effects of size of nano‐crack on the field intensity factors near the crack tip induced by mechanical, electrical and magnetic loadings for the piezoelectric (PE), piezomagnetic (PM) and MEE materials with surface effect. The interaction between the stress field, electric field and magnetic field around the nano‐hole is analyzed. The results show that the obtained solution is close to the classical elasticity solution with increasing size of the nano‐crack.

A numerical method for magneto-hygro-thermal postbuckling analysis of defective quadrilateral graphene sheets using higher order nonlocal strain gradient theory with different movable boundary conditions

Many researchers work on the mechanical analysis of perfect graphene sheets while these structures have some defects actually. In this paper, postbuckling of the defective quadrilateral single layered graphene sheets (SLGS) is presented for the first time. Three types of defects including single vacancy (SV), double vacancy (DV) and Stone–Wales (SW) in conjunction with the influence of vacancy defect reconstruction are considered. Nonlocal higher order strain gradient theory with three parameters for size effects is used. The quadrilateral graphene sheet is subjected to temperature, moisture and in-plane magnetic loads. The elastic foundation is modelled by Pasternak medium. The equations of motion are obtained imposing higher order shear deformation theory and Hamilton’s principle. The transformed weighing (TW) and differential quadrature (DQ) method are applied for postbuckling load–deflection relation of the structure. Due to the hygrothermal load, different movable boundary conditions are used. The influences of various parameters such as defect types, defect degree, defect reconstruction, hygrothermal load, magnetic field, nonlocal parameters, 7 different quadrilateral SLGS, boundary conditions and elastic medium on the postbuckling behaviour of the quadrilateral graphene sheet are shown. The numerical results are validated with other published works in the literature. Results show that with increasing the defect degree, the buckling load decreases.