Showing papers on "Magneto published in 2014"

Sensor Applications of Soft Magnetic Materials Based on Magneto-Impedance, Magneto-Elastic Resonance and Magneto-Electricity

Abstract: The outstanding properties of selected soft magnetic materials make them successful candidates for building high performance sensors. In this paper we present our recent work regarding different sensing technologies based on the coupling of the magnetic properties of soft magnetic materials with their electric or elastic properties. In first place we report the influence on the magneto-impedance response of the thickness of Permalloy films in multilayer-sandwiched structures. An impedance change of 270% was found in the best conditions upon the application of magnetic field, with a low field sensitivity of 140%/Oe. Second, the magneto-elastic resonance of amorphous ribbons is used to demonstrate the possibility of sensitively measuring the viscosity of fluids, aimed to develop an on-line and real-time sensor capable of assessing the state of degradation of lubricant oils in machinery. A novel analysis method is shown to sensitively reveal the changes of the damping parameter of the magnetoelastic oscillations at the resonance as a function of the oil viscosity. Finally, the properties and performance of magneto-electric laminated composites of amorphous magnetic ribbons and piezoelectric polymer films are investigated, demonstrating magnetic field detection capabilities below 2.7 nT.

Global regularity of the two-dimensional magneto-micropolar fluid system with zero angular viscosity

Abstract: We study the two-dimensional magneto-micropolar fluid system. Making use of the structure of the system, we show that with zero angular viscosity the solution triple remains smooth for all time.

Analysis of Smart Piezo-Magneto-Thermo-Elastic Composite and Reinforced Plates: Part II – Applications

Abstract: Abstract A comprehensive micromechanical model for the analysis of a smart composite piezo-magneto-thermoelastic thin plate with rapidly varying thickness is developed in Part I of thiswork. The asymptotichomogenization model is developed using static equilibrium equations and the quasi-static approximation of Maxwell’s equations. The work culminates in the derivation of general expressions for effective elastic, piezoelectric, piezomagnetic, dielectric permittivity and other coefficients. Among these coefficients, the so-called product coefficients are determined which are present in the behavior of the macroscopic composite as a result of the interactions between the various phases but can be absent from the constitutive behavior of some individual phases of the composite structure. The model is comprehensive enough to also allow for calculation of the local fields of mechanical stresses, electric displacement and magnetic induction. The present paper determines the effective properties of constant thickness laminates comprised of monoclinic materials or orthotropic materials which are rotated with respect to their principal material coordinate system. A further example illustrates the determination of the effective properties of wafer-type magnetoelectric composite plates reinforced with smart ribs or stiffeners oriented along the tangential directions of the plate. For generality, it is assumed that the ribs and the base plate are made of different orthotropic materials. It is shown in this work that for the purely elastic case the results of the derived model converge exactly to previously established models. However, in the more general case where some or all of the phases exhibit piezoelectric and/or piezomagnetic behavior, the expressions for the derived effective coefficients are shown to be dependent on not only the elastic properties but also on the piezoelectric and piezomagnetic parameters of the constituent materials. Thus, the results presented here represent a significant refinement of previously obtained results.

The magneto-elastica: from self-buckling to self-assembly

Abstract: Spherical neodymium–iron–boron magnets are permanent magnets that can be assembled into a variety of structures owing to their high magnetic strength. A one-dimensional chain of these magnets responds to mechanical loadings in a manner reminiscent of an elastic rod. We investigate the macroscopic mechanical properties of assemblies of ferromagnetic spheres by considering chains, rings and chiral cylinders of magnets. Based on energy estimates and simple experiments, we introduce an effective magnetic bending stiffness for a chain of magnets and show that, used in conjunction with classic results for elastic rods, it provides excellent estimates for the buckling and vibration dynamics of magnetic chains. We then use this estimate to understand the dynamic self-assembly of a cylinder from an initially straight chain of magnets.

Magneto-Mechano-Electric (MME) Energy Harvesting Properties of Piezoelectric Macro-fiber Composite/Ni Magnetoelectric Generator

Abstract: Abstract Asymmetric and symmetric magnetoelectric (ME) laminates structures of piezoelectric macro-fiber composite (MFC)/nickel (Ni) were fabricated and investigated their ME and magneto-mechano-electric (MME) energy harvesting responses to an applied magnetic/mechanical stimulations. Both the structures strongly revealed the dependence of ME voltage coefficient (αME) on applied magnetic field directions with an important feature of a zero-bias field ME response. This is much more beneficial for designing the magnetic field sensors. The fabricated MFC/Ni structures exhibited good energy harvesting response to applied simultaneous magnetic/mechanical vibrations of lab magnetic stirrer. The electric power was successfully harnessed from magneto-mechanical stimulations; the resulting potential and power were up to ~20 Vp–p and ~6 μW respectively, which are quite enough power to light a commercial red LED with traditional rectifier circuit and capacitor. Hence, the present MFC/Ni ME generators provide their future feasibility having self-biasing feature for designing the magnetic field sensors as well as for powering small consumer electronic devices and wireless sensor network systems by exploiting mechanical/magnetic stimulations from surrounding.

Magnetic FEM Design and Experimental Validation of an Innovative Fail-Safe Magnetorheological Clutch Excited by Permanent Magnets

Abstract: This paper describes the magnetic design of an innovative fail-safe clutch based on magnetorheological fluid (MRF). A cylindrical arrangement of permanent magnets (PMs) is used to excite the fluid. The suitable distribution of magnetic field inside the MRF and the transmissible torque is obtained by moving the PMs along the axial direction. The device is designed using a magneto/mechanical FEM model, developed on purpose and based on a three-dimensional (3-D) finite-element code, which takes into account the B-H and τ-H functions of the nonlinear materials (e.g., MRF, PM, and ferromagnetic materials). The flux density maps and the shear stress maps inside the fluid are carefully analyzed. Furthermore, in order to validate the FEM model, some preliminary experimental measurements are performed on a prototype. Finally, the magnetic axial force acting on the PM system is investigated.

Interfacial waves between two magneto-electro-elastic half-spaces with magneto-electro-mechanical imperfect interface

Abstract: The propagation of shear horizontal waves between the interface of two magneto-electro-elastic materials with an magneto-electro-mechanical imperfect contact has been studied. Mechanical, electrical and magnetical imperfections are modelled by means of a spring, a capacitor and an inductor, respectively. A general expression for the dispersion relation is given in an explicit form. Some limit cases are analysed in detail. The influence of imperfect contacts is shown in some numerical results.

Micromagnetic Modeling of Magneto-Mechanical Behavior

Abstract: A magneto-mechanical static modeling of ferromagnetic particle based on minimization of an energy function is presented. This modeling is made of a conjugate gradient method coupled with finite-element method for the mechanical problem resolution. Two-dimensional computational results highlighting the influence of magneto-mechanical coupling on the magnetic microstructure and behavior are reported.

3-D stochastic micropolar and magneto-micropolar fluid systems with non-Lipschitz multiplicative noise

Abstract: We study the stochastic micropolar and magneto-micropolar fluid systems with multiplicative noise in three-dimensional space. Without Lipschitz continuity condition on the noise, we show the existence of a weak martingale solution by applications of Prokhorov and Skorokhod’s theorems, followed by de Rham’s theorem generalized to processes.

Control device for internal combustion engine

Abstract: Provided is a control device for an internal combustion engine, employing a microprocessor to control a load other than an ignition device, the control device being provided to an internal combustion engine in which is installed a magnet generator that has a magneto coil for successively generating, in association with revolution of the internal combustion engine, a first half wave voltage, a second half wave voltage of different polarity than the first half wave voltage, and a third half wave voltage of identical polarity to the first half wave voltage; and the magnet generator employing the second half wave voltage to drive the ignition device The device is provided with an electricity storage element which draws excess power from the output that is output by the magnet generator for the purpose of driving the ignition device, and which is charged by the first and second half wave voltages, as well as being charged by the second half wave voltage as well at times that the internal combustion engine is in the exhaust stroke, in order to supply power to the load and to the microprocessor The power source circuit is constituted to use the energy stored in this electricity storage element to generate power source voltage for presentation to the microprocessor and to the load other than an ignition device

Novel stator magneto type magnetic flux switching motor

Abstract: A novel stator magneto type magnetic flux switching motor is provided. The motor comprises three stators and a combined type rotor, the rotor portion is formed by combining an axial magnetic flux switching motor rotor and a radial magnetic flux switching motor rotor. By employing the structure, the utility rate of space of the motor can be effectively improved, and the load capability and the fault-tolerant capability of the motor are improved.

Efficiency measurements of multiband and circularly polarized magneto-dielectric antennas by the equivalent-circuit wheeler cap

Abstract: Accurate Wheeler cap measurements, either in a narrow or a wide band, are critically affected by the postprocessing method employed to deduce efficiency values from raw data. Stringent cases like multiband or circularly polarized (CP) antennas cannot be handled accurately by typical postprocessing methods, but lend themselves to post-processing based on equivalent circuits. This paper revisits the equivalent-circuit Wheeler cap (EC-WCap) and modifies all steps of the algorithm, thus significantly enhancing its simplicity and speed, while maintaining a wideband measurement capacity. This enhancement of EC-WCap was driven by the need to accurately characterize multiband CP magneto-dielectric antennas built on externally biased ferrimagnetic compounds, which resist characterization by other Wheeler-cap-related post-processing methods.

Development of a new module for the measurement of the magneto-electric direct and converse effects based on an alternating current susceptometer.

Abstract: A new module for the measurement of magneto-electric properties was developed as an add-on for a magnetic AC susceptibility option of a Physical Properties Measurement System (PPMS). The module is capable of recording direct dynamic and static converse magneto-electric effect, i.e., the change in electric polarization due to the application of a small AC magnetic field with a DC magnetic field bias, or the change in the magnetic moment induced by an applied electric field. The versatile module setup supports both measurements in a sequential order without the need of removing or repositioning the sample. Furthermore, AC and DC magnetic susceptibilities can be recorded while performing direct and inverse magneto-electric measurements, respectively, which adds outstanding capabilities to the existing instrument while saving time and resources. Measurements are fully automated and integrated in the PPMS Multivu software platform. Magneto-electric behavior of a BaTiO3/CoFe2O4 and BaTiO3/NiFe2O4 magneto-electric composites, and a Pb(Fe0.5Nb0.5)O3 single phase compound were recorded as test measurements.

A Scanning, All-Fiber Sagnac Interferometer for High Resolution Magneto-Optic Measurements at 820 nm

Abstract: The Sagnac Interferometer has historically been used for detecting non-reciprocal phenomena, such as rotation. We demonstrate an apparatus in which this technique is employed for high resolution measurements of the Magneto-Optical Polar Kerr effect-a direct indicator of magnetism. Previous designs have incorporated free-space components which are bulky and difficult to align. We improve upon this technique by using all fiber-optic coupled components and demonstrate operation at a new wavelength, 820 nm, with which we can achieve better than 1 μrad resolution. Mounting the system on a piezo-electric scanner allows us to acquire diffraction limited images with 1.5 μm spatial resolution. We also provide extensive discussion on the details and of the Sagnac Interferometer's construction.

Pyroeffects on multiphase magneto-electro-elastic sensor patch bonded on mild steel plate

Abstract: The magneto-electro-elastic (MEE) material under thermal environment exhibits pyroelectric and pyromagnetic coefficients resulting in pyroeffects such as pyroelectric and pyromagnetic. The pyroelectric and pyromagnetic effects on the behavior of multiphase MEE sensors bonded on the top surface of a mild steel plate under thermal environment is presented in this paper. The aim of the study is to investigate how samples having different volume fractions of the multiphase MEE sensor behave due to pyroeffects using finite element method. This is studied at an optimal location on the plate, where the maximum electric and magnetic potentials of the MEE sensor are induced due to pyroeffects under various boundary conditions. It is assumed that plate and sensor are perfectly bonded to each other. The maximum pyroelectric and pyromagnetic effects on electric and magnetic potentials are observed when volume fraction is vf = 0.2. Additionally, the boundary conditions significantly influence the pyroelectric and pyromagnetic effects on electric and magnetic potentials of the sensor.

Magneto-Rotational Symmetry in Chiral Magnetoelectrodeposition

Abstract: The chiral activities of electrodeposited surfaces fabricated under vertical magnetic fields were theoretically examined. Chiral activities arise from the micro-vortexes, called micro-MHD (magnetohych-odynamic) flows (MMF), activated under a tornado-like vortex called vertical MHD flow (VMF). It was concluded that the interaction between MMF and VMF determines the activities.

Effect of Co Addition on the Magneto-Caloric Effect of Fe-Based Metallic Glasses

Abstract: Magnetic refrigeration, based on the magnetocaloric effect (MCE), has already been applied in low temperature applications. There are, however, limitations in room temperature applications, and many researchers are now working on this issue. The refrigeration capacity (RC), which reflects the MCE, of amorphous materials has been proven to be generally larger than that of crystals. Among various amorphous magnetic materials, although the Fe-based materials have general MCEs, their advantages of high Curie temperature ( C T ) and low cost have attracted considerable attention and investigation. In order to enhance the MCE, the influence of Co addition on a Fe-based amorphous material was investigated in this study. Fe76-xCoxSi5Cr4Zr5B10 (x=0, 2, 4, 6) ribbons were fabricated and their MCE was studied under a maximum field of 1193.7 kA/m. The results show that Fe74Co2Si5Cr4Zr5B10 ribbon demonstrated good performance when both refrigeration capacity and Curie temperature are taken into consideration (Tc=295K, RC=56.1J/kg). Since the Curie temperature of this alloy is close to room temperature. It is envisaged that with further improvement of its RC, this material is promising for magnetic refrigeration at room temperature.

Alternator overvoltage protection circuit

Abstract: Disclosed is an alternator overvoltage protection circuit having a TRIAC and a MOSFET. The TRIAC is electrically connected to the MOSFET and the TRIAC is electrically connected to a magneto. The TRIAC is configured to ground the magneto when triggered by the MOSFET. The MOSFET is electrically connected to an alternator and configured to conduct when the alternator operates in an overvoltage condition. Also disclosed is a method of alternator overvoltage protection for a piece of outdoor power equipment, the method including providing a TRIAC and an alternator rotated by an engine having a magneto, wherein the alternator outputs a voltage when rotated by the engine. The method further includes configuring the TRIAC to ground the magneto when the alternator operates in an overvoltage condition, thereby disabling the magneto, which stops the rotation of the engine and stops the alternator from outputting voltage.