bluuebunny/crossref_metadata_2025 huggingface dataset:
Active magnetic bearings for a flywheel peak power buffer for electric vehicles
Authors: Wu Y. , Bingham C.M. , Peel D.J. , Howe D.
Published: December 2018

The performance of electric vehicles may be improved significantly by incorporating a flywheel peak power buffer into the power-train. An annular carbon fibre composite flywheel rim offers a high specific energy capability, although a high rotational speed is necessary for a high stored energy, whilst operation in a vacuum is conducive to a low aerodynamic loss, and necessitates the use of magnetic bearings. The electromagnetic design of such a flywheel system is described, and a dynamic analysis that predicts the free vibration modes and frequencies, is presented. Finally, the magnetic bearing control system is described, and it is shown that the vibration damping capability of the bearings is such that natural vibration frequencies within the flywheel operating speed range can be accommodated, and performance objectives commensurate with operation in a vehicle drive-train can be achieved.
A simulation of MPC application for linear motor position control
Authors: Hirano Keiichi , Um Yongsu , Kano Yoshio
Published: December 2018

Nonlinear modeling ideas of a Linear Reluctance Motor (Linear RM) as an MIMO system are proposed here. Fast settling time and an interesting input trajectory are performed on Model Predictive Controlled DC motor position simulation. Prospects for the nonlinear MPC simulation and the advantages to apply the method for linear motor controller are discussed.
Image processing in eddy-current testing for extraction of orientations of defects
Authors: Taniguchi T. , Nakamura K. , Yamada S. , Iwahara M.
Published: December 2018

This paper presents an image processing method for eddy-current testing for the detection of the defects with a specific orientation. The method utilizes the fact that a line-shaped signal is, throught the Fourier transform, mapped onto a line passing through the origin and perpendicular to the orientation of the original signal. Hence, nonseparable fan filters is used to select the frequency components corresponding to the defects orientated in a specific direction. This approach enables more precise control of the extraction characteristics of signals compared to the iterative application of one-dimensional (1-D) filtering in the vertical and horizontal directions, in which the shape of the pass band is restricted to a geometry made from squares. The effectiveness of the proposed method is shown by a demonstration using a metallic sample with a defect aligned in a number of directions.
Network methods in electromagnetic field modelling II: Local modelling and system identification
Authors: Cangellaris Andreas , Russer Peter
Published: December 2018

Network concepts in electromagnetics motivate and faciltate the application of complexity reduction methods to the state equations describing the discretized electromagnetic field. Two general approaches toward such reduction are reviewed in this paper. The first involves the application of model order reduction methodologies in the context of the state space representation of the discrete electromagnetic model. The second considers the application of system identification and parameter estimation methods for reduction of computational time and automatic generation of lumped element equivalent circuits.
Modeling of waveguide circuits based on generalized transmission line equations and impedance/admittance transformation concept
Authors: Pregla Reinhold , Helfert Stefan F.
Published: December 2018

Algorithms for the modeling of waveguide circuits are described. The material parameters can be anisotropic. Starting with generalized transmission line equations, suitable expressions for the analysis are derived. The introduction of the admittance/impedance transformation concept guarantees numerical stable expressions even in case of long devices or high numbers of concatenated sections. The presented algorithm is validated by comparing numerical results with those obtained by measurement and other numerical methods.
New numerical algorithms for the investigation of robust positivity of polynomials with uncertain parameters
Authors: Tibken Bernd , Dilaver Kamil Fatih , Hachicho Ossama
Published: December 2018

This paper addresses the problem of global robust positivity for polynomials with coefficients depending linearly on uncertain parameters. Based on considerations from real algebraic geometry, numerical LMI solvers and the theorem of Ehlich and Zeller we propose two algorithms for the estimation of the convex region in the space of coefficients, for which a polynomial is globally positive. Illustrative examples are given.
Sensitivity estimation for magnetic devices using a double-layer model
Authors: Mueller C. , Scheinert G. , Uhlmann F.H.
Published: December 2018

The paper describes an approach to general-purpose design sensitivity analysis for electromagnetic devices. Microsystem technology often requires the assessment of manufacturing techniques or effects of tolerances. Emphasis is therefore put on the adaptability to different requirements, depending on desired accuracy, computational effort and significance. By introducing a distributed sensitivity function, the effect of small contour distortions can be described. The design sensitivity is based on a magnetic double-layer model. It is shown that sensitivity can be expressed in terms of virtual anti-parallel double-layer currents, flowing in a movable contour. The sensitivity is explicitly derived for two-dimensional coordinate systems using the finite-difference method within a commercially available field computation program. The proposed method is demonstrated by two examples.
Active electromagnetic levitation control of a flexible beam by using disturbance observer
Authors: Sasaki Minoru , Kobayashi Yoshimitsu , Hori Yasuro , Fujisawa Fumio
Published: December 2018

This paper describes an active electromagnetic levitation control of a flexible beam using current and magnetic flux instead of a position sensor. An observer is used to estimate the position based on current, magnetic flux, fundamental, 1st and 3rd modes of vibration of the beam, and input voltage to the electromagnet. The controller combines state-feedback with the observer output to arrive at a new input voltage. Results obtained with a conventional observer and disturbance observer are discussed. Simulation and experimental results demonstrate the feasibility of the approaches.
Applicable detent force reduction methods in steel-cored Permanent Magnet Linear Synchronous Motor based on manufacturing feasibility
Authors: Jung Sang-Yong , Jung Hyun-Kyo
Published: December 2018

This paper reports the methodological approaches to detent force reduction in the steel-cored Permanent Magnet Linear Synchronous Motor (PMLSM). For the detail investigations and overviews on the detent force, analytic solutions considering the various reluctances in the air-gap were obtained using the Space Harmonic Method. The validity of this method was confirmed by comparing the results of the FEM. With the thorough investigation of the causes of detent force, the reduction methods that minimize the force ripple under the consideration of manufacturing feasibility are introduced, and certified by experimentation of the test machine.
Effects of non-uniform magnetization on the performance of a magnetic bearing
Authors: Tan Qing Chang , Kou Zun Quan , Li Wei , Pei Yong Chen
Published: December 2018

In the present work, the distribution of non-uniform magnetization of magnetic rings is experimentally measured and analyzed. The effects of non-uniform magnetization and the soft-magnetic material on the performance of a magnetic bearing are investigated using the theory of magnetic charges, and a model for predicting magnetic force of magnetic-thrust bearings constructed from permanent magnets is developed. The model is verified using the experimental rig built. From the model, fluctuations of the magnetic force and bearing stiffness caused by the non-uniform magnetization are calculated and analyzed.
Efficient numerical evaluation of superconducting microstrip structures with bianisotropic layers
Authors: Toscano Alessandro , Vegni Lucio
Published: December 2018

An efficient procedure is developed for characterizing the frequency-domain behavior of superconducting microstrip planar structures with non conventional (bianisotropic) layers. Most of the frequency domain techniques in computational electromagnetics result in a matrix equation, which is solved at a single frequency. In the proposed technique, a rational function expansion around that frequency is applied to the matrix equation. This paper addresses three aspects in employing such an expansion: a) a generalization of the spectral domain analysis of superconducting patch antennas over bianisotropic layers, b) a robust and reliable estimation of confidence in the interpolated values, c) a criterion for selecting new sample frequencies. As a first numerical example, the radiation efficiency as a function of thickness for a copper and superconducting square patch antenna is presented.
Modelling of electromechanical systems with variable structure using the linear complementarity problem
Authors: Enge Olaf
Published: December 2018

The usage of the linear complementarity problem (LCP) for modelling electrical systems with variable structure is shown. Starting point is a method for modelling electromechanical systems (EMS) using a unified mathematical theory based on the Lagrange formalism. The variable structure is represented by unilateral constraints depending on the characteristics of the switching components. This makes it possible to include such components into the unified theory and, this way, to extend the class of EMS which can be covered.
Dynamic analysis of a permanent magnet synchronous motor under different starting schemes
Authors: Jabbar M.A. , Dong Jing , Liu Zhejie
Published: December 2018

A field – circuit coupled approach has been used to compute the magnetic field of a permanent magnet synchronous motor. The motor drive system has been modeled using field equations to represent its magnet system, which is coupled with equivalent circuit equations to represent the stator windings, the rotor cage bars and various control circuits. A time stepping finite element method for the solution is used. A good match between the computational and experimental results has been achieved.
A measurement system utilising magnetoresistive sensors
Authors: Da Luz Jeanine M. , Longhi Luís G.S. , Zaro Milton
Published: December 2018

This work presents the development of a measurement system based on magnetoresistive sensors. The experimental system is used to measure small moves in the space, being suitable for applications where the absence of contact is required. The developed apparatus is described, modelled, and an experimental run is presented to illustrate its behaviour.
Use of the Modified Rayleigh Conjecture method for determining the shape of an acoustically-soft bounded 2D body from the scattered sound field
Authors: Wirgin Armand
Published: December 2018

The idea of the Modified Rayleigh Conjecture (MRC) [1], in the inverse scattering context, is to obtain the partial wave amplitudes directly from the scattered field, assumed to be known on a circle completely enclosing the body, and then to obtain the shape of the body by employing the Rayleigh hypothesis ansatz of the scattered field [2] in the boundary condition. This method does not require matrix inversions, contrary to the one exploited in [2]. It is shown that in one of the forms of the MRC, the local radius of the body, for a given polar angle, can be obtained by solving a single non-linear equation, just as in the ICBA method [3]. The MRC method, like the ICBA method, leads to solutions of the inverse problem that are not unique. A technique is suggested for reducing this non-uniqueness.
Development of an ER bypass damper for railway car relief couplers
Authors: Wang Feng , Tanaka Mami , Nakada Naoto , Hayase Tsuyoshi , Chonan Seiji
Published: December 2018

This paper is a study on the development of an active damper for the couplers of railway cars using electrorheological (ER) fluid as a functional material with the purpose of lowering the coupler force between a relief and a failed train set, which is a very important design factor for the structure of the super express bullet train. A prototype damper is fabricated, which consists of a hydraulic cylinder, an ER bypass slit valve and a PID controller. The buffering force is developed in the ER fluid both through the bypass slit and at the piston-cylinder gap and controlled by adjusting the applied electric field to the ER fluid. Function of the damper is tested through experiments on control the buffering force under various running conditions.
Influence on brushless DC motor performance due to signal distortion of the position sensor and DC link voltage ripple
Authors: Kim Tae Heoung , Lee Ju
Published: December 2018

In this paper, we introduce the analysis method of Brushless DC Motor (BLDCM) with long commutation period and large DC link voltage ripple using time-stepped voltage source Finite Element Method (FEM), and investigate the influence on motor performance such as torque ripple and radial force due to signal distortion of the position sensor and DC link voltage ripples. Simulation and experimental results are also presented to verify the proposed analysis method.
Torque optimisation for small spindle motors based on reduced-basis finite element formulation
Authors: Jabbar M.A. , Azeman Azmi Bin
Published: December 2018

A Reduced-Basis Finite Element Method has been used for fast and accurate alternative to standard Finite Element algorithms for optimisation problems. Improvement in computational speed is derived from the use of a single static mesh for 'basis' calculations and through application of geometric transformations for regions where variations are required. The method is applied on an 8-pole/9-slot spindle motor used in Hard Disk Drives for the minimization of cogging torque. The desired outcome is a robust algorithm possessing the accuracy of Finite Element Analysis and improved speed of computation.
Numerical simulation of the laser dynamics and laser/matter interactions, and its applications for laser micro-machining
Authors: Yashkir Yuri , Nantel Marc , Hockley Bernard
Published: December 2018

This paper is focused on the systematic computer-based numerical research of processes taking place during laser/matter interaction on the nanosecond time scale. Special attention is paid to the dynamics of a laser with passive Q-switch and intra-cavity nonlinear frequency doubling. The model accounts for the whole set of processes: laser beam attenuation and absorption in the material, heat generation, heat diffusion, phase transitions (solid to liquid, liquid to gaseous state), material removal and melted material re-solidification. Through analysis and simulation of the laser model, we investigate the laser pulse formation and laser parameter optimization. Numerical experiments are used to explain crater shapes, rate of material removal, dependence on laser pulse duration, etc.
Strain evaluation of tensile test by attractors of Barkhausen noise
Authors: Tsuchida Yuji , Enokizono Masato
Published: December 2018

This paper presents a strain evaluation of mild steel plates by attractors constructed from Barkhausen noise. The strain of magnetic materials affects the magnetic domain. Hence the strain can be evaluated by Barkhausen noise. Barkhausen noise from magnetic materials is a very complicated non-linear wave. Thus Barkhausen noise is examined before and after the tensile stress by attractors to make clear the chaotic behaviour to use it for the strain evaluation.
Online NDE of mechanical-technological material characteristics of cold rolled steel strips by using the harmonic analysis of eddy current signals
Authors: Heutling B. , Reimche W. , Krys A. , Grube L. , Stock M. , Bach Fr.-W. , Kroos J. , Stolzenberg M. , Westkämper G.
Published: December 2018

The online-measurement of mechanical-technological characteristic values is made necessary by the need of the steel plants to control the quality of steel sheets continuously during its production under rough industrial environmental conditions. In this paper it is shown that continuous online measurements based solely on the data of the harmonic analysis of eddy current signals are well established by now. The presented online measuring system provides reliable mechanical-technological characteristic values showing clearly changes of the material which are caused e.g. by variations of the furnace temperature or degree of skin-passing or levelling.
Magnetic fluids in flow meters network for gases
Authors: Popa Nicolae Calin , Siblini Ali , Jorat Luc
Published: December 2018

The volumetric flow meter for gases with magnetic fluid is built using a sensing unit (without moving solid mechanical components but exploiting the properties of magnetic fluids) and an electronic measuring system. The sensing unit consists of two sensors, one for differential pressure in gases(equipped with a laminar flow-measuring tube) and another for acceleration or inclination angle. Starting from some technical characteristics (of these sensing units) obtained by a numerical simulation method (or by an analytical one), the paper presents the possibility of using this kind of transducers in a N+1 flow meters network for gases. Every N flow meters of closed range are supervised by another flow meter of higher range. This structure can warn (by software) about any problem (e.g. gases leakage) in the network.
Optimized thrust control of linear induction motors by a compensation approach
Authors: Woronowicz Konrad , Palka Richard
Published: December 2018

This paper describes a solution to the control problems that can be associated with the application of the linear induction motor (LIM) in urban transportation. In order to meet the principle objective of LIM control – the peak thrust tracking – a new compensation technique is presented. The control system has additionally been verified by use of the appropriate finite element field calculations of the LIM and measurements done on the test machine.
Numerical study of resonance characteristics with magnetic damping on higher vibration modes
Authors: Tanaka Yoshikazu , Furuki Syuuji , Shintaku Eiji , Fujimoto Yukio
Published: December 2018

This paper describes the resonance characteristics with the magnetic damping on higher vibration modes. Using the frequency response function obtained from the symmetric matrix equation of the magnetically damped vibration, the differences between the characteristic of the magnetic damping and those of the proportional viscous damping are discussed. Since the downward tendency of amplitude with the magnetic damping is different from that of the proportional viscous damping, it is shown that to perform analyses with considering magnetic damping is important for design activity of such structures.
Formation of virtual diverging channel by use of pair of inclined magnets
Authors: Yamane Ryuichiro , Oshiama Shuzo , Park Myeong-Kwan
Published: December 2018

Formation of the magnetically produced virtual diverging channel is experimentally verified with the two permanent magnets set face to face and inclined with each other, and the water is able to flow through it without contact with the solid walls. The diverging angle increases with the increase in the inclination of the magnets. The diverging angle of the flow follows better to the inclination of the magnets with the increase in the concentration of the magnetic fluids.
Consideration of the AC-part force of electromagnetic stirring in MHD calculation
Authors: Satou Shouji , Fujisaki Keisuke , Furukawa Tatsuya
Published: December 2018

In the continuous casting process, it is very important to make the dynamic behavior of free surface of molten steel clear, because surface quality of steel is almost decided by conditions of free surface. The conventional MHD calculation, which has been used to design the process, was using only the constant electromagnetic force in the time. Then, we developed new MHD calculation also taking the cyclic electromagnetic force into account, and confirmed that free surface vibrates more intensely than conventional result. Therefore, to make the dynamic behavior of free surface clear, cyclic electromagnetic force must be considered.
Analysis of magnetic field distribution in C-yoke system
Authors: Tumanski Slawomir
Published: December 2018

Magnetic field distribution in the C-yoke magnetizing system was analyzed. This numerical analysis was verified experimentally using Magnetovision scanning system. Various magnetizing circuits have been tested.
3-D MHD Calculation in consideration of mold heat transfer
Authors: Fujisaki Keisuke , Nishi Shunji
Published: December 2018

A 3-D Magnetohydrodynamic calculation in consideration of mold heat transfer is developed to obtain the precise mold thermal flux and the mold design. By means of modeling the heat transfer coefficient between the solidified steel and the copper mold in casting direction distribution, the temperature distribution in the mold is in good agreement with the operating data. The mold temperature at the meniscus position is higher than the others. From the cross section temperature at the mold, the corner is higher than the center position.
Resonant excitation of waveguide SH acoustic modes in a piezoelectric plate
Authors: Nowacki J.P. , Alshits V.I. , Lyubimov V.N. , Radowicz A.
Published: December 2018

An excitation of waveguide SH acoustic modes is studied for a layer piezoelectrically coupled with a substrate through a narrow gap. The idea of the method is based on a resonance reflection of plane waves occurring in the substrate close to the tracing speeds of the spectrum of waveguide SH eigenwaves in the layer. Such reflections in the substrate are accompanied by the waveguide components in the layer with rather large amplitudes proportional to the inverse coefficient of electro-mechanical coupling. The shape of resonant peaks of excitation is theoretically studied. The physical limitations for the parameters of resonance are discussed.
Inversion techniques for eddy current NDE using optimization strategies and a rapid 3D forward simulator
Authors: Chen Zhenmao , Yusa Noritaka , Rebican Mihai , Miya Kenzo
Published: December 2018

In this paper, new progress on the ECT-based crack sizing techniques is presented. At first, a fast and accurate forward simulator, which is indispensable in the inversion of ECT signals, is briefly introduced. Several schemes for inversion of crack signals are presented then for EDM cracks, stress corrosion cracks (SCC) respectively. In addition, scheme and reconstruction results for multiple cracks, deep cracks and cracks in the welding part are also given. From the numerical results, it is demonstrated that sizing of single crack from ECT signals has become possible even for a natural crack or a crack as deep as 10 mm. For multiple cracks, more effort is necessary for its modelization and reconstruction.
Improvement of starting characteristic for moving magnet type linear oscillatory actuator using spring damper
Authors: Kim Mi-Yong , Lee Dong-Yeup , Kim Gyu-Tak , Kim Duk-Hyun
Published: December 2018

This paper deals with the improvement of starting characteristic for Moving Magnet type Linear Oscillatory Actuator (MM-LOA) using a spring damper. MM-LOA is applied to variable loads such as vacuum pumps and compressors. However, it has the characteristic of over-displacement in starting state because of the low inertia of mover. To improve the starting characteristic, a spring damper has been adopted in a mechanical system. The design parameters have been computed by 2-D Finite Element Analysis (2-D FEA). In addition, dynamic characteristic analysis has been performed by time differential method. The propriety of improved starting characteristic is verified by a comparison of analyzed results with those of experiments.
Image and conductivity reconstruction of a variable conducting cylinder in a half-space
Authors: Chien Wei , Chiu Chien-Ching , Li Ching-Lieh
Published: December 2018

In this paper we address an inverse scattering problem whose aim is to determine the geometrical and the physical properties of a variable conducting cylindrical body buried in a half-space. The variable conductivity boundary leads to a mathematically ill-posed nonlinear equation. To overcome this difficulty, the attained system of nonlinear integral equations is reformulated into an optimization problem and solved by using the genetic algorithm. The genetic algorithm is employed to search the global extreme of the object function, such that the shape and the variable conductivity of the scatterer can be reconstructed. Even when the initial guess is far away from the exact one, the genetic algorithm can avoid the local extreme and attain to a global extreme solution sucessfully. In such a case, the gradient-based methods often get stuck in a local extreme. It is found that multiple incident waves from different directions permit good reconstruction of the shape and, to a lesser extent, the conductivity in the presence of noise for the measured data. Numerical results are given to show the effectiveness of the genetic algorithm.
Estimation approach for structural health monitoring using piezoelectric impedance based measuring method
Authors: Morisaki Tetsuya , Jiang Zhongwei
Published: December 2018

A truss structure consisting of aluminium beams and L-shape joints was used for investigation of the evaluation of the joint connection. Since the fastening state of bolts affects the mechanical impedance in the joint, near which a pair of PZT patches was utilised and embedded on the structure. Therefore, a high accuracy result on the mechanical impedance variation can be obtained by measurement of the electric impedance change in PZT patches. In the experiment, the joint fastening condition is given by tightening and loosening a bolt with a torque wrench. In order to improve the estimation accuracy whether the joint is in safe or not, two new evaluation indices ε, area difference, and Δ S, template shift distance, are proposed by impedance spectrum curve matching method. The experimental results show that damage overlooking can be improved by the indices ε and Δ S with aid of the impedance peak amplitude ratio δ and the peak frequency shift Δ F, which were proposed in our previous work.
Determination of the magnetic and nuclear structure of Ni_{2.17}Mn_{0.83}Ga
Authors: Fröhlich K. , Dennis B. , Kanomata T. , Matsumoto M. , Neumann K.-U. , Ziebeck K.R.A.
Published: December 2018

The structure of Ni _{2.17} Mn _{0.83} Ga has been investigated as a function of temperature using neutron powder diffraction. Above T = 310 K the compound has the cubic L2 _{1} structure, with lattice parameter a = 5.79 Å, and with the excess nickel atoms occupying the vacant manganese sites. Magnetisation and resistivity measurements indicate a Curie temperature of T = 340 K with a further transition at T = 301 K associated with a structural phase transition. The martensitic phase was found to have a tetragonal structure with cell parameters a = b = 3.87 Å and c = 6.47 Å and space group I4/mmm. Although there is negligible change in atomic volume the lattice parameters a and b change by ∼ 5.5% and the c-axis by almost 12%. The large change in cell parameters and the relatively high transition temperature make the compound a promising candidate for applications.
Application of a DC-bias to reduce acceleration sensitivity in quartz resonators
Authors: Yong Yook-Kong , Patel Mihir S.
Published: December 2018

A quartz resonator subjected to acceleration will deform due to inertial effects. The deformation stresses and strains in the plate will in turn cause a shift in the resonator frequencies. A method is proposed to actively minimize the inertial stresses and strains by a DC-bias electric field. Finite element models are created to calculate the effects of acceleration on resonant frequency and to compare the results with experimental data. The non-linearity and non-homogeneity induced by the inertial forces are modeled by using the concept of a superposed state. The model results for the acceleration effects are shown to compare well with the experimental results. The models are then used to calculate the effects of a DC electric field bias and to demonstrate the reduction of acceleration sensitivity.
On the correction of the higher-order Mindlin plate theory
Authors: Wang Ji , Yu Jiun-Der , Yong Yook-Kong
Published: December 2018

The Mindlin plate theory was developed to provide accurate solutions of vibrations in the vicinity of the fundamental thickness-shear mode, which has a very high frequency compared to flexural vibrations. The most important application of the theory is the high frequency vibrations of crystal plates although it has been applied to many problems beyond the original purpose. Recent studies found that, to improve the frequency solutions for plates with larger aspect ratios, the third-order plate based on Mindlin's power series expansion has to be used. It was shown through comparisons with three-dimensional elasticity solutions that the fundamental thickness-shear frequency is almost exact. The third-order theory was applied to frequency, mode shape, and other related analyses. In this study, we reconfirm that the third-order plate theory is very accurate because it has an almost exact cut-off frequency for the fundamental thickness-shear mode. By adopting a procedure developed by Mindlin, we find the inaccuracies in cut-off frequencies of the fundamental thickness modes and their overtones can be improved through the introduction of new correction factors. Corrections can be made with either the natural or symmetric procedure. Correction factors for natural and symmetric procedures based on stresses will be given.
A continuum modelling for the reversible behavior of electrorheological media
Authors: Drouot R. , Racineux G.
Published: December 2018

A continuum electromechanical description of electrorheological materials in their solid phase is proposed. This solid phase of the suspension is obtained when an adequate electric field is applied. The main effect concerns the presence of a prestressed state and we are interested in the reversible behavior of the media under mechanical and electrical loadings in the frame of small pertubation theory. A linearization formalism is developed and the role of the prestressed state is assessed. The point of view presented here is a special case of "Elastic Dielectrics" introduced by Eringen and Maugin; it is different from the study of Klingenberg who considers the solid phase without electric field and unstressed in its initial configuration, the main effect described being electrostriction.
Cracking in ferroelectric ceramic actuators caused by domain switching
Authors: Jeong K.M. , Beom H.G.
Published: December 2018

Cracking near the edge of an internal electrode embedded in ferroelectric ceramic actuators is analyzed. The boundary of the domain switching zone near the edge of the internal electrode in a ceramic multilayer actuator is determined based on the nonlinear electric theory. Under small-scale conditions, the stress intensity factor induced by ferroelectric domain switching is numerically obtained for dissimilar crack surface boundary conditions: the insulating crack and the conducting crack. It is found that the stress intensity factor for a crack emanating from an internal electrode depends strongly on the ratio of the coercive electric field to the yield electric field.
Preliminary mechanical "training" andσ_{θ}-ε_{θ} curves of thin coils with rectangular conductors exhibiting linear work hardening
Authors: Deviatkin E.A.
Published: December 2018

Bending stress in conductors of small solenoids often exceeds thermal and Lorentz stresses. This stress is primarily responsible for heat generation due to plastic deformation during magnet energizing and strain degradation of the critical current in strain-sensitive superconductors. Stresses arising in components of a thin solenoid coil after its fabrication and subsequent mechanical "training" by means of an internal pressure are studied in the paper. It is assumed that theσ-ε diagram of a composite superconductor can be approximated by a diagram with linear work hardening whereas an interlayer insulation and impregnation are linear elastic. The case where one plastic zone develops in the conductor during its bending and a new zone does not appear after the removal of the bobbin is considered. It is shown that the mechanical training allows to decrease the bending stress, stretch the constituents and increase the limit for elastic deformation of the coil. To predict the results of the training, theσ _{θ} -ε _{θ} curve of the coil is derived. A training level which provides elastic deformation of a Cu/NbTi conductor during the first energizing is estimated.
Analysis of a piezoelectric ceramic shell in thickness-shear vibration as a power harvester
Authors: Jiang S.N. , Jiang Q. , Hu Y.T. , Li X.F. , Guo S.H. , Yang J.S.
Published: December 2018

We study mechanical-to-electrical power conversion in a piezoelectric ceramic shell mechanically forced into thickness-shear vibrations. A theoretical analysis is performed. The efficiency of energy conversion, the power density of the device and their dependence on various physical and geometric parameters are examined. The structure may be used as an electric power source for wireless devices.
Multi-modal damping by shunted piezo-patches: Possible aeroelastic applications
Authors: Agneni Alessandro , Del Sorbo Matteo , Mastroddi Franco , Polli Gian Mario
Published: December 2018

Piezoelectric devices shunted on resistive-inductive loads typically operates on a single mode of a structure as their mechanical counterparts: the vibration absorbers. Similarly, multiple piezo patches, operating on different vibrating modes, may be used to perform a multi-modal damping. This result may be achieved either connecting different piezo patches to different electrical circuits, either connecting to a single multiple mode network one single set of piezo-electric elements. Several ladder networks were proposed in the past in order to damp more modes simultaneously. In this paper a Cauer network has been adopted together with notch filters having the duty to filter out one mode at a time. The possibility to use this type of circuit has been investigated studying the elastic and aeroelastic vibrations of a small glider wing by means the aeroelastic analysis performed by a commercial code based on a modal approach.
Stress relaxation during superelastic behavior of TiNi shape memory alloy
Authors: Pieczyska E.A. , Gadaj S.P. , Nowacki W.K. , Tobushi H.
Published: December 2018

Martensitic and reverse transformations in TiNi shape memory alloy subjected to tension test at room temperature are investigated using a thermovision camera. Stress relaxation stages during the loading and unloading branches are induced, respectively. A very large stress drop, caused by the phase transformation, is observed during the stress relaxation in both the course of loading and unloading, while, for the temperature-controlled test, in the unloading branch the stress increases under constant strain; due to the recovery. The non-uniform temperature distribution reflecting the inhomogeneous phase transformation at its initial stage is observed to start again at the end of the relaxation break and develop during the reloading process.
Energy evaluation for twinning plane movement under magnetic field in ferromagnetic shape memory alloys
Authors: Kakeshita Tomoyuki , Fukuda Takashi
Published: December 2018

We have made an energy evaluation for the rearrangement of martensite variants (RMV) under a magnetic field using four types of ferromagnetic shape memory alloys: an Fe-31.2at. %Pd with so-called fct martensite, a Ni _2 MnGa with the 10 M martensite, a Ni _{2.02} Mn _{1.09} Ga _{0.89} with the 14 M one and a Ni _{2.14} Mn _{0.92} Ga _{0.94} with the 2 M one. The RMV by a magnetic field occurs at any temperature for the Fe-31.2Pd and the 10 M martensite. However, it occurs in a limited temperature range for the 14 M martensite and does not occur at any temperature for the 2 M martensite. The reason of such different behavior is quantitatively explained by evaluating two shear stresses: the magnetic shear stress acting across a twinning plane τ _{mag} , and the stress required for the twinning plane movement τ _{req} . That is, by comparing the value of τ _{mag} and τ _{ req} thus evaluated, we have confirmed that the following condition is universal regardless of temperature, field direction and structure of the martensite phase: the value of τ _{mag} is larger thanτ _{req} when the RMV occurs by magnetic field and vice versa.
Fabrication of Ti-Ni alloys for proportional control
Authors: Nam Tae-hyun , Yu Cheo-am , Lee Yun Jung , Liu Yinong
Published: December 2018

Phase transformation and deformation behavior of temperature-gradient annealed (TGA) equiatomic Ti-Ni alloy wires were investigated by means of differential scanning calorimetry (DSC), thermal cycling under constant load and tensile testing. TGA treatment in a temperature range of 658∼823 K caused variations of 10 K in T_{R} * and 14 K in M_{s} along the length of the specimen. Temperature dependence of specimen elongation (dε/dT) of TGA treated Ti-Ni alloy wires was in the range of 0.12∼0.43%/K depending on annealing temperatures. The lowest dε/dT was obtained in the sample annealed in the temperature range of 658∼713 K. The stress for martensite reorientation remained nearly constant for the specimen annealed in the temperature range of 740∼823 K, whereas that for the specimen annealed in the temperature range of 658∼740 K increased continuously with increasing strain.
Effect of grain size on amount of deformation-inducedε martensite and shape memory effect in Fe-Mn Alloy
Authors: Jee K.K. , Han J.H. , Kim Y.B. , Jang W.Y.
Published: December 2018

In this work, a new method of measuring volume fraction ofε martensite formed both by cooling and deformation using volume change and endothermic heat on ε→γ transformation, respectively. The variation in the amount ofε with grain size is determined for an Fe-21Mn alloy, and its influence on shape memory effect is investigated. As grain size increases, the amount of ε martensite forming on cooling increases. However, with a decrease in grain size, moreε is induced by deformation, improving shape memory effect.
Time-dependent magnetostrain and thermal phonons in the Ni-Mn-Ga magnetic shape-memory alloys
Authors: L'vov V.A. , Glavatska N. , Glavatskiy I. , Ge Y. , Heczko O. , Söderberg O. , Hannula S.-P.
Published: December 2018

The isothermal time-dependent deformation of the ferromagnetic Ni-Mn-Ga martensite in the steady magnetic field has been studied both experimentally and theoretically. The role of long wavelength thermal phonons in the deformation process has been disclosed by means of evaluation of the fluctuating mechanical stress, which these phonons induce inside the experimentally observed elements of martensitic structure. A simple relationship between the magnitude of effective fluctuating stress, temperature-dependent elastic modulus and twin width has been derived. In this way, a strong interdependence between the twin width and the effect of thermal phonons on the twin structure is predicted. The fluctuation mechanism of reversibility of the magnetically induced deformation has been deduced from the experimental and theoretical results.
The modeling of the deformation behavior of Cu-Al-Nb shape memory alloys containing primary particles
Authors: Lelatko Józef , Morawiec Henryk
Published: December 2018

Models elaborated for the metal-matrix composite materials were modified in order to enable the control of the deformation properties of the Cu-Al-Nb type shape memory alloys containing significant number of primary particles.

The modified model of the continuum mechanics approach based on the effective medium approximations and supplemented by the dislocation plasticity model enabled analysis of the deformation course of the Cu-Al-Nb alloys. By comparing the simulated and experimental stress – strain curves for these alloys, the effect of particle size, volume fraction and their elastic properties on the deformation response is given. This model allows showing that hardening of the alloy during deformation results from the presence of hard and elastic particles in the martensite matrix as well as dislocations formed at the partial accommodation of the residual stresses created during the alloy quenching.
One- and two-step phase transformation in Ti-rich NiTi shape memory alloy
Authors: Paula A.S. , Mahesh K.K. , dos Santos C.M.L. , Canejo J.P.H.G. , Fernandes F.M. Braz
Published: December 2018

In the present study, the phase transformations in the Ti-rich (51.0 at% Ti–Ni) NiTi Shape Memory Alloy (SMA) was analyzed using four characterization techniques: Differential Scanning Calorimetry (DSC), Electrical Resistivity (ER), Dilatometry and X-Ray Diffraction (XRD). During the phase transformations various physical parameters of the material are modified and each technique senses different physical phenomena. In order to distinguish the different types of sequences (one-step versus two-step) the observations are discussed highlighting the capability of each technique to analyze the phase transformations in NiTi SMAs.
Sputtered Ni-Mn-Ga thin films
Authors: Dubowik J. , Kudryavtsev Y.V. , Gościańska I.
Published: December 2018

We report results of ferromagnetic resonance measurements on sputtered Ni _{x} Mn _{y} Ga _{z} films of various compositions annealed from 620–973 K. Anomalous magnetic behavior of the Ni-Mn-Ga films annealed at T<800 K results from their columnar microstructure and changes in the magnetic anisotropy due to the martensitic transformation. The films annealed at the highest temperatures have the magnetic behavior typical of normal ferromagnetic films, in which the effect of the martensitic transformation is strongly reduced due to constraint of a substrate.
Characterization and study of a single TiO_{2}-coated optical fiber reactor
Authors: Danion Anne , Disdier Jean , Guillard Chantal , Abdelmalek Fethi , Jaffrezic-Renault Nicole
Published: December 2018

A TiO _{2} -coated optical fiber photoreactor was built and studied in order to optimize different parameters before the development of a multi-optical fiber reactor. The physico-chemical properties of the TiO _{2} film prepared by a sol-gel method on an optical fiber were first determined. A thickness of about 30 nm per layer and a roughness of 2 nm were estimated by ESEM and AFM, respectively. The refractive index of the TiO _{2} coating was determined by a simulation method. Then, the influences of the film thickness, coating length and coating volume on the light transmission within the fiber were investigated. The intensity of transmitted light was found to decrease exponentially as the volume of TiO _{2} increased. Afterward, the dependence of the photocatalytic degradation of hydroxybutanedioic acid on the incident light intensity, the TiO _{2} coating thickness and the coating volume was studied and modelized. The photocatalytic degradation was found to be stabilized above a TiO _{2} volume of 200 μ m ^{3} for a fiber of 1 mm and 100 μ m ^{3} for a fiber of 0.6 mm. Finally, a multi-fiber reactor was built and its degradation rate of hydroxybutanedioic acid was compared to that obtained in a single optical fiber reactor.
Magnetostrictive Terfenol-D material linear simulation using finite element method
Authors: Jarng Soon Suck
Published: December 2018

This paper describes the application of the coupled FE-BEM (finite element-boundary element method) for the numerical harmonic analysis of the linear dynamic behavior of a magnetostrictive Terfenol-D rod in water. The magnetostrictive rod is three-dimensionally modeled to transduce applied electric current in a helical coil around the rod to mechanical displacement. The steady-state resonance response of the displacement is shown.
Fast-response and high-precision positioning using iterative learning control
Authors: Kawafuku Motohiro , Igarashi Hitoshi , Iwasaki Makoto , Hirai Hiromu
Published: December 2018

The present paper proposes a novel fast and precise positioning strategy using an iterative learning control. The authors have previously proposed an effective positioning algorithm by applying the command shaping technique using an FFT-based inverse model of a closed loop system. On the other hand, the modeling error and/or variation of the plant system causes deterioration of the positioning performance due to the lack of robustness of the controller with respect to these errors. In the present research, in order to ensure the above-mentioned robustness, an iterative learning control technique in the frequency domain is introduced, in which the position command is successively shaped to satisfy the positioning specifications. The effectiveness of the proposed control strategy has been verified experimentally using prototype machine tools.
Sensorless control for linear compressors
Authors: Sung Ji Won , Lee Chel Woong , Kim Gyu-Sik , Lipo T.A. , Won Chung-Yuen , Choi Sewan
Published: December 2018

A closed-loop sensorless stroke control system for a linear compressor has been designed. The motor parameters are identified as a function of the piston position and the motor current. They are stored in ROM table and used later for the accurate estimation of piston position. Also it was attempted to approximate the identified motor parameters to the 2nd-order surface functions. Some experimental results are given in order to show the feasibility of the proposed control schemes for linear compressors.
Auditory illusions in the brain after visual/auditory training
Authors: Koh Yuri , An Kwang-Ok , Lee Chany , Jung Hyun-Kyo
Published: December 2018

Previous studies demonstrated that visual stimuli activate auditory cortex in deaf subjects [1,2]. In this paper, we used electroencephalography(EEG) in hearing subjects to evaluate whether auditory cortex comes to serve the visual modality after visual/auditory training. In the perceptual feedback training, the hearing subjects were trained to relate certain visual sources to particular sound sources. In the results, we found that visual activity was observed in the auditory cortex when only the visual stimuli were given to the subjects and feedback training improved the subjects' ability to associate visual actions with particular sound sources.
An improved vector evolutionary algorithm for multiobjective designs of electromagnetic devices
Authors: Nie Man , Yang Shiyou , Ni Guangzheng , Ho S.L. , Ni Peihong
Published: December 2018

Thanks to the success in the design of a simple sharing function, the introduction of a novel fitness assignment strategy, and the development of a new local search procedure, this paper proposes an improved evolutionary algorithm for optimal problems involving several, often conflicting objectives. The simulation results on solving a mathematical function and a prototype problem reveal that the proposed method is effective in sampling the entire Pareto-optimal front and in distributing the generated solutions over the trade-off surface.
A fast global optimal method based on combinations of MLS and PSO algorithm
Authors: Luo Ping , Yang Shiyou , Yao Lihai , Ni Peihong , Ho S.L. , Ni Guangzheng
Published: December 2018

To reduce the computation time needed in solving a practical optimization problem of electromagnetic devices, a fast and efficient global optimization method based on the combination of the Moving Least Squares (MLS) approximation and the Particle Swarm Optimization (PSO) method is proposed. Numerical examples are given to demonstrate the efficiency and robustness of the proposed method.