International Journal of Applied Electromagnetics and Mechanics - Volume 22, issue 3-4

Authors: Zhou, Zhi_Dong | Nishioka, Toshihisa

Article Type: Research Article

Abstract: In this paper a steady semi-infinite mode III crack growth along the midplane of a piezoelectric layer sandwiched between two identical half spaces is considered. The Fourier integral transform is used to reduce the mixed boundary value problem to the Wiener-Hopf equation by introducing an auxiliary function. The complete stress and displacement distributions along the crack line can be obtained and further the dynamic stress and electric displacement intensity factors and the energy release rate are …presented in explicit form. The results show that the crack propagation speed and coupled material constants influence on the dynamic stress and electric displacement intensity factors, moreover the dynamic energy release rate is dependent on the crack propagation speed and material 2 for this geometry. Show more

Keywords: Crack growth, dynamic field intensity factors, piezoelectric materials, sandwich composite, Wiener-Hopf equation

DOI: 10.3233/JAE-2005-696

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 22, no. 3-4, pp. 121-132, 2005

Authors: Waszak, Michal-Wolfgang

Article Type: Research Article

Abstract: This paper presents an efficient method for eddy current analysis in permanent magnets (PM) used in electric machines. Due to appreciable electric conductivity of sintered PM the energy losses related to induced eddy currents cannot be neglected. Since the resulting increase of temperature may weaken the magnetomotive force or even demagnetize the PM material. Two numerical approaches for eddy current calculations in massive materials are commonly applied: 2d model (assuming infinite axial length) and 3d model …(usually suffering from numerical inefficiency). In this paper we discuss numerically efficient method for eddy current computation taking actual axial length into account. We propose to extend the 2d field-circuit-motion time-stepping model to 3d model of induced electric field in the area of massive conducting elements, for instance, the PM of electric motor. Design study of a brushless dc motor is presented. During numerical experiments two contributions to the PM losses are characterized: idle run losses due to stator slotting, and armature reaction losses due to high frequency current switching. The influence of the PM segmentation on the eddy current losses is studied. Show more

DOI: 10.3233/JAE-2005-697

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 22, no. 3-4, pp. 133-139, 2005

Authors: Tian, W.-Y. | Rajapakse, R.K.N.D.

Article Type: Research Article

Abstract: A theoretical study of a magnetoelectroelastic composite plane with a single conducting crack is presented. Crack is assumed to be arbitrarily oriented with respect to the poling direction of the medium. General solutions for fully coupled magnetoelectroelasticity expressed in term of complex potential functions are used to formulate the problem. The formulation of a conducting crack is reduced to a classical Riemann-Hilbert problem and explicit analytical solutions are derived for the field intensity factors, total and …mechanical energy release rates and crack tip hoop stress. The formulation is then extended to obtain common fracture parameters of an arbitrarily oriented permeable crack. Selected numerical results are presented for a conducting and a permeable crack in magnetoelectroelastic composite BaTiO_{3} -CoFe_{2} O_{4} . It is found that crack orientation, volume fraction of piezoelectric phase and magnitude of electro-magnetic and mechanical loading have a significant influence on fracture parameters. Show more

Keywords: Conducting cracks, energy release rates, fracture mechanics, magnetoelectroelastic materials, permeable cracks, piezoelectricity

DOI: 10.3233/JAE-2005-698

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 22, no. 3-4, pp. 141-158, 2005

Authors: Hamid, A.-K. | Bettayeb, M.

Article Type: Research Article

Abstract: Analytic solution to the problem of scattering of a TE polarized plane electromagnetic wave by a lossy dielectric loaded semi-elliptic channel is investigated. The incident, scattered and transmitted fields in every region are expressed in terms of complex Mathieu functions. Applying the boundary conditions at metal surface and dielectric interface along with the partial orthogonality properties of angular Mathieu functions, the unknown scattered and transmitted field coefficients are obtained and written in matrix form. The …presented numerical results show that the semi-circular channel has strong resonances compared with the semi-elliptic channel and the presence of a lossy dielectric material reduces the magnitude of the backscattered field. Show more

DOI: 10.3233/JAE-2005-699

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 22, no. 3-4, pp. 159-167, 2005

Authors: Weyand, Kurt | Ketzler, Rainer | Kitschke, Manfred

Article Type: Research Article

Abstract: In order to calibrate field coil standards a new setup has been developed by which the field profile of field coils is recorded. From the profile the centre field strength can be related to the SI units of electrical current and length. The main components of the apparatus are a modified, commercially available fluxgate magnetometer, an optical length measuring device, and a motor driven positioning system which moves the fluxgate sensor along the axis of the …coil under test. Depending on size and type of the coil a relative uncertainty of some parts in 10^{-5} is achievable. Recording the flux profile provides additional information about the device under test, even if its centre field value has been determined by means of Nuclear Magnetic Resonance using protons in pure water, which must be regarded at present as the most accurate method for magnetic field calibration. Show more

Keywords: Field profile measurement, magnetic field standards, fluxgate magnetometer

DOI: 10.3233/JAE-2005-700

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 22, no. 3-4, pp. 169-175, 2005

Authors: Drouot, R. | Racineux, G.

Article Type: Research Article

Abstract: 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. Show more

Keywords: Electrorheology, prestress, continuous media

DOI: 10.3233/JAE-2005-701

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 22, no. 3-4, pp. 177-187, 2005

Authors: Herdem, S.

Article Type: Research Article

Abstract: The average value of the magnetic susceptibility of the particles occurring in the real technological liquids and captured by magnetic filters and separators is not known at the beginning of the filtration process. Since the magnetic susceptibility of the captured particles varies with the magnetic field intensity, the relation between the magnetic field intensity and the magnetic filter performance in the magnetic filtration equation cannot be assumed exactly correct. This problem can be overcome by using …the average value of the magnetic field in the pores and determining the average susceptibility of the particles in this field. Approximate results can be obtained for the properties of the filtration process by considering the magnetic properties of the filter elements and the properties of the magnetic field occurring in the pores of the filter matrix. The obtained results make possible to determine the technological properties of the magnetic filtration and separation systems, and hence to optimize and control easily of the filtration processes. Show more

Keywords: Magnetic filters, filter performance, magnetic susceptibility

DOI: 10.3233/JAE-2005-702

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 22, no. 3-4, pp. 189-197, 2005

Authors: Xu, Lizhong | Hao, Xiuhong

Article Type: Research Article

Abstract: In this paper, the operating principle and basic structure of the drive are introduced. An electromechanical coupled dynamic model of the drive is presented by means of electromagnetic theory and mechanical principle. The electromechanical coupled dynamic equations of the drive system are given. The concept of the electromagnetic mesh stiffness is presented and their calculating equations are obtained. Then, the natural frequencies and mode shapes of the electromechanical coupled dynamic system are analyzed. Finally, …Changes of the natural frequencies of the electromechanical system along with the mechanical and electric parameters of the drive are analyzed, respectively. Show more

Keywords: Toroidal drive, electromechanical integrating, dynamic model, generalized composite drive

DOI: 10.3233/JAE-2005-703

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 22, no. 3-4, pp. 199-211, 2005

Authors: Jeong, K.M. | Beom, H.G.

Article Type: Research Article

Abstract: 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. Show more

Keywords: Cracking, ferroelectric ceramics, domain switching, electrical nonlinearity

DOI: 10.3233/JAE-2005-704

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 22, no. 3-4, pp. 213-220, 2005

Authors: Deviatkin, E.A.

Article Type: Research Article

Abstract: 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 the σ-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, the σ_{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. Show more

DOI: 10.3233/JAE-2005-705

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 22, no. 3-4, pp. 221-232, 2005

Authors: Krawczyk-Stando, Dorota | Rudnicki, Marek

Article Type: Research Article

Abstract: Ill-posed problems occur frequently in science and engineering. Regularisation methods are used for computing stable solutions to the ill-posed problems. The purpose of regularisation is to incorporate more information about the desired solution in order to stabilise the problem and find a useful and stable solution. The most common and well-known form of regularisation is that of Tikhonov in which the regularised solution is searched as a minimizer of the weighted combination of the residual norm …and a side constraint. The weight given to the minimisation of the side constraint is controlled by the regularisation parameter. Thus, the regularisation parameter is an important factor that controls the quality of the regularised solution. A good regularisation parameter should fairly balance the perturbation error and the regularisation error in the regularised solution. There are several methods for choosing regularisation parameter. In the paper we demonstrate another method: the L-curve criterion for choosing the regularisation parameter. The L-curve is a plot of the seminorm of the regularised solution versus the corresponding residual norm thus expressing the compromise between minimisation of these two terms. The L-curve method efficiency is demonstrated on examples of synthesis of magnetic field of different kind. Show more

DOI: 10.3233/JAE-2005-706

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 22, no. 3-4, pp. 233-242, 2005