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A balanced armature receiver (BAR) as a special type of electromagnetic acoustic transducers plays a significant role in reproduction of music and speech, active noise control in modern hearing aid and in contemporary in-ear monitors. This paper aims to present a static analysis of the balanced armature receiver based on the lumped network approach (LNA) and the finite element method (FEM).

In this paper, the LNA and two-dimensional FEM are applied to model deflections of the BAR’s armature from the equilibrium position. Results of calculations are compared with measurements.

The derived analytical formulas and developed procedure allow for calculation of the armature deflection.

Comparing to the previous papers, the reluctance’s nonlinearity of the armature has been considered.

Lorentz force evaluation is a non-destructive evaluation method for conducting specimens. The movement of a specimen relative to a permanent magnet leads to Lorentz forces that are perturbed in the presence of a defect. This defect response signal (DRS) is used for defect reconstruction. To solve a linear inverse problem for defect reconstruction, an accurate and fast forward computation method is required. As existing forward methods are either too slow or too inaccurate, the purpose of this paper is to propose the single voxel approach (SVA) as a novel method.

In SVA, the DRS is computed as a superposition of DRSs from single defect voxels, which are calculated in advance, by applying the boundary element source method. This research uses a setup of an isotropic conducting specimen, a spherical permanent magnet and defects of different shapes at different depths. With the help of simulations, this study compares the SVA to the previously proposed approximate forward solution (AFS) and the extended area approach (EAA) using the normalized root mean square error (NRMSE). Simulated data using the finite element method serve as the reference solution.

SVA shows across all simulations NRMSE values <2.5 per cent compared to <8 per cent for EAA and <12 per cent for AFS.

The superposition principle of SVA allows for the application of linear inverse methods for defect reconstruction while providing sufficient accuracy of the forward method.

The impedance boundary condition is widely used in order to reduce a multiple region electromagnetic field problem to a magnetic field problem analyzed in a nonconducting region only. It is obvious that the solution to the latter problem is much easier to obtain than those for conducting regions. There are several versions of the impedance boundary condition formulation which depend mainly on the choice of a field state variable and the solution technique applied.

The paper presents the features of an interactive “cube lens” approach to overcome some problems of visualization of 3D scalar or vector magnetic field. The “cube lens” is defined as a cubic part of the space where the 3D field is calculated using any method. The field data are given over a regular cubic grid. Several methods of scalar and vector fields visualization are presented.

This paper describes numerical tests for a three dimensional infinite element suitable for finite element modelling of open boundary field problems. The infinite element has four nodes and is compatible with conventional cuboids. The effectiveness of the infinite element in the interior — finite element region is shown by comparing the accuracy and the CPU time when various boundary conditions are applied. The possibility of computing the external fields is also illustrated.

The purpose of this paper is to present a novel electromagnetic non-destructive evaluation technique, so called Lorentz force eddy current testing (LET). This method can be applied for the detection and reconstruction of defects lying deep inside a non-magnetic conducting material.

In this paper the technique is described in general as well as its experimental realization. Besides that, numerical simulations are performed and compared to experimental data. Using the output data of measurements and simulations, an inverse calculation is performed in order to reconstruct the geometry of a defect by means of sophisticated optimization algorithms.

The results show that measurement data and numerical simulations are in a good agreement. The applied inverse calculation methods allow to reconstruct the dimensions of the defect in a suitable accuracy.

LET overcomes the frequency dependent skin-depth of traditional eddy current testing due to the use of permanent magnets and low to moderate magnetic Reynolds numbers (0.1-1). This facilitates the possibility to detect subsurface defects in conductive materials.

The interface between two conducting fluids in a magnetic fluid dynamics (MFD) problem was identified by means of external magnetic field measurements. Genetic algorithms (GA) were applied to solve the inverse problem.The principal component analysis (PCA) was used to speed up the process of interface reconstruction.

With respect to the experimental results we have designed a general technique for mode identification and/or interface reconstruction. Two main procedures are available to solve the inverse problem, the full interface reconstruction and the principle component analysis (PCA) mode. In the case of full reconstruction, it can be decided whether an algorithm for fast identification of the dominant modes applying a FFT module should be performed or not. The full interface reconstruction applies stochastic optimization methods ((GA) or evolution strategies (ES)) for the estimation of the interface shape characteristics. The main goal of the PCA mode is to find the dominant mode of the interface shape and its amplitude. The PCA mode is realized by means of stochastic optimization methods (GA, ES) and a simple direct searching (DS) using the golden section technique.

PCA with GA procedure enables the identification of the dominant mode of the interface shape between two conducting fluids with sufficient accuracy for simulated magnetic fields. Time of identification is strongly reduced due to a redefinition of the genotype representations in the PCA mode. Accuracy of reconstruction depends on the noise level, i.e. signal to noise ratio and a geometrical model used in the reconstruction phase. The correlation between the noise level and values of cost function for identified modes has been found if a proper geometry modelling is applied.

The paper describes a new, fast technique for solving an inverse field problem of a MFD problem where the interface between two conducting fluids has to be identified using a magnetic field tomography measuring system.

The purpose of this paper is to present a 3D model of deep welding of dissimilar metals and to show how to model the electron beam deflection due to thermoelectric fields caused by temperature gradients in some dissimilar metals (Seebeck effect).

A 3D thermoelectric and heat conduction model is used to estimate the deflection of the electron beam used during welding of dissimilar metals. A weak coupling between analysed fields is assembled. Additionally, the influence of the deflection on the calculated fields was not taken into account. The problem is solved using a finite element method.

It is possible to model Seebeck effect in a relative simple way using the finite element approach.

The paper presents a detailed description of modelling procedure of a complex coupled field problem.

To provide a new semi‐analytical procedure which is much faster than FEM and for this reason can be applied in a reconstruction of an interface between two conducting fluids (magnetic fluid dynamics problem) by means of magnetic field tomography.

Three approaches are compared: a simple analytical solution (AS1), a modified semi‐analytical solution (AS2), and the finite element method solution. The modified semi‐analytical approach takes into account an information about azimuthal spatial harmonics received from the Fourier analysis of magnetic flux density distributions calculated by FEM. AS1 and AS2 have been compared for different modes of the interface using FEM solution as a reference.

It is shown that for small perturbations the AS2 in every case provides smaller errors than AS1 although for some modes (14,24) the quality of the solution is still not satisfactory.

This paper describes a new technique for the analysis of electromagnetic field which can be also applied in other problems.

Investigations which have been carried out up to the present have shown that trajectories of the arc spot over the extinguishing plate drift always towards the plate axis. Results of calculations presented in this paper are different from the results which have been obtained till now. The calculations have been made with the use of computer programs based on the boundary element method. The results of the calculations show that for some areas of plates of specific shapes potential gradient of a field of forces acting against the arc spot may approach zero. When the arc reaches any point of such an area it is stopped and the arc spot trajectory does not end at the plate axis.