Materials Science Forum Vol. 856

Abstract: At the present time the polymers are reliable and effective alternative to more traditional materials for many applications especially for bioengineering. Achievement of high quality biopolymeric components demands particular conditions for the machining process and its control. This report is devoted to method for operation control of the high speed cutting process by measurement of vibrating acceleration.

Abstract: The paper deals with modelling of the time varying electric field, applied to composites structures of inorganic materials (containing metal and metal oxide). The structural changes at the initials stages of sintering, characterised by the number of contact per particle and an increase of the areas of interparticle contact have been modelled and examined. The aim of study was estimation of the electric field strength, current density, power losses and forces, acting along the contact area between particles. The field models have been obtained using finite element method and QuickField 5.6 software package.

Abstract: A reconfigurable THz complex medium, consisting of fundamental piezoelectric micro-devices, is introduced in this paper. By actuating the piezoelectric modules, a controllable metamaterial, presenting enhanced bandwidth tunability, is accomplished. Two diverse polarization topologies are examined, revealing the anisotropic performance of this material. The advantages of the proposed component are sufficiently clarified through several numerical data, derived by a robust finite element method (FEM).

Abstract: This paper presents our proposed frequency sweeping excitation and spectrogram method (FSES method) by a magnetic sensor for non-destructive testing of hardened low carbon steels. This method can evaluate the magnetic properties of low carbon steels which were changed after induction heating treatment. It was examined by our proposed method that the degrees of yield strength of low carbon steels were varied depending on hardened conditions.

Abstract: In the present research work the determination of residual stress distribution in welded non-oriented electrical steel samples is discussed. Tungsten Inert Gas and Electron Beam Welding were used as the welding methods. The residual stresses induced by welding estimated by the magnetic, non-destructive method of Barkhausen noise and were compared with the values resulting from the semi-destructive method of X-ray diffraction Bragg-Brentano (XRD-BB). In order to evaluate accuracy and reliability of the magnetic methods applied, the steel samples were subjected in both compressive and tensile stress and the magnetic noise values were correlated to residual stress values through an appropriate calibration curve. Furthermore, the fluctuations of the residual stresses in the welding zones of the welded samples were discussed on the basis of the experimental evidence and the microstructural changes occurring during welding. It was found that the residual stress determined by MBN method was in good agreement with the XRD-BB results. However, the residual stress determined by magnetic permeability method was not in good agreement with the XRD-BB results. In contrast to the XRD-BB method, the magnetic techniques required a precise calibration procedure in all zones with noticeably different microstructure.

Abstract: The effect of Cu substitution for Cd an Te atoms in CdTe crystal were examined by using ab initio calculations. Depending of location of Cu atom in the super cell, band gap changes and metallic behaviour of CdTe has been obtained.

Abstract: The presented paper deals with determination of the excited magnetic field magnitudes at different points around the device guarantying maximal output signal. Investigated object is electromagnetic flow meter. The output signal is polarization voltage through the circle cross section of the polarization transducer between its electrodes. Except the magnetic field distribution some geometrical parameters of the device and physical characteristic of the inside moving dielectric are varied. The forward field problem is solved by the use of the Comsol, version 5.0 software package. The inverse problem is solved using skills of the Response Surface Methodology (RSM), Design of Experiments (DOE) and Nonlinear Programming. The numerical approach for finding optimal magnetic field distribution is discrete at chosen points. Applying spline interpolation after that the analytical description of the optimal field distribution is defined.

Abstract: New Hybrid (HB) type Active Magnetic Bearing (AMB) is proposed in this paper. It is intended to apply to high speed turbo machinery. This magnetic bearing is easily controlled by a standard linear power amplifier. The proposed magnetic bearing is analyzed and designed through Finite Element Method (FEM). The designed characteristics are compared with the standard electro-magnet type magnetic bearing. The results show good characteristics of high efficiency, good dynamic property and easy manufacturing. The proposed magnetic bearing is fabricated and the simple tests are carried out.

Abstract: The rotor geometry of a permanent magnet (PM) machine greatly affects the machine performance and therefore, it is very important to develop an initial conceptual structural topology of a PM rotor. We proposed an optimization method which is the combination of a topology optimization method and a method taking into account ease of manufacturing. This paper has manufactured an optimized rotor of a PM synchronous machine. Experimental results show that when operating as a generator, the designed machine has 46 % higher output voltage than that of a commercialized one. The efficiency of the designed machine is improved by about 2 % comparing with the commercialized machine. Therefore, it is experimentally confirmed that the optimized PM machine has a better performance than the commercialized one.

Abstract: In this work, a split transformer topology is proposed for use in a wireless electric vehicle charger. The topology presents desirable characteristics concerning minimization of the air gap, easiness of alignment, weight and cost. Comparison is performed with spiral topologies presented in relevant literature. The coupling coefficient of the system for various air gaps and misalignment conditions is extracted by 3D finite element simulations and experimentally validated by a 3 kW prototype inductive power transfer system. The magnetic field at nominal power of operation is also simulated for evaluation of the compliance to the human exposure limits.