Materials Science Forum Vol. 721

Abstract: The purpose of this paper is to present the results of observation of material degradation process in steel samples under combined conditions of static and cyclic dynamic loading, using selected electromagnetic NDT methods. To evaluate damages a Barkhausen noise observation, an AC magnetization, a magnetic flux leakage and eddy current method were used.

Abstract: In this paper, we present a new magnetic property measurement system. We developed a miniature transducer, with a 16-mm2 footprint, for measuring the local magnetic properties of a motor stator core. The construction of the transducer and measurement system is proposed, and experimental results show the validity of the measurements.

Abstract: Modern industry makes extensive use of various composite materials In this paper terahertz imaging method is proposed for evaluation of various composite materials adhesive joints. The results of inspection (A-scans and C-scans) as well as 2-D distributions of proposed parameters are presented for method validation.

Abstract: The paper presents technologies for developing efficient high temperature permanent magnet machines implemented in aerospace drive applications. Selection criteria and experimental investigation of the permanent magnet material is undertaken and design considerations enabling to meet the specifications set are described. The proposed control algorithm for an appropriate PWM inverter is introduced.

Abstract: This paper proposes an improved dynamic E&S vector hysteresis model to increase modeling accuracy especially for non-elliptic B-waveforms, and its implementation to finite element method. The major improvements of the suggested model are on the determination of the geometric parameters of a non-elliptic B-waveform, and the calculation of the magnetic reluctivity and hysteresis coefficients. The proposed model is combined with FEM and applied to the iron loss analysis of a three-phase transformer.

Abstract: Abstract. Space diversity, where antennas are separated in space at the receiver, is considered one of the most effective ways of eliminating unwanted signals in order to maximize the signal to noise ratio of the desired signal. Moreover it may be used to receive a signal that has gone through less fading when the direct path signal may have undergone deep fade. In this paper we use analytical electromagnetic solutions for the radiated signals to implement antenna space diversity on small handheld receiver units of mobile stations. While using the standard time difference of arrival method to obtain a first approximation of the mobile station position, the electromagnetic model is used to determine a more accurate position of the mobile station. The performance of this method with a multi-element mobile station antenna is shown to give good position estimation in the presence of various of kinds noise. A three element mobile station receiver is for the first time reported to be able simultaneously to null a deeply faded signal in the Rayleigh fading environment, and maximize the signal strength. It is shown that a three element antenna may be used to eliminate an undesired signal, while it may maximize the reception of the desired signal. The transmitter does not require a training sequence, as in the case of an equalizer, since the entire signal processing of the electromagnetic signal is done at the mobile receiver.

Abstract: The paper presents a design optimization procedure appropriate for distribution transformers with amorphous alloy cores. Several considerations and the main differences from the design practice of conventional transformers are presented and discussed in detail. Moreover, comparison of results present the significant benefit in the transformer energy efficiency by the selection of amorphous alloy core, despite its initial higher installation cost.

Abstract: A novel reliability calculation algorithm is developed and applied to a robust optimization of electromagnetic device with uncertain design variables taken into account. The proposed algorithm, to calculate the reliability of a given design, incorporates sensitivity analysis based on finite element method with Monte Carlo simulation (MCS) method so that it has higher numerical efficiency than conventional methods: MCS and first-order reliability methods. Through numerical examples, its applicability to a reliability-based robust optimal design of electromagnetic device is demonstrated.

Abstract: Iron losses of grain-oriented electrical steels, is sensitive to the distortion of the supply voltage waveform of the excitation winding. As a result, magnetic cores of electrical machines and transformers manufactured of grain-oriented electrical steels present significant increase of iron losses when working under distorted supply voltage waveform. In the present paper, an experimental apparatus is developed in order to evaluate the effect of distorted supply voltage waveform on iron losses of grain-oriented electrical steels. Also, a theoretical analysis based on the hysteresis design tool of Matlab and the finite element method considering hysteresis is carried out.

Abstract: The apparent viscosity of magnetorheological (MR) fluids changes in the presence of a magnetic field. The stronger the magnetic field applied, the more the apparent viscosity increases. An increase in the apparent viscosity increases the restriction on the flow of MR fluids. In this study, we perform a qualitative analysis to investigate the effect of a magnetic field on MR fluids under an impact load. An experimental apparatus that consists of a drop-test tower was developed to simulate the impact load, and an MR fluid in a U-pipe was subjected to the impact load via a piston rod. In the experiment, we measured the displacement and velocity of the piston rod. On the basis of the results, the influence of a given magnetic field on the behavior of MR fluids under an impact load is discussed.