An Fe-0.2C-5Mn-2.5Al medium manganese steel is studied for three different intercritical annealing temperatures TIA to observe the effects of variations of retained austenite stability on the mechanical work hardening in uniaxial tension. Digital image correlation (DIC) showed that both Luders bands and type A Portevin-le-Châtelier (PLC) bands occurred in samples with a lower TIA, but both disappeared when TIA was increased. In-situ measurements of sample magnetization with a correction for stress effects on the magnetic properties of the sample allowed for continuous measurement of the retained austenite volume fraction. This method provided a complete characterization of the kinetics of transformation-induced plasticity (TRIP) in the sample over the course of tensile testing. It is shown that the martensite transformation was purely strain-induced and coincided with the passage of both Luders and PLC bands. An Olson-Cohen model was applied to magnetic data to attempt to explain the differences in TRIP kinetics with varying TIA.

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Coincidence of strain-induced TRIP and propagative PLC bands in Medium Mn steels

Recent improvements in magnetic material characteristics and switching devices have generated a possibility to replace the electrical buses with high-frequency magnetic links in microgrids. Multiwinding transformers (MWTs) as magnetic links can effectively reduce the number of conversion stages of renewable energy system by adjusting turn ratio of windings according to the source voltage level. Other advantages are galvanic isolation, bidirectional power flow capability, and simultaneous power transfer between multiple ports. Despite the benefits, design, and characterization of MWTs are relatively complex due to their structural complexity and cross-coupling effects. This paper presents all stages of numerical design, prototyping, and characterization of an MWT for microgrid application. To design the transformer for certain value of parameters, the reluctance network method is employed. Due to the iterative nature of transformer design, it presented less computation time and reasonable accuracy. A prototype of designed transformer is implemented using amorphous magnetic materials. A set of experimental tests are conducted to measure the magnetic characteristics of the core and series coupling and open-circuit tests are applied to measure the transformer parameters. A comparison between the simulation and experimental test results under different loads within the medium-frequency range validated both design and modeling procedures.

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Design and Implementation of an Amorphous High-Frequency Transformer Coupling Multiple Converters in a Smart Microgrid

A concept of non-linear electromagnetic system with the rotational magnetic pendulum for energy harvesting from mechanical vibrations was presented. The system was stimulated by vertical excitation coming from a shaker. The main assumption of the system was the montage of additional regulated stationary magnets inside coils creating double potential well, and the system was made with a 3D printing technique in order to avoid a magnetic coupling with the housing. In validation process of the system, modelling of electromagnetic effects in different configurations of magnets positions was performed with the application of a finite element method (FEM) obtaining the value of magnetic force acting on the pendulum. A laboratory measurement circuit was built and an experiment was carried out. The voltage and power outputs were measured for different excitations in range of system operational frequencies found experimentally. The experimental results of the physical system with electrical circuit and numerical estimations of the magnetic field of a stationary magnet’s configuration were used to derive a mathematical model. The equation of motion for the rotational pendulum was used to prove the broadband frequency effect.

Modelling of Electromagnetic Energy Harvester with Rotational Pendulum Using Mechanical Vibrations to Scavenge Electrical Energy

The purpose of this paper is to propose an efficient method to compute propagation modes in helicoidal waveguides. An helicoidal system of co-ordinates is introduced to define the structure and to set up the problem. These co-ordinates, albeit non-orthogonal, preserve the translational invariance in a way that allows a two-dimensional finite element model similar to the one of classical straight waveguides.

https://ieeexplore.ieee.org/iel5/5754893/5754894/05754927.pdf

Finite Element Analysis of Helicoidal Waveguides

Magnetostriction is the magnetisation-induced strain in ferromagnetic materials. It highly depends on mechanical stress. Stress state in electromagnetic devices is usually multiaxial and its effect on magnetostrictive properties is not easily predicted. In this paper, an original three-parameter analytical model for the stress-dependent magnetostriction strain of ferromagnetic materials is proposed. It is based on a simplified energetic description of magneto-elastic behaviour. It follows a similar method previously adopted for the description of the effect of stress on the magnetic permeability of magnetic materials. It is applied for the first time to the magnetostriction behaviour and results in a simple formula to express the effect of multiaxial magneto-mechanical loadings on the magnetostriction strain. The approach also naturally includes the description of the so-called ΔE effect. The analytical formula is derived in the paper. It shows very satisfying agreement with experimental results on iron–cobalt alloy and pure iron specimen.

/pdf/an-analytical-model-for-the-magnetostriction-strain-of-3i17v8e55d.pdf

An analytical model for the magnetostriction strain of ferromagnetic materials subjected to multiaxial stress

Magnetic hysteresis at the domain scale of a multi-scale material model for magneto-elastic behaviour

Modern hi-tech systems rely heavily on communication networks while operating in increasingly harsher electromagnetic conditions. To protect transmitted data from corruption, Error Correcting Codes are widely used. In this paper, the effectiveness of the Hamming code is evaluated under harsh electromagnetic disturbances. Our simulations show that, under certain conditions, the impact of the introduced overhead cannot be compensated by the single error correcting capabilities of the Hamming codes. Moreover, for specific bit and disturbance frequencies and for larger data sets, the use of a Hamming code provides limited to no advantage.

/pdf/effectiveness-of-hamming-single-error-correction-codes-under-2m22t626qc.pdf

Effectiveness of Hamming Single Error Correction Codes Under Harsh Electromagnetic Disturbances

In this paper, the effectiveness of applying an extra time delay to the data transmitted over redundant channels to cope with harsh electromagnetic interference is studied. The redundant system is compared with and without extra time delay and compared with a non-redundant system, which is the reference situation. The geometries under study are disturbed by strong incident fields, which represent reverberation room conditions. These conditions refer to the planewave integral representation, where multiple planewaves with random angles, polarisations and phases are combined and normalised, to create a reverberation room like environment. A reciprocity based technique is used to efficiently calculate the induced voltages and the resulting bit error rate for the different situations. Because of the properties of the geometries that are under test and the introduction of a time-delay in the transmitted datastream, the moment the induced voltage due to EMI is sampled is different, which causes an EMI-diverse system. The results show that using time-diverse signals optimized for the main disturbance frequency to be expected, is a very effective way of creating EMI-diverse behaviour. In a majority voting (2oo3) system it is possible to eliminate all triple occuring faults. Even for higher field strengths and different EMI frequencies, the time diversity method performs well (better than other EMI-diverse techniques).

/pdf/effectiveness-of-time-diversity-to-obtain-emi-diverse-ktdrzsx562.pdf

Effectiveness of Time Diversity to Obtain EMI-Diverse Redundant Systems

This paper studies the effectiveness of inversion diversity to cope with EM disturbances caused by strong incident fields under reverberation room conditions. Here, reverberation room conditions refers to the situation where multiple plane waves are incident onto the system-under-study, each with a random angle-of-incidence, polarization and phase. Two different geometries are compared: a non-redundant system comprising a single trace on a PCB and a redundant system comprising two parallel traces on a single PCB. A reciprocity-based technique is used to efficiently calculate the induced voltages and the resulting bit error probability in the different geometries. It is shown that with increasing distance between the two traces, the probability on false positive (i.e. two identical, but incorrect bits at the comparator) increases.

Effectiveness of inversion diversity to cope with EMI within a two-channel redundant system

Modern programmable electronic devices are becoming more and more susceptible to Electromagnetic Interference, meanwhile relying heavily on communication networks. In those networks, Cyclic Redundancy Checks (CRCs) are widely used to validate the correctness of transmitted data. However, this paper shows that, at specific bit and disturbance frequencies, CRC can generate false positives. A formula to predict those is presented. By using an in-house simulation framework, different case studies are simulated to find if false positives can occur. At some frequencies, the amount of false positives can rise asymptotically to up to 50% of all received data words. Techniques to overcome this downside are provided and reviewed.

Dries Vanoost

Papers

Magnetic hysteresis at the domain scale of a multi-scale material model for magneto-elastic behaviour

Effectiveness of Hamming Single Error Correction Codes Under Harsh Electromagnetic Disturbances

Effectiveness of Time Diversity to Obtain EMI-Diverse Redundant Systems

Effectiveness of inversion diversity to cope with EMI within a two-channel redundant system

Effectiveness of Cyclic Redundancy Checks under harsh electromagnetic disturbances