PROBLEMS OF PREISACH MODEL APPLYING IN FINITE ELEMENT METHOD

The paper deals with determination of magnetic field, calculated by finite element method with regard to magnetic nonlinearity. The hysteresis loop of the material is modelled by the scalar Preisach model. A hysteresis motor problem was selected for the demonstration of the hysteresis effect

Magnetic flux simulation for the inspection of local thinning of ferromagnetic plates

Magnetic flux simulations were utilized in a novel magnetic measurement method performed for the detection of local thinning of ferromagnetic plates. It was shown by numerical simulation, how parameters affect detectability of the defects. Linear relationship was found between the evaluated parameters and size of the artificial slot. Good correlation was found between theoretical and experimental results

Szerkezeti anyagok degradációjának kimutatása elektromágneses elven alapuló roncsolásmentes módszerekkel = Detection of structural materials' degradation by electromagnetic nondestructive methods

A kutatás során olyan mérési technikát fejlesztettünk tovább, ami a hagyományos örvényáramú mérést nagyérzékenységű mágneses térméréssel kombinálja. Mérések sorával igazoltuk a módszer előnyeit, a nagy mélységbeli felbontóképességet, valamint a megnövelt érzékenységet. Elvégeztük az örvényáramú szenzor kalibrációját és optimalizált mérési adatbázist készítettünk vezető anyagban keletkezett repedések rekonstrukciójához. Mágneses alapkutatásokat végeztünk a szenzor vasmag anyagának optimalizására, amely segítségével az eszköz működési paraméterei jelentősen javíthatók. Jelentős vastagságú (5-10 cm) vezető anyagok belsejében keletkezett repedések kimutatására javasoltunk egy új módszert, amely a mágneses szenzor előnyös tulajdonságait használja ki. Kimutattuk, hogy egyenáramú mágneses szenzorok alkalmazásával kiváló eredmény érhető el, amennyiben a vezetőn átfolyó áram mágneses terének az anyaghiba által okozott perturbációját mérjük. Az eljárás realizálhatóságának vizsgálatára számítógépes szimulációt készítettünk.Kidolgoztunk egy új, a mágneses hiszterézis alhurkok szisztematikus mérésén alapuló eljárást, ami a ferromágneses anyagokban bekövetkező szerkezeti változások nagy érzékenységű, roncsolásmentes nyomonkövetésére szolgál, és mérésekkel igazoltuk a módszer hatékonyságát. Megkezdtük az általunk kifejlesztett módszerek gyakorlatban történő alkalmazására irányuló fejlesztéseket. | A novel technology has been developed within the project, which combines the conventional eddy current technique with high sensitivity magnetic field measurement. We have proved by series of measurements the advantageous features of this method, i.e. the improved depth resolution and sensitivity. The calibration of the eddy current sensor has been performed and measurement data base has been made for the reconstruction of the cracks in conductive materials. Magnetic basic research has been performed for the optimization of the sensing material. The operation parameters of the device can be improved by using these results. A novel method has been suggested for the detection of cracks, existing in the thick (5-10 cm) conductive material, by using the advantageous characteristics of magnetic field sensor. We have found that excellent result can be achieved if the perturbation of magnetic field, generated by the current, which flows through the material is measured. A numerical simulation has been presented for the realization of the method. We have developed a novel method, which is based on the systematic measurement of magnetic minor hysteresis loops. It is possible to follow the structural degradation of ferromagnetic materials by this nondestructive method. The effectivity of this method has been proved by measurements. We have started the development aiming the practical application of our methods

Modeling stationary moving medium by static magneto-electric material

The electromagnetic equivalence of a stationary moving medium to magneto-electric materials is studied. The equivalent material characteristics of the medium at rest is obtained in terms of the diffusion tensor coefficient of the governing partial differential equation. Special attention is paid to the transition condition of field quantities on the boundary of the moving medium; it is found that the nonmoving magneto-electric equivalent model must be supplied with surface sources. The method is demonstrated through examples and verified by finite element simulation

Inverse problem characterization using an adaptive database

International audienceIn this paper, the characterization of electromagnetic inverse problems is addressed. As it is well known, an inverse problem can be ill-posed, i.e., its solution is not necessarily unique and might be quite sensitive to the measured data. To characterize such an inverse problem a combination of a surrogate model --based on an optimal database-- and an inverse mapping of some sort, both using kriging prediction as tools, is proposed. The database (a kind of discrete representation of the electromagnetic model) is generated using an adaptive sampling strategy aiming to find a set of optimal input parameter-output data pairs. Once the latter has been computed, both qualitative and quantitative conclusions about the related inverse problem can be drawn. The illustrative examples are drawn from eddy-current nondestructive testing. month =au