Low frequency electromagnetic fields and magnetic materials

The subgroup on electromagnetic field calculations, magnetic material modelling and characterization has attained worldwide recognition regarding magnetic material modelling and characterization in the past 15 years. The magnetic measurement laboratory is unique in Belgium and Flanders, and is one of the few top laboratories for magnetic measurements in Europe. Currently measurements (B, H, losses, magnetostriction, …) are possible from DC up to a few kHz; the measurements can be performed under both unidirectional and rotating excitation, and with or without externally imposed stress.

Studying in detail the electromagnetic or electromechanical phenomena in electromagnetic devices, like electrical machines, power electronic components, actuators, sensors often results in solving Maxwell’s equations.  Given the increasing performance of computer technology, the absence of computational electromagnetism is unimaginable.  The performance of electromagnetic devices may be strongly related to the behaviour of the magnetic materials of which they are constructed.  Therefore, the development of solution techniques of Maxwell’s equation in materials with complex constitutive relations and the experimental identification of the magnetic and magneto-elastic behaviour of ferromagnetic materials become important issues. 

The research field ‘Low frequency electromagnetic fields and magnetic materials’ includes for EELAB:

1. Numerical computations of electromagnetic fields in devices using finite element-, finite difference-methods, magnetic network methods, complementary principles, functional analysis…
2. Experimental evaluation of magnetisation, magneto-elastic and magnetostriction properties of laminated ferromagnetic materials
3. Material modelling of electromagnetic properties under complex magnetic and mechanical conditions, taking into account memory behavior (hysteresis) by using advanced hysteresis models
4. Relation between microstructural properties of magnetic materials and the parameters in hysteresis models; microstructural optimisation of materials.
5. Physical interpretation of magnetization curves, hysteresis loops and electromagnetic losses.

Additional relevant research topics for EELAB, using the available expertise in the field of 'electromagnetic fields and magnetic materials' are magnetic non destructive evaluation (see also Universal Network for Magnetic Non-destructive Evaluation) and micromagnetism.

Available Expertise

• Experimental expertise
  
  
• Numerical field computations

  Next to analytical methods, EELAB has expertise with several numerical techniques, such as the Finite Element Method, the Circuit Method and the Network Method. All techniques use nonlinear and hysteretic material models that have been developed based on data from our experimental facilities. The numerical computations are combined with optimization routines in order to solve inverse problems in a wide variety of electromagnetic applications

Present Research

• Non-destructive evaluation

  Magnetic non-destructive evaluation of material degradation (metal fatigue, hardening and embrittlement) by means of magnetic hysteretic and magneto-elastic properties.

• Inverse problems in bio-electromagnetism

  Analysis of the electrical sources in the electro-encephalogram (EEG) and magneto-encephalogram (MEG) , Computer-assisted transcranial magnetic stimulation, quantitatively conductivity estimation using Magnetic Resonance Electrical Impedance Tomography (MR-EIT), magnetic nanoparticle estimation and manipulation, thermal ablation of liver tumors.

• Magnetic shielding

  Due to the increasing number of electric apparatus in companies and households, more and more electric and magnetic fields are produced in our neighbourhood. To create a safe environment for electric devices and also for human beings, active and passive magnetic shielding are studied at the laboratory.

• Micromagnetic modelling

  Simulation of macroscopic magnetic  material properties starting from the microstructure of the material.  The magnetization dynamics in ferromagnetic materials is studied on a microscopic space and time scale.

• Magnetostriction modelling

  Measurement and modelling of the macroscopic magnetostriction effect in electrical steels and application in numerical methods for the calculation of vibrations and noise in electromechanical devices.

• Macroscopic hysteresis modelling

  The macroscopic magnetic hysteretic behaviour, resulting from magnetization processes in ferromagnetic materials, may be described by material models, like the Preisach model, under complex magnetic and mechanical working conditions.

• Local magnetic measurements
  Local magnetic measurements are carried out in magnetic circuits with non-uniform electromagnetic field patterns, including excitation windings and/or air gaps, as in the case of rotating electrical machines.