Simulating the magnetic domain structure of electrical steel and the resulting ultra-small-angle scattering of neutrons with respect to material properties and applied magnetic field
| Topic | 58 |
| Main supervisor | Tobias Neuwirth (Tobias.Neuwirth@frm2.tum.de) |
| MLZ institution | TUM |
| Local supervisor 1 |
Felix Briza
|
| Institution |
Hoffmann Eitle
|
| Local supervisor 2 | Nore Leuning |
| Institution |
RWTH
|
| Local supervisor 3 | – |
| Institution | – |
| Local supervisor 4 | – |
| Institution | – |
| Title |
Simulating the magnetic domain structure of electrical steel and the resulting ultra-small-angle scattering of neutrons with respect to material properties and applied magnetic field
|
| Description |
In the transportation sector, battery electric vehicles (BEVs) are an option to reduce the consumption of fossil fuels, aiming to slow down climate change. The typically used drive types in BEVs require careful magnetic flux guidance. Conventionally, cutouts in the non-grain-oriented electrical steel comprising the magnetic core of the drive guide the magnetic flux. The downside of this approach is that the cutouts reduce the rotor’s mechanical strength, thereby limiting the maximum rotational speed.
As part of an interdisciplinary priority program (SPP2013) supported by the DFG, we have already demonstrated the suitability of replacing these cutouts with embossed areas. The embossing introduces residual stress, which locally reduces the magnetic permeability and guides the flux while maintaining mechanical strength. By optimizing the embossing parameters, the achievable rotational speed of the electric drive increases and the stray fields are reduced, subsequently increasing efficiency. Neutron grating interferometry (nGI) is an advanced neutron imaging technique that uniquely maps the displacement of magnetic flux in the bulk of electrical steel. The size of magnetic domains changes depending on the local magnetization state of the electrical steel, which is determined by the local magnetic flux. The distribution of magnetic domains creates an inhomogeneity in the micrometer regime of the magnetic neutron scattering length density. Variations in the magnetic and nuclear scattering length density cause ultra-small-angle scattering of neutrons (USANS) which can be detected by nGI. Hence, the change in the distribution of magnetic domains and, therefore, the influence of embossing on the magnetic flux can be tracked. While the recovery of the orientation and size of magnetic domains using analytical methods is possible, linking these properties to the magnetic permeability and other parameters measured using global magnetic measurements is not trivial. However, these properties are required to optimize these novel electric drives. With this project, we want to improve the understanding of the link between the properties measured by nGI and the local magnetic parameters. You will work on creating a finite element method simulation of the magnetic domains dependent on the applied magnetic field, the residual stress and material parameters. Using this simulation, the USANS signal measured by nGI can be further analyzed and information such as the local magnetic permeability can be extracted. By comparison with already acquired nGI data and global magnetic measurements, the simulation will be validated. |