Neutron grating interferometry investigation of punching-related local magnetic property deteriorations in electrical steels

Weiß, H.; Steentjes, Simon; Tröber, Philipp; Leuning, Nora; Neuwirth, Tobias; Schulz, Michael; Hameyer, Kay; Golle, Roland; Volk, Wolfram

doi:10.1016/j.jmmm.2018.10.098

Cited by 18 publications

(13 citation statements)

References 42 publications

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“…www.nature.com/scientificreports www.nature.com/scientificreports/ magnetic yoke 33 used for the experiment. The width was arbitrarily chosen to be 10 mm.…”

Section: Methodsmentioning

confidence: 99%

“…As a result of the highly improved visibility over a large FoV, experiments with samples exhibiting only small variations in scattering contrast or requiring short measurement times now become more accessible. In this work we demonstrate the capabilities of our novel nGI setup to study the magnetic domain structure of non grain-oriented electrical steel sheets 33 . Typically, highly performing electric motors are limited in rotational speed and efficiency by the cut-outs machined into their magnetic core, which are required to guide the magnetic flux 34,35 .…”

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confidence: 95%

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A high visibility Talbot-Lau neutron grating interferometer to investigate stress-induced magnetic degradation in electrical steel

Neuwirth

Backs

Gustschin

et al. 2020

Sci Rep

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neutron grating interferometry (nGi) is a unique technique allowing to probe magnetic and nuclear properties of materials not accessible in standard neutron imaging. the signal-to-noise ratio of an nGI setup is strongly dependent on the achievable visibility. Hence, for analysis of weak signals or short measurement times a high visibility is desired. We developed a new talbot-Lau interferometer using the third Talbot order with an unprecedented visibility (0.74) over a large field of view. Using the third talbot order and the resulting decreased asymmetry allows to access a wide correlation length range. Moreover, we have used a novel technique for the production of the absorption gratings which provides nearly binary gratings even for thermal neutrons. the performance of the new interferometer is demonstrated by visualizing the local magnetic domain wall density in electrical steel sheets when influenced by residual stress induced by embossing. We demonstrate that it is possible to affect the density of the magnetic domain walls by embossing and therefore to engineer the guiding of magnetic fields in electrical steel sheets. The excellent performance of our new setup will also facilitate future studies of dynamic effects in electric steels and other systems. Neutron radiography is a method allowing for non-destructive analysis of the inner structure of an object 1. Because the neutron cross-sections show no systematic dependence on the atomic number, both light and heavy elements can be visualized. Moreover, the contrast between different materials can be varied by using isotopes. Therefore, neutron imaging has been established to be a very efficient technique in materials science, research in cultural heritage, archaeology, and engineering, where imaging with X-rays fails to produce sufficient contrast. Neutron imaging is, however, limited by the coarse spatial resolution imposed by the limitations in neutron flux and the spatial resolution of the neutron detectors. Currently, the achieved spatial resolution is in the low single μm range 2-7. Paths towards resolving structures with higher resolution (e.g. water transport in fuel cells) are, for example, improving the detector resolution 3-6 or in some cases using neutron grating interferometry (nGI) 8,9 as a spatially resolved ultra-small-angle scattering technique. nGI simultaneously gathers spatially resolved information about the transmission-(TI), the differential phase contrast-(DPCI) and the scattering/dark-field (DFI) of a sample. Most notably, the contrast provided by the DFI 10,11 is generated by ultra-small-angle neutron scattering (USANS) off structures on a length scale similar to the correlation length of the interferometer setup, which is typically in the range 0.1 μm to 10 μm. Such structures are caused by variations of the nuclear or magnetic

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“…www.nature.com/scientificreports www.nature.com/scientificreports/ magnetic yoke 33 used for the experiment. The width was arbitrarily chosen to be 10 mm.…”

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 95%

A high visibility Talbot-Lau neutron grating interferometer to investigate stress-induced magnetic degradation in electrical steel

Neuwirth

Backs

Gustschin

et al. 2020

Sci Rep

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“…The measurement of the specimens was conducted under the influence of different magnetic fields to analyze the effect of magnetization on the behavior of magnetic flux barriers. The yoke, described in [15] induces the magnetic field in the specimens, which is generated by an electric current in the coils. In Tab.…”

Section: Neutron Grating Interferometrymentioning

confidence: 99%

Analysis of Cylindrically and Spherically Embossed Flux Barriers in Non-oriented Electrical Steel

et al. 2021

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In reluctance and permanent magnet synchronous machines, flux barriers are crucial for magnetic flux guidance. Designed as cutouts, flux barriers reduce the mechanical strength of the rotor construction. To operate these electric drives at higher rotational speed, an alternative flux barrier design is required. Since residual stress influences the magnetic properties of soft magnetic materials, this paper deals with embossing induced residual stress as flux barriers in nonoriented electrical steel with 2.4 wt% silicon and a sheet thickness of 0.35 mm. The investigated flux barriers were fabricated with a cylindrical or spherical punch at two different penetration depths and were compared to a flux barrier fabricated as cutout. A residual stress analysis using Finite Element Analysis helps understanding the mechanism of embossed flux barriers. Additionally, the influence of induced residual stress on the magnetic material behavior is measured using standardized single sheet tests and neutron grating interferometry measurements. This investigation aimed at a better understanding of the flux barrier design by local induction of residual stress.

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“…Edge effects also have an important role in material processing procedures [7][8][9] . Several a) Electronic mail: ngcastrath@uem.br methods including laser interferometry have been used for investigating surface properties 10,11 , local magnetic property deteriorations in metals 12 , micro-damage evolution 13 , fatigue failure 14 , mechanical properties 15,16 , and as optical image hiding method 17,18 . This technique reveals how nanostructured surfaces and structures can be characterized, such as textured stainless steel 19 , Mylar polymer films 20 and biomaterials, for instance, polymerized hexamethyldisiloxane 21 and hydroxyapatite materials 22,23 .…”

Section: Introductionmentioning

confidence: 99%

Influence of edge effects on laser-induced surface displacement of opaque materials by photothermal interferometry

Flizikowski

Anghinoni

Rohling

et al. 2020

Journal of Applied Physics

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We demonstrate the influence of edge effects on the photothermal-induced phase shift measured by a homodyne quadrature laser interferometer and compare the experiments with rigorous theoretical descriptions of thermoelastic surface displacement of metals. The finite geometry of the samples is crucial in determining how the temperature is distributed across the material and how this affects the interferometer phase shift measurements. The optical path change due to the surface thermoelastic deformation and thermal lens in the surrounding air is decoded from the interferometric signal using analytical and numerical tools. The boundary/edge effects are found to be relevant to properly describe the interferometric signals. The tools developed in this study provide a framework for the study of finite size effects in heat transport in opaque materials and are applicable to describe not only the phase shift sensed by the interferometer but also to contribute to the photothermal-based technologies employing similar detection mechanisms.

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Neutron grating interferometry investigation of punching-related local magnetic property deteriorations in electrical steels

Cited by 18 publications

References 42 publications

A high visibility Talbot-Lau neutron grating interferometer to investigate stress-induced magnetic degradation in electrical steel

A high visibility Talbot-Lau neutron grating interferometer to investigate stress-induced magnetic degradation in electrical steel

Analysis of Cylindrically and Spherically Embossed Flux Barriers in Non-oriented Electrical Steel

Influence of edge effects on laser-induced surface displacement of opaque materials by photothermal interferometry

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