TY - CONF A1 - Kling e Silva, Lucas A1 - Pereira, Gabriela Ribeiro A1 - Jardim, Paula Mendes A1 - Sonntag, Nadja A1 - Skrotzki, Birgit T1 - CARACTERIZAÇÃO MAGNÉTICA DOS EFEITOS DE DEFORMAÇÃO EM AÇOS ESTRUTURAIS ATRAVÉS DA TÉCNICA BITTER MODIFICADA T2 - 72nd ABM Annual Congress N2 - The plastic deformation results in irreversible microstructure changes in the steel, which can be considered as the initial stage of the fracture process. However, detecting, monitoring and evaluating, damage states and small defects non-destructively in advance still proves challenging. It was reported in literature the phenomenon of the spontaneous emergence of weak magnetic fields in structural steels and pipelines, which originates due to heterogeneous mechanical and / or thermal stresses. This observation is not associated with induced phase transformations by deformation and appears to be a promising tool for the prior characterization of damage in ferromagnetic steels. To provide a better understanding of the physical bases of the process, the magnetic microstructure of such materials and the change of magnetic domains after undergoing plastic deformation were studied. For this purpose, a colloidal solution with paramagnetic particles in the nanometer scale (ferrofluid) was used, through the Bitter technique, in order to, not only observe a change in size of the magnetic domains of the material, but also changes in their morphology. Ferritic steels with different carbon contents (0.08%; 0.22% and 0.45%) were studied in this work. T2 - ABM Week 2017 CY - Sao Paulo, Brazil DA - 02.10.2017 KW - Magnetic domains KW - Steels KW - Ferrofluid KW - Plastic deformation PY - 2017 DO - https://doi.org/10.5151/1516-392X-30810 SN - 2594-5327 VL - 72 IS - 1 SP - 3003 EP - 3013 PB - Blucher Preceeding CY - Brasilien AN - OPUS4-48876 LA - por AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sonntag, Nadja A1 - Skrotzki, Birgit ED - Beck, T. ED - Charkaluk, E. T1 - Imaging of potential crack initiation sites in ferritic steels by the Bitter method T2 - LCF8 Eighth International Conference on Low Cycle Fatigue N2 - It is widely known that the magnetic domain structure of stress-sensitive ferromagnetic materials may be altered by external or internal mechanical stresses due to magnetoelastic effects. In this contribution, localized magnetic domain changes arising from inhomogeneous deformation and multiaxial loading conditions are imaged by the Bitter method for the first time. It is demonstrated that these domain changes provide deformation-related information and thus, allow for the visualization of macroscopic strain gradients in fine-grained polycrystalline steels, while keeping a sufficient spatial resolution. This approach has been developed within the framework of BAM-MI-project “MICRONET”. T2 - LCF8 Eighth International Conference on Low Cycle Fatigue CY - Dresden, Germany DA - 27.06.2017 KW - Bitter method KW - Magnetic domains KW - Strain gradients PY - 2017 SN - 978-3-9814516-5-8 SP - 263 EP - 265 PB - DVM Deutscher Verband für Materialforschung und -prüfung CY - Berlin, Germany AN - OPUS4-40862 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sonntag, Nadja A1 - Nolze, Gert A1 - Kuntner, Markus A1 - Skrotzki, Birgit T1 - Imaging of potential crack initiation sites in ferritic steels by the Bitter method N2 - It is widely known that the magnetic domain structure of stress-sensitive ferromagnetic materials may be altered by external or internal mechanical stresses due to magnetoelastic effects. In this contribution, localized magnetic domain changes arising from inhomogeneous deformation and multiaxial loading conditions are imaged by the Bitter method for the first time. It is demonstrated that these domain changes provide deformation-related information and thus, allow for the visualization of macroscopic strain gradients in fine-grained polycrystalline steels, while keeping a sufficient spatial resolution. This approach has been developed within the framework of BAM-MI-project “MICRONET”. T2 - LCF8 Eighth International Conference on Low Cycle Fatigue CY - Dresden, Germany DA - 27.06.2017 KW - Bitter method KW - Magnetic domains KW - Strain gradients PY - 2017 AN - OPUS4-40863 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -