@article{SchmittGottwaltWinkleretal.2021, author = {Schmitt, Matthias and Gottwalt, Albin and Winkler, Jakob and Tobie, Thomas and Schlick, Georg and Stahl, Karsten and Tetzlaff, Ulrich and Schlip, Johannes and Reinhart, Gunther}, title = {Carbon Particle In-Situ Alloying of the Case-Hardening Steel 16MnCr5 in Laser Powder Bed Fusion}, volume = {11}, pages = {11060896}, journal = {Metals}, number = {6}, publisher = {MDPI}, address = {Basel}, issn = {2075-4701}, doi = {https://doi.org/10.3390/met11060896}, year = {2021}, abstract = {The carbon content of steel affects many of its essential properties, e.g., hardness and mechanical strength. In the powder bed fusion process of metals using a laser beam (PBF-LB/M), usually, pre-alloyed metal powder is solidified layer-by-layer using a laser beam to create parts. A reduction of the carbon content in steels is observed during this process. This study examines adding carbon particles to the metal powder and in situ alloying in the PBF-LB/M process as a countermeasure. Suitable carbon particles are selected and their effect on the particle size distribution and homogeneity of the mixtures is analysed. The workability in PBF-LB is then shown. This is followed by an evaluation of the resulting mechanical properties (hardness and mechanical strength) and microstructure in the as-built state and the state after heat treatment. Furthermore, potential use cases like multi-material or functionally graded parts are discussed.}, language = {en} } @article{GottwaltKubaschinskiWaltzetal.2025, author = {Gottwalt, Albin and Kubaschinski, Paul and Waltz, Manuela and Tetzlaff, Ulrich}, title = {Influence of shear cutting parameters on the edge properties and the fatigue behavior of non-oriented electrical steel sheets}, volume = {56}, journal = {Materials Science \& Engineering Technology}, number = {4}, publisher = {Wiley}, address = {Weinheim}, issn = {0933-5137}, doi = {https://doi.org/10.1002/mawe.202400094}, pages = {537 -- 548}, year = {2025}, abstract = {The fatigue behavior of a fully processed, non-oriented electrical steel sheet is investigated for different shear cutting parameters. Therefore, three cutting clearances (15 μm, 35 μm and 50 μm) in combination with two different punching tool wear states (sharp and worn) are compared regarding their mechanical properties. For this purpose, surface measurements, nanoindentation tests and stress-controlled fatigue tests with a positive load ratio are performed for all six parameter sets. During shear cutting the material gets locally strain-hardened and a deformed surface with micro-notches is created. Compared to a polished reference condition, the fatigue strength of the shear-cut sheets is severely deteriorated. However, the intensity of deterioration varies depending on the shear cutting parameters. For small cutting clearances, the highest fatigue life is observed for a sharp cutting tool. In contrast, for medium and high cutting clearances, samples that are cut with a worn tool achieve higher fatigue lives. Surface characteristics in the fracture zone, which act as a failure-critical crack location, are considered as the main influencing factor.}, language = {en} } @article{GottwaltKubaschinskiWaltzetal.2022, author = {Gottwalt, Albin and Kubaschinski, Paul and Waltz, Manuela and Glatzel, Uwe and Tetzlaff, Ulrich}, title = {An experimental setup for fatigue testing of thin electrical steel sheets}, volume = {2022}, pages = {106987}, journal = {International Journal of Fatigue}, number = {162}, publisher = {Elsevier}, address = {Oxford}, issn = {0142-1123}, doi = {https://doi.org/10.1016/j.ijfatigue.2022.106987}, year = {2022}, abstract = {In this study, the fatigue behavior of thin electrical steel sheets under cyclic loading is investigated. Results from strain-controlled and stress-controlled fatigue tests with different specimen geometries and different test setups are presented and compared with conventional testing methods. The results imply that conventional testing methods should be adjusted for testing thin electrical steel sheets because the fatigue life depends significantly on the test setup as well as the specimen geometry. Therefore, this study proposes an improved specimen geometry and test setup for stress- and strain-controlled fatigue tests of thin electrical steel sheets depending on the desired testing parameters.}, language = {en} } @article{KubaschinskiGottwaltTetzlaffetal.2023, author = {Kubaschinski, Paul and Gottwalt, Albin and Tetzlaff, Ulrich and Altenbach, Holm and Waltz, Manuela}, title = {Modelling and simulation of the hardness profile and its effect on the stress-strain behaviour of punched electrical steel sheets}, volume = {54}, journal = {Materials Science \& Engineering Technology}, number = {4}, publisher = {Wiley}, address = {Weinheim}, issn = {0933-5137}, doi = {https://doi.org/10.1002/mawe.202200283}, pages = {512 -- 526}, year = {2023}, abstract = {The shear cutting of electrical steel sheets has a significant influence on the magnetic and mechanical material properties. Due to plastic deformation and strain hardening in the area of the punched edge, the electrical steel sheets exhibit a characteristic hardness profile. This study deals with the modelling of the resulting hardness profile by means of finite-element simulations. Elastic-plastic material properties are obtained from spherical nanoindentation testing as a function of the local hardness. In particular, representative stress-strain values are determined by applying Tabor's concept of indentation stress-strain curves. The choice of the appropriate stress- and strain-constraint factors is discussed with respect to the nanoindentation test setup used. Following this, the representative stress-strain values are analytically described to determine true stress-strain curves for the local assignment of different material models depending on the hardness. The implementation of the modelling approach in a finite-element simulation is presented for a punched electrical steel sheet specimen under monotonic loading. The simulation results are basically in good agreement with experimental data and confirm the expected influence on the mechanical material behaviour due to the shear cutting process.}, language = {en} } @article{KubaschinskiGottwaltTetzlaffetal.2022, author = {Kubaschinski, Paul and Gottwalt, Albin and Tetzlaff, Ulrich and Altenbach, Holm and Waltz, Manuela}, title = {Calibration of a combined isotropic-kinematic hardening material model for the simulation of thin electrical steel sheets subjected to cyclic loading}, volume = {53}, journal = {Materials Science \& Engineering Technology}, number = {4}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1521-4052}, doi = {https://doi.org/10.1002/mawe.202100341}, pages = {422 -- 439}, year = {2022}, abstract = {The combined isotropic-kinematic hardening model enables the description of the cyclic transient elastic-plastic material behaviour of steel. However, the determination of the material model parameters and understanding of their influence on the material response can be a challenging task. This study deals with the individual steps of the material model calibration for the simulation of thin electrical steel sheets under cyclic loading. Specific recommendations are made for the determination of kinematic and isotropic hardening material parameters. In particular, the isotropic hardening evolution is described by Voce's exponential law and a simple multilinear approach. Based on the multilinear approach, which allows for different slopes in the evolution of the yield surface size, an alternative calibration of the isotropic hardening component is proposed. As a result, the presence of the yield plateau in the first half cycle can be accurately captured, while convergence issues in the material model definition for numerical simulations can be avoided. The comparison of simulated load cycles with experimental cyclic tests shows a good agreement, which indicates the suitability of the proposed material model calibration for electrical steel.}, language = {en} } @article{GottwaltKubaschinskiWaltzetal.2023, author = {Gottwalt, Albin and Kubaschinski, Paul and Waltz, Manuela and Tetzlaff, Ulrich}, title = {Influence of the cutting method on the fatigue life and crack initiation of non-oriented electrical steel sheets}, volume = {2024}, pages = {108073}, journal = {International Journal of Fatigue}, number = {180}, publisher = {Elsevier}, address = {Oxford}, issn = {1879-3452}, doi = {https://doi.org/10.1016/j.ijfatigue.2023.108073}, year = {2023}, abstract = {The fatigue behavior of thin electrical steel sheets under cyclic loading is investigated in dependence on the edge surface. Therefore, four different edge conditions are compared, whereas the edge is either laser cut, shear cut, wire cut, or polished. Strain- and stress-controlled fatigue tests are performed to determine S-N curves in the low cycle regime as well as in the high cycle regime. Microstructural data is collected by non-contacting (optical) Profilometry, Nanoindentation, X-Ray Diffraction, and Electron Backscatter Diffraction to understand the differences in fatigue life by considering surface roughness, residual stresses, hardness, and microstructure. Shear cut specimens achieve the lowest fatigue life, while the other edge conditions reach relatively similar values in the LCF regime. Crack initiation is mainly intergranular in the case of defect-free edges. This tendency has a considerable influence on the observed fatigue behavior.}, language = {en} } @article{GottwaltKubaschinskiWaltzetal.2023, author = {Gottwalt, Albin and Kubaschinski, Paul and Waltz, Manuela and V{\"o}lkl, Rainer and Glatzel, Uwe and Tetzlaff, Ulrich}, title = {Cyclic deformation behavior of non-oriented electrical steel sheets}, volume = {2023}, pages = {145684}, journal = {Materials Science and Engineering: A}, number = {886}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0921-5093}, doi = {https://doi.org/10.1016/j.msea.2023.145684}, year = {2023}, language = {en} } @article{GottwaltKubaschinskiWaltzetal.2024, author = {Gottwalt, Albin and Kubaschinski, Paul and Waltz, Manuela and Tetzlaff, Ulrich}, title = {Influence of Subsequent Heat Treatment on Fatigue Behavior of Shear-Cut Electrical Steel Sheets}, volume = {3}, journal = {Alloys}, number = {4}, publisher = {MDPI}, address = {Basel}, issn = {2674-063X}, doi = {https://doi.org/10.3390/alloys3040017}, pages = {281 -- 294}, year = {2024}, abstract = {The fatigue behavior of a fully processed, non-oriented electrical steel sheet is investigated in dependence on shear-cutting parameters and a subsequent heat treatment. For this, stress-controlled fatigue tests are performed before and after annealing at 700 °C for a total of six different shear-cutting settings. For all parameters, the fatigue strength of shear-cut sheets is improved by the heat treatment. This is due to reduction in a large part of the strain hardening region as well as the reduction in tensile residual stresses. Both were introduced during shear cutting and act detrimental to the fatigue strength. However, the intensity of this improvement depends on the shear-cutting parameters. This is related to the corresponding edge surfaces characteristically being formed during shear cutting. Specimens cut with a worn cutting tool show a more pronounced increase in fatigue life. In contrast, specimens produced with a sharp-edged cutting tool and high cutting clearance hardly benefit from the heat treatment. This appears to be caused by differences in surface topography, in particular coarse topographical damage in the form of grain breakouts. If these occur during shear cutting, the crack formation is not significantly delayed by additional annealing.}, language = {en} }