@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} } @inproceedings{KubaschinskiBaruthTetzlaffetal.2022, author = {Kubaschinski, Paul and Baruth, Albin and Tetzlaff, Ulrich and Altenbach, Holm and Waltz, Manuela}, title = {Untersuchungen zur Ermittlung der zyklischen Kennwerte von d{\"u}nnem Elektroblech im Rahmen der rechnerischen Lebensdauerabsch{\"a}tzung}, pages = {BF-2022-014}, booktitle = {Betriebsfestigkeit - Wissensmanagement und Methodenentwicklung entlang der Wertsch{\"o}pfungskette}, publisher = {DVM}, address = {Berlin}, doi = {https://doi.org/10.48447/BF-2022-014}, pages = {163 -- 178}, year = {2022}, language = {de} } @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{ErnstKubaschinskiSchiessletal.2024, author = {Ernst, Benedikt and Kubaschinski, Paul and Schiessl, Andreas and Waltz, Manuela and H{\"o}ppel, Heinz Werner and Tetzlaff, Ulrich}, title = {Comparison of the Young's modulus of the lead free solder alloy Sn-Ag3.8-Cu0.7 determined by hot tensile tests, ultrasonic measurements and 𝛽-Sn single crystal calculations}, volume = {2024}, pages = {147354}, journal = {Materials Science and Engineering: A}, number = {916}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1873-4936}, doi = {https://doi.org/10.1016/j.msea.2024.147354}, year = {2024}, abstract = {Sn-based solders are known for their tendency to form coarse grained microstructures. In combination with the high elastic anisotropy of 𝛽-Sn, the overall elastic properties and their interpretation require a careful discussion of the structure-property-relationship as elastic constants are often important input parameters for creep or fatigue models. This study therefore investigates the influence of microstructure and testing method on the Young's modulus E for the widespread lead free solder alloy Sn-Ag3.8-Cu0.7 (SAC387) using bulk specimens. Due to its already high homologous temperature at room temperature (Thom ≈ 0.6 = T/Tm for Tm being the melting temperature), hot tensile tests generally bear the risk of superimposed creep deformation. Mechanical testing becomes even more challenging, since yield strengths are usually low for these alloys. Consequently, in addition to the hot tensile tests executed for the engineering strain rate 𝜖̇𝑒 = 1 ⋅ 10-3 s-1, two supplemental methods are used to determine the Young's modulus comprising of the dynamic resonance frequency measurement and the calculation of the Young's modulus based on single crystal compliance data of the majority phase 𝛽-Sn.Young's moduli yielded from dynamic resonance frequency measurement and calculations based on single crystal compliance data showed comparable results of (E35 ◦C ≈ 55 GPa, E80 ◦C ≈ 51 GPa and E125 ◦C ≈ 48 GPa). Hot tensile tests showed similar data with the largest deviation at 80 ◦C, where E80 ◦C ≈ 53 GPa was determined. These absolute values and their temperature dependence can be attributed to the microstructure of the cast specimens which show a general preferred orientation of 𝛽-Sn grains close to <110> after analysis via electron backscattered diffraction (EBSD). A comparison with literature data revealed significant differences in the Young's moduli which are likely to be attributed to differences in the preferred orientation of 𝛽-Sn grains.}, 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} } @phdthesis{Kubaschinski2024, author = {Kubaschinski, Paul}, title = {Rechnerische Absch{\"a}tzung der Schwingfestigkeit von Elektroblech unter Ber{\"u}cksichtigung des Fertigungseinflusses}, publisher = {Otto-von-Guericke-Universit{\"a}t Magdeburg}, address = {Magdeburg}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:573-53390}, pages = {XX, 164}, school = {Otto-von-Guericke-Universit{\"a}t Magdeburg}, year = {2024}, abstract = {Zur betriebsfesten Auslegung schwingbeanspruchter Bauteile werden bereits in fr{\"u}hen Entwicklungsphasen rechnerische Lebensdauernachweise gef{\"u}hrt. Um die Schwingfestigkeit bewerten und die ertragbaren Beanspruchungen korrekt absch{\"a}tzen zu k{\"o}nnen, muss das zyklische Werkstoffverhalten unter Ber{\"u}cksichtigung verschiedener Einflussfaktoren erfasst werden. Neben den werkstoffabh{\"a}ngigen Materialeigenschaften ist dabei in erster Linie der Bearbeitungszustand des Bauteils mit einzubeziehen, da sich dieser unmittelbar auf die Schwingfestigkeit des Werkstoffs auswirkt. Die vorliegende Arbeit zeigt am Beispiel von Elektroblech auf, wie sich die festigkeitsbe- stimmenden Fertigungseinfl{\"u}sse bei der rechnerischen Absch{\"a}tzung der Schwingfestigkeit beschreiben und im Lebensdauernachweis nach dem {\"o}rtlichen Konzept ber{\"u}cksichtigen lassen. Dazu werden einzelne Einflussgr{\"o}ßen infolge des Herstellungs- und Verarbeitungsprozesses untersucht und der Zusammenhang mit dem mechanischen Werkstoffverhalten anhand entsprechender Simulationsmodelle hergestellt. Die Betrachtungen beinhalten sowohl die aufgrund der Halbzeugfertigung resultierenden richtungsabh{\"a}ngigen Materialeigenschaften als auch den durch Scherschneiden erzeugten Kantenzustand. Zudem erfolgt die mikrostrukturbasierte Modellierung und Simulationen des Elektroblechs. Der rechnerische Lebensdauernachweis setzt die Kenntnis der zyklischen Kennwerte des Werkstoffs voraus, die entweder experimentell zu ermitteln oder mithilfe von Absch{\"a}tz- methoden zu bestimmen sind. Dar{\"u}ber hinaus muss entschieden werden, mit welchem Sch{\"a}digungsparameter das Nachweisverfahren gef{\"u}hrt werden soll. Die experimentelle Ermittlung der zyklischen Kennwerte erm{\"o}glicht erwartungsgem{\"a}ß die genaueste Be- schreibung des stabilisierten zyklischen Werkstoffverhaltens. Im Fall der rechnerisch abgesch{\"a}tzten zyklischen Kennwerte k{\"o}nnen in Kombination mit den Sch{\"a}digungspara- metern PRAM und PRAJ dennoch zufriedenstellende Ergebnisse bez{\"u}glich der berechneten Anrisslebensdauern erzielt werden. Die fertigungsbedingten Einflussgr{\"o}ßen werden bei der rechnerischen Lebensdauerab- sch{\"a}tzung im Rahmen eines erweiterten Berechnungsablaufs ber{\"u}cksichtigt, welcher die Bestimmung der {\"o}rtlichen Beanspruchung auf der Grundlage der erstellten Simulations- modelle erlaubt. Am Beispiel von zwei bauteilnahen Proben kann eine weitestgehend gute {\"U}bereinstimmung zwischen den berechneten und experimentell aufgenommen Anrisslebensdauern festgestellt und der erweiterte Berechnungsablauf dadurch validiert werden. Eine {\"U}bertragung der Erkenntnisse auf den allgemeinen Anwendungsfall des rechneri- schen Lebensdauernachweises f{\"u}r Stahlfeinbleche ist prinzipiell m{\"o}glich.}, language = {de} } @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} }