TY - CONF A1 - Madia, Mauro T1 - Determination of the Kitagawa-Takahashi diagram for the EA4T railway axle steel by means of the cyclic R-curve method N2 - The Kitagawa-Takahashi (KT) diagram is a well-established tool in the fatigue community for the prediction of the fatigue limit of metallic materials in presence of defects. Nevertheless, its determination is associated with a large number of fatigue tests carried out on specimens with artificial defects (notches) to describe the fatigue limit-defect size relationship in the short crack regime. The preparation of the specimens and the execution of the tests is time expensive. Therefore, few phenomenological models have been introduced in the past to provide a first approximation of the KT diagram based solely on the fatigue limit for smooth specimen and the fatigue crack propagation threshold for long cracks. Despite the use of such models is widely spread, these suffer from problems related to the uncertainties of the material parameters. Furthermore, the mechanics of short cracks, which is the physical mechanism behind the concept of the fatigue limit, is not considered. This work discusses the advantages and drawbacks of using short fatigue crack propagation models for predicting the fatigue limit of flawed metallic materials. The KT diagrams for a EA4T railway axle steel in as-received and full-hardened condition are approximated by means of the cyclic R-curve method. T2 - 13th International Fatigue Congress CY - Hiroshima, Japan DA - 06.11.2023 KW - Fatigue limit KW - Crack propagation KW - Short crack KW - Cyclic R-curve KW - EA4T railway axle steel PY - 2023 AN - OPUS4-58867 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yang, Keke A1 - Sowada, Matthias A1 - Olfert, Viktoria A1 - Seitz, Georg A1 - Schreiber, Vincent A1 - Heitmann, Marcel A1 - Hein, David A1 - Biegler, Max A1 - Jüttner, Sven A1 - Rethmeier, Michael A1 - Meschut, Gerson T1 - Influence of liquid metal embrittlement on the failure behavior of dissimilar spot welds with advanced high-strength steel: A component study N2 - This study investigates the effects of liquid metal embrittlement (LME) cracks on the mechanical performance of resistance spot-welded joints in zinc-coated advanced high-strength steel (AHSS) at the component level. To this end, a novel component-level test specimen featuring a hat and L-shaped profile was developed to identify critical failure points under three-point bending loads. Load-bearing capacity tests were subsequently conducted under both quasi-static and impact loading conditions, specifically targeting LME cracks with an average depth reaching 63.6% of the sheet thickness. By monitoring the surface strain of spot welds affected by LME cracks, the study visualizes stress concentration effects at the crack tips and traces the propagation of these cracks into the base material, which ultimately leads to material tearing and joint failure. The findings reveal that the effect of LME cracks in reducing load-bearing capacity is more pronounced under impact loading than under quasi-static loading, highlighting a previously underexplored aspect of LME behavior under impact loading. Specifically, the peak load decreased by 3.9% and 10.8%, while energy absorption declined by 52.2% and 78.3% under quasistatic and impact loading, respectively. KW - Liquid metal embrittlement KW - Resistance spot welding KW - Impact loading KW - Crack propagation KW - Advanced high-strength steel PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-621727 DO - https://doi.org/10.1016/j.jmrt.2024.11.166 VL - 33 SP - 8321 EP - 8328 PB - Elsevier B.V. AN - OPUS4-62172 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Roveda, Ilaria T1 - Effect of heat treatment on the microstructure, residual stress state and fatigue properties of PBF-LB/M AlSi10Mg N2 - Al-Si alloys produced by Laser Powder Bed Fusion (PBF-LB/M) techniques allow the fabrication of lightweight free-shape components. Due to the extremely heterogeneous cooling and heating, PBF-LB/M induces high magnitude residual stress (RS) and a fine Si microstructure. As the RS can be deleterious to the fatigue resistance of engineering components, great efforts are focused on understanding their evolution before and after post-process heat treatments (HT). T2 - Alloys for Additive Manufacturing Symposium 2022 (AAMS22) CY - Munich, Germany DA - 12.09.2022 KW - Neutron diffraction KW - X-ray diffraction KW - Crack propagation PY - 2022 AN - OPUS4-55871 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -