SDSS 2025

Anisotropic Fracture Behaviour of Hot Rolled Structural Steel

  • Obkircher, Debora (Norwegian University of Science and Technolog)
  • Costas, Miguel (Norwegian University of Science and Technolog)
  • Morin, David Didier (Norwegian University of Science and Technolog)
  • Clausen, Arild Holm (Norwegian University of Science and Technolog)

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Hot-rolled steel profiles used in structural applications are usually treated as isotropic. However, the hot rolling process leads to microstructural anisotropy due to factors such as crystallographic texture, segregation-induced banding and the orientation of non-metallic inclusions. Although this anisotropy has only a minor effect on the plastic behaviour, it considerably alters the ductility [1]. Ductile fracture of steel is predominantly driven by the nucleation, growth, and coalescence of voids, which often originate from inclusions and second-phase particles. During hot working, inclusions such as manganese sulphide (MnS) become elongated in the rolling direction, promoting faster void coalescence and reducing ductility in specimens tested perpendicular to the rolling direction [1,2]. For applications where ductility and energy dissipation are decisive, the consideration of mechanical anisotropy for fracture strain is therefore essential. In this study, the mechanical behaviour of S355J2 steel is investigated by performing material tests under different stress states. Emphasis was laid on the anisotropy of fracture strain and tests in both rolling and transverse directions were performed. Numerical simulations were used to characterise the material behaviour and to assess different damage models. The results show that while yield strength and tensile strength are only slightly affected by the orientation of the specimen, the specimens tested in the transverse direction exhibit significantly lower ductility for this type of steel. [1] Berns, Hans, and Werner Theisen. Ferrous materials: steel and cast iron. Springer Science & Business Media, 2008. [2] Gao, Xiao-yong, Hong Wei, and Li-feng Zhang. "Effect of oxide inclusions on MnS precipitates and tensile mechanical property of high-strength low-alloy steel." Journal of Iron and Steel Research International 31.5 (2024): 1210-1220.