PSI - Issue 61

Shahriar Afkhami et al. / Procedia Structural Integrity 61 (2024) 53–61 Shahriar Afkhami et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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axis of the lamination plane was parallel to the axis of the tensile load. In addition, titanium and aluminum oxide particles were present on the fracture surface (marked by red arrows in Fig. 5; these particles were chemically identified via electron diffraction spectroscopy used in conjunction with SEM), but fractography analysis did not indicate any determining role for these brittle phases in the final rupture of the welded S1100. Finally, regarding the welded specimens having an R of 10 and failing along the fusion line, fracture surface analysis indicated porosities as the main contributor to the material rupture, triggering a brittle and premature failure in this specimen, as shown in Fig. 5. This failure mechanism caused a fully brittle fracture front on the surface of the failed specimen, separated with a dashed red line from the rest of the surface in Fig. 5. Conclusions This study investigated the effect of cold-forming on the mechanical properties, plastic deformation, and fracture mechanism of welded ultra-high strength steel S1100 in the concept of a modified joint design applicable to the corners of bent and cold-formed ultra-high strength steels. Following the results of this research and comparing them with data available from the authors’ previous work [4], these concluding remarks can be made: - The thermal gradient and cooling route experienced by the material in the modified joint design slightly differed from the common joint design used to weld the bent profile of structural steel. The changes in the thermal gradients can cause microstructural changes that alter the mechanical performance of the material in its HAZ area, especially the hardness. However, the microstructural features require further research in future studies and were excluded from this research due to its scope being mainly focused on the plastic deformation and fracture of the cold-formed and welded material. - S1100, with a maximum degree of cold-forming of ≈ 12%, was safe to weld via gas-metal arc welding along its cold-formed area. Such results can help complement the data required by steel structures standards and codes, such as EN 1993-1-8, to expand their covered materials and joint designs.