PSI - Issue 16

Ihor Dzioba et al. / Procedia Structural Integrity 16 (2019) 97–104 Ihor Dzioba, Sebastian Lipiec/ Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 1. Microstructure of S355JR steel: (a) – FP, origin layered microstructure; (b) – FC, after heat treatment

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Fig. 2. Mechanical properties of S355JR steel at different temperatures: (a) – stress-strain curves; (b) – fracture toughness.

The results obtained during the research were arranged in the shape of a classic curve describing the brittle-ductile transition (Neimitz and Dzioba (2015, 2017)). On the lower plateau, fracture toughness values of the specimens that cracked brittle are placed (Fig. 3a). On the upper plateau – values of fracture toughness of specimens, which cracking are carried out according to the ductile mechanism (Fig. 3c). In the transition area, both ductile and brittle mechanisms are observed on the fracture surface of the specimens (Fig. 3b), and a growth of fracture zone by the ductile mechanism is observed with the temperature increase. The results presented in the further part of the article were obtained on representative specimens selected from each area of the brittle-plastic transition curve.

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Fig. 3. SEM pictures of the specimens fracture surface: (a) fully brittle, (b) mix brittle-ductile, (c) completely ductile