PSI - Issue 28

Jesús Toribio et al. / Procedia Structural Integrity 28 (2020) 2432–2437 Jesús Toribio / Procedia Structural Integrity 00 (2020) 000–000

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The term MFM was coined and used in the 80s and 90s by Toribio (1987, 1997) and by Toribio and Vasseur (1996) and further developed by Toribio (2002, 2004), Toribio and Ayaso (2004, 2009). The idea is used in recent papers by Toribio and Ayaso (2020) and Toribio and Vergara (2020). 2. Micro-fracture maps (MFMs) in notch-induced fracture of pearlitic steel in air Fig. 1 (Toribio, 1987; 1997) shows micro-fracture maps (MFMs) in notched samples of pearlitic steel with very different geometries (very distinct notch depths and radii), thereby generating a wide range of stress triaxiality (constraint). The microscopic modes of fracture are micro-void coalescence (MVC), cleavage (C) and shear lip (L). The cleavage fractography shows the typical river patterns : (i) locally convergent , indicating the sense of fracture propagation; (ii) globally divergent , marking the direction of unstable propagation from a localized origin.

Fig. 1. Micro-fracture maps (MFMs) in notch-induced fracture of pearlitic steel.

3. Micro-fracture maps (MFMs) in notch-induced fracture of cold drawn pearlitic steel in air Figs. 2 and 3 (Toribio and Ayaso, 2009) shows micro-fracture maps (MFMs) in notched samples of progressively cold drawn pearlitic steel with very different geometries (very distinct notch depths and radii), thereby generating a wide range of stress triaxiality (constraint). The microscopic modes of fracture are micro-void coalescence (MVC), cleavage (C) and special micro-void coalescence (fibrous zone) (MVC*). Microscopic fracture modes range from predominant C (brittle) in slightly drawn steels to predominant MVC (ductile) in heavily drawn steels.