PSI - Issue 26

Jesús Toribio et al. / Procedia Structural Integrity 26 (2020) 354–359 Toribio / Structural Integrity Procedia 00 (2019) 000 – 000

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3.3. Macro-structural integrity The concept of macro-structural integrity is applicable to real structural elements (at laboratory scale) or experimental specimens. Fig. 5 shows the fracture profile in a notched specimen of cold drawn pearlitic steel (Toribio, 2018) with evidence of anisotropic fracture behavior with its related crack path deflection.

Fig. 5. Fracture profile in a notched specimen of cold drawn pearlitic steel.

3.4. Micro-structural integrity The concept of micro-structural integrity refers to the microstructural level of the materials. Fig. 6 shows a special ( non-conventional ) microstructural unit, the so-called pearlitic pseudocolony , a term coined by Toribio et al . (1997) and described in detail by Toribio (2020) in a companion paper in this issue.

Fig. 6. Pearlitic pseudocolony in a heavily cold drawn pearlitic steel.

3.5. Nano-structural integrity As studied by Toribio and Ovejero (1998), in the most heavily cold drawn steels, the pearlite interlamellar spacing is about 0.030  m, i.e., 30 nm, so that they can be considered as micro-composites or nano-composites formed by alternate layers of ferrite (Fe) and cementite (Fe 3 C). In this conceptual framework, the innovative concept of nano structural integrity is adequate for nano-cracks at the nano-scale: the fractured cementite lamellae (Fig. 7).

Fig. 7. Enlarged view (x8000 magnification) of a pearlitic pseudocolony in a heavily cold drawn pearlitic steel.