PSI - Issue 3

Jesús Toribio et al. / Procedia Structural Integrity 3 (2017) 3–10

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Author name / Structural Integrity Procedia 00 (2017) 000–000

they have an extremely high tensile strength, greater than conventional materials, only limited by cleavage fracture ( cleavage limited strength ), (ii) they really behave as micro-composites (Toribio, 2006) from the mechanical point of view, so that their oriented lamellar microstructure influences their fracture behaviour and a materials science link can be established between the micro- and the macro-levels, (iii) they react in a non-conventional manner due to their inherent anisotropy induced by the manufacturing process in the form of multi-step (progressive) cold-drawing. This anisotropy is related to yielding and plastic behaviour ( anisotropic plastic behaviour ), as reported by Toribio et al. (2011) and also linked with fatigue and fracture performance ( anisotropic fracture behaviour ), as described elsewhere (Toribio et al. (1997), Toribio and Toledano (2000), Toribio and Ayaso (2001), Toribio and Ayaso (2003), Toribio et al. (2013), He et al. (2017)), with the result of mixed-mode fracture and strength anisotropy . In the matter of fractography associated with the afore-said anisotropic behaviour, a special type of cleavage has been described by Toribio and Ayaso (2002a), and the concept of exfoliation fracture has been used (Toribio and Ayaso (2004)), as well as the idea of delamination cracks (Tanaka et al. (2016)). This paper reviews previous research by the author in the field of relationship between drawing-induced microstructure evolution in cold-drawn pearlitic steels and macroscopic fracture performance, thereby establishing a materials science link between the micro- and the macro-approach. 2. Cold drawing of pearlitic steels Manufacture of prestressing wires is made by progressive (multi-stage) cold drawing of pearlitic steels to increase the strength by a strain hardening mechanism. Fig. 1 shows two views of a real cold drawing chain, whereas Fig. 2 shows an schematic presentation of the cold drawing process with multiple passes.

Fig. 1. Manufacture of prestressing wires by progressive cold drawing: two views of a real cold drawing chain.

Fig. 2. Schematic presentation of the cold drawing process with multiple passes through the dies.