PSI - Issue 26

Jesús Toribio et al. / Procedia Structural Integrity 26 (2020) 376–382 Toribio / Structural Integrity Procedia 00 (2019) 000 – 000

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evolution of material’s performance throughout the service life, due to the double and varying influence of the previous mechanical loading history and the surrounding physico-chemical environment. The key- idea was launched in Spanish (“el material es él y su circunstancia”) by Toribio (1992a) when he reached the Full Professorship in the Spanish University (BOE, 1991; 1992). In a review paper Toribio (2000) re-formulated the idea in English (“the material is itself and its circumstance”). In this conceptual framework, a given material does not have a behavior per se , but can exhibit one or another depending on the circumstance . In engineering materials, the first role of circumstance (in the sense proposed by Ortega y Gasset) is played by the manufacture process, e.g., in the production of commercial prestressing steel wires (Toribio, 1992b) by increasing cold drawing during which a strain hardening mechanism is activated, so that the cumulative plastic strain produces an increase of yield strength and ultimate tensile strength (UTS), as recently described by Toribio (2017a); thus they can be considered as high-performance structural materials (Toribio, 2006). In addition, the loading scheme (type of loading: monotonic, cyclic, tension, compression…) also plays such a role. Furthermore, the external environment of a material is another sort of circumstance affecting material’s behavior. In the paper by Toribio (2000) hydrogen plays the role of circumstance, the presence of such a chemical element The key issues of the fatigue & fracture crack paths in a given structural material recall the words of the Spanish poet Antonio Machado: “se hace camino al andar” (from the poem “Cantares” in Spanish language), indicating that there is no previous path, but the path is made as the crack grows (and such a path is influenced by the material microstructure). In the matter of the link between poetry and fracture mechanics, an in the framework of the concept of path, a connection may be also established between the path-independent J-integral proposed by Jim Rice (1968) and the Machado’s “se hace camino al andar”, because the latter suggest no specific path, but any path (with certain conditions) produces the same mathematical result ( J-integral value ). With regard to fatigue & fracture of cold drawn pearlitic steels (Toribio 2018a; 2018b), and in order to include the idea of the material science effect, i.e., the influence of the oriented lamellar pearlitic microstructure (that generated during manufacture by cold drawing) on the fatigue & fracture performance and on the crack paths, one can remember the wonderful poetry of Fray Luis de León, major Spanish poet and Professor of the University of Salamanca (Fig. 1): “y entrambas a porfía mezclan una dulcísima armonía”, resulting that the fight (the mixture) between voices ( the counterpoint ) generates the sweetest harmony, in the same manner as the mixture between ferrite and cementite lamellae produces a very noble material (pearlitic steel), that can be considered, following this particular way of reasoning, a Fray Luis de León (F LL) based material , as suggested by Toribio (2018a). In the same manner as the fatigue & fracture crack path generates a wake in the particular structural material (with tortuous shape affected by the microstructure), a wave in the sea generates its corresponding wake. In this conceptual and poetic framework, the present section of the article (about the innovative and creative relationship between poetry and fracture mechanics ) is metaphorically written also as a poetic suggestion to relate art and science, following the wake of Antonio Machado and Fray Luis de León . In the matter of environmental effects on fatigue & fracture performance of engineering materials, as pointed out previously, in the paper by Toribio (2000) hydrogen plays the role of circumstance , showing the effect of history (of hydrogenation versus cracking) from the viewpoint of fracture mechanics, damage tolerance and microstructural integrity, thereby demonstrating the important role of previous history (the yesterday influences the today, and the latter does the same on the tomorrow), recalling the beautiful words of the major Spanish poet Antonio Machado “hoy es siempre todavía”, and also the poetry of Thomas Stearns Eliot “and all is always now” (Toribio, 2000). 3. Cinema and fracture mechanics Previous research by Toribio (2018a) on fracture of notched samples of cold drawn pearlitic steels of very different geometries (very distinct degree of constraint) shown the necessity of both microstructural orientation and triaxiality level to obtain fracture path deflection, cf. Fig. 2 showing the fracture profile for a slightly cold drawn pearlitic steel, resembling John Ford’s movies and producing a kind of Monument Valley Profile (MVP), cf. Fig. 3. promoted by a cathodic environment. 2. Poetry and fracture mechanics