PSI - Issue 41

Jesús Toribio et al. / Procedia Structural Integrity 41 (2022) 712–717 Jesús Toribio / Procedia Structural Integrity 00 (2022) 000–000

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3. Multi-perspective approach to the concept of crack path With regard to the evolution of macro-crack aspect ratio during fatigue (analyzed in the horizontal plane containing the crack), it represents the analysis of crack path evolution in the matter of macro-crack aspect ratio ( multi-perspective approach ). In the matter of fatigue macro-crack aspect ratio evolution in progressively cold drawn pearlitic steels, the problem was addressed by Toribio et al. (2008). In the macro-fractographs obtained by fatigue and posterior fracture of the wires, both the hot rolled bar and the cold drawn wire exhibit an elliptical crack front , as shown in Fig. 5.

Fig. 5. Crack shape evolutions in steel wires E0 (hot rolled bar) and E7 (cold drawn wire). Steels with intermediate drawing degree exhibit a retardation of fatigue crack growth in the central area of the wire section (Fig. 6) due to the presence of compressive residual stresses in that core area affecting the fatigue crack growth (Toyosada et al ., 1997, Vasudevan et al ., 2001; Cai and Shin, 2005) and producing a gull -shaped crack front. In the hot rolled bar (not cold drawn at all) and in the fully drawn wire (commercial prestressing steel wire which has undergone a stress-relieving process) the retardation effect ( gull -shaped crack front) does not appear (cf. Fig. 5).

Fig. 6. Crack shape evolutions in intermediate steps (from left to right, steels E2, E4 and E6). 4. Reverse approach to the concept of crack paths : A Scientific Tribute to James R. Rice

The reverse approach ( crack paths versus paths near cracks ) provides the idea of paths in cracks, or paths near cracks, in the framework of the mathematical formulation of a path independent integral near a crack tip (a path near a crack, and an integral whose value is independent of the particular path), so that this paper is a heartfelt tribute to James R. Rice and his J-Integral . 5. Conclusion This paper advances towards a new concept of crack path, including three innovative approaches:

(i) A multi-scale (macro- & micro-) approach: crack path profile . (ii) A multi-perspective approach: crack aspect ratio evolution . (iii) A reverse approach: crack paths versus paths near cracks.