Issue 48

F. V. Antunes et alii, Frattura ed Integrità Strutturale, 48 (2019) 666-675; DOI: 10.3221/IGF-ESIS.48.63 672 Figure 6 : Variation of plastic CTOD range with crack growth (a) R n =1 mm. (b) R n =2 mm. (c) R n =4 mm. (d) R n =8 mm. D ISCUSSION he present study involves two topics of major relevance for FCG, which are notches and short cracks. For short crack, the hypothesis of small-scale yielding may be violated, therefore the use of plastic CTOD instead of  K is of major importance. The stress concentration associated with the notch reinforces this need. In fact, Miller  25  suggested the use of elastic-plastic fracture mechanics to analyse short fatigue crack growth. The increase of crack length produces several effects: - the increase of the distance to the notch and consequent reduction of stress concentration. - the increase of crack length and, therefore, of crack tip stresses and  p . - the increase of crack closure as the plastic wake is formed. This is more relevant for plane stress state. It reduces the effective load range and therefore  p . The crack closure concept is widely used to explain the short crack behaviour  26,27  . 0 0.2 0.4 0.6 0.8 0 0.5 1 1.5 2  p [  m] x n [mm] Plane stress Plane strain 0 0.2 0.4 0.6 0.8 0 0.5 1 1.5 2  p [  m] x n [mm] Plane stress Plane strain 0 0.2 0.4 0.6 0.8 0 0.5 1 1.5 2  p [  m] x n [mm] Plane stress Plane strain 0 0.2 0.4 0.6 0.8 0 0.5 1 1.5 2  p [  m] x n [mm] Plane stress Plane strain T (a) (b) (c) (d)