PSI - Issue 39

Lucia Morales-Rivas et al. / Procedia Structural Integrity 39 (2022) 515–527 Author name / Structural Integrity Procedia 00 (2019) 000–000

517 3

ℎ = ΔK th � ( 2 + 0 )

(3) where is the reference dimension of the defect or crack in the component, and 0 continues to be the El-Haddad parameter obtained by Eq. 2. The shape factor, α , comprised in Eq. 3, is necessary in analyses of real components and encompasses three significant parameters, namely component geometry, the defect size and the defect position [Atzori, et al.(2003, Atzori, et al.(2005)]. This solution (Eq. 3) differs from the well-known Murakami(1985) equation, which is frequently employed as an approximate equation with a high accuracy for a variety of cracks, initiated at small defects. Murakami´s theory, as opposed to Atzori´s, applies when the shape of the defect/crack within the component is irrelevant. Atzori´s approach, instead, includes the fatigue limit analysis of different geometries having a notch or crack, not necessarily confined to the centre of the specimen and subjected to the remote load, and can be used for different locations and sizes of the defects within the finite component dimension. A major result from Atzori´s work is the proposal of a normalized dimensionless parameter regarding the defect or crack size: 2 0 . Herein, it should be noted that a normalized (or universal) version of the diagram generated by Atzori has been validated for a range of materials including structural steels, carbon steels, special alloy steels and aluminium alloys, with different notches’ and defects’ geometries such as V-shaped notch in a cylindrical bar, double lateral notch in a flat plate, hole in a flat plate, and drilled hole in a cylindrical bar [Atzori, et al.(2003, Atzori, et al.(2005)]. The value = 0.1 0 2 .can be interpreted as the limit between microstructurally-short and physically-short cracks (see this value in Fig. 1, which applies for the solid red curve, corresponding to Eq. 3 with =1). Additionally, a long crack solution, when 0 is negligible with respect to , can be easily deduced from Eq. 3: ℎ = ΔK th √ (4) In Fig. 1 it can be observed that for = 10 0 , the curve corresponding to Eq. 3 with =1 (solid red line) starts being well described by Eq. 4 (line 2). The normalized value = 10 0 2 can be, thus, considered as a realistic limit between the (physically) short-crack regime and the long-crack regime.