Issue 41

J. Toribio et alii, Frattura ed Integrità Strutturale, 41 (2017) 139-142; DOI: 10.3221/IGF-ESIS.41.19 140 crack propagation [9] and stress corrosion cracking (SCC) phenomena [10]. With regard to fatigue, the eccentricity reduces the time to reach the critical situation [11,12] and increasing the instability [13]. In spite of the afore-said references, there is a lack of information in the scientific literature regarding SIF values in points of the crack different from the central one. This paper tries to fill this gap by providing solutions along the crack front. N UMERICAL MODELING he finite element method (FEM) together with the MSC.Marc code was employed to obtain the SIF in cylindrical bars with a non-symmetric external annular crack under tensile loading. The resistant ligament, characterized as a circle, is not centered in relation to the bar axis, so a quarter of the solid was modeled (Fig. 1) with the adequate boundary conditions. Figure 1 : 3D mesh of the bar with a non-symmetric annular crack. Isoparametric hexahedral elements with 20 nodes were used in the computations, and the middle nodes of the first core surrounding the crack tip were shifted to the quarter-point position to reproduce the r –1/2 singularity. In addition, a mesh sensitivity analysis was performed. Figure 2 : Detail of the finite element mesh in the vicinity of the crack tip. The mode I (opening) SIF K I was computed from the J integral by using the expression (for plane strain conditions), I ν = − 2 1 EJ K (1) where E is the Young’s modulus of the material and ν the Poisson coefficient. The geometry of the cracked bar was characterized my means of the following parameters: bar diameter D , maximum crack depth a max , minimum crack depth a min , ligament diameter d , = − − max min d D a a (2) and eccentricity, ε , ε − = max min 2 a a (3) T