Issue 49

R. Suresh Kumar et alii, Frattura ed Integrità Strutturale, 49 (2019) 526-535; DOI: 10.3221/IGF-ESIS.49.49 530 Figure 5: Mode-I crack initiation stress (MPa) distribution in the plate specimen Figure 6: Mode-I crack initiation stress (MPa) distribution in the pipe bend specimen F ATIGUE CRACK GROWTH (FCG) SIMULATION he FCG simulation for both the plate, as well as pipe bend specimen, has been performed using the FRANC3D software. This software is adopted as it can simulate 3-D FCG analysis together with the general-purpose Finite Element (FE) solvers. The magnitude and direction of the crack growth depend upon the stress intensity factor (SIF) and the local ‘Kink angle’ respectively. Kink angle is defined as the angle that maximises the ratio between maximum SIF (K I max ) computed based on the maximum tensile stress at the crack front and the directionality dependent material resistance to crack growth (K c  ). The convergence of the crack growth simulation is decided by maximising the ratio K I max /K c  . The direction of crack propagation is determined based on the ‘Kink angle’ measurement at the base of the crack front. The SIF is computed based on the M-integral concept at mid-side nodes along the crack front using the maximum tensile stress [12]. The sub modelling concept, deployed in the FRANC3D, helps in local mesh-refinement at the cracked portion of the component geometry for efficient computation. Higher mesh density is provided for a shallow crack. Also, a pattern of elements with controlled mesh size and shapes are placed around the crack front for accurate estimation of SIF. T