Issue 49

R. Suresh Kumar et alii, Frattura ed Integrità Strutturale, 49 (2019) 526-535; DOI: 10.3221/IGF-ESIS.49.49 531 These elements take the form of generalised cylindrical tubes with the crack fronts serving as the axes. 3-D Wedge shaped elements are placed immediately adjacent to the crack fronts, and rings of brick elements surround the crack front. The magnitude of SIF depends upon the crack dimensions, applied stress and other geometrical parameters. The local direction of crack advancement is determined based on the local ‘kink’ angle. The FCG simulation is performed as per the Paris law, defined as da/dN = C (  K) m , where da/dN is in m/cycle,  K is in MPa  m and C & m are the respective FCG material parameters. The values of C and m used for the plate geometry are 1.2 x 10 -8 and 2.84, respectively [4]. The corresponding values for the plate geometry are 3.982 x 10 -12 and 3.188, respectively [5]. The results of the FCG analysis are presented below. FCG on Plate Specimen For the plate specimen, the initial elliptical surface crack length (2c 0 ) is 80 mm, and the crack depth (a 0 ) is 2 mm. The locations A and B in Fig.7 represent the crack surface location (crack length ‘c’ direction) and the deepest crack location (crack depth ‘a’ direction). The orientation of the initial crack is along the X-direction (ref. Fig. 7) such that the applied bending stress will enhance the mode-1 crack propagation. The finite element model of the cracked geometry is shown in Fig.7. There are 245964 elements in the specimen. It houses a combination of the 3D tetrahedron, hexahedron and wedge elements. Figure 7: FE sub-model of the cracked plate geometry Figure 8: SIF variation for plate geometry at the critical location - B