Issue 48

F. V. Antunes et alii, Frattura ed Integrità Strutturale, 48 (2019) 676-692; DOI: 10.3221/IGF-ESIS.48.64 678 Figure 1 : Geometry and loading of CTS specimen. Figure 2 : Mixed-mode loading device (  =60º). A 2D analysis was developed numerically, assuming a plane strain state. Due to lack of symmetry in terms of loading and geometry of the crack, the whole specimen was analyzed. The boundary conditions considered are presented in Fig. 3, and intend to avoid rigid body movement without affecting the global rigidity of the specimen. The material was assumed to be homogeneous, isotropic with linear elastic behaviour. The elastic properties considered were E=74000 MPa and  =0.33. The physical model was analyzed using CosmosM 2.0, a commercial finite element package. Quadrilateral isoparametric elements with 8 nodes were considered. Singular elements with nodes at quarter-point positions were considered at the crack tip. Fig. 4 presents the finite element mesh considered for x=52.5 mm, y=0 and  =20º. The crack kinks at x=0, however the crack slope relevant is that at the crack tip. Location of (x, y) Cartesian coordinates and slope at the crack tip (  ) are defined in Fig. 1. The meshes had 4804 elements and 15075 nodes. The geometry of crack remote from its tip does not influence K values. Si Other Tensile strength,  UTS [MPa] 300  2.5 Yield strength,  YS [MPa] 245  2.7 Elongation,  r [%] 9 Cyclic hardening exponent, n' 0.064 Cyclic hardening coefficient, K' [MPa] 443 Fatigue strength exponent, b -0.0695 Fatigue strength coefficient,  ' f [MPa] 485 Fatigue ductility exponent, c -0.827 Fatigue ductility coefficient,  ' f 0.773 Table 2 : Mechanical properties of the 6082-T6 aluminium alloy  3  . The accuracy of numerical predictions was checked by comparing with literature solution presented in Appendix A for  =0º  16  . Differences lower than 2% were obtained for K I and K II which is a good indication for the accuracy of the results. A numerical analysis was also done using MARC-Mentat 2000 considering square elements with 8  8  m at the crack tip for a total number of 6700 elements and 20727 nodes. Mode I predictions were similar to CosmosM results.