Issue 38

S. Tsutsumi et alii, Frattura ed Integrità Strutturale, 38 (2016) 244-250; DOI: 10.3221/IGF-ESIS.38.33 247 Constitutive equations of the material Preliminary single-quadrature point numerical code was created implementing the constitutive equations of the subloading surface model coupled with the damage variable to verify the material response. Numerical simulations were performed considering cyclic loading with a constant stress range and loading ratios ( R = -1/0/0.5), and two analyses were performed where the loading amplitude varied during cycles. The algorithm was used in commercial FE code (Abaqus/Standard ver. 6.14-4) via a subroutine for studying real steel component behavior. Fig. 5 shows the geometry and mesh adopted in the FE simulations of a non-load carrying fillet joint test, where the welded toe shape is assumed as rounded. For simplicity, 1/4 of the whole bar was modelled owing to the double symmetry of the sample. A mesh refinement (0.05 mm minimum element dimension) was performed around the welding toe, where the largest stress concentration tends to appear. A total of 4262 plate elements (plane strain assumption) were used in the discretization, amounting to a total of 4356 nodes. The numerical simulations were conducted for cyclic loading with a constant amplitude ( R = 0, σ max = 180 MPa), and four combinations of variable loading amplitudes. Figure 5 : Model and boundary conditions used. Material σ max changes every 100 cycles ( R = -1) Name Order of loading [MPa] H d = 1 [cycles] mat.UpDown 303 →340→303→268→303 1054 mat.DownUp 303 →268→303→340→303 1178 Weld joint σ max changes every 25 cycles ( R = 0) Name Order of loading [MPa] D = 1 [cycles] H d = 1 [cycles] W.UpDown1 180→300→180→100 15,095 408 W.UpDown2 300→180→100→180 14,567 389 W.DownUp1 180→100→180→300 15,568 422 W.DownUp2 100→180→300→180 15,124 409 Table 2 : Variable loading conditions and crack initiation life