Issue 24

G. Cricrì, Frattura ed Integrità Strutturale, 24 (2013) 161-174; DOI: 10.3221/IGF-ESIS.24.17 169 q 1 = 1.25; q 2 = 0.98; q 3 = 1.56 In Fig. 6, the comparison between the FE model of the cell and the homogenized law (1-6) stress-strain curve is reported for the two load cases. 0.00 0.20 0.40 0.60 0.00 400.00 800.00   cell result homogenized law 0.00 0.05 0.10 0.15 0.20 0.25 0.00 500.00 1000.00 1500.00 2000.00   cell result homogenized law Figure 6 : Global cell response compared with eq. (1-6) for the two load cases. Nucleation parameters In the present work, the nucleation parameters have been considered as correction parameters, not directly related to the microstructure. Then, the parameters f N ,  N , S N have been used to fit the experimental-numerical results in the residual strength curve, and their values are reported in the following section. In Fig. 7 the coalescence law (11) has been included into the constitutive law, with the imposed values f c = 0.2 for the starting point, and  = 0.1 for the curve slope, as established before. It is shown that the energy related to the coalescence process is a non negligible part of the total cell energy. 0.00 0.05 0.10 0.15 0.20 0.25 0.00 500.00 1000.00 1500.00 2000.00   cell result homogenized law cohalescence Figure 7 : Global cell response compared with eq. (1) and the coalescence law. R-C URVE DETERMINATION he R-curve calculation procedure has been tested on an M(T) specimen model, which experimental results have been published in [2]. The M(T) specimen used for the residual strength results is made by a 1.28 mm thick 2024 sheet material. The T