Issue 18

S. Marfia et alii, Frattura ed Integrità Strutturale, 18 (2011) 23-33 ; DOI: 10.3221/IGF-ESIS.18.03 30 Figure 3 : Numerical results obtained adopting the Model 1. a) Mechanical response of whole structure; b) Mechanical behavior of interface; c) Body tensile response. From Fig. 4, it is observed that in the Case 3 the body does not develop damage and for this reason the softening response of the mechanical system depends only on the evolution of the damage interface. With reference to Fig. 3 and Fig. 4, it appears evident that in the Case 3 the analyses, performed adopting the proposed coupled interface formulations (Model 1 and Model 2), lead to the same numerical results. In the Case 1 and in the Case 2, the body damage occurs before the interface one; the maximum tensile stress is lower than the value obtained in the Case 3 and it is equal to the tensile strength of the body, as it is achieved in the Model 1. In the Case 1 and 2 the softening response, obtained adopting the Model 1 and 2, presents some significant differences. In fact, the results carried out adopting the Model 1, show that the softening behavior is strongly influenced by the evolution of the body damage until the interface damage becomes higher than the body one. From this point of the analysis, the body damage does not increase anymore and the softening behavior is only governed by the evolution of the interface damage. On the other hand, in the results obtained considering the Model 2, the softening behavior is strongly influenced by the body damage during the whole detachment process, also when the interface damage becomes to develop and the body damage does not evolve anymore. Thus, the degradation process results faster for the Model 2 than for the Model 1. v [mm]  [MPa] 0 0.05 0.1 0.15 0.2 0.25 0 1 2 3 4 5 Case 1 Case 2 Case 3 s N [mm]  [MPa] 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0 1 2 3 4 5 Case 1 Case 2 Case 3 Interface constitutive law 0 0.5 1 1.5 2 2.5 3 3.5 x 10 -3 0 1 2 3 4 5 Case 1 Case 2 Case 3   [MPa] N a) b) c)