Issue 18

V. Di Cocco et alii, Frattura ed Integrità Strutturale, 18 (2011) 45-53; DOI: 10.3221/IGF-ESIS.18.05 48 Furthermore, the gross engineering strain has been correlated to the effective engineering strain by a finite element simulation as reported in the following section. a) b) Figure 3 : Isothermal stress-strain curve of the investigated alloy carried out at room temperature (T=298k): a) monotonic loading to fracture and b) loading-unloading cycle. Figure 4 : Uniaxial miniaturized specimens. R ESULTS AND DISCUSSION inite Element Analyses (FEA) were carried out in order to correlate the gross engineering strain (  g ) to the effective engineering strain (  e ), i.e. to the experimentally measured engineering stress-strain curve of Fig. 3. To this aim a 2D FE model was made, by using a commercial software, to simulate the testing conditions of the miniature specimen, and a standard non-linear solutions were adopted to model the complex stress strain behavior of the material illustrated in Fig 3. In particular, a quarter of the miniature specimen was modeled, due to symmetric geometry and boundary conditions, together with a part of the loading frame, and contact conditions were defined between them in order to reproduce the testing conditions as close as possible to reality. Fig. 5.a illustrates the FE mesh which consists of about 800 4-noded plane stress quadrilateral elements while Fig. 5.b shows the equivalent stress fringes corresponding to the maximum elongation of the specimen during cyclic tests (  =2.4 mm and  g =15%). F