Issue 29

V. Sepe et alii, Frattura ed Integrità Strutturale, 29 (2014) 85-96; DOI: 10.3221/IGF-ESIS.29.09 91 different porosities are illustrated in Figure 3, where the average normal stress versus the average normal strain along the 1 x -direction is plotted. Figure 1 : Porous NiTi SMA periodic unit cell. Figure 2 : Mechanical responses of the porous UCs along 1 x -direction for the first loading history. From Fig. 2 and Fig. 3 it can be pointed out that the constitutive model adopted to reproduce the porous SMA response is able to correctly capture the pseudoelastic effect for both the loading histories characterized by different values of the maximum average strain prescribed at the end of the loading phase. It can be observed that for the homogeneous SMA specimen with no pores (Fig. 2 and Fig. 3) the stress-strain slope occurring during transformation is rather high due to the fact that the analyses are performed under plane strain conditions. Moreover it can be remarked that for both the loading histories the value of the maximum average normal stress along the 1 x -direction ( max 11  ), reached at the end of the loading step, decreases for increasing values of porosity. 0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02 -200 0 200 400 600 800 1000 1200 1400 Vv=0% Vv=5% Vv=10% Vv=20% Vv=35% Vv=45% Vv=55%   11 MPa  11 