Issue 50

G. Khandouzi et alii, Frattura ed Integrità Strutturale, 50 (2019) 29-37; DOI: 10.3221/IGF-ESIS.50.04 33 Moreover, the crack path after the simulation is shown in (Fig. 4). Stress intensity factor according to (Fig. 5) is also presented in Eqn. (4). Figure 3 : Using displacement extrapolation in order to define stress intensity factor [22]. Figure 4 : Points and direction for displacement extrapolation method and crack path simulation. Figure 5 : Stress intensity factor according to displacement extrapolation.     &    I if y K x r   (4)   6 0     8 * 10 * 0 499032     0.5  Id Id r K K Mpa m       . To verify numerical simulation in this paper, experimental data, CSOD graph, as shown in (Fig. 7) , is obtained and compared with experimental results measured by Chen et al (2009) [19], Dai et al (2010) [20] and Dai et al (2011) [21]. There is a good agreement between curves’ trends of numerical and experimental results. Also, the crack path and crack initiation angle in the X-FEM code is compared and verified with the experimental results of Kalthoff and Winkle (1987) and John and Shah (1990) [10].