Issue 41

A. Mardaliazad et alii, Frattura ed Integrità Strutturale, 41 (2017) 504-523; DOI: 10.3221/IGF-ESIS.41.62 520 calibrated based on the Berea sandstone (experimental data of the triaxial compression test), two main conclusions can be drawn. Apart from the authors' hypothesis of a similar mechanical response of Pietra Serena and Berea sandstone, the efficiency of the KCC model for numerical modelling of rock materials, and in particular sandstones, has been evaluated here. Maximum Load [kN] Maximum Displacement [mm] Flexural Strength [MPa] KCC Automatic 3.10 0.137 7.13 KCC Calibrated 3.54 0.337 8.14 LDP 7.07 0.891 16.25 “95% CI” of experimental data [3.1433 - 4.5275] [0.36737 - 0.74223] [7.2530 - 10.7140] Table 9 : The numerical results of the flexural test, and the “95% CI” with respect to the average experimental data. Fig. 15 indicates the comparison of the numerical results and the experimental test after failure. The contour plots represented in Fig. 15a and b represent the “scaled damage measure, δ” and the maximum principal plastic strain at failure, respectively. As can be seen, the SPH particles formed at the instant of failure express the crack patterns observed during the experimental test (see Fig. 15c). Figure 14 : The load-displacement diagram; the numerical results compared to the experimental ones. C ONCLUSION he Four-Point Bending tests were performed based on the protocols of the ASTM standard. The average experimental flexural strength of Pietra Serena was measured as 8.98 MPa and Pietra Serena and Berea Sandstone show similar mechanical properties. The numerical simulations using the FEM-coupled to-SPH method were implemented in conjunction with the KCC and LDP material models. The KCC model showed a significant improvement when the material input parameters were calibrated and directly inserted into the material keyword, instead of the automatic input generator mode. While the LDP material model showed some limitation in analyses of the state of stress in which tensile behaviour is present. The specifications of the KCC calibrated material model are summarized in Tab. 10. Load [kN] T