13th International Conference on Fracture June 16–21, 2013, Beijing, China -6- For the C(T)-BM specimen, when an exponential shape traction separation law is adopted, good agreement between the numerical and experimental results can be obtained in terms of FCOD and JR curves when T0=1180 MPa and Г0=18.5 N/mm are applied (Fig. 7). The trapezoid shape traction-separation law is also adopted to study the fracture behavior of the C(T)-BM specimen. As can be found in Fig. 8, good agreement between the numerical and experimental results can be obtained in terms of FCOD and JR curves when T0=1180 MPa and Г0=23.6 N/mm is used. This means that both exponential and trapezoid shape traction separation law can predict the crack propagation of C(T) specimens obtained from the BM well when different parameter sets are chosen. (a) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 0 10 20 30 40 50 Exponential softening F (KN) COD (mm) experiment--BM Cohesive--Τ 0=1180 MPa, Γ 0=17 N/mm Cohesive--Τ 0=1180 MPa, Γ 0=18 N/mm Cohesive--Τ 0=1180 MPa, Γ 0=18.5 N/mm (b) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 0 100 200 300 400 500 Exponential softening,T0=1180 MPa experiment--BM Cohesive--Γ 0=17 N/mm Cohesive--Γ 0=18 N/mm Cohesive--Γ 0=18.5 N/mm J-Integral (N/mm) Δa (mm) Fig. 7: Comparison of experimental and numerical (a) force vs. Crack Opening Displacement (COD) curves, and (b) fracture resistance curves for C(T) specimens with initial crack located in the BM when an exponential shape of the traction-separation law is adopted. (a) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 0 10 20 30 40 50 Trapezoidal softening, Τ 0=1180 MPa experiment--BM Cohesive--Γ 0=23.8 N/mm F (KN) COD (mm) (b) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 0 100 200 300 400 500 Trapezoidal softening, Τ 0=1180 MPa experiment--BM Cohesive--Γ 0=23.8 N/mm J-Integral (N/mm) Δa (mm) Fig. 8: Comparison of experimental and numerical (a) force vs. Crack Opening Displacement (COD) curves, and (b) fracture resistance curves for C(T) specimens with initial crack located in the BM when trapezoid shape traction separation law is adopted. For the C(T)-FZ, as what has been observed in Fig. 2, the FZ showing more brittle behavior, a linear decreasing traction-separation law is required for the cohesive model. The numerical FCOD curve matches the experimental one well before the sudden rupture, showing the cohesive model
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