13th International Conference on Fracture June 16–21, 2013, Beijing, China -4- versus the diameter reduction curve coincides with the experimental one until crack initiation, where the experimental curve drops suddenly. At this point, the maximum value of stress distribution over the cross section of the specimen is determined from the simulation and set equal to the cohesive stress T0. After the comparison of simulation and experiment for the BM, T0=1180 MPa was found. The exponential and trapezoid traction-separation laws are used to study the fracture behavior of the C(T)-BM specimen. Because the structure shows symmetry with respect to the crack plane, only half of the C(T)-BM specimen is modeled, loading is defined on the loading point (Red point) by the displacement, the finite element mesh and boundary conditions are shown in Fig. 5. Fig. 6 shows the detailed mesh around the initial crack tip. (a) 0 10 20 30 40 50 F (KN) CT--BM CT--FZ CT--HAZ 3.0 2.5 2.0 1.5 1.0 0.5 0 COD (mm) (b) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 0 100 200 300 400 500 C(T)--BM C(T)--HAZ J-Integral (N/mm) Δa (mm) Fig. 2: Experimental (a) Force vs. Crack Opening Displacement (COD) and (b) fracture resistance JR curves of compact tension (C(T)) specimens with the initial crack located in the BM, in the middle of the FZ and at the interface between the FZ and the HAZ, respectively. (a) (b) Fig. 3: (a) Axisymmetric finite element mesh and boundary conditions of the notched round specimen and (b) detailed mesh. Notch radius R=4 mm Symmetry plane Loading direction Rotation axis
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