13th International Conference on Fracture June 16–21, 2013, Beijing, China -7- can predict the FCOD curve of the C(T)-FZ specimen well, as can be seen in Fig. 9. For the C(T)-HAZ specimen, an exponential traction-separation law is chosen for the cohesive model. Good agreement between the numerical and experimental results can be obtained in terms of FCOD and JR curves when T0=1350 MPa and Г0=16.5 N/mm is used, as can be found in Fig. 10. 0 1 2 3 4 5 6 7 0 10 20 30 40 50 60 Linear softening, T0=1600 MPa experiment--FZ Cohesive--Γ 0=70 N/mm COD (mm) F (KN) Fig. 9: Comparison of experimental and numerical force vs. Crack Opening Displacement (COD) curves for C(T) specimen with the initial crack located in the center of the FZ. (a) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 0 10 20 30 40 50 Exponential softening, T0=1350 MPa experiment--HAZ cohesive--Γ 0=16.5 N/mm COD (mm) F (KN) (b) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 0 50 100 150 200 250 300 350 400 450 500 Exponential softening, T0=1350 MPa experiment--HAZ Cohesive--Γ 0=16.5 N/mm J-Integral (N/mm) Δa (mm) Fig. 10: Comparison of experimental and numerical (a) force vs. Crack Opening Displacement (COD) curves, and (b) fracture resistance curves for C(T) specimens with the initial crack located at the interface between the FZ and the HAZ when an exponential traction separation law is adopted. 4. Conclusions Crack propagation was studied on S355 EBW joints using the cohesive model. Stress-strain curves of respective weld regions are derived from the tensile test results of flat specimens which are obtained from these regions. Three different C(T) specimens, i.e., the C(T)-BM, the C(T)-FZ and the C(T)-HAZ are investigated. Based on the axial stress versus diameter reduction curve of notched round specimens, the cohesive strength T0 is fixed. When choosing different parameter sets for different traction separation laws, the cohesive model can predict the FCOD and JR curve of C(T)
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