13th International Conference on Fracture June 16–21, 2013, Beijing, China -5- meshes respectively. The regular mesh contains 24000 square shell elements, 7600 interface elements and 24682 nodes. The element size of the mesh is 0.5 mm¯0.5 mm. The irregular mesh shown in Fig. 5 contains 29320 shell elements, 9296 interface elements and 30006 nodes and the nominal element size of which is 0.5 mm. The curves of load vs. deflection by FE analysis, experiment and analytical solutions were presented in Fig. 6, in which the analytical solution is obtained using a corrected beam theory for mode I case. It can be seen that the coincidence of the simulation results between regular and irregular meshes is very well. The predicted strength is closed to the experimental one. The simulated result of load vs. deflection curve achieves good agreement with experimental and analytical results. The mesh with the new interface elements is easy to be built for the same geometric form as brick elements. The longitudinal stress contours are exhibited in Fig. 7 on the deformed meshes at different moments of loading. The scaling factor of the deformation display is 4.0. 0 2 4 6 8 0 10 20 30 40 50 60 70 80 Applied load (N) Displacement (mm) Experimental result Regular mesh(shell model) Irregular mesh(shell model) Analytical solution Status A Status B Status C Figure 6. Results comparison for DCB Figure 7. S11 stress contour of DCB specimen at different status (regular mesh) 4. Conclusions A combined interface element is proposed to be used together with shell element to establish finite element model of the shell structures and conduct interfacial fracture analysis. The new interface element comprised of a zero-thickness cohesive zone element and a number of rigid beam elements. The shell thickness offset and nodal translational and rotational degrees of freedom are considered by the use of rigid beams. A bilinear constitutive law is applied to the new interface element. The modeling technique greatly reduces the model scale as compared with the model built with solid elements. By the simulations of double cantilever beam test, good agreements are achieved among the results of simulation, experiment and analytical solution. References [1] E.F. Rybicki, M.F. Kanninen. A finite element calculation of stress intensity factors by a modified crack closure integral. Engineering Fracture Mechanics, 1977, 9: 931-938. Initial Crack Region Initial Crack Region Initial Crack Region (A) Status A (b) Status B (c) Status C
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