13th International Conference on Fracture June 16–21, 2013, Beijing, China -5- crack tip element deformation is very large. Hence, to detect the crack tip element, the following criterion is adopted in the present paper. 1 t ε ε > (13) In which 1εis the first principle eigenstrain value of strain tensor. 4 . simulation example To show the validation of the present method, a three-point-bending(TPB) test reported in[6] is presented simulated. The material parameterrs provided by [6] are: the Young’s modulus 30.5 E= GPa, Poisson ratio 0.2 ν= ; tensile strength 3.8 tf = MPa and fracture energy 62.5 f G = N/m. With these parameters, the calibrated parameters are 3 0.2486 10 tε − = × and 3 2.486 10 cε − = × . The specimen, boundary conditions and mesh configuration are shown in Fig.3. The displacement controlling loading scheme is adopted. Each step is 0.002486mm. P Fig.3 The specimen and boundary conditions of TPB test. 0.075 D= m and the sample thickness is 0.05m. The simulation results are shown in Fig.4 and Fig.5. From Fig.4, it is seen that crack propagates gradually with loading increasing. The propagation pattern agrees with the observation in the experiment[6]. Fig.5 shows the comparison between the experimental and the simulated results. From Fig.6 it is seen that the present method can well predict the fracture propagation, free of the element size sensitivity problem.
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