13th International Conference on Fracture June 16–21, 2013, Beijing, China -4- 3. Results and Discussion The solution presented in the previous section can provide reliable and accurate prediction of the stress field caused by the dynamic interaction. The method can be used to treat interaction between different defects [8,10,11]. Although only the single crack solution is presented in the previous section, solutions of other single defects can be similarly and easily assembled into Eq. (10). In this section, typical examples are presented to illustrate the dynamic interaction between different defects. The numerical simulation is conducted by solving Eq. (10) and the convergence of the solution has been carefully evaluated. Specifically, numerical results are presented to illustrate the dynamic interaction between a main crack and a second crack or an inhomogeneity. The incident antiplane wave is perpendicular to the crack surface. To evaluate the accuracy of the current method, Fig. 3 shows the static interaction between a circular inhomogeneity and a collinear crack subjected to an initial stress intensity factor (K0). Comparing with the closed form solution (lines) [14] excellent agreement is observed. Figure 3. Static interaction Figure 4. Interacting cracks Fig.4 shows the effect of a collinear crack of length 2a on the normalized stress intensity factor crack of a main crack of length 2c. a/c=0 corresponds to the case of a single crack. Comparing these curves indicates that significant interaction between cracks exists for low frequencies. But the interaction effect is significantly reduced at higher frequencies. Fig.5 shows the result of interaction between a crack and an inhomogeneity. The variation of the normalized stress intensity factor for different crack-inhomogeneity configurations is presented. Unlike the collinear crack case where only amplification effects are observed, when the inhomogeneity, with a higher stiffness, is ahead of crack, the stress field is shielded. i.e. the dynamic stress intensity factor at the main crack attains a value lower than the dynamic single crack solution. Fig.6 presents the result of a similar inhomogeneity with a partially debonded interface near the crack tip, as shown. With the increase of the size of the debonded interface, the stress intensity factor at the crack tip increases and indicates an amplification effect. For high loading frequencies, the interaction effect becomes insignificant because the distance between the crack and the inhomogeneity is much larger than the wave length.
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