13th International Conference on Fracture June 16–21, 2013, Beijing, China -3- equilibrium principle. Analytical relations can be extracted in specimens of complex configuration using SSM method. No analytical relationship has been reported in papers for obtaining the stress intensity factors for the CCNSCB specimen and it is rather difficult using experimental or numerical methods. Every slice in CCNSCB is considered as a SCB with the straight crack. In fact, the central portions of CCNSCB with the straight crack front width b need not to be cut into thin slices. Since analytical solutions exist for the calculation of the stress intensity factor in the SCB specimen with a straight crack, an equation can be written for each portion and also for the middle section and finally with combining the stress intensity factors of these two sections, the formula for calculating the dimensionless stress intensity factor of the CCNSCB is obtained. More details on the procedure can be found in [13], but the general equation is written as: 1 * 1 2. ( ) . ( ) α β α − = ⎡ Δ ⎤ =⎢ + ⎥ ⎣ ⎦ ∑ N i i b B t B Y Y Y (4) where Δt and N are the thickness of each slice and the number of slices, respectively. Y is the dimensionless stress intensity factor of SCB with straight crack and i ia R =α where ia is the crack length of ith slice. Parameters Δt , αi and b are related to the dimensionless crack length ( α). Figure 2. Slice synthesis method for CCNSCB specimen β reflects the difference between the stress intensity factor of the central part and that of the lateral part. β can be calculated as: )5 ( 1 1 α α β γ α − = + B The important and difficult part of the SSM method is the calculation of β. By comparing the results of three-dimensional finite element analysis, Wang et al. [13] predicted the coefficient γ to be 0.9 in CCNBD specimens. Here, we employed SSM method in the CCNSCB specimen used previously by Kuruppu [8] and by comparing the results of SSM with the results of kuruppu [8], γ=0.5 was found an appropriate value. Thus, to find the minimum dimensionless stress intensity factor in CCNSCB, it is sufficient to minimize equation (4) as: )6 (
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