13th International Conference on Fracture June 16–21, 2013, Beijing, China 7 uniform shear stress when 0 0.5 a . It can be found that the normalized DSIFs increases quickly with time up to the peak, and then the oscillations gradually decay until corresponding steady-state value. The peak time of DSIFs appears more or less for 2 01 / 1.5 c t a , and then exhibit a slight oscillation after reaching a peak. The peak values of 0 ( , ) / II K a t k and 0 ( , ) / II K b t k increase or decrease with an decrease of regardless of the value of 0a . Figure 6. The influence of crack orientation angle on the DSIFs under crack surface shear ( 0 0.5 a ) Figure 7. The influence of crack orientation angle on the DSIFs under crack surface shear ( 0 0.5 a ) Based on the premise that the peak dynamic stress intensity factors may induce brittle fracture, such peaks are plotted in the sequel as a function of the crack orientation angle in Figs. 8-9. For 0 0.5 a , as shown in Fig.8, the peak value of the mode I DSIFs in crack tip a increases with an decrease of , while the peak value of the mode I DSIFs in crack tip b increases with an increase of . For 0 1.0 a or 1.5, the peak value of the mode I DSIFs in crack tip bincreases with , going through the maxima at some angle, and then begin to decrease at the enlarged crack obliquity,
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