13th International Conference on Fracture June 16–21, 2013, Beijing, China -9- 5.2. Analysis of crack paths based on the local approach Figure 10 shows the computed profiles of von Mises equivalent strain range ahead of the successive crack fronts for specimens CCP5a and CCP2a. Since ΔK increases as the crack grows, so does the equivalent strain range. Δεeq rises near side surfaces. According to the fatigue criterion presented above, this should trigger a change in fracture mode (normal to slanted crack growth) there. Figure 10: Profiles of ∆∊eq ahead of various crack fronts for a) specimen CCP5a and b) specimen CCP2a Figure 11 shows the profiles of predicted twist angles. A progressive increase in twist angle as the crack grows is predicted near side surfaces. In some cases, as for the measured twist angles shown on Fig. 1b and 1d, the peak value of θ was not found at the free surface but somewhat inside. Figure 11: Profile of predicted twist angles for a) specimen CCP5a and b) specimen CCP2a The shear lips width, ts, was computed from such profiles, as the width of the part where ≥ °4 θ in average. Figure 12 compares the predicted and measured evolutions of ts. The model qualitatively captures the progressive increase in ts. Figure 12: Predicted and measured evolution of shear lips width. a) ccp5a and b) ccp7a. a) b) a) b) a) b)
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