applied fracture mechanics

Interacting Cracks Analysis Using Finite Element Method 371lower a/W . The CIL and CUL also differ with different b/a . From Fig. 3, the identifiedCUL is at a/ W 0.1 and CIL approximately at a/ W 0.5 .32.82.62.4b/a = 3.0Brown & Strawley (1966)Present (ct1)Present (ct2)Jiang et al. (1990)IntersectionpointCrack interaction factor, γ I2.221.81.61.4Intersectionpointf I , ref , BS1.21 I , in , Ji ( , )I , in, D I , in, D, ct1 I , in, D, ct2Figure 3. Variation of I , in,D against a/W for b/ a 3.0Another significant improvement of present I , in,Dis the moving intersection point asa/W decreases for every b/a , as shown in Fig. 3-6. From Fig. 4, the moving intersectionpoint can be noticed moves from a/ W 0.1 to a/ W 0.075 . The moving intersection pointexhibits similar prediction trend of, ,I in D. The intersection point also can be denoted as thecrack unification limit (CUL) point, which indicates the starting point of strong interactionregion start approximately at a/ W 0.07 .The intersection point is also observed to move from a/ W 0.075 for b/ a 2.5 ,a/ W 0.06 for b/ a 2.5 , a/ W 0.05 for b/ a 2.0 and a/ W 0.05 for b/ a 1.5 , asshown in Fig. 4-6. It means that the CUL is not in a fix limit, it exist in dynamic conditionwhich depends on crack interval ratio b/a . Conversely, the I , in,Jiprediction modeloverruled the FFS codes because it does not lead to a single independent or combined crackbecause of not having any intersection point. The intersection point could not be defined by prediction model.I , in,Ji0.80.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5Crack- to-width ratio , a/W