Stress intensity factor K and the elastic T-stress for corner cracks

The stress intensity factor K and the elastic T-stress for corner cracks ha ve been determined using domain integral and interaction integral technique s. Both quarter-circular and tunnelled corner cracks have been considered. The results show that the stress intensity factor K maintains a minimum val ue at the mid-plane where the T-stress reaches its maximum, though negative , value in all cases. For quarter-circular corner cracks, the K solution ag rees very well with Pickard's (1986) solution. Rapid loss of crack-front co nstraint near the free surfaces seems to be more evident as the crack grows deeper, although variation of the T-stress at the mid-plane remains small. Both K and T solutions are very sensitive to the crack front shape and cra ck tunnelling can substantially modify the K and T solutions. Values of the stress intensity factor K are raised along the crack front due to crack tu nnelling, particularly for deep cracks. On the other hand, the difference i n the T-stress near the free surfaces and at the mid-plane increases signif icantly with the increase of crack tunnelling. These results seem to be abl e to explain the well-observed experimental phenomena, such as the discrepa ncies of fatigue crack growth rate between CN (corner notch) and CT (compac t tension) test pieces, and crack tunnelling in CN specimens under predomin antly sustained load.