ON THE COMPUTATION OF TOTAL STRAIN-ENERGY RELEASE RATE IN SURFACE CRACKS UNDER CYCLIC LOADING

Computation of strain energy release rate in surface cracks plays an i mportant role in determining the preferred propagation pattern (PPP). Semi-elliptical cracks, growing due to cyclic loading of plates, under go significant shape change during the propagation process. These grow ing cracks change their shapes such that they follow preferred propaga tion patterns. It is shown that for a given cyclic-loading field, the PPP represents an upper limit on the aspect ratio of any surface crack growing due to this cyclic loading. Numerical integration techniques have been employed to compute total strain energy (TSE) release rate. The variation of TSE with crack depth (a/t) for different bending rati os (R(b)) is presented and discussed. Some initial analyses have alrea dy been presented in a prior paper [D. Gera and M. A. Mahmoud, Engng F racture Mech. 41, 515-528 (1992)], which discussed the energy variatio n trends in the fatigue growth of surface cracks under tension and ben ding.