On the computation of total strain energy release rate in surface cracks under cyclic loading

Abstract

Computation of strain energy release rate in surface cracks plays an important role in determining the preferred propagation pattern (PPP). Semi-elliptical cracks, growing due to cyclic loading of plates, undergo significant shape change during the propagation process. These growing cracks change their shapes such that they follow preferred propagation 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 ratios ( R b ) is presented and discussed. Some initial analyses have already been presented in a prior paper [D. Gera and M. A. Mahmoud, Engng Fracture Mech. 41, 515–528 (1992)], which discussed the energy variation trends in the fatigue growth of surface cracks under tension and bending.