Some aspects of the energy based approach to fatigue crack propagation

The energy based approach to fatigue crack growth was first proposed by Weertman. This original approach was later modified to take into account the plastic energy dissipated at the crack tip. It has also been proposed that the specific energy to create a unit surface is not a constant and depends upon the crack growth micro-mechanism. Recent studies suggest, on the contrary, that the specific energy is a constant and equivalent to the static energy release rate at rupture. Some studies have shown that the measured plastic energy is much higher than the theoretical estimates in the plastic zone. These aspects are reanalyzed to bring out the salient features of the energy based approach. The advantages of the energy based approach are brought out in the case of variable amplitude fatigue crack growth.