Volume 33, Issue 3 (May 2005)
A Model for Mixed-Mode Fatigue
The initial use of fracture mechanics to characterize crack growth by fatigue was by Paris. Since then, the application of fracture mechanics to fatigue problems has become routine. In the case of fatigue under mode I loading, the method of analysis, under conditions of constant amplitude and small-scale yielding, is well established. However, apart from the conditions of variable amplitude loading, large scale yielding, and short existing cracks, the procedures for analyzing fatigue under mode II and mixed-mode loading still have not been resolved. A general model, applicable to pure and mixed-mode fatigue crack growth, has been developed based on the unified model. The formulation of the general model is in terms of a power law relationship that is an extension of Paris. The experimental procedures for the measurement of mode II and mixed-mode fatigue crack growth, and verification of the proposed fatigue model, are dealt with herein. The verification has been confined to conditions of constant amplitude and small-scale yielding.