A TRANSGRANULAR FATIGUE-CRACK GROWTH-MODEL BASED ON RESTRICTED SLIP REVERSIBILITY

This article presents a transgranular fatigue crack growth model based on a restricted slip reversal process where the transgranular crack g rowth rate is related to the cyclic plastic strain range ahead of the crack tip. Upon applying deformation and fracture kinetics theories, a physically based constitutive law for fatigue crack growth rate is de rived. In the absence of any environmental contributions to crack grow th, the model takes the form of the Paris equation with a power law ex ponent of 3 at positive R values. The model expresses the fatigue crac k growth rate explicitly in terms of material properties, such as yiel d strength. work-hardening coefficient, microstructural quantities suc h as activation energy, activation volume, and work factor, as well as test constraints such as DELTAK and R. The absence of a fatigue thres hold is predicted for test conditions where environment does not influ ence the crack growth process and the material microstructure remains stable.