ON THE CALCULATION OF CLOSURE-FREE FATIGUE-CRACK PROPAGATION DATA IN MONOLITHIC METAL-ALLOYS

A computational method is described for the determination of Delta K-b, corresponding to a fatigue crack growth rate of b/cyc, where b is the Burgers vector for a monolithic metal alloy. Delta K-b is found to be numerically equal to E root b for the case of closure-free crack growth behavior. Given that the closure-free FCP rate of many monolithic metals varies with Delta K-3, the growth rate of metal alloys at Delta K greater than or equal to Delta K-b is given by da/dN=(Delta K/E)(3)(1/root b). Excellent agreement is found between experimental and computed FCP data for the case of monolithic metal alloys. The limits of these relations for metal-matrix composites and ceramics are discussed.