Abstract: The paper presents a review of a fatigue life prediction method by using the small-crack theory. The approach is to apply continuum mechanics, the fracture-mechanics-based ΔK analyses, and the crack-closure concept to naturally occurring small cracks and large crack growth, and to make total-fatigue-life predictions solely based on crack growth from the assumed initial materials defects. The methodology has been successfully verified by experiments for a wide variety of aeronautical materials including two high-strength steels: 9310 and 30CrMnSiNi2A, four high-strength aluminum alloys: 7075-T6, 7075-T73 (forged), LC9cs and LY12, and two titanium alloys: Ti-6Al-4V and TC11, and the load types include constant amplitude, Mini-Twist and a helicopter rotor spectrum. Results show that the predicted total fatigue lives are in good agreement with the experimental data. Thus, the feasibility for the establishment of a link between the classical S-N fatigue (safe-life) and the modern damage-tolerance methodologies is demonstrated.

Key words: fracture mechanics, small-crack, fatigue, crack growth, total life prediction