On the hysteretic nature of variable-amplitude fatigue crack growth

Local Stress–Strain (LSS) approach as applied in notch fatigue analysis is extended to the fatigue crack in order to simulate the effect of variable-amplitude loading on near-tip stress and strain. Simulated near-tip stress–strain response appears to explain load sequence sensitivity of near-threshold fatigue crack growth. This observation is supported by fractographic evidence of near-threshold variable-amplitude fatigue crack in an Al–Cu alloy under closure-free conditions.