Study of Fatigue Crack Growth Rate of AA6061 at Different Stress Ratios

摘要

In the present work, fatigue crack growth behaviors of AA6061 are studied at different stress ratios, R = 0.1, 0.5 and 0.9. The fatigue crack growth rate and stress intensity factors at steady-state regime were determined by fatigue test on compact tension specimens. Fatigue tests were performed according to ASTM standards using Biss 25-kN, servo-hydraulic testing machine with graphic interface and auto-calibration. Lower fatigue crack growth rate as well as a higher fatigue crack growth threshold for stress ratio, R = 0.1, was observed and compared to R = 0.5 and 0.9. The dependency of crack growth on stress ratio is also modeled based on Walker approach, and Walker exponent was identified to model the dependency of fatigue crack growth rate of AA6061-T6 on stress ratios. The mathematical model developed shows 95% adj R square, which is acceptable.