INFLUENCE OF STRESS RATIO ON FATIGUE CRACK PROPAGATION BEHAVIOR OF AZ31 MAGNESIUM ALLOY

Although the resistance to fatigue crack propagation (FCP) is one of the most important design criteria for structural materials, there have been limited studies on the FCP behavior of magnesium alloys, particularly in the near-threshold region. In the present study, the influence of the stress ratio on the FCP behavior of an AZ31 alloy was investigated in conjunction with crack closure phenomena. FCP experiments were carried out under constant load amplitudes at ambient temperature. The Delta K-th value of the AZ31 alloy was affected by the change in stress ratio. The Delta K-th value decreased with increase in the stress ratio, while the Delta K-eff,K-th showed an almost constant value regardless of the stress ratio. The crack closure levels were high in the near-threshold region and decreased with increasing FCP rates. It was found that the crack closure effect diminished in the high stress ratio region.