Study on Fatigue Behavior Of Magnesium Alloy to Establish A standard Testing Method

摘要

The fatigue specimen shape with smaller gage diameter and larger radius at the fillet position is recommended to avoid the fracture at the gripping part under high humidity condition.Low fatigue strength is shown in a die-cast material because inherent flaws due to manufacturing process play as a fracture origin.Humidity affects on the fatigue property of a magnesium alloy significantly. Testing environment must be controlled in a constant condition during the fatigue test by using an environmental chamber, for example. It is recommended that in case of that if the test can not be carried out under the constant environment condition, the environmental condition must be shown with the data of the fatigue test. The knee in S-N curves is appeared under low humidity condition. However, fatigue strength continuously decreases under high humidity condition. It is necessary to determine the fatigue strength at a certain number of cycles depending on the equivalent of practical design.High surface roughness can induce degradation of fatigue strength. However, the specimen surface polished by an emery paper with grit number of #1500 is considered to be enough for fatigue test. Fatigue limits obtained under different stress ratio lie in one line in fatigue limitdiagram.