Research Of Ellipsoidal Micropore For Fatigue Crach Initiation

In all kinds of casting defects on the fatigue life of materials, micropore is the mostone. The method of finite element simulation use in this paper, to find out the impact ofdifferent variables of the flat ellipsoidal micropore around stress and strain. And as a basisfor this, to analysis the affect of fatigue by micropore.The three-dimensional finite element model is established to find out six differentvariables, which has the effect in geometric relationships between flat ellipsoidal andmaterials. Classify the different variables for further research.Analysis when the different variables changes alone, the impact of the stress fielddistribution around the micropore. The size of two variables are ellipticity andCompression ratio. When the ellipticity larger, the greater the stress concentration factor.When the compression ratio more hours, the greater the stress concentration factor. Andwhen these two variables change the same time, they are independently of each other.Secondly, the three different angle has the similar impact of the stress field. They willreduce the degree of stress. And they are independently of each other too. Lastly, is thedepth. When micropore tangent to the surface, stress concentration factor becomemaximum. The Change of depth has very large impact on stress field around micropore.The research on strain is based on the research of stress. According to the law ofcorrect Coffin-Manson, discussed the impact of fatigue with size and depth. Found whenthe ellipticity larger and compression ratio more hours, the initiation life of fatigue crackshorter. The study of depth have shown that, the deeper the micropore in materials, theshorter the life of the initiation fatigue crack.