Fatigue Life Prediction Of Functionally Graded Material

Security analysis of functionally gradient materials (FGMs) has attractedlarge attention, as they are finding their way in engineering application more andmore often. Currently, researches on the problem of fatigue failure of FGMsmainly focus on fatigue crack propagation behaviors, but specific study on thecrack initiation is rarely carried out. Therefore, the comprehensive study on theprediction method for fatigue crack-initiation life is of great significance.The paper embarks on the constitutive description of the graded SICparticulates reinforced Al matrix composites under fatigue loading. Thecumulative damage theory is introduced in the research on the fatigue lifeprediction. The finite element software ABAQUS is used to simulate the fatiguetest. The damage accumulation rules under different fatigue loadings areanalyzed with the simulation results. Based on the damage accumulation rules,six damage models are modified to estimate the fatigue crack-initiation life.From the study on the prediction method for fatigue crack-initiation life, itcan be found that the number of cycles and the stress ratio has no effect on thecrack-initiation position and crack propagation orientation. Through contrastiveanalysis, we may discover that the maximum values for six different damageparameters are aggrandized with the increasing of the stress ratio. It can beconcluded that the material will be deteriorated easily when the material issubject to great fatigue loading. This reaction conforms to actual situation.Besides, as the number of cycle increases, the values for six damage parameterskeep a linear trend. This means the damage accumulation rules are linear, and theaccumulation rate of fatigue damage is aggrandized with the increasing of stressratio.Comparing the present fatigue lives with the experimental results underdifferent fatigue loadings, we can found that the crack-initiation life based onthis model agree well with the experimental ones.