Abstract
Considering the relationship between inhomogeneous plastic deformation and fatigue damage, deformation inhomogeneity evolution and fatigue failure of superalloy GH4169 under temperature 500 °C and macro tension compression cyclic loading are studied, by using crystal plasticity calculation associated with polycrystalline representative Voronoi volume element (RVE). Different statistical standard deviation and differential entropy of meso strain are used to measure the inhomogeneity of deformation, and the relationship between the inhomogeneity and strain cycle is explored by cyclic numerical simulation. It is found from the research that the standard deviations of each component of the strain tensor at the cyclic peak increase monotonically with the cyclic loading, and they are similar to each other. The differential entropy of each component of the strain tensor also increases with the number of cycles, and the law is similar. On this basis, the critical values determined by statistical standard deviations of the strain components and the equivalent strain, and that by differential entropy of strain components, are, respectively, used as fatigue criteria, then predict the fatigue–life curves of the material. The predictions are verified with reference to the measured results, and their deviations are proved to be in a reasonable range.
Highlights
To evaluate the fatigue behavior of metals, we need to have a stress- or strain- fatigue–life curve obtained from a series of fatigue test data by fitting
From the studies by Basquin, Coffin, Manson, Morrow and other researchers, the fatigue–life curve was regarded as the basic information on fatigue characteristics of the material and was used to evaluate the fatigue performance of structures [1]
To investigate the relationship among the inhomogeneous hysteresis behavior, damage and the fatigue life, the crystal plasticity analysis utilizing representative Voronoi volume element (RVE) models for polycrystals were performed for exploring the mechanism of low-cycle fatigue of metal at the grain level
Summary
To evaluate the fatigue behavior of metals, we need to have a stress- or strain- fatigue–. In a cyclic loading process, the random irregular mesoscale structure and anisotropy of the material cause the meso-level inhomogeneity in mechanical properties This produces the considerable difference in local strain or stress and may generate the fatigue damage accumulation and potential source of local fatigue failure. To investigate the relationship among the inhomogeneous hysteresis behavior, damage and the fatigue life, the crystal plasticity analysis utilizing representative Voronoi volume element (RVE) models for polycrystals were performed for exploring the mechanism of low-cycle fatigue of metal at the grain level. The local cumulative plastic strain and specific plastic work at the tension peak of the cycles increase monotonously, in an approximately constant rate They can be applied to fatigue damage analysis conveniently, without tracking the whole cyclic process. Searching and verifying the FIPs suitable to measure fatigue damage accumulation and to predict the fatigue–life curve of the material
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