Evaluation of effect of crystal grain size on nonuniform deformation of polycrystalline pure copper specimen inducing stress gradient

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  • 応力こう配が生じる多結晶純銅試験片の不均一変形に及ぼす結晶粒径の影響の評価

Abstract

<p>To investigate an interaction between macroscopic and microscopic nonuniform deformation of polycrystalline pure copper, uniaxial tensile tests using various specimens having different curvature and different crystal grain size were performed. Specimens were annealed by different to vary grain size, and radius of curvature was changed in gage section to induce various stress gradient. To evaluate heterogeneous strain field in the surface of specimen, digital image correlation method was used in this study. The maximum stress for each specimen under uniaxial tension was also evaluated. Similar to Hall-Petch relation, the maximum stress increases with decreasing grain size. The curvature of specimen also affects to the maximum stress. The macroscopic nonuniform deformation enlarges the microscopic nonuniform deformation, and it increases the hardening due to GND. This trend was found for each annealing temperature. In fine grain specimen, strain distribution depends on specimen shape. In contrast, if grain size is large, order of microscopic heterogeneity approaches order of macroscopic nonuniform deformation. In such case, strain distribution depends on not only specimen configuration, but also grain distribution.</p>

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