単結晶マイクロピラーのサイズ効果を考慮した降伏関数

Abstract

To explain the size effect mechanism observed in the micrometer-sized pillars under uniaxial compression, the critical resolved shear stress (CRSS) in a single-crystalline micropillar was newly proposed in consideration of an effect of dislocation pile-up. The yield surface for the multiaxial stress state was obtained based on the proposed CRSS by changing the crystallographic orientation. Under the plane stress condition, shape of the obtained yield surface is reasonably changed from the Tresca type with respect to the maximum shear stress to the Rankin type with the principal stress. Also, by changing the diameter of pillar, the yield surface becomes larger due to the size effect contribution of dislocation length.