多結晶体中における微視組織的微小表面き裂の応力拡大係数

抄録

Avaraging the anisotropy of each crystal, the macroscopic behavior of polycrystalline materials is isotropic and homogenous in terms of elastic deformation. However, the anisotropic and/or inhomogeneous property influences on the stress field ahead of a crack if the crack size is small in comparison with the grain. This bring about the change in the stress intensity factor (SIF). In present study, in order to invistigate the cause and magnitude of the change in the SIF, the finite element analysis is performed. The calculations are carried out for the polycrystal cracked plate model, which consists of hexagonal pillar shape of crystal grains with random orientation. The results implied that the SIF of microstructurally small crack is greatly affected by the deformation constraint caused by the difference in elastic modulus of grains near the crack. The statistical scatter of SIF due to the random orientation of crystal orientation in a polycrystal is examined by a Monte Carlo simulation. The variation in the SIF becomes large as the crack size decreases and anisotropy of the material increases. We propose an equation for estimating the variation in the SIF of the microstructurally small crack.