Stress concentrations at grain boundaries due to anisotropic elastic material behavior

摘要

Scanning electron microscopy (SEM) examinations on samples of the beta-titanium alloy LCB (low cost beta by TIMET) after fatigue tests revealed a strong influence of the crystallographic misorientation of adjacent grains on crack initation and short crack growth. From that point of view the knowledge of the anisotropic elastic properties of individua;p grains and their influence on the stress distribution within the microstructure is of great importance to understand crack initiation and propagation mechanisms. For this purpose the microstructure of polycrystals at sites where cracks initiated was simulated by means of three dimensional finite element (FE) claulations, considering the elastic anisotropy of the grains. However, to ensure a realistic simulation, epxerimental data like the grain geometry and crystallographic orientation were used, which had been measured by the electron back-scattered diffraction (EBSD) technique. Beside this, the values of the elastic constants of the single-crystalline material were required.