Discrete Dislocation Analysis of Fatigue Crack Kinking Behavior
Atsushi SUGETA, Yasuko MOTOYASHIKI, Yoshihiko UEMATSU, Takuya MORIYAMA and Masahiro JONO
Abstract:The discrete dislocation (DD) method is one of the mesoscopic scale computer simulation procedures, which can deal with each dislocation movement in a cracked body. In this paper, the fatigue crack growing under mixed Mode I and II condition with kinking was analyzed by the 2-dimensional DD method. The material analyzed was iron with bcc structure, which has two preferred slip directions inclined }54.7 to the direction perpendicular to the loading axis. The fatigue crack was assumed to grow along one of two slip directions in order to simulate the crack growth behavior under mixed mode condition, observed microscopically by an atomic force microscope (AFM). The effect of a grain boundary was also introduced to figure out crack kinking behavior. The crack tip displacement along the crack growth direction, which was defined by the number of dislocations annihilated at the crack tip, was found to become smaller as crack grew due to the constraint of slip deformation by the grain boundary. The crack kinking was assumed to take place when the crack tip displacement along the crack growth direction was exceeded by that along the other slip direction. Key Words:Discrete dislocation method, Fatigue crack growth, Crack kinking, Crack tip shear displacement