FATIGUE CRACK GROWTH BEHAVIOR OF ANISOTROPIC ROLLED STEEL PLATE WITH SPECIAL REFERENCE TO LAMINATED STRUCTURE AND INCLUSIONS.

The authors deal with the fatigue crack growth behavior of an anisotropic rolled steel plate (SB56M). Two groups of materials were prepared by annealing and spheroidizing treatments, so that the effects of the laminated structure and the mechanical fibering of inclusion, both of which were produced by rolling, could be separated. The fatigue crack growth behavior in various anisotropy directions was examined microscopically as well as macroscopically. The crack growth behavior was much more anisotropic with the annealed material than with the spheroidized material. It is concluded with this class of the steel plate investigated that the anisotropy in the behavior of crack growth on the microscopic and macroscopic levels was primarily affected and controlled by the laminated structure, while the inclusions gave a secondary effect on the anisotropy of crack growth.