Abstract
Analytical procedure to evaluate the surface irregularity of fatigue fracture surfaces for S25C carbon steel and A5052 aluminum alloy was developed by applying a concept of fractal and a hyperbola model. Main conclusions obtained in this study are summarized as follows ; (1) Fatigue fracture surfaces for analytical object have the fractal nature. Especially, the fracture surface for S25C carbon steel under stress ratio R=0.5 has the complete self-similarity in wide-resolution range. (2) Striation mark on the fatigue fracture surface has a significant effect on the fractal dimension D. (3) Geometrical irregularity of the surface is also well evaluated by combining the fractal dimension and additional indices termed as "index of fracture surface nature". (4) Fractal dimension and each index of fracture surface nature have a definite relation to the stress intensity factor range ΔK.
