The box-counting method has been applied to the evaluation of fractal dimensions of the fracture surfaces by using the gray scale values of the bit map images of SEM (scanning electron microscope) photographs. As specimens, gray cast iron (FC200) was adopted and the effect of the fracture mode (brittle or ductile) on the fractal dimensions of the fracture surfaces was investigated. The fracture mode was controlled by changing the temperature at the fracture tests. It has been clarified that the fractal dimension changes considerably with the magnification of SEM in the case of brittle fracture comparing with the case of ductile fracture.
