Abstract
Fracture surface observations were enforced after cyclic bending fatigue test, three point bending test and impact test. It was confirmed that striation pattern, dimple pattern and cleavage was formed on each fracture surfaces. These patterns corresponded with each failure modes. Pearlite phase was only observed on fatigue fracture surface. These obtained data will be applicable to compare to the fracture surface, when the machine part made in gray cast iron was damaged. Because the crack occurred on gray cast iron is apt to propagate along it due to stress concentration and stress intensity factor increase in the graphite, that is why if some pattern was formed on the fracture surface of machine part, but it is difficult to judge whether actual failure mode is suggested due to its pattern or not.
