Abstract
Fatigue test system with electrolytic-polishing apparatus was developed to study the effect of specimen diameter on the fatigue strength of metallic micro-materials. In the system, a specimen with small cross-section was formed after the wire with 1.0mm in diameter was gripped to the fatigue test machine, where the formation was conducted by the electro-polishing. Commercially pure aluminum or commercially pure iron wires were employed for the present experiment. In either metal, variations of fatigue lives were very large compared with those of bulk specimens. In the pure aluminum, fatigue lives were shorter and the scatters of fatigue lives were larger for smaller specimens at the same stress amplitude, while there were small effects on the specimen size in pure iron. Two types of fracture morphologies were observed. Those were with or without fatigue fracture surface. The latter were necked at the final stage of the life.
