Abstract
To ensure long life reliability of the machine parts with mechanical notches, ultrasonic fatigue tests were performed on the rod specimens with U- or V- shaped circumferential notch at the center. High temperature tempered S35C and low temperature tempered SNCM439 were used as the test materials. The results were compared to the dumbbell type results. No difference was observed in the fatigue behavior by the notch shape. However, some difference was observed in the fatigue strengths, especially those below (10)^7 cycles, by the notch shape. Notched specimen with high stress concentration factor seemed to show a little higher fatigue strength than the one with low stress concentration factor.
