抄録
It has been well known that the observed fatigue life for the constant repeated stress is scattered widely.
This experimental study was carried out in order to investigate the character of the frequency distribution of the fatigue life of steel.
The specimen was a flat bar with a circular hole in its center and not annealed. Its material was SS 41 steel.
The sort of repeated stress was the pulsating tension stress and the stress levels were 30kg/mm2, 27kg/mm2, and 24kg/mm2, 20 specimens were tested each stress levels with Lcsenhausen Fatigue Testing Machine (U. H. S. type). Besides these, to 20 specimens the stress level 24kg/mm2 was applied to failure after stress level 27kg/mm2 were applied 50000 cycles, in order to investigate the scatter of fatigue life of the specimen to which two different stress levels were applied.
Experimental errors were analized statistically.
The conclusion from experiment was as follows:
1. The scatter of fatigue life was well interpreted by introducing the probability of fracture μ.
2. The method to estimate the probability of non-fracture was obtained.
3. The scatter observed in this experiment was considerably smaller than that reported by other investigators.
4. It was clarified that the scatter of fatigue life was not obtained from the experimental errcrs only.
