鋼の疲労の統計的性質および疲労強度と非金属介在物

抄録

Three series of specimens were specially prepared so that they may contain various degrees of MnS non-metallic inclusions, other parameters being kept constant especially the amount of manganese in solution as much as possible. Fatigue tests were carried out with a rotating bending fatigue machine.
The results obtained are as follows:
(1) The definite relationship could not be recognized between the inclusion ratings and the statistical nature of fatigue life of steel, which is in accordance with the previous work by one of the present authors, but contrary to the result by Epremian and Mehl.
(2) The ferrite grain size is a predominant metallurgical factor in the statistical nature of fatigue fructure of steel.
(3) For the same stress amplitude, the scatter of fatigue life increases and the probability of fructure decreases with the decrease of grain size.
(4) For the equivalent stress amplitude, the scatter of fatigue life appears not to be affected by inclusion ratings and ferrite grain size.
(5) The longitudinal fatigue strength of carbon steel is not so much affected by the content of MnS as inclusions. The effect by ferrite grain size or other statistical parameters may also be large.