Studies on the Size Effect of Bending and Twisting Fatigue Strength

抄録

The relation between the twisting fatigue strength and the bending fatigue strength varies with temperatures and specimen sizes, as well as with presence of notches, flaws, and environments. In the present paper, the size effect of fatigue strength is discussed by calculating the probability of flaws on the surface which affect the fatigue strength of materials by 1/(1+2μ) under bending and by 1/(1+μ) under twisting. And fatigue tests are carried out at elevated temperatures and at a low temperature for smooth specimens and also for notched specimens under bending and twisting moments. These results and the various past experimental results are applied to the calculation of the size effect discussed above, and the following explanation is given in a unified form : the relation of size effect under bending fatigue and under twisting fatigue, the size effect of smooth specimens and notched specimens, the effect of flaws, environments, and temperatures on the fatigue strength and notch factor, and the distribution of the fatigue strengths for various sizes of specimens.