抄録
One of the authors has reported previously on the fatigue deformation of various steels under repeated bending and torsion. In this report the similar experiments under repeated torsion were carried out on the spring steel which contains boron for the purpose to improve hardenability. Results obtained are as follows:
(1) Fatigue deformation grows rapidly at the beginning of stress repetitions, and the increasing rate decreases gradually. We denoted the stress which causes 0.2% permanent shear strain under repeated torsion as the fatigue yield limit.
(2) The fatigue yield limit lies fairly below the static yield limit. So that the safe stress range on the endurance limit diagram must be determined considering this fact.
(3) The effect of plastic torsional working on the endurance limit and the fatigue yield limit has been obtained. To prevent fatigue deformation, torsional working of about 0.1% permanent shear strain seems to be appropriate.
(4) The effect of plastic torsional working on the fatigue deformation was considered theoretically, and the calculated results agreed with experimental results.
