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.

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This paper deals with the experimental research on the effects of wire drawing conditions, mainly the shape of die wall and the amount of reduction of diameter in drawing on the fatigue strength of drawn wire.
We have investigated the endurance limit of 0.41% carbon steel wires drawn under several kinds of drawing conditions, using a Haigh-Robertson type fatigue testing machine.
Results obtained may be summerized as follows;
(1) The endurance limit of the wire drawn with a die of larger radius of curvature of drawing surface revealed higher than that of smaller radius.
(2) The endurance limit increased sharply with the increase of reduction of diameter in the range of low reduction, tending to a constant value when the reduction of diameter was more than 10%.

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The spiral springs for wrist-watch use, which have considerable residual stresses as the authors have already published, sometimes fail by fatigue or creep in services. The authors considered these troubles in springs should be cleared off by fatigue testing and constructed a new fatigue testing machine for spiral springs. With this fatigue testing machine, the following results were obtained. The residual stresses which were as high as 60kg/mm² in the surface were not changed during fatigue testing of about 1000 stress repetitions. The creep of springs were considerable during two or three turns in the beginning, but after that a little creep was recognised. Lubricating oils of anti-friction were useful for elongation of service life.

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Fatigue Strength of Concrete due to Sustained Loading.
The crushing strength under sustained loading in ratio to the statical crushing strength is difficult to be determined, because the actual strength of the sustaindly loaded specimen itself is previously unknown. According to the literatures available, the ratio of fatigue strength to statical strength is believed to be roughly 80-95%. The auther takes the compressive strain at the begining of loading as a measure of limit avoiding to crush down and comes experimentally to the conclusion that the initial limiting strain is 1‰.
Almost independently of the ultimate strength of concrete the stress/strength ratio is about same for a given strain value which is sufficiently large. Corresponding to Strain of 1, 3‰, for instance, the stress/strength ratio becomes 88%. From this fact the auther assumes that, corresponding to 1‰ strain, the crushing strength under sustained loading is about 76% of the statical strength.

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