軟鋼の回転曲げによる疲れの方向性

抄録

It has been generally considered that the thickness of the fatigued layer of round bar of mild steel under rotating bending is uniform at the cross section, but the author have had a different idea and his experiment has proved that the thickness of the fatigued layer is not uniform. In his experiment, the thickness of the fatigued layer was not uniform, but the fatigued part and unfatigued part had an elliptical boundary as shown in Fig. 1, and the boundary can be seen by etching with Fry's reagent. The author's idea concerning the fatigue under rotating bending is as follows ; In the first, the fatigue of a certain outermost part of the specimen occurs on one of maximum cyclic shearing stress planes, although such planes are considered to be innumerable. The fatigue at any other outermost parts takes place in the plane parallel to the first one. And thus the fatigue spreads all over the length of the specimen and then proceeds from the outermost part to the inner part only on the plane on which fatigue occured for the first time, The relation between the thickness of the fatigued layer and the stress of the outermost layer computed with the above mentioned idea comformed very closely to the results of experiments of other investigators as well as author's, as shown in Fig.7, 8 and 9.