On the Yielding of Twist Steel Bar

The yielding of steel proceeds in successive appearance of flow layers. Having been taken account of it, the yielding phenomena of bending steel bar has been fully explained by the authors. In the present paper the yielding phenomena of twist steel bar is discussed as an another example of yielding of steel under uneven distribution of stress. In the first part are exhibited the results of measuring the stress existing in a yielding bar subjected to pure torsion. It leads to the conclusion that the twisted bar yields by the same mechanism as that of the yielding of bent steel beam. Then the problems of elasto-plastic torsion may generally be treated analytically in the same fashion as in the case of bending

On the Yielding of Steel Under Bending Moment

It is an important problem to know how high rises the so-called yield point under uneven distribution of stress. Much efforts made in this field is found in the papers hitherto reported. Among which, F. Nakanishi's theory concerning the yield point of mild steel under bending moment is noted. This is, however, not adequate for explaining the elasto-plastic bending of ordinary carbon steel except of mild steel. Therefore it encountered serious opposition of recent investigators such as German researchers and authors as well, who performed experiments by means of X-ray stress measurement. This report is made on the recent experimental results of the measured stress existing on a yielding bar under bending moment. Basing on the experimental results the authors' opinion is proposed concerning the mechanism in yielding phenomena of bending a steel bar. The theoretical treatment of yielding mechanism is then explained with correlation between the theoretical and the experimental relation of moment and deflection

Effect of Free Surface on the Yielding Resistance of Materials

In the present paper the authors pointed out the necessity of seeing the metals as the inherent figure, an aggregation of crystal grains, when they are deformed plastically. Although other factors affecting the yielding resistance of polycrystalline metals, it may be considered the mutual restriction is here thought to play an important role. As, at present, no theory is found connecting yielding resistance of single crystals to that of polycrystalline metals, the authors' view discussed would be recommended, untill a far better theory is developed

The Investigation on the “X-ray Stress Measurement”

To measure the stress by X-ray was proposed in 1930 by G. Sachs and J. Weerts in the case ~f duralumin. Since, in 1935, R. Glocker ascertained the fact that the surface stress is perfectly measurable by means of X-ray, it interested researchers of stress problems and achieved far greater development especially in our country and Germany. “X-ray stress measurement” is excellent in the following points : 1) not only the stress of a test piece but also of machine parts can be measured directly without any additional or harmful working for objects. 2) local stress of objects is more clearly demonstrated as compared with any other method hitherto tried. We personnel performed laboratory experiments using the principle of “X-ray stress measurement”. and examined the results. Moreover, we have designed and produced an “X-ray stress measuring instrument”, which is very convenient for actual use in applying the method beyond the laboratory, and ascertained the possibility of the shop-measurement