A New Criterion for the Strength of Metals under Combined Alternating Stresses

Matsumura's theory of malleable materials, stating that “the elastic failure occurs in malleable materials when the maximum shear stress reaches a definite value depending on shear strain energy” is fairly well applicable to results of experiments, so far as the material is ductile; but the theory is not applicable to brittle materials. Extending Matsumura's theory to all materials, ductile and brittle, the authors propose now a new criterion and applying it to the case of fatigue, they think that “the fatigue failure occurs in ductile materials when the greatest maximum shear stress induced by combined repeated stresses reaches a definite value depending on shear strain energy at the instant, and that the fatigue occurs in brittle materials when the greatest maximum principal stress induced by the combined repeated stresses reaches a definite value depending also on shear strain energy at the instant.”From this new criterion on fatigue, they derive the conditions of fatigue failure under the combination of various stresses. Comparing the results of calculation with those of experiments, it is established that the new criterion is fairly well applicable to results of experiments in every case

The Strength of Metals under Combined Alternating Bending and Torsion with Phase Difference

A new fatigue testing machine capable of making experiments under combined alternating bending and torsion with any phase difference has been devised and proved to be satisfactory in operation by the authors. From the test results obtained by experiments carried out on some metals with the machine, the effect of phase difference on the strength of the metals under combined bending and torsion has been made clear

Repeated Stressing and Crystalline State of Annealed Steel

The action of repeated loading, especially of repeated compression for the crystalline state of 0.41% carbon steel was investigated by X-ray. As a result it was established that the crystal fragmentation occurs when the maximum stress exceeds the lower yield point of that material but has no direct relation with fatigue failure. In the case of alternate tension and compression with equal amplitude (mean stress equals zero), the specimens break down far below the yield point, of course, but is not necessarily preceeded by the crystal fragmentation. Then, what is the true nature of fatigue of metals is our problem. According to the authors' view, failure begins when the accumulation of crystal distorsion exceeds a certain limit proper to the individual grain

The Strength of Metals under Combined Alternating Bending and Torsion

Fatigue tests under combined bending and torsion were carried out for several ferreous and nonferreous metals with a testing machine specially designed. As the results of tests, strength of metals under combined alternating bending and torsion were expressed by a simple relation, using fatigue strength of each metals under simple bending and torsion. And some considerations about fatigue fracture were made

Studies on Fatigue of Mild Steel by a Corrosion Method

The fatigued zone in mild steel can be detected by a corrosion method as well as when yielded parts are shown as a strain figure. By the corrosion method, the authors have studied the appearances of the fatigued zone and fatigue crack in each specimen at progressive stages of fatigue. Consideration has also been made of the mechanism of fatigue failure with specimens having a smooth surface and having various notches

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

Fatigue Strength of Metals under Alternating Stresses of Varying Amplitude

The criterion on fatigue damage and the formulas which can predict the fatigue lives and fatigue limits of metallic members under alternating stresses of varying amplitude, are established. The fatigue tests under alternating stresses of varying amplitude were carried out by the specially designed testing machines of three types, using unnotched or notched specimens of low-carbon steel, high-carbon steel and duralumin. And it is concluded that the fatigue lives and fatigue limits of metals subjected to varying repeated stresses like this can be determined by the analysis introduced in this paper

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