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

Elastic Hysteresis Property of Several Steels under Fatigue Load

Observations were made on the plastic strain amplitude on five sorts of carbon steel when they were subjected to the alternating stress. The behaviour of the plastic strain occurring in the specimen of respective steel were compared to each other, and some patterns of variations were stipulated referring to the carbon content. Linear relations between the plastic strain, as well as the hysteresis energy, and the number of cycles to failure were confirmed to hold excepting the case of 0.25% carbon steel. Stress-strain relations under repeating stress were discussed in detail to a certain extent

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

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

Fatigue Deformation Preceding Fracture Under Combined Cyclic and Steady Loads

In the problems of materials fatigue, the most researches have been made on fatigue brittle fracture. But when both the steady and cyclic loads work on the specimen, the fatigue deformation (creep) occurs and it often becomes larger than that under the static load of the same maximum value. So the behavior of the fatigue deformation must be investigated to clarify the mechanism of the fatigue fracture. In this paper the investigations were made to obtain and consider the fatigue deformation at the room temperature under push-pull loads with various stress amplitudes and various mean stresses on ferrous and non-ferrous metals. Opposed to the ordinary concepts, the permanent plastic tensile strain is observed to be generated even under completely reversed push-pull loads. The stress generating no fatigue deformation is in the range with the compressive mean stress. The fatigue yield point is generally different from the static yield point, and also the value of fatigue deformation under the tensile mean stress is different from the same absolute value of that under the compressive mean stress. It seems to be materials nature. The new relations between stress conditions and fatigue deformations were discovered and represented by a criterion

Effects of Some Pre-cyclic Stressings on the Fatigue Strength Containing the Low Cycle Fatigue Range

It is already known that iron and many ferrous alloys show a characteristic coaxing or understressing effect. In this report, some programmed fatigue tests were carried out to investigate the pre-stressing effect. Also, the micro Vickers hardness and macro residual stress of the specimen were examined. Experimental results are outlined, suggesting that the coaxing effect is due to the ability of steel to undergo strain hardening or strain aging especially at the crack tip area by strain cycling. It was found that only a small number of cycles of large overstressing can destroy the coaxing effects

Stress Distribution around a Screw Dislocation in a Thin Crystal

This paper presents the result of calculations on the stress distribution around a screw dislocation in a thin foil-crystal calculated by use of the IBM digital computer. In an infinite medium, it is well known that a screw dislocation makes a stress field with one stress component τθz, where z is the direction of the Burgers vector. In a thin foil-crystal, it was found that a screw dislocation makes a stress field with not only τθz which vanishes at free surface but τγθ which concentrates at the surface