As the countermeasure for the teeth failures in the nose-suspended type traction gears of the Japanese National Railways which are caused by the end tooth bearing, the pinions are heavily crowned in order to prevent the end tooth bearing. As the degree of crowning is extremely great, the tooth bearing of such crowned gear is localized and the method of calculation of gear stress in such gear is not established up to the present time.
The author has derived a theoretical method of calculation of gear stress in the heavily crowned gear, and recently conducted an experiment in order to measure the lengthwise distribution of gear stress while the electric locomotive, equipped with a crowned traction gear, was running. The results are as follows:
(1) It was demonstrated by the experiment that, in order to calculate the stress of traction gear which is heavily crowned so as to prevent the end tooth bearing, it would be proper for us to use the solution of the theory about two elastic bodies in contact with each other as the load of tooth face and then to apply the theory of a very long cantilever plate with infinite width.
(2) In this experiment with the ground traction gear of the electric locomotive having the traction motors mounted on bogies and the gears installed rigidly on axles, the distribution of the values of the ratio (dynamically added load+statical load) versus (statical load) was widely scattered due to the high acceleration of the unsprung masses, its maximum value being 2.45 and minimum value 0.85 in the test range of locomotive speeds below 55km/hr, namely under 11m/sec of the circumferential speed of pitch circles of gears.

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The strain-aging processes in mild steel sheets which were stretched in tension and temperrolled, were compared with each other by means of measuring changes of yield stress, yield ratio, total elongation, yield-point elongation, and hardness, and further, the optimum temperrolling reduction was studied from a view-point of the strain-aging and the formability.
The results obtained may be summarized as follows:
(1) The values of yield stress which were measured immediately after temper-rolling, became lower than those of annealed sheets in a certain range of temper-rolling reduction. This may be caused by the comprehensive effect of hardening action due to inhomogeneous deformation, and saftening action by a kind of the Bauschinger effect, because the tensile test may result in effect, in a different kind of working for the temper-rolling.
(2) The yield ratio of the temper-rolled sheets increased with the aging process, therefore, the formabitity of the sheets may decrease with the aging process.
(3) The aging curves for total elongation and the yield-point elongation showed no appreciable change in the earlier stage of the strain-aging process and these curves showed different form from those for yield stress, yield ratio, and hardness. Total elongation and the yield-point elongation may have no unitary relation-ship to the strain-aging.
(4) When the aging curves in the temper-rolled sheets were compared with those in the stretched sheets, the apparent retardation of the strain-aging was recognized in the temper-rolled sheet concerning the aging curves for yield stress, in spite of good agreement with the curves for hardness measurement. Such retardation of the strain-aging in the temper-rolled sheets has a practical meaning.
(5) The activation energies which were calculated from changes in hardness and yield stress of the stretched and the temper-rolled sheets indicated a comparable good agreement with those of other workers. Therefore, the difference of the rate of the strain-aging by the method of pre-straining as stated above may be nothing but apparent, and the basic mechanism of the strain-aging may not be affected by the method of pre-straining.
(6) From the point of view of formability and strain-aging, the optimum temper-rolling reduction is in a range of from 1% to 1.5%. In the case of laying special emphasis on the formability, rolling reduction will have to selected from a range of from 0.5% to 0.8%, and when the straining of formation of stretcher strain marking is to be emphasized, rolling reduction may have to be selected from larger values than 1.5%.

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This investigation was planned for researching the effect of the repeated stress upon the longitudinal residual stress existing in the cold drawn carbon steel wire. For the specimen, 0.65% carbon steel wires drawn with 60% and 80% reductions were used, and the diameter of these wires was 1.3mm.
For the measurement of the longitudinal residual stresses existing in these fine steel wires, the present writers adopted the mechanical method and electro-magnetic method.
Hunter fatigue testing machine was used in this investigation, and from S-N curves of these wires the fatigue limit stress and three stresses over the fatigue limit were chosen as the repeated stress to research the behavior of residual stress. The fatigue test specimens were taken out from the fatigue testing machine at 10⁷ and 10⁶ cycles for the fatigue limit stress and at the number of cycle just before the break down cycle for each stress over the fatigue limit, and then the specimens for measurement of residual stress were cut out from the middle part of these fatigue test specimens. The distributions of longitudinal residual stresses of these specimens subjected to the repeated stresses were measured and those were compared with that of the standard specimen not subjected to the repeated stress.
From the results obtained by this investigation, it was made clear that if the longitudinal tensile residual stress existing in the outer part of the wire was about 20-30kg/mm², the distribution of longitudinal residual stress of the cold drawn steel wire was little affected by the repeated stress under rotating bending over the fatigue limit, and that which is equal to the fatigue limit, either.

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In order to investigate about the effect of surface decarburizing on the corrosion-fatigue properties of carbon steel (0.61%C), the cantilever rotating-beam fatigue tests were made in city-water.
Results obtained may be summarized as follows:
(1) The inclination of corrosion fatigue S-N curves of specimens, whose decarburized depth are 0.15-0.3mm, change steeply down to the 10⁷ cycles showing no horizontal part as is formed by the ordinary curves tested in air. But the specimens of the 0.4-0.5mm decarburized depth have a tendency to become horizontal at about 10⁷ cycles.
(2) The corrosion fatigue strength of the non-decarburized and 0.15-0.3mm decarburized depth specimens in the long-term test (10⁷ cycles) under lower alternating stress are 14-23% smaller as compared with the fatigue strength in the air, but as the decarburized depth increases up to 0.4-0.5mm, they becomes stronger by about 8-9% than that in the air.
(3) The corrosion fatigue strength of decarburized steels in the short-time test (3×10⁵ cycles) are stronger than that in the air. The difference between these two strengths in the air and city water becomes greater with increase in the depth decarburized.
(4) The microscopic test was carried to find out the causes of the difference concerning the corrosion fatigue strength of each specimen. On the surface of non-decarburized specimen, many number of cracks are found and their depth are shallow. On the other hand, when the specimen has a thin decarburized layer, the number of cracks on the surface are few, and their depth are deep and wide. But when the depth of decarburized layer come to 0.4-0.5mm, these cracks become small in number, and shallow.
(5) Each of the above mentioned phenomenon is supposed to be based on the resultant effect from some items in the following causes.
a) The machanism of corrosion.
b) The magnitude of tensile internal stress at the surface zone of decarburized steel bar.
c) The corrosion resistance of ferrite zone in the surface layer.
d) The rise of temperature expected under the alternating stress is disturbed due to the cooling action of corrosive medium, that is, water.

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Setting process is often practiced on coil springs in order to improve their fatigue resistance and prevent their creep deflection. Torsional residual stresses are produced by this process, and it is generally understood that these stresses would play a role in improving the fatigue properties. In this experiment, round bar specimens of the spring steel SUP2 were used, and after being twisted by the torsional moment 25% beyond that corresponding to the yield point, they were subjected to the fatigue test in alternating torsion. The distribution of residual stresses was measured by the etching method, by measuring the angle of torsion during the etching process. Three stress levels were employed in repeated stressing and the number of stress cycles was made to be the same in each stress level. As a new attempt, we studied the fading of residual stresses under repeated stressing in successive two stress levels.
The results obtained are summariaed as follows:
(1) Residual stresses produced by plastic torsion are of the thermal stress type near the surface, being negative at the surface layers.
(2) Residual stresses subjected to repeated stressing fade noticeably in the first stage of fading and then gradually with the repetition of stress cycles. In the second stage of fading, the relation obtained between the ratio of surface residual stresses τ_r/τ_o, (τ_r is the current value and τ_o is the initial value of surface residual stress) and the logarithm of cycle ratio n/N, formed straight lines, and experimental formulas concerning the fading of residual stresses were established.
(3) In repeated stressing under successive two stress levels, the fading of residual stresses is larger in the case of descending stressing than in the case of ascending stressing, when the same numbers of stress cycles are given to each stress level, respectively. Hardness has also the same tendency as the residual stress.

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