The investigation was carried out to obtain the most suitable condition of surface rolling for the purpose to increase the rotating bending fatigue limit of filleted or V-notched specimen.
A surface rolling apparatus was designed specially for this investigation.
The results obtained are as follows:-
(1) The most suitable surface rolling pressure and the increasing rate of fatigue limit increase with the sharpness of notch.
(2) The limiting value of increasing rate of fatigue limit is (β-1)×100% at the filleted specimen, where β is the fatigue strength reduction factor.
(3) The maximum increasing rate of fatigue limit is 133% at the V-notched specimen with the 0.4mm radius of notch.
(4) The influence of number of rolling on the increase of fatigue limit was made clear.

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A new fatigue testing machine for high speed roller chain is designed. The principle of testing method of this machine is to give repeated impact to a test piece by a sprocket tooth. A test piece is composed of several pitches of roller chains and it is stretched by two helical springs with any inital tension. A block which has only one tooth form of sprockes it reciprocated by a crank mechanism, and gives impact to the test piece. The dynamical relation is analogous to the chain gearing at high driving speed. Usually rollers come into failure by repeated impact. Taking the driving speed as ordinate and number of impact repetitions as abscissa, we obtain S-N curves as in usual fatigue tests. As an example, we showed some experimental results. If the testing machine is driven at low speed with a long reciprocating stroke, the test piece receives small impact and high repeated tensile stress. Then link plates of roller chains fail. Many experimental results carried out by the new testing mahine will be shown in later reports.

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As a method for reinforcing timber beam, authors devised a new method by using steel bars, and carried ont an experimental study. By that result, it became clear that the method has following efficiency.
The initial upward deflection produced by initial tension in steel bars decreases the restriction of deflection limit in designing floor timber beams.
This method gives to timber beam greatly higher bending elasticity and effects to increase its final strength.

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In the testing of wood for resistance to wear, a laboratory test should simulate the conditions of service in timber floors. In this respect the two abrasive action-one the impact of the heel and the other scuffing action by the sole of footwear-should take into consideration.
This paper is a report including: (1) the preliminary test result-to impart impact blows by a stamper on the surface of wood exerts considerable influences on the conditions of abrasion: (2) the trial of two abrading apparatus-one a iron board studded with many pan head studs to impart impact blows and the other a rubber, wire-brushes are employed, to abrade the surface-with which a comparatively similar condition to service wear is obtained; and (3) the laboratory abrasion test results of some soft and hard woods and the relation between specific gravity and percentage loss in weight.

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By the simple twisting test of many sorts of wire ropes, we defined so-called modulus of transverse elasticity for twisting rigidity, G_r. It is found to be approximately constant for particular to their constructions, independent of their sizes, and we knew that torsionability of wire rope could be represented by the “Torsionability Number”-ratio of the torsional rigidity of steel round bar having a diameter equal to that of wire rope to the torsional rigidity of wire rope.
So we propose to use the “Torsionability Number” as the measure of torsionability of wire ropes, as well as the “Flexibility Number” to the bending rigidity, presenting the standard values of “Torsionability Number” for the wire ropes of some typical constructions.

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