In order to measure the strain on the surface of wide structures with mechanically amplified strain-meters, it was necessary to fix the strain-meter by electric magnet, or suckers made of rubber. It was considered by the authors that the measurement of the strain of wide structures will be simplified if the strain-meter is fixed on the structure by any adhesives. Fifteen sorts of adhesives were put in test to obtain those adhesive tensile strength. Some of adhesives were tested after heat treatment. Tests at high temperatures were also carried out.
For the present purpose in which any heat treatments are not desirable, such adhesive was the most excellent that a nitrate of cellulose was placed between surfaces to be adhered which were coated by a little amount of butyl acetate. The adhesive tensile strength from 18 to 42kg/cm² was attained after one hour drying in room temperature by this adhesive. A satisfactory strain measurement was carried out with the mechanically amplified strain-meter which was fixed with this adhesive.

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It is now very popular to apply the wire strain gage to the measurement of stress and strain in various cases for the reason of its convenience. But in the case of the rotating disc, it is necessary to contrive a special devise to pick up the change of electrical resistance of the gages, which are stuck on the face of the rotating disc.
In this paper, they first studied the variation of the contact resistance between the copper pole and mercury bath, and affirmed that the variation of the contact resistance between the copper pole and mercury bath is negligible small, if the immerged depth is adequate and this devise is adoptable. Having used the copper ring with the sharp edge as the pole, they could measure fairly well the strain of the rotating disc whose peripheral speed was about 300 meter per minute or less at the edge of the ring.
Applying this electric connecting devise, we have first measured the strains which were produced in a rotating circular disc of uniform thickness, secondly the disc having symmetrically placed four noncentral holes and finally the tangentially stepped circular disc.

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In quantitative measurement of strain by brittle coatings, it is very important to know the drying condition of coating. As the measure showing the drying condition, the critical strain is used. In order to know the critical strain, the following method is adopted. When a cantilever coated on the tension side is loaded, the coating cracks first at a certain strain value. This strain is called the critical strain.
It was found by the experiment that the critical strain varies with the variation of strain gradient in the tensile direction, even though the cantilever coated under the constant condition is used. Then the authors investigated the experimental results from the standpoint of weak point of coating.

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In order to utilize the data on corrosion fatigue test to practical design, the correlations of corrosion fatigue strengths under various stress conditions are researched. In the paper, the reduction rate of fatigue strength due to corrosion, which we call corrosion effect β_c, is compared under alternating bending and torsional stresses. Under the similar conditions of tests, β_c in torsion is found always lower than in bending, and the relation of the both values is explained using authors' criterion on fatigue failures. Further, the effect β_ck of simultaneous notch and corrosion on fatigue strengths is studied by means of varying sharpness of circumferential notches of rotating bending test pieces. β_ck becomes less than β_c×β_k with sharpening of notches, and the progress is made clear.

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To use the full strength of the riveted member in tension, the section weakened by the rivet holes must be reinforced suitably.
The authors tried two methods of reinforcement, one increases its thickness by reinforcing plates attached on the surface of the main plates by fillet welds, and the other increases its breadth by reinforcing plates attached to both sides of the main plates by butt welds. These reinforcement increase the static tensile strength of the member up to its full strength, but, on the contrary, the stress concentrating effect due to welding will decrease its fatigue strength. To examine this reduction in strength under fatigue loading, the authors performed fatigue tests on riveted joint specimens and its reinforced one, and the experimental results show that each reinforcement attempted are effective below limited cycles for failure respectively, but decrease the fatigue strength at ranges over these limited cycles.

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A new fatigue tester to measure the flexing fatigue which may be considered most probably occuring in practical using, is deviced and several experiments were carried out with it.
The principle of this tester is very simple and easy to handle and gives more accurate results than the other fatigue testers.
Following relationship between the load W and the life N (the cycle number of repeated stresses) has been given,
W=A-1/Klog N where A and K is the constant; that is, A is the value of W extrapolating the linear part of W vs. log N curve to log N=0 and might correspond to the tensile strength of the cord, and K is the slope of this line.
In order to make good tire cord, it is desirable to make the value of A and K more greater.
The results of experiment with this tester show that the following conditions such as (a) sorts and qualities of oiling reagents, (b) number of twisting, (c) temperature of heat treatment, (d) cord gauge, (e) radius of curvature of bending, could not change K value but change A value.
From such results, therefore, it appeared that K is independent of aftertreatment of the fiber and dependent on its inherent nature.

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Generally, a natural clay is weakened in its strength as a result of a change of its structure by remolding. This character is called the sensitiveness of a clay, and it is designated by the sensitivity which is a ratio of an unconfined compressive strength of an undisturbed clay to one of the same clay in the state of fully remolded.
For many kinds of clay, sensitivities have been measured, but the quantitative relations between an amount of remolding given to clay and its weakening have not yet been investigated.
In order to make clear these relations, the authors have devised a remolding apparatus which gives a simple shearing deformation to a clay specimen under the constant volume, and with this apparatus they have experimented with a blue clay.
Results obtained are as follows:
(1) The more the clay is deformed, the more its strength decreases.
(2) When the clay is remolded repeatedly under a certain amplitude of the angle of shearing deformation, there is a linear relation between the degree of its weakening _nq_uθ/₁q_uθ and the number of repetition n, if both are represented in the logarithmic scale, till a considerably great value of n.
Then, with these results, the trafficability of a track type tractor on a clayey ground has been investigated.

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