A testing apparatus to measure coefficient of sliding friction between bolt and nut is producted. The axial compressive force is measured by three compressive helical coiled springs as shown in Fig. 1 and 2. A, B is the first set of bolt and nut, and A', B' the second. The spindle C fixed to A and A' by means of serration of C is turned slowly, and the torque to resist sliding friction between A and B, A' and B', is measured by F which is attached to the center of pendulum-shaft of torsion testing machine. The value of coefficient of friction is calculated by this torque and axial compressive force of springs, using equation (2). The value of coefficient of friction is about 0.2 between slightly lubricated mild pieces, and the value decreases with the increase of compressive force, as shown in Fig. 11-17. The typical diagrams of torque and twisted angle are shown in Fig. 5-10.

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In strain measurements we can not obtain the true strains at restricted points but observe the mean values of them along some finite gauge length, and the observed maximum strain usually becomes smaller than the true value.
A new graphical method of correction for such a case is presented in this paper as shown in Fig. 3.

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Previous studies have shown that the dynamical behaviour of rubber vibration absorber is explained by the fundamental stress strain relation of materials having hereditary characteristics which was proposed by Sawaragi and Tokumaru. This report described the influence of carbon black contents on the dynamical behaviour of rubber vibration absorber. As the behaviour of these materials is complex, for simplicity we took a test procedure of constant rate of loading.
We obtained the distribution functions of retardation time and hysteresis stress which characterize the behaviour of vulcanized rubbers and discussed the relation between the distribution function of hysteresis stress and the dependence of dynamic modulus and internal friction on amplitude.

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In order to research for the relation between the microscopic structure of steels and the process in progress of fatigue, we measured the changes of magnetic properties due to torsional fatigue in 0.8% C steel wires with various heat-treatments and as drawn. The changes of magnetic properties were measured from differential hysteresis loops between the test- and standard specimen on the cathode-ray oscillograph. From this experimental results, we found that the processes in progress of fatigue differed between the steels with fibre structure and heat-treated structure. That is, in the steel with fibre structure, fatigue did not make progress until a certain number of cycles of twisting stress was repeated, and after that made progress rapidly. But in the steels with heat-treated structure, fatigue made progress gradually or rapidly with the increase of the number of cycles.

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At present, the water-cement ratio that we use in the execution of the concrete building is 50-70 per-cent. The compressive strength of the concrete in this water-cement ratio is not so high, and generally, it is about 150kg/cm² at 28 days. Therefore, the proportion, or water-cement ratio that is generally used can not be applied in the P. S. concrete which needs very high compressive strength.
This is the experiment of the high quality concrete, whose strength is over 500kg/cm² at 28 days, especially on the materials, the proportions, the curings, and the time of the vibration at concreting, to which the compressive strength of the concrete is subjected.

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The anode graphite used in the electrolysis of sodium chloride solution is attacked and therefore the procedure of the electrolysis is greatly affected. In this case, sulphate ions contained in the solution permeate into graphite lattices and bring about swelling and breaking down of the graphite. The more the graphitic degree develops, the severer the action is. Natural flake graphite has good electric conductivity and other good point, although it has bad point that causes the phenomenon above described and contains large quantities of impurities. Many attempts to remove these impurities have been made, but the procedures are difficult and impractical. Today ores having high carbon content are refined several times with oil floatation, and consequently the carbon yield is very low.
Applying the swelling phenomenon above mentioned, we have succeeded in the purification of natural graphite in high yield by the use of oxidation reagents and oil floatation.

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