In this paper, authors describe on the results of some mechanical tests concerning the brittleness of unplasticized polyvinylchloride.
The size of specimens which were used in our experiment was of J.I.S.
Tensile test, slow bend test and charpy impact test for specimens with or without U-notch were carried out at room temperature and each low temperature above-60°C.
From the results of these experiments, the authors have found that, there are nearly equal tendencies, as compared to the properties of carbon steel, concerning the effects of temperature and loading velocity on the absorbed energy per unit volume and transition temperature of this material.

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In designing the vibration isolator, it is highly desirable to minimize creep strain of rubber. Therefore, a study was made to make comparison as to the creep characteristics using specimens mentioned in the first and second reports having the same title. The first creep curves were got by loading nearly same stress in a moment. Then taking off the constant stress instantly, we investigated a permanent set from the recovery curve. At the same time, the characteristic function Φ(v) was determined from the creep curve. As a result, some interesting facts were observed. In case of single rubber, the instantaneous strain (6sec. after loading) of Neoprene and Hycar is smaller than the others and the creep rate of Hevea and Neoprene is lower than the other two. In the case of blended rubber, the difference of instantaneous strain and that of creep rate which are shown in every single rubber have disappeared and their deviation are small. The recovery creep tests were continued in order to find out a permanent set. The permanent set of blended rubbers and single rubbers can be compared with each other by the equivalent coefficient of viscosity. η of single and blended rubbers are in same order. Concerning in the case of Silicone rubber, the permanent set could not be obtained in the range of our experiments. Comparing the first and second curves, creep rates in the formers' are larger than those of laters', except Hevea stocks. Silicone rubber showed a considerable variation. An instantaneous strain in the first creep is evidently larger than in the cases of first recovery and second creep curve. As previously reported, the oil resistancy and dynamic properties of blended rubber are inferior to those of single rubber, but in the range of our experimenes, blended rubbers in any combination showed creep characteristics almost similar to those of Hevea stocks.

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This paper deals with theoretical cosiderations of dynamics on the special wide V belt when running. There are very few papers reported in the literatures, especially theoretical ones. Therefore it is not useless to study the dynamics theoretically. This paper consists of two treatments. One is the study on vibration taking place on the running belt, and the other is on the stability of running belt.
1. Firstly the shape of vibrations which occur on the running belts has been examined to clarify the most harmful form of the wave in order to prevent the damage, and it found that the most easiest and effective method to prevent the harm is to change its tension a little to guard against the resonace of belt caused by outer forces.
2. Among V betls used in the variable speed mechanism, there are special belts having a wide breadth than ordinary one. Employing these belts, we sometimes encountered with happenings which seemed to have been caused by the buckling where the belt ran into a pair of sheaves. The reason of it can be explained as follows: The buckling force is occured when the side pressure of belt comes unevenly to the upper part of the belt. In order to hold the stability of running belt, the maximum side pressure can be obtained as an action of bredth thickness, young's modulus and Poisson's ratio.

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In the previous paper on some behaviors of rubber vibration absorber in the torsional fatigue test, we reported the relation between the fatigue life and the hardness of the specimen. Here we want to explain more in detail the fatigue cracks under various test conditions and the fatigue life.
The test was carried out for specimens 30mm. in diameter and about 5mm. in length using the hysterograph.
The obtained results were as follows:
(1) The fatigue crack observed in the torsional test was produced in the direction of the angle about twice that calculated from the shearing angle on the surface of the specimen.
(2) The fatigue crack observed on the specimen which was given an initial compression was making an angle of about 25 degrees with the pasted plane and developed obliquely into the interior forming a cone. Furthermore, if we compressed the specimen and cut off the protruding part along the cylindrical surface connecting the circumferences of the pasted parts, then we observed that the angle between the pasted plane and the tangential plane of the depressed part was about 25 degrees.
(3) In the case of the fatigue test which was carried out on the specimen given either initial tensile or compressive deflection, the amplitude of the torsional moment either decreased or increased compared respectively with the value obtained for the specimen which was not given any initial deflection. The fatigue life, that is the repeated cycles until the crack appeared, increased or decreased for the cases respectively.
(4) The fatigue life of the specimen was very long in the case where the protruding part produced by the initial compression was cut off along the surface connecting the circumferences of the parts. For example, under the same shearing angle, even if the specimen undergoes the same amplitube of the torsional moment, the fatigue life of the specimen given the abovementioned operation was about three times longer compared with the specimen which was not given any intial compression.

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It is well known that concrete fails at a stress smaller than its static strength, when subjected to sustained or repeated load. But the information on failure of concrete under these loads is meager, and the information on ability of concrete to resist these loads has never been established to the extent which it can be accepted without question.
In this paper, the stress-strain relation for concrete beam subjected to flexure was studied and the following conclusions were obtained.
(1) The relationship between flexural stress and tensile strain, plotted on logarithmic graph, is rectlinear up to a certain point, and at this point, the slope of stress-strain relation varies abruptly.
(2) Test Results show that the strain corresponding to the first point at which the slope of stress-strain relation varies represents maximum deformation which concrete is capable of developing without undesirable effects. Then, the author named it "deformation limit" of concrete.

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