[in Japanese]

View full abstract

By means of the previously mentioned thermal fatigue testing machine of high-frequency induction heating and water cooling type, this study was performed to as certain the effect of the amplitude of temperature variation on the thermal fatigue life of 18-8- and 13 Cr steels under conditions of transient temperature gradient.
The results obtained in comparison with Coffin's type thermal fatigue data are summarized as follows:
(1) In the case of thermal fatigue under conditions of transient temperature gradient, the compressive strain which had been introduced on the heated surface in the heating process was reduced gradually during the holding time at elevated temperature, and then in the cooling process, it turned into the tensile strain. The higher the temperature on the heating surface rose, the larger the reduction of the compressive strain and the tensile strain became.
(2) When this compressive strain decreased, it was considered that there was tensile stress on the heated surface. By this tensile stress at elevated temperature, the thermal fatigue life of 18-8 steel on the amplitude of temperature variation of 600 deg (C) showed about one-tenth of Coffin's type thermal fatigue life.
(3) But, in the thermal fatigue under conditions of transient temperature gradient, it showed that between the total strain range and the number of thermal cycles to the definite crack length, there was the same linear relationship in logarithmic coordinate as Coffin's type thermal fatigue data.

View full abstract

Many investigations have been made to clarify the fatigue strength of piano wires in the air, but few investigations have so far been made of the fatigue strength under the corrosive condition. Wire ropes and power-transmission wires stretched over the sea are exposed to the sun, rain and sea-breeze. The wire ropes used in manufacturing districts or coal-mining areas are exposed to the sun, smog and rain too. It is inferred accordingly that they suffer from the corrosion fatigue too. It is one of the most important problems what the characteristic of piano wires is and that of power-transmission wires is each with respect to the corrosion fatigue.
This paper gives some results of the corrosion fatigue tests made on piano wires of 0.85% carbon content by spraying hard water on them, and of the measurement of their natural electropotential.
It is clarified as the result, that the fatigue strength of the piano wires subjected to corrosion is much lower than that in the piano wires left in the air. In the air, the endurance limit of piano wires drawn and blue-hardened after drawing increases with the total reduction and takes the maximum value when the total reduction reaches about 75%. While the fatigue strength of piano wires decreases with the total reduction when hard water is sprayed over them. This may be affected by the value of the electro-potential of piano wires. The value of the electro-potential of piano wires blue-hardened after drawing is higher than that of piano wires drawn.

View full abstract

The Charpy method and the Izod method are usually applied to test of impact strength of rigid PVC plate. There are some differences between various standards on shapes and dimension of the Charpy impact test specimens. Ten kinds of rigid PVC plates have been tested according to the JIS, the ISO and the ASTM Charpy impact testing methods, and also to the ASTM Izod impact testing method. The results obtained are summarized as follows:
(1) JIS Charpy impact strengths (JIS·a_kC) of the test plates take the values from 2.3 to 8.4kg-cm/cm².
(2) ISO Charpy impact strengths (ISO·a_kC) of the test plates, except an extruded one, take roughly a constant value i.e. 2.5kg-cm/cm².
(3) ASTM Charpy impact strengths and ASTM Izod impact strengths show similar characteristics. Their characteristics are both divided into two groups, i.e. ductile group (JIS·a_kC>5kg-cm/cm²) and brittle group (JIS·a_kC<5kg-cm/cm²). The characteristics of ductile and brittle groups are similar to those of JIS·a_kC and ISO·a_kC respectively.
(4) The above mentioned phenomenon is caused mainly by the difference of notch depth.
(5) There are approximately linear relationships between various impact strengths except a few values. The regression lines shown in Table IV can be used for conversion of an impact strength into another one.

View full abstract

The moduli of elasticity of plastics are ordinarily determined by extensometers. But no extensometer can work well when the measurement of the modulus has to be made in the furnace or in the immersion testing equipment.
In this paper, a new method is proposed to determine the moduli of elasticity of plastics without using the extensometer, and a report is made of an examination performed as to whether this method is applicable to several commercially available plastics.
The results show that the estimated values calculated by this method are in good agreement with the values measured by means of the extensometer.

View full abstract

A study was made of the effect of additives on the high-temperature synthesis of zircon from zirconia and silica.
The silica used in this test was chemically pure being about 99.8%. It was identified by X-ray analyses as α-quartz. The zirconia used was about 99.9% and in the monoclinic form. Its X-ray analyses and differential thermal analyses were made in the synthesis test. The crystallographic forms present and their proportions were determined in all cases by X-ray analyses of the cooled specimens. The effects of additions of various additives on the rate of synthesis of zircon were evaluated and may be summarized as follows:
(1) CuO, PbO, CdO and V₂O₅ are effective on the degree of synthesis of zircon as shown in Table I.
(2) The minimum temperature at which zircon can be synthesized is about 1000°C in the presence of large amounts of CuO, PbO or CdO respectively. At 1100°C there are definite indications of synthesis in all three cases.
(3) The higher the additive oxide content, the more complete is this reaction at the same rate of time and at the same temperature.
(4) Cu⁺⁺ or Cu⁺ is present in quartz at about 1000°C, and the formation of PbSiO₃ melts and CdSiO₃ accelerates the quartz-cristobalite transformation. The formation of cristobalite may effectively increase the speed of the reaction between silica and zirconia.

View full abstract