The phases in Cu-Al and Cu-Al-Mn alloys (10.0∼14.5% Al and 0.0∼14.0% Mn) subjected to slow-cooling, air-cooling, oil-quenching and water-quenching have been observed by the use of an optical microscope; and the hardness of the phases tested by Rockwell hardness tester (B scale). The relation between the phase and the hardness in their alloys has been investigated in detail. The main results obtained are as follows: (1) The appearance of filamental α phase increases the hardness of the alloys. (2) The maximum hardness will be reached within the range of appearance of the filament α phase, and migrates to lower Mn content with the increase of Al content. (3) The maximum migrates to the lower content of Al or Mn, with the increase of the cooling rate.
This experiment concerning the changes in mechanical strength at the room and elevated temperatures showed that after inflicting thermal damage, that was, the repeated heating and cooling rapidly on the austenitic stainless steels, the thermal cycles did not always weaken the strength of the materials. The following results were obtained: (1) By the damage caused by rapid heating and cooling, what is called“strain enhanced precipitation” occurs with increase of hardness due to the slip for thermal stress. The influence of this damage is more remarkable on the bending fatigue characteristics than on the tensile. (2) When the accumulative thermal damage is moderate, its strength breeds a negative damage and gains at the room and at the high temperature. When it exceeds a certain value, however, the strength drops due to the growth of precipitation particles. Their effect on the strength is more remarkable at the high temperature than at the room temperature. (3) The precipitation caused by the thermal damage is different in nature from that of ordinary heating, fine precipitation particles occurring within each grain itself, and increasing their resistance to the dislocation movement. However, the cracks due to the damage become the source of fatigue cracks. (4) The thermal resistance to the repetition of rapid heating and cooling is greater in the type 304 stainless steel than in the types 321 and 347.
The cold processing of amorphous linear polymers is performed mainly due to the solid freezing of the deformation strain at room temperature. In crystalline polymers, the cold plastic deformation occurs, which is understood to have been caused by slip etc. in the crystalline domains at room temperature. It is added to the above mentioned frozen strain. Hence the residual strain in cold processing of crystalline polymers is more stable and more permanent than that of amorphous polymers. Such new cold-treatment of crystalline polymers is experimentally studied in the compression test of polyacetal resin (Delrin) and acetal-copolymer resin (Duracon) and is examined in terms of the practical cold working of upsetting and bulging.
As is well known, the structure of the so-called“Foam”material is very complex and irregular. In the experiment of this report, we constructed a model of structure for hard P.V.C. foam, and then tried to calculate theoretically the elastic modulus as a function of the apparent specific gravity. The results of the experiments on the theory show a very good agreement with the observed values over the whole range of the apparent specific gravity except for the very small value of the apparent gravity. By using the results of this theoretical calculation, we could evaluate the elastic modulus of the material constructed by the foams when the specific gravity and the elastic modulus of the material before foaming were given. Next, we derived a distribution curve of the diameter of the foams theoretically under the assumption that volume of each foam was decided randomly, and followed Poisson's distribution. The good agreement between the results of theory and our observation has been confirmed.
Compacted soil-cement has come to be used as a road construction material in recent years. The mechanical property of soil-cement has been investigated. However, only a few experimental works have been made as to the deformation mechanism of soil-cement. Hence, this paper reports some results of the investigation on the deformation mechanism of soil-cement. In this study, the deformation characteristics of soil-cement was considered from the following three aspects. (1) Stress-strain relation under short time loading (2) Strain-time relation under constant stress (3) Deformation characteristics under dynamic stress The soil-cement dealt with in this paper is the one in a narrow sense, and contains more cement than the so-called“cement-modified soil mixture.”The cement used was normal portland cement, and the soil aggregates used was from the hills in Kyoto. The compacted soil-cement specimens were stored for a certain period in a moist room at 80 percent relative humidity and approximately at 20°C. The test specimens subjected to the sustained load were 32cm high, with 8cm diameter cylinders, and other specimens used in the dynamic test were 30cm high, with 10cm diameter cylinders. The loading apparatus was Amsler type compression testing machine, and in the creep tests the sustained load was applied by means of the spring type loading rigs. Repeated stresses were applied by a low frequency loading machine. The deformation of the soil-cement cylinder in the creep test was determined by means of a 10 in. Huggenberger strain gage and the strain in a short time compression test by means of an electric resistance strain gage. The results obtained were summarized as follows: (I) The short time stress-strain relation of soil-cement The stress-strain curve of the soil-cement, composed of coarse grade soil aggregate, showed a similar characteristics independent of the cement content, or water content. However, the characteristics of the stress-strain curve of soil-cement containing fine grade soil aggregate depends strongly upon the cement content and on the water content. (II) The creep mechanism of soil-cement (1) The effect of the water content on the creep deformation characteristics was comparatively small for the soil-cement of coarse grade soil aggregates. However, as to the soil-cement of fine grade soil aggregate, the more water content there is, the more ultimate creep deformation will be made. (2) The test environment had a considerable effect on the creep deformation characteristics. (3) Generally the cement content had a little effect on the creep deformation characteristics. (4) The results of the analysis using the mechanical model showed that the creep deformation of soil-cement was essentially due to the irrecoverable creep deformation with some retardation time. (III) The deformation characteristics under the repeated loading The stress-strain curve of soil-cement having no loading history was concave with respect to the strain axis. However the repeated stress changed the above characteristics into a convex curve.
Studies were carried out on the improvement of radiographic relative fault sensitivity, and attempts were made to find out a suitable penetrameter in order to establish a technique on the radiographic inspection by X-rays for solid composite propellants up to 400mm in diameter. The solid rocket propellants have small absorption coefficient for X-rays, so it is necessary to use lower energy X-rays in comparison with the thickness of the metals and to perform the testing in as low X-ray voltage as possible. The relative fault sensitivity thus obtained is 0.5 to 1.0 percent for the solid composite propellants of 400mm in diameter. It has been found that the hole type penetrameter is the most suitable for the solid composite propellants among various sorts.