In order to clarify the effect of particle-crushing on the shear characteristics of granular materials, high-pressure triaxial compression tests were made on two kinds of sands and the change in surface area of the samples during shearing was examined. It was shown that the surface area S depends not only on stress but also on strain, and hence it was suggested that S may be a function of plastic work done W. It was also found that the ratio (dS/dW)f of a specimen at failure, which was defined as a measure of particle-crushing property, is closely related with the dilatancy rate (dv/dε1)f and the maximum principal stress ratio (σ'1/σ'3)f at failure. Thus a new method was established here to relate the particle-crushing property to the shear characteristics of granular materials under triaxial stresses.
Copper particles, glass beads and enamel frit-polymer compound powders were prepared by the air suspension coating method, the spray drying method and the liquid suspension coating method. Epoxy resin, methyl methacrylate resin and polystyrene were employed as polymers. The mean particle sizes of the compound powders prepared by the air suspension coating method and the liquid suspension coating method were about 100μm, while the size of the powder prepared by the spray drying method was about 10μm. The compound powder was pressed into a disc and the corona-charging potentials of the powder layers were measured. The corona-charging properties of the compound powders depended on the kind of polymers and on the preparation method. The compound powders using epoxy resin generally showed high surface potentials and the decaying of the surface potential was slow. The surface potentials increased with an increase in polymer content for all compound powders. The compound powders prepared by the air suspension coating method and the spray drying method showed high surface potentials, while the surface potentials of the corona-charged powder layers decayed very rapidly for the compound powders prepared by the liquid suspension coating method. The complexing situations of core materials and polymers are assumed to affect the corona-charging properties of compound powders.
The vacuum freeze drying by using zeolite as an adsorbent of water vapor was applied to food materials such as carrot and shrimp, and from the result of our experiment the following conclusions were drawn. (1) The time needed for drying can be shortened substantially as compared with the conventional method, by circulating air current into the layered beds of food materials and zeolite. (2) The dried products retain their original form and do not get stale during a long period of preservation (about two years). (3) The zeolite which has adsorbed water vapor hardly desorbs under the pressure (10Torr∼0.4Torr) tried in this experiment, but easily desorbs when heated at about 500°C and can be used repeatedly. (4) Natural zeolite was found to possess as much effectiveness as synthetic one. When economy is taken into account, the use of natural zeolite is highly recommendable.
In this investigation, the pore structure and the tortuosity factors with respect to gas flow and diffusion were studied for glass bead sintered pellets (GB) and several practical porous materials. The above three characterizing properties were measured by a marcury penetration method, a permeation method and a Wicke-Kallenbach type diffusion apparatus. The obtained results are as follows: (1) On the basis of Parallel Pore Model, the effective diffusion coefficient De for a practical porous material can be estimated well from both the pore diameter and the tortuosity factor τD of 2.35 obtained for GB. (2) The difference between τF and τD seems to be attributable to the difference in each effective pore space for flow and diffusion.
The adsorbed amounts of organic vapors, i.e. CH3OH, (CH3)2CO and (C2H5)2O, on NaBr particles preadsorbed by water Vapor have been determined at -78, -63.5, -45 and 0°C. Three different amounts of the preadsorbed water, Va, Vb and Vc, are used in this study, where Vb=2Va and Vc=3Va. The value Va was approximately equal to the value necessary for covering the unit surface area of NaBr particles with localized monolayer of water. The monolayer capacity of methyl alcohol estimated from its adsorption isotherm for NaBr surface Va-preadsorbed was found to agree closely with the amount of preadsorbed water. This result is explained by the following two assumptions that water molecules are adsorbed on (100) planes of NaBr crystals in the ratio of one watar molecule to two adjacent anions at Va-adsorption and that methyl alcohol molecules are adsorbed on such localized water molecules in a ratio of 1:1. Moreover, the adsorptive activity of Vb-preadsorbed NaBr surface for ethyl ether was slightly larger than that of the Va-preadsorbed surface. Therefore, in the Vb-preadsorbed surface, water molecules in the upper layer, i.e. second layer, are expected to adsorb on the localized monolayer so as to interact strongly with ethyl ether molecules. By using the three organic vapors in such“double adsorption”system, some significant informations were obtained about the adsorptive structure of water molecules attached on NaBr surface, and the interactions between preadsorbed water molecules and the organic molecules. From these results, the double adsorption method is considered to be an effective tool for studying the mechanism of a solid-gas adsorption.
Effects of temperature gradient and particle orientation on moisture transfer coefficients in the earthenware and the kaolinite plastic mass during drying process have been investigated by determining moisture distribution curves under a condition of one dimensional water transfer. The results are summarized as follows: (1) During the constant-rate period, the temperature gradient scarcely affects the moisture transfer coefficient, whereas, in the falling rate period, the moisture transfer coefficient increases steeply up to four-fold in comparison with that under no temperature gradient when the interior temperature of specimen is higher than the temperature of drying surface. On the other hand, it decreases to one-half under the inverse temperature gradient. (2) The moisture transfer coefficients in the direction parallel to the particle orientation for the constant- and for the falling-rate period are several and nearly one hundred-fold larger than those in the direction perpendicular to the particle orientation, respectively. The results could be ascribed to a larger tortuosity in the path of moisture movement and to a smaller number of capillary per unit area in the perpendicular than in the parallel direction to particle orientation.
In order to investigate the axial segregation characteristics of binary solid mixture in a horizontal rotating conical vessel, experiments were carried out by using binary mixtures of particles having various sizes, densities and shapes. On a basis of the assumption that the axial segregation in a conical vessel is controlled by two factors; one is the radial segregation of binary mixture in the vessel and the other is the cascading angle difference between particles of the mixture, each of these factors was measured in a horizontal rotating cylinder. As a result, it was obtained that the final axial segregation can be estimated by the segregation characteristics given by the above factors.
Recently the authors proposed the following experimental formula expressing the rate constant of degradation of under-size particles, Kx, during ball mill grinding. Kx=C1x/xfHV-0.47Wx-1.5 where xf is the feed size, x, the sieve size and Wx, the feed weight. On the other hand, Work Index Wi proposed by Bond is inversely proportional to the ball mill grindability Gb·p0.82, and Gb·p is proportional to Kx·Wx. From the above results, it was found that Work Index Wi can be expressed by the dimensionless Vickers hardness HV and density ρ of the material. Wi=C5·(x/xf)-0.32HV0.39·ρ0.41
Recent developments in ceramic fabrication processes enable one to produce transparent and translucent polycrystalline ceramics. These ceramics are fully densified and have near zero porosity in order to eliminate the dispersion of light and internal reflection due to heterogeneities of their texture. This is achieved by sintering a well prepared raw material under carefully controlled atmosphere, temperature and time schedule. In the present study, transparent alumina was prepared by a sol-gel method. The fabrication process comprises the four stages of precipitation of aluminum monohydroxide, formation of the sol, formation of the gel, and firing to alumina. The thin plate of gel was formed by very slow dehydration of an aqueous sol at ambient pressure and temperature, and then it was heated in air to obtaine a transparent alumina. The resultant alumina was transparent up to 1000°C, above which it was opalized gradually with temperature accompanying the formation of α-alumina phase. The following sequence of transition was identified by the X-ray powder diffraction; Boehmite gel-δ-alumina-θ-alumina-α-alumina
The interaction force between microparticles was measured with an electrobalance directly in various atmospheric conditions, particularly in the humidity controlled air, nitrogen and vacuum. The interaction force of glass microspheres in a dried atmosphere changed inversely as the square of the distance between two particles. It was considered that the attractive force was resulted from the Coulomb force between the particles. However, it was difficult to establish the relation between the attractive force and the particle size, because the attractive force was influenced strongly by the experimental condition. The interaction force between the hydrophilic particles in humid air was so little as to be neglected when the particles were brought close together. But the cohesive force of the particles needed to separate them each other was larger than the Coulomb force and it varied with humidity of air. The cohesive force did not change at the lower humidity range, but increased rapidly at the humidity of 60% or above. These results suggest that in a humid atmosphere the interaction force between the particles results from the capillary condensation of water vapor associated with the contact of two particles.
The energy dispersive X-ray fluorescence technique was successfully applied to a sedimentation method to analyze particle size of each component in powder mixtures. The most simple technique is the measurement of the fluorescent X-rays from a deposit through the bottom window of a sedimentation cell. In this case, however, it is difficult to get the high sensitive and precise analysis especially for minor components because of limitation in thickness of deposit due to the self absorption. In order to facilitate the analysis in wide ranges of sample quantity, component concentration, atomic number, and particle size, two types of apparatuses were devised. (1) Deposit transfer type; a thin film as a belt extending at the bottom of the cell is incorporated to remove the deposit whose quantity reaches to a limit, and the measurement is successively performed in real time. (2) Fraction preparation type; a top-sealed and bottom-opened cell is moved in a vessel filled with the liquid, and thus prepared deposits are taken out from the liquid, as specimens directly usable to the X-ray analysis. Applications were made to analysis of airborne particulates and rock powders, and to investigation of the component behavior in a slurry mixture.
Thermoluminescence glow curves above room temperature and the related optical absorption spectra have been studied on MgO single crystals irradiated by electrons, X-rays or UV-light, with emphasis on conditions which are of interest for applications to radiation dosimetry. The relatively pure MgO specimens show high response, in which the intensity of thermoluminescence is linear for a wide range of radiation doses. The glow peak temperatures depend somewhat on impurities contained in the samples, but not on the kind of radiations. The first peak appearing at about 87°C is intimately related to the V- centers. Its intensity decreases in proportion to the optical bleaching of the V- band even under the room light. The third and fourth peaks appearing at about 144 and 180°C are thought to be most suitable for dosimetry use.
The tensile properties and isothermal and thermal fatigue life at high temperatures were measured on the centrifugal casting HK40, which had been used for chemical plants at high temperature for a long time. The results obtained showed that these properties have a tendency to increase a little at higher temperature than 700°C, as the material is aged by using for a Long time. Further, it is found that the area of cyclic σ-ε hysteresis loop and fracture tensile strain can be used to predict the isothermal fatigue life, and that the thermal fatigue life is nearly equal to the isothermal fatigue life at the maximum temperature.
Fatigue tests were conducted on tufftrided low carbon steel specimens with various notch conditions. The notch radii were 13.5, 4.3, 1.9 and 0.8mm, and the values of stress concentration factor α were 1.1, 1.3, 1.6 and 2.0, respectively. Fatigue test on the smoothed specimen was also carried out. The hardness distribution and the microstructure of each specimen were investigated before and after the fatigue tests. Based on these results, the discussion was carried out on the improvement mechanism of fatigue strength in tufftrided steel. The conclusions were summarized as follows: (1) The fatigue limits of notched specimens with α of 1.1 and 1.3 are larger than that of a smoothed specimen in case of tufftrided steel. (2) When tufftrided specimens are subjected to reversed stress, the hardness and the hardened depth at the inner part of the specimens increase and nitrogen precipitates as Fe4N at the same time. (3) The increasing rate of hardness and the amount of nitrogen precipitated by reversed stressing decrease with an increase of α, and these phenomena are hardly observed in case of the notched specimen with α of 2.0. (4) The increase in hardness and hardened depth by reversed stressing contributes to the improvement of fatigue strength in tufftrided steel, and the degree of contribution is influenced by the amount of nitrogen precipitated by reversed stressing.
At present, Hot-dip Galvanized high strength hexagon bolts having high strength levels of above 95kg/mm2 are frequently used for fastening structural members of outdoor structures such as a transmission steel tower in Japan. Though Hot-dip Galvanizing is very superior in corrosion resistance in general, delayed fracture has occurred presumably due to hydrogen embrittlement. Therefore, we thought the following two reasons for the delayed fracture occurance: Hydrogen enters into the steel by acid pickling in the Hot-dip Galvanizing process and stays in. Or the cracks occur in the Galvanized layer under fastening, and then, hydrogen enters into the steel from the environmental atmosphere. To ascertain the above consideration, we performed the static bending test and delayed fracture test etc. on the Cr-steel specimens subjected to the same heat treatment as that for the bolt. As the result, we obtained the following conclusions. (1) Delayed fracture occured even in a short dipping time. (2) The thick Galvanized layer makes transmission of hydrogen atoms difficult, so that it is not possible to remove hydrogen from the steel by the usual baking treatment. (3) Delayed fracture almost never occurs when the acid-dip process is not incorporated. (4) Delayed fracture often occurs because cracks nucleate in the Galvanized layer by adding impact energy on a bolt.
When the properties of FRP are discussed in terms of its interface, the following three kinds of interface in FRP must be taken into consideration: fiber/matrix interface as a constitution of FRP, matrix/matrix interface as a representative of laminating condition and FRP/FRP interface as a characteristics of adhesion. Since these interfaces are aligned in a series in the flatwise direction of FRP, the individual property of interface or the relation among the three interfaces can be evaluated by applying tensile load in this direction. In this paper, the relation between fiber/matrix and FRP/FRP interfaces and its dependence on the type of matrix used were studied. Two types of matrices selected were orthophthalic and isophthalic unsaturated polyester resins which show obvious difference in their adhesiveness. The reinforcement was roving glass cloth. The results obtained showed the validity of the method used in the present study. The main conclusions were as follows: (1) In the case of FRP having sufficiently high bond strength at fiber/matrix interface, the relation between fiber/matrix and FRP/FRP interfaces is affected by the matrix, adhesive and curing condition, so that the location of the weakest interface varies. (2) The dependence of the bond strength of fiber/matrix interface on the type of matrix can be determined by testing FRP with various fiber/matrix ratios. But it must be cautioned that the fracture mode also depends on the type of adhesive and rigidity of FRP specimen. (3) The property of matrix can be evaluated by changing the surface roughness of FRP, since the location of the weakest interface depends on the type of matrix.
Elastic-plastic plane stresses in the notched specimens made of duralumin and carbon steel were measured by means of both the photoelastic coating method and the X-ray method. When plastic stresses were analyzed by means of the photoelastic coating method, the following assumptions were employed; the materials are isotropic and obeyed Mises yield condition and Prandtl-Reuss stress-strain rule. From these experiments, we have obtained the following results. The stresses measured by means of the photoelasto-plastic method were in good agreement with those by the X-ray method in the case of the elastic plane stress state, but in the case of the plastic stress state, the stresses by the X-ray method were smaller than those by the photoelastic coating method. The propagating velocity of plastic region across the center section was smaller in the specimen with smaller notches than in that with larger notches, and moreover the velocity in carbon steel specimen was greater than that in duralumin. Furthermore, the rate of decrease in the plastic stress concentration factor at the bottom of notches of carbon steel was greater than that of duralumin.