This paper presents a three-dimensional solution for the stresses in an infinite elastic solid which contains two spherical cavities of the same size. The stress field at infinity is assumed to be uniaxial tension in the direction perpendicular to the common axis of the cavities. The solution is based upon the Papcovich-Neuber stress function approach and make use of the spherical harmonics. Numerical results are presented in graphs and the interference of the two sources of stress concentration is discussed.

View full abstract

Up to now, to analyse the problems of contact between two optional elastic bodies is very difficult because the contact area S varies nonlinearly with the contact load Ρ or displacement δ. This paper deals with the development of an automatic procedure for the analysis of the general problems of elastic bodies in contact. In this procedure, the point-matching method, which is utilized for several contact problems, is introduced into the automatic design system to form an optimum pattern. Moreover, by applying the above mentioned method the identation problem of a circular or wedgewise rigid punch into an elastic band plate is analysed in detail.

View full abstract

A continuum theory of cumulative damage of materials which contain various types of distributed defects is proposed. At first, a study is made of general kinetic models representing three types of defect growth in the elastic material. Here it is assumed that the mechanism of such defect growth is governed by a kind of pure birth process. When the nucleation process of defects is know, the damage accumulation functional at any time after the application of loads is given by the convolution integral of the probability density of defects and the nucleation rate of the defect. The internal structural change of the material brought about by the cumulative damage is ascribable to the nucleation and propagation of the defect, and can be described by introducing internal state variables. This theory is applied to the description of the mechanical and thermodynamical stability condition of equilibrium and steady state in cumulative damage.

View full abstract

The authors classified measuring methods of internal stress in deposited layer into two kinds, i.e., depositing method and removing method, and proposed a series of the measuring theories for a plate, a cylinder and a sphere. In the present paper, they propose a new method of applying X-ray to a multi-layered sphere in depositing process and show a compensating formula about a measured stress for the difference between base temperature and measuring one in the case of a two-layered sphere. As application of their theory, they measured the internal stresses of two-layered spheres chromium deposited under two different conditions on steel balls and compared the results with those obtained by applying the removing method to the same specimen.

View full abstract

The control characteristics of a shaking machine are seriously influenced by load weight of test structures. In this paper, this influence is discussed and the relations between the load weight and the optimum feedback gains of the control system are shown. In addition, an automatic feedback gain controller is developed to adjust the feedback gains to the optimum values depending on the load weight. This method has been successfully applied to a shaking machine with 1.7 ton table.

View full abstract

In this paper, acceleration control of a shaking machine is investigated, and a control system with feedforward and feedback loop is discussed. It is shown that the response of the control system is improved without losing its stability by pole-zero cancellation when feedforward signals and feedback signals are added with proper rate. This method was confirmed experimentally on a shaking machine and has been applied to some actual shaking machines.

View full abstract

In order to make clear the unsteady flow in the inlet duct of a centrifugal fan operating in the stare of rotating stall, this paper presents a method of measuring the flow by a capped hot-wire probe whose directional characteristic is very excellent. The following results are obtained. The flow mentioned above is composed of two different flow regions. One of them is a reverse flow region near the duct wall, and the other is a forward one. These flow regions are not axisymmetric and rotate at constant speed which is determined only by flow rate. In a certain range of flow rates a helical stream tuber moving forward is formed at the center of the duct near the impeller, and it rotates around the duct center. Furthermore, time averaged flow is measured by Pitot tube and compared with unsteady flow mentioned above.

View full abstract

In this report, we observe the flow pattern in a horizontal agitated thin film evaporator under the condition that thermal effects are excluded. The test model is a horizontal cylinder which has the wiping blades inside. The working fluid is water. We researched the liquid volumetric flow rate and the revolution of the wiping blades which affect the profile of the wiped liquid fillet, the state of the thin liquid film, the residence time in the apparatus and the axial dispersion. We also researched the profile of the fillet in a two-dimensional shallow water tunnel.

View full abstract

In the casting process, the air-gap formation takes place at a certain time after metal pouring, and heat is transferred by radiation and conduction through a thin gas layer in the gap at the ingot-mould interface. It is a key point in the study on casting heat transfer process to make clear the air-gap formation and the solidification mechanism at the early stages of casting process. By the experiments on the lead casting with the cylindrical chill moulds, authors investigated the casting heat transfer process with numerical calculations and continuous measurements of temperatures in ingots and chill moulds, and measured the thermal expansions of the moulds. It was found that a great and sudden decrease of the heat transfer coefficient at the ingot-mould interface took place at the time when the ingot surface separated from the mould inner surface, that is, the time of the air-gap formation.

View full abstract

In order to determine spray droplet size in diesel engine, fuel was injected into high pressure gaseous environments with a diesel engine injection system. Droplet size was measured using the liquid immersion sampling technique with the mixtute of water-methylcellulose solution and ethanol used as an immersion liquid for diesel fuel oil. The volume distribution of diesel spray droplet is well correlated with chi-square distribution with freedom, φ=8 in the range of this investigation. The Sauter mean diameter increased with increasing back pressure, with the amount of fuel in a spray and with decreasing pump speed. An empirical correlation was developed between effective injection pressure, air density, the quantity of the fuel delivery and the Sauter mean diameter of spray droplets.

View full abstract