In this paper, the technique to estimate the fracture behavior of a porous material, which may be counded as one of the grain dispersed composite materials, is researched by using a simplified simulation model and the F. E. M. The simulation model is composed of the unit elements (a) and (b), (a) being made of a matrix only, and (b) of an element of pore enclosed by a matrix. The deformation behavior of this model may be analyzed by the F. E. M of the substructure model or the equivalent element model and from these results the elastic and the fracture behaviors can be estimated. As one of the applications of the simulation technique to the actual materials, a two-dimensional porous model is analyzed and the results are compared with the experimental values of a polyester material.

View full abstract

Torsional fatigue tests were conducted on plain and pre-cracked specimens with different combinations of the stress axis and the anisotropy direction. The fatigue behavior was observed microscopically as well as macroscopically. For the plain specimen, anisotropy was observed in total fatigue lives which was caused by the difference of microscopic fatigue process due to laminated structures and inclusions. However, no anisotropy was found either in slip band formation at an early stage of fatigue process or in macroscopic appearances of fatigue-failured specimens. For the cracked specimens in which band structures ran parallel to one of the principal stress axes. Effect of inclusions on macroscopic fatigue process was found more remarkable for the plain specimens than the pre-cracked specimens.

View full abstract

The dynamic response of an infinite circular cylindrical shell, which is suddenly imposed with equal and opposite radial loads, is treated within the framework of Flugge's and Donnell's shell theories. Donnell's theory is not recommended as compared with Flugge's theory for predicting the deformations but is satisfactorily accurate for predicting the stresses. In the case of the concentrated loads, the bending moments beneath the load are equal to infinity but the stress distributions agree approximately with the stress distributions under the loads applied constantly over a small area until the radius of the area equals to roughly ten percent of the radius of the cylindrical shell.

View full abstract

The present paper deals with quasi-static coupled thermoelastic problems for an infinite medium with a spherical cavity and for a solid sphere, and the effect of thermoelastic coupling on variations of temperature and thermal stresses is examined in detail. From results obtained by numerical calculation the difference between the uncoupled and coupled solutions for a solid sphere is recognized to be larger than that for an infinite medium with a spherical cavity. Particulary, with regard to a solid sphere the following fact is obtained. Even for usual industrial materials, e.g. aluminum alloy, the difference between the values of the uncoupled and coupled stresses amounts to about 10 per cent in some portions of the sphere at a certain time. Maximum values of the coupled thermal stresses become larger than those of the uncoupled ones and the former increases with a larger coupling coefficient and a smaller Poisson's ratio. Moreover, under consideration of the thermoelastic coupling effect, it can be explained that an adiabatic change of volume and a variation of temperature occur even in the region where heat flow from the boundary has not reached.

View full abstract

This paper is concerned with axisymmetric problems of an elastic half-space with body forces acting in the interior of the elastic solid expressed in cylindrical co-ordinates. General solutions for the problems mentioned above are shown separately: (a) the boundary is assumed to be free from applied forces; (b) the boundary is kept fixed. Employing the general solutions shown, exact solutions for the stresses and displacements of an elastic half-space subjected to radial forces, which act on a finite line vertical to the boundary surface, are obtained. As simple examples of application of the general solutions shown in the paper, solutions for problems of (i) a radial force acting at a point, (ii) a torsion force acting on the circumference of a circle and (iii) a single force acting at a point, are also presented.

View full abstract

The paper reports the results of an examination into the performance of a variable stiffness-type dynamic damper which is intended to increase the cutting performance of machine tools with a long overhung ram. The spring stiffness of the damper is changed externally by adjusting the position of a damper mass. Investigation is made to establish a condition for tuning the damper to maximum efficency when changes in the length of the ram take place in cutting operations. The demanded damping properties are confirmed through the measurements of frequency and step responses. Therewith, results of cutting tests are presented, illustrating the degree of chatter elimination obtained by use of the damper.

View full abstract

This paper presents a systematic design of servodamper systems from a point of view of output feedback control. Firstly, by using a parameter optimization technique, the output feedback control law is derived. In the case of incomplete feedback problems, however, the instability of the system must be considered in contrast to the optimal control system. Secondly, this paper presents a new concept of "the best performance point", which minimizes the mean square value of a state. Thirdly, in accordance with the best performance point, the determination of the output control law o f a servodamper system is demonstrated and the resulting system is compared with the optimal control system. The experiment of the servodamper system subject to the application of the output feedback control law is also derived.

View full abstract

This paper presents a short survey of the more analytical development of the second-order theory which was formulated in the previous paper (Ref. 1). The method of matched asymptotic expansions is applied to the integro-differential equation for the case of the small jet momentum coefficient C_j, which was previously derived in the first-order theory on a twodimensional supercavitating jet-flapped foil between two parallel solid walls. The lift slopes are found as series expansions in powers of δ and logδ valid for δ≤1, where the small parameter δ is proportional to C_j. Expressions of the lift slopes which are found to the third order expansions for δ agree closely with the numerical results obtained by earlier study (Ref.1), even near δ=1.

View full abstract

The flow pattern in a rotating, radial passage is largely affected by the flow conditions, rotational speed, and geometrical configuration of the channel. In this report the velocity distribution including primary and secondary flows as well as the pressure distribution in a rotating, conical diffuser, with the opening angle of 2θ=10° and the area ratio of 4:1, is studied. The following results are obtained; (1) With the channel rotation the velocity near the pressure side is increased, while the velocity near the suction side is decreased. (2) When the rotational speed exceeds a certain limit, separation begins on the suction wall and the pressure recovery in the diffuser is largely reduced.

View full abstract

An experiment was carried out on cylindrical chokes with unnegligible inlet length for the purpose of clarifying their dynamic characteristics. The results were compared with the analytical solutions derived with use of the equivalent viscosity. In the experiment the frequency response was obtained on various chokes with spring loads at their outlet, where the fluctuating pressure at the choke inlet was taken as the input, and that at the outlet and the piston displacement as the output. Further the analysis was extended to the case of two chokes connected in series. The test results showed good agreement in a comparatively wide frequency range with the analytical solution of the equation linearized on the basis of the equivalent viscosity, and the solution was found to give characteristics similar to the first order system. In addition it is pointed out that the characteristics of two chokes in series can be obtained as in the case of single choke by solving the fundamental system equations expressed with use of the equivalent viscosity.

View full abstract

In order to discuss the thermal aspect of a cylinder under grinding or rollers, a brake disc and a gear under operation, temperature distribution caused by the moving heat source should be analyzed as the first step. Authors studied to rearrange the definition of Green function in accordance with Entropy Minimum Theory, and by means of variational method, introduced the Green function of a cylindrical body for 48 various boundary and thermal boundary conditions. Then, formulas of temperature distribution about the following three examples are obtained, (1) a cylindrical body with infinite length, heated by a moving band heat source; (2) a cylindrical body with finite length, heated by a band heat source with longitudinal distribution; and (3) a disc heated by a moving face heat source upon the disc. Finally, numerical results of Example (1) are graphically illustrated.

View full abstract

This investigation is experimentally carried out on the dependence of heat transfer on the intensity of free turbulence and on the superficial heat capacity of a suspension loaded with glass spherical particles of 55 μm. The experiments are performed using a flat plate, which has a comparatively low temperature surface to make it possible to neglect radiative heat transfer coefficients at a constant surface temperature. A large increase in heat transfer coefficients is shown at loading ratio m<0.8 due to the moving turbulent inducer of particles, when the initial turbulence intensity of main stream is small. In contrast, when the main stream is already in high turbulence, the particles reduce turbulence intensity and in this region the increase in heat transfer is mainly performed by superficial heat capacity of working fluid.

View full abstract

A new method of simultaneous measurement of thermal properties--- thermal conductivity, thermal diffusivity and heat capacity ----- of plane-shaped solids by continuous heating is presented. The principles of the measurement are based on the iterative calculations, that is, the numerically calculated temperature responses of a specimen with assumed thermal properties are compared with the experimental ones, and the above procedure is iterated until the calculated temperature responses coincide with the experimental ones. Necessary conditions of measurement and calculation are determined by theoretical analysis. This method is examined theoretically and experimentally and is shown to be useful for rapid estimation of temperature dependencies of the above thermal properties.

View full abstract

In search of ways to obtain uniform outlet temperature distribution on crossflow heat exchangers, theoretical analyses by means of Laplace transformation are further developed, and experimental investigations are carried out on both the plate fin type and the fin tube type crossflow heat exchangers. The analyses and experiments are conducted under the conditions of (1) various distribution patterns of fluid flow rate and (2) various distribution patterns of heat transfer area, and the results thereof are compared. In consequence, by setting the fluid flow rate distribution, as confirmed by the analyses, uniform outlet temperature in an appreciable degree can be obtained over a wide range of NTU, and better temperature efficiency is achieved. By varying the heat transfer area distribution, similar results are obtained, but this method is impractical compared with the former.

View full abstract

For the application to film cooling of turbine blades, experimental investigations are made on the blowing characteristics of a single hole on a circular cylinder in cross flow, and on film cooling with injection from rows of holes located near the leading edge of a flat plate model with a blunt nose, and on the change in the flow pattern of the injected flow around the model by visualizing technique. It is concluded that the flow rate coefficient of an ejection hole varies under the influence of the main flow, and that the film cooling effectiveness downstream of rows of blowing holes is sometimes lowered by excessive injection, and that the inclination of ejection holes in the spanwise direction shows very high cooling effectiveness.

View full abstract

The distributions of temperatures and species concentrations within a small combustor of can-type were measured for the inlet air temperatures of 320 and 430 K and for various swirler vane angles. A higher inlet air temperature accelerated the combustion process in the primary zone, the resultant higher temperature level throughout the combustor reducing the emission of carbon monoxide. No significant difference in nitric oxide emission, on the other hand, was observed in the range of inlet air temperatures studied. The concentration of carbon monoxide decreases more rapidly as a greater part of the combustion process takes place in the upstream part of the combustor. The formation process of nitric oxide is also affected by the combustion process but in a more complicated manner.

View full abstract

An axi-symmetrical, two-dimensional model of gas turbine combustors of can-type has been developed in which both turbulent diffusion and chemical reactions of finite rate are taken into account simultaneously. On the basis of this model, the distribution maps of the velocities, temperatures, equivalence ratios and the concentrations of oxygen and nitric oxide, as well as the axial profile of combustion efficiency were predicted numerically, which have several features common with the observed ones. This suggests the availability of the present model for examining the roles of various parameters in the formation process of nitric oxide. Its capacity in predicting the blowout behaviors of combustors was also anticipated.

View full abstract

The relative behavior of an apex seal to the walls of the sealing slot, that is, the lateral movement of an apex seal in the slot is analyzed experimentally by measuring, in synchronization with each travel of the apex seal along the trochoidal housing, the change in electrical resistance between a side of an apex seal and an electrode located in the trailing wall of the slot, by the use of a pair of coils and a slip ring. The objectives of this work were to measure the lateral movement itself and to investigate the effects of engine speed, load and the side clearance in the slot on the lateral movement of the apex seal. The comparison between experimental and analytical results was also made to bring to light the primary factors of the lateral movement.

View full abstract

Distribution of stresses on cutting blade and cutting force in soil cutting are analyzed by experiment. The variable parameters are the kinds of soils (dry quartz sand and plastic loam) and the cutting conditions (cutting angle, depth of cut and cutting speed). Stresses are measured by miniature pressure cells and friction cells which have been developed by authors. In sand cutting, the pressure p and the frictional stress f on the cutting blade both increase in proportion to the depth, and the relation f=up is always valid between p and f. In loam cutting, pressures change according to the cutting conditions, but frictional stresses are always distributed uniformly on the cutting blade regardless of the cutting conditions. Moreover, the relations between cutting-force-application point and the cutting conditions are analyzed. Important things for earth-moving machines are explained from the results of these experiments.

View full abstract