We analyze the stress distribution in a thick elastic plate under torsional displacements by a pair of annular rigid punches. If the distribution of contact shear stresses on the punch regions is assumed as an appropriate series, the problem is reduced to the solution of an infinite system of simultaneous equations. Numerical results are illustrated for the distributions of displacements and stresses in the plate.

View full abstract

Sandwich plates are often used with several surrounding reinforcements or connections, forming a complicated construction. At present, for these analyses, F.E.M. (Finite Element Method) is found valid and recommendable comparing with the usual analytical method. However, the representation with sufficient precision has not yet been obtained for this problem. A practical method for the problem was proposed, and it was confirmed that the method had sufficient accuracy and favorable characteristics of convergence shown by numerical examples. Next, several experiments on rectangular plates with various aspect ratios were made and the results compared with the values calculated by our method. Experimental results show satisfactory agreement with the calculated ones even in the case of concentrated load. As a result, this method is considered one suitable practical use with sufficient accuracy and convergency.

View full abstract

Crystalline and amorphous polymers were hydrostatically extruded at room temperature with pressures up to 4 kilobars. Polymers studied include polyethylene, polypropylene, nylon, polyacetal, polyvinylchloride, ABS-co-polymer, polymethylmethacrylate and polycarbonate. Within the range of reduction percentages studied, 20-85%, the extention showed higher flow stress and lower elongation than the starting materials except PMMA: Fourfold increase in elongation with essentially unchanged flow stress was observed with the amorphous polymers. Dimensional stability of the crystalline extrusion at room temperature and also at 100°C decreased with an increasing reduction percentage and reached a minimum at 60% reduction, followed by an increase with higher reduction. On the other hand, with the amorphous polymers, the higher the reduction percentage, the poorer the dimensional stability. A linear relation was established between the extrusion pressure and the extrusion ratio. The polymers were also tested for compression, bending, specific gravity and hardnees, and correlation among the test results was discussed under assumption of a possible structural change due to hydrostatc extrusion.

View full abstract

To improve the modal damping of a structure, some types of active dampers such as an electro-dynamic or an electro-hydraulic servo damper were investigated and reported. However, they have a few defects such as the large size of force generator and their expensiveness. A simple servo damper which has a couple of electro-magnets in push-pull operation is introduced, and three types of servo damper constructions are tested to decrease the peak resonances of the ram system such as a planer machine tool and with good results.

View full abstract

According to a potential flow analysis, the variation of blade thickness affects not only the circulation of the axial blade row, but also the optimum inflow condition. From this point of view, a calculating method has been proposed, by which the design camber and stagger are corrected theoretically so as to operate at the optimum condition when the thickness deviates from the basic profile. The method has been applied to NACA 65-series compressor blades, and compared with some classical theories. Correcting diagrams for the camber and the stagger are prepared by use of the carpet plotting technique. The necessity of further experimental studies by considering the variation of loss coefficient is suggested.

View full abstract

In this paper a numerical method for supersonic conical flow without axial symmetry was developed as follows: the governing equations for conical flow without axial symmetry were derived from a pair of stream functions of conical flow and a vorticity equation, and were transformed into Stocker & Mauger's coordinate system. By this method the numerical solutions were also presented for the supersonic flow past conical bodies which produced elliptic conical, nearly conical, and pseudo-triangular conical shock waves, and were compared with other investigator's solutions.

View full abstract

If the flow area of a duct is reduced beyond a limiting value, the flow will be choked and, after a transient period of wave propagation, it will become steady and the flow rate will be decreased. At present, however, the choking phenomenon is not well understood. In this paper, the limiting conditions and the strength of a shock wave which propagates upstream when choking occurs are calculated, assuming that the flow is one-dimensional. Next, the transient flows around six kinds of wedges which were set in the low pressure channel of a shock tube were observed optically both by the schlieren method and a Mach-Zehnder interferometer. As the results, the choking process of the flow and the effect of the choking on the shape and behavior of the reflected shock wave were clarified. When the flow is choked at the wedge section, the experimental results of the velocity of the reflected shock wave agree well with the values calculated by the present one-dimensional method.

View full abstract

Measurement of viscous frictional moment and a visual study of flow between eccentric rotating cylinders, of which the outer one rotates, are done for the relatively large clearance ratios. Friction factors are considered for various eccentricity ratios in the laminar, the transient and the fully developed turbulent flow region, respectively. In the fully developed turbulent flow region, friction factor C_M can be given by C_M^∝ R_ω^-0.3 for various eccentricity ratios m. In the transient region where a turbulent spot or a spiral turbulence is observed, the oscillatory change of friction factor can be measured. But such an oscillation is damped, as the flow becomes fully turbulent. Critical Reynolds number decreases significantly with an increase of eccentricity ratio.

View full abstract

Impinging jet flames are obtained on the surface of an object attached by impinging of fuel gas and air mixture to it. The flames have a ring shape and wide stabilizing regions. Experiments were carried out to determine the stabilizing limit of the flames for various shape objects such as flat plate, concave and circular cone. Highest blow-out velocity of the flame is obtained when H/D ≑ l for position of the burner tube against the object, where H is the distance between the object and the burner tube exit and D is the diameter of the burner tube. Blow-out velocity of the flames become higher with an increasing fuel concentration of the jetted gas mixture. Stabilizing limits of the flame are widened with a decreasing concave radius of the object; but for a smaller radius of concave beyond a certain value, the flame is stabilized by another mechanism due to a recirculating flow around the burner tube.

View full abstract

A most general form of the mobility equation is presented, which predicts the number of inputs required to drive a single loop mechanism having such geometrical constraints as passive freedoms and redundant freedoms. Passive rotational freedoms and redundant translational freedoms are described with use of spherical indicatrices and closure equations. Applying graph theory, a method of synthesizing single loop overconstrained mechanisms is given, which is illustrated through examples.

View full abstract