Using electro-polished low carbon steel specimens, the change in surface states and the incipient fatigue cracks of plain and notched specimens subjected to rotating bending stress were investigated. The main results obtained are as follows. (1) When the limit stress for macro-crack initiation σ_w1 is repeated, the amount of slip bands appearing at the root of notch is nearly equal, not only after 10⁷ cycles but also at every cycle ratio, even if the maximum stress ασ_w1 at the bottom of notch is different in various radii of the notches. (2) In the specimens with various radii of the notches, the limit stress for slip bands initiation σ_ws is almost proportional to the stress σ_w1, that is, σ_ws≌(0.85∼0.9)σ_w1. (3) The incipient fatigue cracks, which appear on plain specimens after 10⁷ cycles of the stress σ_w1, can hardly sustain the tensile stress statically and dynamically.

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The superficial Rockwell hardness tester comes into use for quality control of thin metal sheets because of quickness of testing. Therefore the establishment of JIS (Japanese Industrial Standard) on this hardness tester is urgently needed. This report makes clear the effects of errors in the preliminary load W₁ kg, the total load W₂ kg and the diameter D mm of the steel ball indenter on the superficial Rockwell hardness reading. The extended Meyer's law that has been successfully used for the Rockwell hardness test is again applied to this test although the loads in the latter are smaller than in the former. The deviation of the hardness reading is theoretically analyzed and the following formula is obtained, taking the Meyer's index n as 2.3. For example, ΔH_R30T=(100-H_R30T)(0.044 9ΔW₁-0.033 7ΔW₂+0.466ΔD). A good agreement is observed between the calculated values and the experimental ones. In addition, the authors' proposal for establishing a tentative JIS is shown.

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The purpose of this paper is to clarify the lateral vibrational characteristics of a leaf spring. The frequency equations are formulated under the assumption so-called "point pressure". For a number of leaf springs, the natural frequencies and their normal modes are calculated, and good agreement with experiments is obtained. Furthermore, for a multi-leaf spring, it is found that the analytical method based on the stepped beam hypothesis fails to predict some of the significant modes in the high-frequency region, while the presented method yields favourable numerical data.

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Linear theory was constructed on a thin, jet-flapped airfoil with fully developed wake which was operated between free surfaces of a free jet stream. This theory was based upon the Tulin's linear theory and the thin jet theory of D. A. Spence (Ref. 1). The basic relation was expressed as a integro-differential equation for the slope of the jet. The solution was expressed as the sum of a Fourier series together with the function possessing the form of logarithmic behavior. Important results are : (1) when the airfoil exists in the jet stream, the lift coefficient decreases as te width of the jet stream becomes narrow ; (2) when an airfoil exists beneath the free surface, the lift coefficient increases as the distance from the free surface becomes small.

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The terminal velocities, which are available for the analysis on the hydraulic transport of solid materials as the important parameters, are investigated experimentally about the retarding effects of pipe wall and of concentration of materials. About the effect of wall on the falling velocity of a single particle, the experimental results are in good agreement with the theoretical ones for R_e «1, where R_e is the Reynolds number based on the diameter of the sphere. For 1⪅R_e⪅100, this effect is greatly influenced by Reynolds numbers, but it is independent of R_e for R_e⪆100. These results are discussed in connection with the flow pattern around a sphere. In the case of a crowd of particles, the floating velocities, which can be measured easily, are applied as the terminal velocities and the correction formula is obtained for the wall and concentration effects.

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The present report describes an experimental study on the distributions of local void fraction along a cross section of a vertical channel in fully developed air-water two-phase flow at atmospheric presure, using a probe method. In bubble flow, a peculiar distribution which was fundamentally different from a power law distribution accepted in previous studies was observed. It had a peak of void fraction near the wall. The position of the maximum void fraction was at (0.5∼0.7)d from the wall where d was a bubble major axis. The authors proposed an empirical formula which was in good agreement with the present and another experimental results and applicable not only to bubble flow but also to slug flow. Comparisons between this formula and previous formulas were made in the experimental results.

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A Simultaneous flow of heat and fluid through porous media was analyzed with the thermodynamics of irreversible processes. The dustry gas model for the porous media was applied, and the gradient of isothermal chemical potetial was transformed into a simple form as a function of measurable variables. The phenomenological equations to account for these phenomena were induced after the above transformation. Each linear relation derived from the above mentioned phenomenological equations was examined by experiments in which a packed bed of standard sand was used as the porous media and air as the fluid in a temperature range of 30°C to 100°C and a pressure range of 0.01 Torr. to atmospheric pressure. The range in which these linear relations were valid was clarified. Furthermore, the thermal transpiration, which was the interaction phenomena between heat and fluid flow through porous media, was investigated by experiments and its effect was found to be very small.

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It can be expected to have a good performance by using a variable geometry turbine as the vehicular gas turbine and the turbocharger of automotive diesel engine. For such usages, it is very important to estimate the performance of the turbine for a wide range of nozzle angles. In the paper, a method of performance estimation for a variable geometry radial inflow turbine is presented by treating the analysis based on so-called one-dimensional flow theory using the nozzle velocity corfficients and degrees of reaction experimentally obtained. This method is applied to the radial turbine experimented in our laboratory and NASA, and the estimated performances are compared with the experimental ones. These comparisons show that both the efficiency and the mass flow can be predicted to within 4% for a wide range of nozzle angles.

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A test engine which is an air cooled single cylinder diesel engine (D×S=88×100 mm) has a stick developed easily.When we put the ring which has a large side clearance in the ring groove or an inside taper ring into the rectangular groove, the ring-stick is prevented. To find out the cause, we measured the piston temperature, quantity of gas leakage, and radial and axial motions of the ring with a special device.

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