The present paper describes experiments and some considerations on notch effect characteristics in low cycle fatigue. The experiments are strain-controlled and stress-controlled push-pull low cycle fatigue tests on unnotched round-bar steel specimens and stress-controlled fatigue tests on round-bar specimens with several types of circumferential notches. Considerations on the test results show that in order to clarify the notch effect in low cycle fatigue, it is necessary to distinguish the fatigue lives for crack initiation and for fracture. The fatigue life for crack initiation can be regarded as a function of the peak value of effective strain range at the notch, but the crack propagation after the crack initiation is almost independent of the notch. The so-called fatigue notch factor K_f, i.e. the fatigue strength reduction factor due to notch effect is discussed in various aspects of fatigue curves at low cycle region.

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Using notched specimens of mild and medium carbon steels, the effects of a gradually increasing or decreasing load and sinusoidally varying load on the crack initiation and propagation are examined and the following results are obtained. i) The linear cumulative damage law is applicable to the crack initiation of low carbon steel. ii) The superposition law is applicable to the crack propagation under a gradually decreasing load, but is not applicable to that under gradually increasing condition. iii) The superposition law is also applicable to the crack propagation under constant load test after imposing a gradually varying load, but is not applicable to the crack propagation under constant load test after imposing a sinusoidally varying load. Moreover, the experiments about the fatigue crack propagation under varying load which were performed by our research group are arranged and the following matter is confirmed. Namely, the approaches from the structural and mechanical point of view are necessary to clarify the fatigue behaviours under varying load conditions.

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The fact that the fretting fatigue strength is significantly influenced by the relative slip amplitude was confirmed experimentally and reported in the previous paper. In the present paper, in order to make clear why the relative slip has a marked influence upon the fretting fatigue strength, the relation between the frictional force and the relative slip is investigated experimentally. As the result, the alternating stress amplitude, σ_fw1, which is the fatigue limit based upon the initation of fatigue cracks under the condition of fretting, could be expressed in the following equation as a function of relative slip, S, σ_fw1=σ_w1-2_μp0{1-exp (-S/κ)}, where σ_w1 is the fatigue strength of plain specimen, μ is the coefficient of friction, and k is a constant.

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The various fatigue tests were carried out using the wheel-axle fatigue testing machine which was newly set in R.T.R.I., JNR. The obtained test results are as follows : (1) The bending stress of the car-axle assumes a superposed sinusoidal wave form, at speeds beyond 100 km/hr. (2) The Frost's formula (σ³l=550) gives the safety-side limit for the crack propagation of aged car-axle, whose cracks have been initiated in actual use. (3) The fatigue strength of actual car-axle is lower than that of the large size press-fitted speciment. (4) The fatigue strength at repeated number 10⁷ of induction-hardened car-axle is about 9 kg/mm² at the inner boss side wheel-seat and is about 6∼7 kg/mm² at the outer boss side wheel-seat. (5) When the (S/2.3-N) curve is used to calculate the fatigue life of an induction-hardened car-axle, the estimated fatigue life agrees well with the actual life.

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This paper deals with the stress field in an elastic circular ring partially supported at the inner rim by a rigid body and stretched under its own weight. It is assumed that the support is bonded so perfectly that no slip and no separation could occur on the bonded part. Complex potentials for the infinite region, bounded internally by the inside circle of the ring, are first constructed in such a way that they satisfy the conditions given along the inner periphery of the ring and have poles at infinity. The parametric coefficients included in the potentials are then determined by the traction-free condition on the outer rim of the ring. The distributions of stresses along the boundaries of the ring are shown graphically for several cases of ring configuration and support-width.

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Linear steady-state thermo-elastic problems of a solid cylinder and a hollow one with a ring of uniformly distributed point heat sources of equal intensity W are solved under plane strain theory using thermo-elastic displacement potential and Airy's stress function. It is assumed that the surface of the cylinder is maintained at a constant temperature. Numerical results for a particular case are given graphically and analyzed to determine the characteristics of the present problems.

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In order to reveal the relation between the mathematical yield condition and the number of slip planes or slip directions of a crystal, the yield stress ratio τ/σ of torsion to tension is calculated for several crystals characterized by its numbers of slip planes and slip directions, adopting Sachs model of polycrystalline aggregates. It is shown that the value τ/σ is most affected by the minor number n_m of slip planes and slip directions, and that the value τ/σ becomes smaller with the increase in n_m until it reaches 0.50 corresponding to the crystal in which slip occurs on any plane in any direction. It is also shown that the calculated value τ/σ is equal in fcc and bcc metals. However, in the case of fcc metal, the optional motion of screw dislocation is expected to reduce the value τ/σ slightly.

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Cavitation erosion has been considered the fatigue failure of the surface due to repeated collapse pressures of cavitation bubbles. The present paper deals with severe erosion tests using the magnetostrictive oscillator vibrating in water, and gives the results. Cavitation damages consist of pitting by impact fracture and falling off by fatigue failure of the surface. The weight loss in the initial period is due to small pits, while the large particles due to fatigue predominate in the weight loss in the stationary period. The small pit is made by a single blow of large collapse pressure of some bubbles which produces the maximum shearing stress beneath the surface, and the falling off of large particles is due to the propagation of fatigue cracks by repeated smaller collapse pressure of numerous bubbles. The frequency distribution of collapse pressure depends on the cavitation conditions and the distribution curve is obtained by using simple hypothesis. As the surface tension of water is decreased by an active agent, the distribution curve shifts toward smaller collapse pressure, and the erosion damage also decreases.

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When the tread brake is applied to the conventional railroad wheel, the temperature in the rim rises and a thermal expansion of the rim occurs. Since this expansion of the rim causes a redial tensile force to act on the wheel disc, it is necessary to know how the force affects the strength of the wheel. In this paper, the temperature distributions in the rim were calculated approximately as a problem of the linear heat conduction through a semi-infinite plate with a line heat source, and the thermal stresses in the wheel disc corresponding to the temperature distributions were analysed, based on the shell theory. On the other hand, brake tests on the actual wheel were conducted on a brake testing bench, and the theoretical results were compared with the experimental values.

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Various theories have been established concerning the two-dimensional type of flexural vibrations of a ring of rectangular cross section. However, for the three-dimensional type no adequate theory is given yet for a wide range of the length-to-diameter ratios of a ring. In this paper, the natural frequencies for both types are obtained by solving the characteristicvalue problem for a finite, circular cylindrical shell with both ends free and by means of a numerical evaluation using a digital computer. The paper involves two kinds of analyses : One starts from Love's fundamental equations for a thin, circular cylindrical shell. The other is based on a Timoshenko-type theory of a shell. Compared with the experimental results, the theoretical results prove to be valid for a wide range of the dimensional parameters of a ring, even for the ring whose length is about equal to or less than the thickness.

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This paper presents a new method for the calculation of the fluid flow forces acting on a valve. Its theory is based on the momentum theory and can explain the inertial force of fluid which was not considered in the former momentum theory. As an example, the dynamics of a single stage relief valve was studied analytically and experimentally. The transient response of the valve was calculated with the original nonlinear form and with a linearized form. Numerical results show the linearization does not carry much error and the linearized equations show that which are useful to explain experimental results.

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The effects of tube diameter on the propagation behavior of a shock front were investigated by using two shock tubes with different sizes and by comparing with the other data. The process of the formation of a shock front when the diaphragm was ruptured was observed by schlieren method. From this experiment, it was found that the observed shock Mach numbers were larger than the values obtained by the simple theory. Such result depends on the opening time of the diaphragm and the diameter of the tube. Therefore, the various factors influencing the opening time of the diaphragm and the shock formation distance were discussed and the functional relations between these factors were clarified using the dimensional analysis. The expression for the shock formation distance derived by the dimensional analysis was in satisfactory agreement with the experimental results.

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To explain the mechanism of the shock formation in a simple shock tube, the multi-stage model was presented, which improved White's theory, and some numerical calculations were carried out. Simple and White's theories correspond respectively to the case of zero or one stage of the present multi-stage model. The shock Mach number calculated by the multi-stage model is always larger than that obtained by the White's model. The difference between them becomes large as the diaphragm pressure ratio increases. Further in order to express the variation of the shock Mach number along the tube a function II (x) was proposed. By using this function, the phenomenon that shocks stronger than that predicted by the simple theory would possibly happen was discussed.

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The generalized solutions are obtained which connect the quasi-steady laminar boundary layer over the shock tube wall with the boundary layers of Blasius', Rayleigh's and Sakiadis'. And the skin friction coefficients and the wall heat transfer rates are expressed by the polynomials with practically high accuracy.

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Formulas for calculating the flow rate ratio of each branch pipe are derived taking the diffuser effect on divided flow and the nozzle effect on confluent flow which is caused by branching streams in a header into consideration. Effects of the divided flow factor σ_D and of the confluent flow factor σ_o in those formulas on the flow rate ratio of each branch pipe are evaluated from the experimental results for water. The factors σ_D and σ_o are dimensionless numbers given by [numerical formula] where η_σ is the diffuser factor which represents the pressure recovery factor due to branching of the fluid from a header, ψ_n is the nozzle factor due to adding of the fluid from branch pipes into a header, (ζ+λι/d) and m are the resistance coefficient of branch pipe and the ratio of crosssectional area of the header to one of the branch pipe respectively. A method for calculating the flow rate ratio of each branch pipe in the case where the inlet or the outlet of header is placed between both closed ends of the header is also presented.

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The float-area-type flow meter, frequently known as a rotor meter, is an important flow rate measuring device for the flow rate is small. The purpose of this report is to introduce relations about the performance of float-area-type flow meters for non-Newtonian fluids following the "power law" model, and to verify the theoretical performance by experiments. It is shown, as a result, that the procedure for obtaining the flow rate characteristics for this kind of flow meter is theoretically formulated. The theoretical results are compared with those of experiments which are carried out with several-percent solutions of CMC and good agreement is found to exist between them.

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The pulsating mechanisms in the two-phase flow composed of alternative gas and liquid blocks were investigated by a stochastic process specified by certain statistical characters. The stochastic approach will be preferred to the deterministic approach in some respects, as the interference between many blocks of gases in a turbulent flow of liquids seems so complicated. In this way, the pulsation, expressed by the measurement of the fluctuations of the dynamic pressure using a pitot-tube, is considered to show a stationary stochastic process. It was found the fluctuations of the amplitude of the dynamic pressure had a normal distribution and the periods of that fluctuation (which were assumed to be the periods of the bubble appearance) and a Rayleigh distribution. These results show a good coincidence with the theoretical consideration from a stochastic point of view. Further it is shown that the two-phase flow will be classified into three groups, referring to the results of those correlations.

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"Eigenvalue method", already proposed by the author for two-phase critical flow, is developed for the axial steady flow equations system where separate momentum conservation can be strictly postulated. Besides the comparisons of physical meanings in two-phase critical flow between energy and entropy, conservation equations are also investigated. The conclusions for steam water mixtures are as follows. (1) "Eigenvalue method"defines the criticality as the discontinuous condition of steady flow differential equations system and can treat easily such a complicated system composed of separate momentum between two phases, energy, and mass conservation equations. (2) The solutions given by the above theory can well explain the former empirical data except for critical slip ratio which has not well been investigated experimentally. (3) Critical condition with energy conservation gives a more accurate solution than one with entropy conservation. But the latter is still good approximation.

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Flow rate, distributions of temperature and pressure and exit steam void fraction in long channel are measured for steam water two-phase mixtures under higher reservoir pressure conditions, resulting the following parameters. critical pressure 4∼48 ata reservoir pressure 9∼70 ata exit steam quality 2∼14% critical flow rate 0.5×10⁴∼3×10⁴kg/m²sec channel diameter 10mm∼50mm channel length 100mm∼2200mm The conclusions are as follows. (1) Saturated condition is satisfied even at the exit of shorter channel (L/D∼3) when steam bubbles are absorbed into channel inlet. (2) Critical conditions among critical pressure, quality and flow rate coincide well with theoretical solutions reported in the previous paper. (3) Measured critical slip ratio may be almost explained by theoretical predictions. (4) Critical pressure ratio gradually decreases with increasing channel length in such a way that has been theoretically predicted. (5) The channel whose diameter is up to 50 mm can be treated as axial saturated flow.

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Saturated water discharging through orifices is theoretically and experimentally studied and the following results are obtained. (1) Saturated critical flow through frictionless channel can be easily treated by combining critical condition with such upstream parameters as static pressure and steam quality, and this method can be applied to predicting of discharging rate of saturated water through orifice except the cases where thermodynamical metastability is established. (2) Ratio between back pressure and upstream pressure is not invariable, but this seems to form one of flow conditions. (3) The magnitudes of orifice diameter and upstream pressure which can be treated by traditional orifice constant of around 0.6 are in a considerably wide range. (4) In the case when orifice flow rate is calculated as homogeneous flow, orifice constant seems to converge around 0.4 as for large orifice size and high upstream pressure. (5) The flow rate through orifice varies with a decreasing back pressure until the critical condition is reached.

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The following problems concerning numerical solutions of one-dimensional heat conduction are clarified as the first step in applying numerical methods by digital computers. (1) Difference equations corresponding to boundary conditions of, no flux across the surface, prescribed flux across the surface, linear heat transfer at the surface, non-linear heat transfer, contact with a well-stirred fluid or perfect conductor, and the surface of separation of two media of different conductivities, are proposed. The stability conditions for these equations are shown. (2) The conditions necessary to obtain stable numerical solutions of the required accuracy-2∼3% of the maximum temperature change-are discussed. These conditions are shown in a specified region of t_min/Δt-at_min/(Δx)² diagrams for each of the above boundary conditions. From the diagrams, the means sufficient to obtain numerical solutions of the required accuracy are revealed to be t_min/Δt≥6 and at_min/(Δx)²≥0.4∼2.6.

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A new method of simultaneous determination of thermal conductivity, thermal diffusivity and heat capacity using a plane-shaped heat source is investigated. The principle of this method is based on the transient temperature rise of an infimite solid by a plane heat source. Conditions and accuracy of measurements by the above principle are determined analytically. Experimental results with apparatus based upon the above conditions, using a nichrome foil heater of thickness 0.03mm and a 60×60×30mm PVC plastics sample, were satisfactory. An accuracy of 5% could be attained. The apparatus for this measuring method is simpler than that of O. Krischer or of W. Knappe.

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The current study presents some experimental results for examining the maximum heat fluxes in pool boiling of saturated water at atmospheric pressure on partly ill-wettable heating surfaces. The experiment was carried out on the electrically heated horizontal strip, at the center of which an artificially ill-wettable portion was installed. The boiling regime on the ill-wettable portion at very low heat fluxes is nucleate boiling whose behavior closely resembles a transition one. Alternatively stable vapour film is formed on this portion at comparatively low heat fluxes of 5×10⁴kcal/m²hr to 10⁵ kcal/m²hr that depend on the geometrical dimension of ill-wettable area and thereafter the simultaneous nucleate-film boiling is realized. Accordingly, in such a system, while the maximum heat fluxes are prescribed by the transition to film boiling for large sizes of ill-wettable part, the formation of stable vapour film is not clear for small sized ill-wettable part on account of drastic hydrodynamic interaction of nucleate boiling. Parallel to the experimental measurements of heating surface temperature at the center of ill-wettable portion for simultaneous nucleate-film boiling regime, simple analytical calculations were performed and, in consequence, favorable consistencies were obtained for the wide ranges of heat fluxes and ill-wettable dimensions of interest.

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This study describes the combustion inhibition effect of a potassium salt on propane-air flames by the change of the activation energy of the overall chemical reaction. The extinction limit of an opposed jet diffusion flame and the laminar burning velocity of a premixed burner flame of propane-air were measured to obtain the activation energies. From a theoretical analysis of the opposed jet diffusion flame, the overall activation energy of the chemical reaction against the seeded quantities of potassium salt was calculated using the extinction limit data. Through increasing the potassium salt percentages, the increase of the activation energy, i.e. the decrease of the chemical reaction rate, was shown both analytically and experimentally. The ratio of the activation energies with potassium salt to the ones without obtained from the burning velocity of the premixed flame closely agreed with that from the opposed jet diffusion flame. The relation between the seeded quantities of potassium salt and the activation energies of the overall chemical reaction of propane-air was quantitatively obtained.

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A study was made to find an indicative factor of the optimum closing angle of an inlet valve for an engine system without intake and exhaust pipe effects. From analytical discussion, the authors derived as this factor the nominal Mach number of incompressible fluid flow through a mean effective valve area into a cylinder due to piston motion at its mean speed. This factor coincides with"Inlet-Valve Mach Index"adopted by C.F.Taylor for estimation of volumetric efficiency. Examination of the computed result of the weight of charge air for a variety of valve lifts and closing angles at motoring has shown that this nominal Mach number defines the relation between volumetric efficiency and valve closing angle. A series of experiments were then made to measure volumetric efficiency under various valve lifts and closing angles at motoring by means of the hydraulic tappet with a leak hole as presented in the previous paper. The results verified the theoretical prediction with rather small errors.

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In this paper is presented a new design formula for the bending strength of a gear tooth based on the true stress on the root fillet of the gear tooth, which differs from conventional design for mulas based on the tooth-form factor. The bending fatigue limit values for gears of various kinds of materials and heat-treatments, obtained after years of experiments, which have been carried out by the authors, are shown in a table. Moreover the values of driving condition factor (alternative load factor) and life factor (load repetition factor) involved in the design for mula are also given in this paper in a table or by a formula. Thus the defects of the conventional design formulas of a gear tooth are expected to be removed.

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In machining operations by multi-spindle machine tools or transfer machines, the choice of tool change procedures, especially the decision of tool change interval is critical to the economy of the production. Due to the inherent variability of the tool life, the optimum solution is not directly reached : however, in this study, a simulation by Monte Carlo method offers a useful means to determine the most economical method and interval of the tool change. From the computed data, it is indicated that the scheduled tool change is more economical than the tool change as the tool fails, and that the total cost and time of production are largely reduced by a proper choice of its interval.

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The self-excited vibration during the grinding process is closely related to the surface waves generated on the grinding wheel. Influences of the wear characteristics of grinding wheel and the grinding stiffness on the generation of waves are investigated. Then, it is concluded that the attritious wear of cutting edges plays an important role in the generation of waves. Namely, the waves are generated at almost the constant magnitude of cutting edge ratio. A practical method, in which the rotational speed of grinding wheel spindle is changed, is proposed for the reduction of self-excited vibration.

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