The effect of definite cycles of overstress σ_os (≅ 1.5 σ_w, σ_w : fatigue limit) which was applied periodically during the repetitions of the stress of fatigue limit σ_w was investigated through the behavior of micro-crack. The main results obtained are as follows ; 1) When σ_os is repeated in n_os cycles at every 10⁷ cycles of σ_w and the value of n_os is within a limited range, the specimen is broken at a small value of the accumulated cycle ratio Σ(n/N). This phenomenon seems to be due to an increase in crack opening ratio under the repetitions of over-stress. In that case, the crack propagates only under the repetitions of σ_w. 2) The value of Σ(n/N) depends on the size of a non -propagating microcrack formed by the first 10⁷ cycles of σ_w. 3) The repetition of 10⁷ cycles of σ_w increases the fatigue life of the specimen under σ_os.

View full abstract

Based on statistical natures of the crack initiation life t_i and the crack propagation life t_p, a method for predicting dependence of the distribution of the total life t_f(=t_i + t_p) on various factors was proposed. Applying the method to stress corrosion cracking(SCC) of a Ni-Cr-Mo steel in 3.5% NaCl solution, notch acuity and temperature dependence of the distribution of t_f were predicted. In order to examine the prediction, statistical SCC tests were conducted. The prediction was in good agreement with the experimental result. Furthermore, the loading type and the stress level dependence of the distribution of t_f were discussed. The experiments also reconfirmed the statistical features of t_i, t_p and t_f as found in the previous study.

View full abstract

In order to obtain the solutions for some problems involving inhomogeneous strain of an incompressible isotropic elastic material undergoing finite deformation, it is necessary to assume an explicit form for the strain energy function W. For the purpose of investigating the form of W for vulcanized rubbers which are known as typical incompressible isotropic elastic material, three kinds of SBR vulcanizates of different degrees of crosslinking were prepared, and their stress-deformation behaviors under biaxial finite deformation were observed. The experimental results confirm the applicability of the Valanis-Landel hypothesis that W can be expressed as the sum of three indentical fuctions w of the extension ratios. Therefore when the function w (λ) was proposed as a form of w(λ)=Σ^^∞__(n=-∞)μ2n(λ²ⁿ-1) good agreement with experimental data was obtained. Then application of this equation to the formulation in terms of strain invariants I₁, I₂ enables ∂W/∂I₁ ∂W/∂I₂ and W to be accurately calculated for any values of I₁ and I₂

View full abstract

In this paper, the integral equation method is presented to be applied to plane-strain boundary-value problems of an elastic body. That is, by solving Fredholm integral equations derived from equilibrium equations, static stresses under uniform tensile field and dynamic stresses due to time-harmonic plane P and SV waves, around various cross-sectional cavities in an infinite elastic medium, were analysed and numerical calculations were carried out. Especially, with respect to dynamic problems, it was shown that this method could deal with arbitrary-shaped cavities which could not be solved by the Wave Function Expansion method. In addition, the influence of the curvature of cavities, the wave number of incident waves and the effect of Poisson's ratio of elastic medium, are presented.

View full abstract

This paper is concerned with the stress concentration problems of an elastic circular solid cylinder (shaft) with an annular groove of a circular-arc form notch under tension (compression). The form factors (stress concentration factors) and the stress distributions at several cross sections of the shaft are shown. The form factors shown in this paper are compared with Peterson's results obtained from the so-called Neuber's formula. The method of solution used in the paper is to distribute axisymmetric body forces in the interior of a shaft with no grooves and to determine the intensities of the body forces thus distributed so as to satisfy the boundary conditions of the surface of an annular groove. For this purpose, we use Green's functions for axisymmetric body force problems of a circular solid cylinder, which were shown in a previous paper.

View full abstract

The anisotropy of ductility of O.46% carbon steel is examined by using small tensile specimens. The axial ductilities increase with increasing cooling rates in the heat-treatments, but the transverse ductilities are not improved by heat-treatment. Thus, a remarkable anisotropy of ductility is produced when the material is subjected to a high cooling rate. The anisotropy of ductility is caused by the sulphide inclusions which are elongated in the axial direction of steel bars, and the anisotropy can be eliminated by reducing the sulphur content or spheroidizing the inclusions. Based on the observations of fracture surfaces by the SEM, a model of crack-propagation is proposed and the mechanism of the anisotropy of ductility is explained.

View full abstract

The purpose of this paper is to study experimentally the curvature effects on the temporal mean and turbulence characteristics of two-dimensional turbulent wall jets along concavely curved surfaces with constant radii of curvature. The surface curvature adopted ranges over b/R=0∼0.1, where b is the half width of the wall jet and R is the radius of surface curvature. The turbulent energy balance in the wall jets is obtained by measuring advection, production and dissipation of the turbulent energy. It shows that their nondimensional magnitudes of the turbulent energy decrease as the surface curvature increases. The effects of curvature on the time-and space-correlations of fluctuating velocities are also considered.

View full abstract

In the preceding reports, a new theory of multifold series expansion for the steady, laminar boundary layers has been presented. The solution is given in a series of the multi-parameters which involve respectively different order derivatives of the characteristic function β(ξ)=(2ξ/U.)(dU./dξ), so that the theory covers an extremely wide range of mainstream velocity distributions. The only problem remaining unsolved is the case of the mainstream U(x) which is described by a function of class C^k(∞>k≥E; 0), that is, the case when the derivative d^k+1 U (x)/dx^k+1 indicates a discontinuity at some x-position. The present paper extends the solution to this problem by replacing the original singular characteristic function with a smooth function which is substantially equivalent to the original one for determining the boundary layer flow characteristics. The theory can be applied widely and gives good result even for a very difficult problem, for example, such as a flow containing separation and reattachment.

View full abstract

This experimental work concerns downward vertical annular mist flows which were made by injecting a small amount of water from a coaxal nozzle into a downward air flow. The apparent velocities were varied from 18.56 to 58.01 m/s for air and from 4.78×10^-3 to 1.47×10^-2 m/s for water. Axial distributions of the water film characteristics, i.e., the film thickness, maximum wave height, wave velocity and frequency were obtained by the electrical conductivity method. The distribution of the friction coefficients at the air-water film interface was obtained from the pressure drop of air flow. The mean and minimum thicknesses of water film increased gradually downward and attained a constant value at a distance x=(30∼100)d from the nozzle exit, where d is the pipe diameter. The interfacial friction coefficient decreased with x and attained a constant value at x=(50∼80)d. The non-equilibrium lengths mentioned above are considerably shorter than that determined on the basis of the axial distribution of the water mists, about 180d, in the first report

View full abstract

In order to make more clear the flow field when manufacturing a film or a sheet cooled by a wall jet, fundamental studies on the combined flow field formed by a moving wall and a two-dimensional wall jet running parallel to it were performed experimentally. The existence of a critical distance, where the gradient of the velocity profile at the surface of the moving wall was changed from positive to negative, was ascertained, and factors influencing the critical distance were identified. It becomes clear that there are some cases where the combined flow field can not be treated by a widely employed relative velocity of the respective reference velocities of the moving wall and the wall jet. Some practical data on the critical distance were given.

View full abstract

A new discrete vortex method which combines the vortex shedding model with the singularity method has been developed for the analysis of an unsteady separated flow. As this method does not use the transformation, it can be more easily applied to the unsteady flow analysis around a body of complicated shape than usual discrete vortex methods. The method is applied to the flow calculations around a square prism with angles of attack 0°, 10°, 20°, and 30°. The calculated values of the lift and drag coefficients and the Strouhal numbers are compared with the available experimental data in good agreement.

View full abstract

Two parallel rotating disks induce an unsteady flow which may be represented by a non -axisymmetric perturbation superimposed upon a rigid rotation of the fluid as a whole. The flow instability occurs as a wave propagating in the azimuthal direction. A secondary flow is observed by the smoke-wire technique of flow visualization. In order to ascertain the mechanism of the instability, a swirling flow with a region of finite thickness in which the velocity decreases from a maximum value to zero is considered. The velocity distribution of the secondary flow, as obtained by inviscid linearized stability theory, shows good agreement with the observed flow pattern.

View full abstract

Experimental results on a channel flow of a finely dispersed suspension of magnetites in water are presented over a wide range of Reynolds numbers and mean shear rates. It is shown that the fluid behaves as a non-Newtonian fluid and the magnetic field causes the non -Newtonian behavior to increase. Another contribution of the field to the flow is an increase of resistance in laminar flow and a decrease of resistance in turbulent flow. Experimental formulas for pipe friction coefficient and transition Reynolds number are presented.

View full abstract

Experiments were made on the natural frequencies of liquid columns in piping systems with tanks at both ends and with a double suction volute pump between the tanks. The natural frequencies of the liquid columns in the pump piping systems depend on the dimensions of the suction and discharge pipes, and the size of the pump. By replacing the pump by an equivalent pipe, the natural frequencies of liquid columns are not affected substantially by the rate of discharge and the rotating speed of the pump.

View full abstract

Among many types of transonic wind tunnels, transonic Ludwieg tube is the most suitable facility for very hiqh Reynolds number transonic testing. However, its starting process is quite complicated and the flow mechanism is not yet understood. In the present paper, the starting process of a transonic Ludwieg tube with a downstream quick-opening valve and a plenum exhaust system was experimentally investigated over a wide range of plenum chamber volumes and flow rates. The result shows that a steady and uniform flow in the test section is established when the mass flow rate through the porous wall of the test section becomes equal to that through the plenum exhaust system. Although this is the same as in the case of an upstream valve system, it has been also shown that the flow mechanism of both cases is quite different between the two.

View full abstract

The present study is to examine numerically and experimentally the transient characteristics of natural convective heat transfer in a rectangular cavity packed with a fluid and spherical solid particles. The natural convection occurring in dependence on the dimensions of the cavity, the porosity and the thermal physical properties of the porous media plays an important role in an evaluation of the transient characteristics of heat transfer in a porous layer. It could be understood that the natural convection occurring in the porous layer had the effects of homogenizing thermally the porous layer and shortening the time period to reach a thermally steady state after starting the heating of the porous layer. Therefore it might be possible to control the transient time period and the amount of heat stored into the porous layer by managing the intensity of natural convection with proper combinations of fluid and solid particles and dimensions of the cavity.

View full abstract

The application of the fluidized bed to a heat exchanger is intended as a means of augmentation of heat transfer. The particles of glass beads are fluidized by air flow in the vertical tube of inside diameter D=60mm. The surface with a stainless foil placed on the inside of tube is heated electrically so that the heat flux is constant. The distribution of the local Nusselt numbers in the vertical direction was measured for particle diameter d_p=0.3∼3.0mm, initial bed height L₀/D=0∼3.33 and air velocity U^^-/U_mf=0.2∼10.0. Moreover, the mean Nusselt number and the volume goodness factor were examined for performance comparison under the condition of constant pumping power. An excellent performance of fluidized bed heat exchanger was shown, and the effective height of heat transfer surface was determined.

View full abstract

In order to measure the gas temperature Tg in a cylinder of internal combustion engine in motoring operation using a cold-wire, a method by the numerical analysis of the heat -equilibrium equation for cold-wire was examined. It was found that Tg was able to be determined from the axial mean temperature Tmc of cold-wire by this method for known gas velocity U. For unknown U, Tg and U were able to be determined by solving the simultaneous heat-equilibrium equations for a cold-wire and a hot-wire.

View full abstract

In this paper, we analyze the asymmetric vibrations of thin barrel-like shells of revolution. The equations of vibration and the boundary conditions are determined from the stationary conditions of the Lagrangian of the shells of revolution. The equations of vibration are solved exactly by a series solution and then natural frequencies and mode shapes are obtained. Effects of various parameters upon natural frequencies are clarified in a discussion of numerical results. We also compare frequencies of shells of revolution with those of circular cylindrical shells. Furthermore, we obtain natural frequencies of shells of revolution which have practically important configurations and boundary conditions such as domes with skylight and so-called bell-type nozzles of rocket engines.

View full abstract

The effects of vibration isolation of a ball screw type damper applied to a simple beam, a clamped-clamped beam or a cantilever beam are discussed theoretically. The damper is composed of a ball screw, a flywheel and a dashpot. Numerical examples are given for a simple beam with one or two ball screw type dampers. It is demonstrated that, when the locations of the dampers are chosen suitably, the first, second and third resonant frequencies can be lowered considerably and the amplitude response factors of the beam at the points of attachment of the dampers are about 1 except in a narrow range of resonant frequencies.

View full abstract

In a rotating asymmetrical shaft with an asymmetrical rotor, the increase rate of total energy and the torque applied to the shaft end change with the angular positions of the static and dynamic unbalances. The response curve also changes with the angular positions of the rotor unbalances. With a rotor mounted on the middle of an asymmetrical shaft, the parallel motion of the rotor is not connected with its conical motion, and the shaft end torque can be directly obtained from the equilibrium of forces and moments. The shaft end torque in an asymmetrical shaft and an asymmetrical rotor changes with the angular positions of rotor unbalances in a similar way to the response curve.

View full abstract

This paper analyzes the vibrational response of square cylinders enclosed in a vessel of liquid and subjected to forced vibrations. Inertia force acting on each cylinder and damping effects are clarified by solving Navier-Stokes equation of motion for fluid under the assumption of viscous flow and using the fluid field network theory, in which the non-steady flow in cylinder-to-cylinder clearance is assumed to be two-dimensional. Comparing and checking the experimental and analytical results from various models of submerged square cylinders arranged symmetrically, we find that both agree well qualitatively and quantitatively.

View full abstract

This paper presents a basic research to the study on the coupled lateral vibration between rail and railway vehicle's wheels. The rail is modeled as an infinitely long beam on an elastic foundation with twosprings with respect to lateral deflection and torsion. The equations of motion describing a coupled vibration between lateral deflection and torsion of rail are introduced. The problems of a lateral and also a vertical steady state vibration of rail are formulated assuming that the contact point between a wheel and a rail moves at constant speed. Besides, the mechanical impedance and displacement function are obtained in order to clarify the dynamic characteristics of rail. Theoretical results agreewell with Remington's experimental results and, therefore, this agreement shows the validity of this analysis.

View full abstract

Various types of wheels were tested for the reduction of wheel/rail noise at SHINKANSEN test track and the characteristics of wheel/rail noise were examined. Thereby, it was verified that the contribution of noise generated by the vibration of wheel to the wheel/rail noise (roar) is comparatively small in high speed operation on straight track. Accordingly, in such a case, a damped wheel is generally ineffective and a resilient wheel shows a little effect. This is considered to be a result of reduction of the wheel/rail force. A study is made on the dominant characteristics of resilient wheel which controls the wheel/rail force.

View full abstract

To suppress the wheel/rail roar noise effectively by use of a resilient wheel, the detailed dynamic characteristics of the wheel must be clarified. In this paper, the resilient wheel is regarded as a ring with T-section supported discretely on a rigid circular cylinder, a method of analysis on its radial dynamic characteristics is proposed and the accuracy of analysis is improved by consideration of shearing deformation and rotatory inertia.

View full abstract

A method for estimating the margins of energy source of a rotor passing through resonances is established for a rotor supported by vibration isolation system with many degrees-of -freedom, and an arbitrary number of unbalances. The equations of motion are introduced as a 7 degrees-of-freedom system. This system consists of a 6 degrees-of-freedom vibration system and a driving system of rotation. The actual analyses of motions are studied using a simplified system with axial symmetry. The dynamic load torque generated by vibrations of rotating unbalances is introduced in the form of vector product and its generation mechanism is made clear. The relation between the center-of-gravity system and the center-of-mode system is made clear.

View full abstract

This paper is the first report in a series of papers which concern the reliability analysis of mechanical component mounted on structures. In this paper, nonstationary random responses are obtained for one and two degrees of freedom systems with bi-linear hysteresis restoration force by using Fokker-Plank equation. The effects of the non-linear spring constant, eigenfrequency of the system and predominant frequency of the seismic excitation on the response and magnification factor are investigated.

View full abstract

In this paper the fracture reliability of structures due to cumulative damage fatigue is obtained by combining the seismic response which is obtained in Part I and the experimental data on the low frequency fatigue, in which the variation of material characteristics due to damage is considered. By using the method, the effect of eigenfrequency of the structures, one and two degrees of freedom systems and magnitude of stress on the probability of cumulative damage fatigue failure is investigated.

View full abstract

There are two evaluating methods for reliabilty of structures subjected to seismic excitation, i.e. first passage failure <(3)> and cumulative damage failure methods <(1)(2)>. By comparing the two methods, it is known that the first passage failure method evaluates the system as weaker than the other method does. This is due to a diference in the selection of failure reference value (usually static strength of material is taken as the reference value). It is made clear in the present paper that when the static strength and stress velocity are used as a function of the failure reference, the reliability of evaluation is very close to that of the cumulative damage failure.

View full abstract

Synchronization between movement and voice is indispensable for both communication among people and improvement of the efficiency of joint working The first object of this research is to develop a quantitative and objective analysis method for movement-voice synchronization by introducing an image analysis method using computers. As an example, mother-neonate (new-born baby) communication, which is one of the primitive forms of communication, is selected as an object to be studied. Secondly, a model of the mother-neonate communication is proposed. The model depends upon the control theory, and its fundamental mechanism is discussed. It is considered that this study will give us a key to the quantitative solution about the synchronization of joint working by voice.

View full abstract

An externally pressurized gas-lubricated thrust bearing with surface-restriction compensation is analyzed theoretically for an angular displacement scheme applying an equivalent clearance model, which considers an equivalent recessed thrust bearing neglecting the local flow components in the bearing clearance, yielding angular stiffness and damping coefficient. The experimental results coincide well with the theoretical ones, which may justify the theoretical flow model. The design criterion of the bearing with surface-restriction compensation is also discussed from the results of theoretical calculations for angular stiffness and damping coefficient.

View full abstract

Hydrodynamic lubricating film between a saddle shaped face and a coned face with cavities is theoretically analyzed by a universal Reynolds equation applied to the continuous film and the cavities. In the experiment, the minimum film thickness and the leakage flow rate of a seal with manually controlled cavities are measured with the conclusions reached as follows : (1) Though the minimum film thickness is reduced, the axial stiffness of the film scarcely increases. (2) In a coned seal, when the outside pressure is higher than the inside one, the film thickness increases remarkably due to the outside pressure. (3) In a coned seal with cavitation, outward pumping is generated, and a high flow rate results from a large axial force and coned angle. (4) When the outside pressure is higher, good lubrication is possible with almost zero leakage if the inward flow due to the pressure difference is balanced with the outward pumping.

View full abstract

Axial force and diagonal moment of a radial face seal with tilted flat faces under fixed average film thickness and tilt corresponding to the development of a cavity are calculated. Then, a seal with three degrees of freedom operating under constant axial force and diagonal moment is theoretically analyzed as a practical model of a flexibly mounted mechanical seal, and the angular stiffness is found to be negative. In the experiment on a seal with three degrees of freedom under constant axial force and diagonal moment, a stable film with single cavity could not be realized. Then, tilting angle and average film thickness of seals with reduced degrees of freedom were measured. The principal conclusion is that lubricating film between flat faces is not stable under constant axial force and diagonal moment.

View full abstract

In order to elucidate the failure mode, load carrying capacity and relation between tooth profile change and dynamic performance in fatigue process of a surface hardened gear, operational fatigue tests were performed using induction-hardened chromium molybdenum steel gears, The failure mode in these experiments was pitting or tooth breakage due to tooth surface fatigue except one example in which tooth breakage occurred at tooth fillet. Tooth root strain, mode in tooth stress frequency distribution, noise and vibration increased as the tooth profile was degraded, and it was also made clear experimentally that the failure prediction by sound level change was difficult for the tooth breakage at tooth fillet and tooth breakage due to spalling.

View full abstract

In this paper, to contribute to the establishment of a calculation method for load carrying capacity of a gear pair for scoring, the effects of specific sliding and sliding velocity on the anti-seizure capacities of EP oils were examined by two cylinder test. As the result, the following conclusions are deduced : (1) EP films formation is closely related to the lubrication states of frictional surfaces and chemical properties of EP additives. In mixed lubrication, EP films are formed only locally. (2) In EP oils also, seizure tends to occur in mixed lubrication and the anti-seizure capacities decrease as specific sliding and sliding velocity increase. (3) In the case when frictional surfaces are in boundary lubrication, the maximum contact surface temperature, and in the case when they are in mixed lubrication, the bulk temperature of outer surface of cylinder can be employed as the index temperatures for seizure respectively. However, these temperatures at seizure occurrence decrease as specific sliding increases.

View full abstract

It was shown experimentally that hard aluminium sheets had better drawability in square cup drawing than annealed ones unlike in circular cup drawing. The reason was investigated from separate measurements of the component loads supported by the side and the corner portion of the punch nose with a newly developed measuring device. It was revealed that the ratio of the side component load to punch load was larger in hard metals than in annealed ones. Some other characteristics of square cup drawing were also clarified from this measurement. The above explanation on drawing characteristics was justified by the fact that the drawability was improved by some artificial drawing methods.

View full abstract

The bone cutting is one of the important operative techniques in the field of orthopaedic surgery, and it is necessary to develop some new surgical instruments having high performance so as to meet the requirements newly arisen. For instance, the artificial hip joint made of ceramics requires a rasp of new type. To develop a new surgical instrument, it is indispensable to grasp exactly the cutting force of the human bone. The purpose of this paper is, therefore, to provide the bone cutting data for the design of new surgical instruments. The bone cutting forces were measured in orthogonal cutting by using various tool materials and cutting conditions.

View full abstract