Showing papers in "Jsme International Journal Series B-fluids and Thermal Engineering in 1972"
TL;DR: In this paper, two criteria of ductile fracture strain are suggested from the theory of plasticity for porous materials, and the following criterion of fracture for a triaxial state of stress is obtained: [numerical formula] where ee_qf is the equivalent fracture strain, σm the mean stress and σ e_q the equivalent stress, a0 and b0 are constants.
Abstract: Two criteria of ductile fracture strain are suggested. From the theory of plasticity for porous materials, the following criterion of fracture for a triaxial state of stress is obtained: [numerical formula] where ee_qf is the equivalent fracture strain, σm the mean stress, σe_q the equivalent stress, a0 and b0 are constants. Except under certain conditions, this criterion shows reasonable agreement with experiment. To improve the accuracy of the prediction of the fracture strain, the above criterion is modified as follows: [numerical formula] where c0 is a constant. It is found that this criterion provides a greater accuracy for prediction of the fracture strain.
187 citations
148 citations
TL;DR: In this article, the authors presented a formulation of the process to generate a solid figure from a three view type drawing automatically by machine, and a practical system was built up for the case of polyhedra.
Abstract: Three view type drawing has been used widely for a long time, and it plays an important role in the field of design engineering. Recently, computer graphics has been developed and applied to practical use, but there are many serious problems remaining unsolved, for example, problems concerning the method to feed the three dimensional information accumulated as a three view type drawing into a computer and so on.In this paper, the author presents a formulation of the process to generate a solid figure from a three view type drawing automatically by machine. According to this formulation, a practical system was built up for the case of polyhedra. Executing several experiments the auther confirmed the effectiveness of this formulation. He points out a "Ghost Figure Problem" of a wired figure obtained during the procedure of this system and presents a method to solve it. Furthermore, he proposes a method to solve a "Hidden Line Problem".
116 citations
TL;DR: Fretting fatigue tests have been made about the effect of clamping pressure, p0, and hardness of materials on the initiation of non-propagating cracks and also complete fracture under the conditions where the relative slip is fully controlled.
Abstract: Fretting fatigue tests have been made about the effect of clamping pressure, p0, and hardness of materials on the initiation of non-propagating cracks and also complete fracture under the conditions where the relative slip is fully controlled. The main results obtained are as follows. (1) Fretting fatigue strength based on the initiation of fatigue cracks, σw1, decreases linearly with the increase of p0. (2) Fretting fatigue strength based on fracture, σw2, decreases gradually with the increase of contact pressure, and reaches a critical strength when p0 is beyond a certain value. (3) These results in (1) and (2) are analogous to fatigue phenomena of notched specimens, when the stress concentration caused by fretting is considered. (4) When the relative slip of fretting is relatively large, σw1 is affected by the susceptibility of materials to wear.
54 citations
TL;DR: In this article, the motion of a vapor bubble in sub-cooled boiling was studied experimentally using slightly subcooled water, ethanol, and carbon-tetrachloride under the atmospheric pressure, and the experimental data for the collapse stage were well correlated by the equations which were derived by assuming a laminar heat trasfrer between the spherical bubble and the surrounding liquid with uniform subcoolings.
Abstract: The motion of a vapor bubble in subcooled boiling was studied experimentally using slightly subcooled water, ethanol, and carbon-tetrachloride under the atmospheric pressure. The degree of subcooling ranged usually from about 2°C to 50°C, and in a few extreme cases it was extended to below 1°C. The experimental data for the collapse stage were found to be well correlated by the equations which were derived by assuming a laminar heat trasfrer between the spherical bubble and the surrounding liquid with uniform subcoolings.
51 citations
TL;DR: In this article, a method for evaluation of contact stresses between two or more elastic bodies with frictional forces on the contact surfaces, by means of a finite element method, is discussed.
Abstract: This paper discusses a method for evaluation of contact stresses between two or more elastic bodies with frictional forces on the contact surfaces, by means of a finite element method. The matrix equation is solved by some nodal points being prepared on the contact surfaces. These nodal points are classified into "adhere to" or "slide over" one another categories, depending upon whether frictional forces are greater than the shearing forces or not, and contact conditions are applied for each case. For example, numerical results for two rectangular plates and two cylindrical columns having different sizes and Young's moduli which are compressed into one another are obtained. Contact pressure along the contact surface of rectangular plates without friction is in good agreement with the exact solution for semi-infinite plate, except near the end of the contact surface. Also the influences of friction on the contact stresses are discussed.
47 citations
TL;DR: In this article, the authors investigated the effect of the eddy diffusivity of the gas flow containing the droplets from the relation between the distribution of velocity and that of shear stress in the gas stream.
Abstract: The experimental results are described on the transfer rate of liquid droplet onto the duct wall, the distributions of the droplet volumetric fraction, the droplet and gas velocities, and the pressure loss for a two-phase (Air-water) annular mist flow through a horizontal rectangular duct. The mean diameter of droplets was in a range from 27 to 40 microns in this experiment. The droplet transfer coefficient onto the wall derived from the experimental results indicates that it is affected by the droplet concentration as well as the gas velocity. Therefore, for investigating the mechanism of droplet transfer, the effect of the eddy diffusivity of the gas flow containing the droplets is discussed from the relation between the distribution of velocity and that of shear stress in the gas stream.
43 citations
43 citations
TL;DR: In this article, the velocity distribution and wall pressure at any section may be predicted if the conditions at an upstream station and the relative roughness of the pipe are specified, using semi-empirical equations.
Abstract: Swirl flow in a long pipe is experimentally investigated. In the major part of the pipe, that is, except at the entry zone with a very weak swirl, the circumferential component of the velocity is proportional to the radius near the wall. The axial component of the velocity is minimum at the center and the radial distribution is similar to the velocity profile of the wake behind a body in a uniform flow. The intensity of swirl is indicated by a parameter. The variation of the parameter and the wall pressure along the length is examined for three pipes with different relative roughnesses and semiempirical equations are derived. Using the equations, the velocity distribution and the wall pressure at any section may be predicted if the conditions at an upstream station and the relative roughness of the pipe are specified.
42 citations
TL;DR: In this article, wake patterns of a translatorily oscillating airfoil in a uniform flow were visualized by Schlieren method, and observed wake patterns were classified into three types: straight, shed vorticities move downstream with uniform velocity, and Kutta-Joukowski's condition holds at the trailing edge.
Abstract: For the calculation of unsteady flow around an airfoil, the following assumptions are usually made: 1) Wake is straight, 2) Shed vorticities move downstream with uniform velocity, 3) Kutta-Joukowski's condition holds at the trailing edge. To estimate the validity of these assumptions, wake pattern of a translatorily oscillating airfoil in a uniform flow was visualized by Schlieren method. Instantaneous wake patterns were photographed at reduced frequency between 1 and 19. Observed wake patterns were classified into three types. The range of reduced frequency and oscillation amplitude for each type was given. Kutta-Joukowski's condition was found to be valid at any test condition in the sense that a dividing stream line detached the airfoil at the trailing edge.
39 citations
TL;DR: In this article, a simplified crack model has been conducted on the wedge action of the viscous fluid in the cracks subjected to the bending moment, and rotating bending fatigue tests have been carried out on carbon steel specimens in paraffin oils of high and low viscosity.
Abstract: Numerical analysis of a simplified crack model has been conducted on the wedge action of the viscous fluid in the cracks subjected to the bending moment, and rotating bending fatigue tests have been carried out on carbon steel specimens in paraffin oils of high and low viscosity. The crack rate decreases when the product of the viscosity and the cycle frequency, ηf, is increased in agreement with the analysis. However, the crack rate increases when ηf is greater than about 105 owing to the poor penetration of oil into the fissures. The protective effect of oil, which limits the access of oxygen to freshly created surfaces, is hardly found. Neither the effect of the viscosity nor that of the cycle frequency is observed in silicone oil. This may be due to the small pressure index and to the weaker adhesion to the crack wall of silicone oil, which is improved by activation with stearic acid.
TL;DR: In this paper, a simply supported column with an initial deflection, which has on end been struck by a mass along the axial line at higher impact velocities than in the previous study, was treated.
Abstract: This paper treats a simply supported column with an initial deflection, which has on end struck by a mass along the axial line at higher impact velocities than in the previous study. The numerical solutions agree with the experimental results. Conclusions are as follows: (1) In the case of the high velocity impact, the column is buckled locally near the impact end. After that, this buckled region spreads towards the supported end. (2) The axial force begins to decrease rapidly by this local buckling, and later a large tensile axial force caused by the effect of unloading wave is observed near the supported end. (3) The higher the impact velocity is, the shorter the buckled wavelength becomes, and then the fracture point approaches the impact end. (4) The phenomena abovementioned are due to the influence of axial force.
TL;DR: In this paper, a new method is tried for the measurement of the local void fraction, based on the principle that if there is a liquid metal at the top of the optical fibre glass probe, the signal light reflects and turns back the fibre glass.
Abstract: The local void fraction is one of the most essential parameters to clarify the precise structure of a two-phase flow. In the report, a new method is tried for the measurement of the local void fraction. The method is based on the principle that if there is a liquid metal at the top of the optical fibre glass probe, the signal light reflects and turns back the fibre glass. If not, the signal light scatters out. In the first report, the measurement is carried out in the case of a mercury-air two-phase flow in a vertical pipe. The present results show good agreement with those obtained by the method of pressure gradient.
TL;DR: In this article, a method of vector analysis based on flow characteristics of a Bingham solid, is presented for a finite bearing and shear stress and velocity distribution in the film are obtained.
Abstract: The qualitative analyses for the core formation inherent in a Bingham solid have already been given by the previous investigations for hydrodynamic lubrication of a Bingham solid. However, they don't make clear the behavior of the solid exactly, because the analyses for finite bearings are not sufficient.In this paper, a method of the vector analysis based on the flow characteristics of a Bingham solid, is presented for a finite bearing and shear stress and velocity distribution in the film are obtained.Using this method, we deduced the equivalent Reynolds equation of a Bingham solid and also established the general theory on the core formation. Consequently it became clear that the core formation is determined by the shear stress distribution which depends on the pressure gradient, the film thickness and the velocity of the slider surface.
TL;DR: In this article, Sneddon's solutions are applied to the contact between gear teeth on the hypothesis that the effect of gear profile can be neglected in discussing local deformation on "line of contact".
Abstract: In this paper, the experimental studies for the basic problem of the contact between gear teeth are presented. When a concentrated load acts on an infinite elastic solid, Sneddon's solutions are applied to the contact between gear teeth on the hypothesis that the effect of gear profile can be neglected in discussing local deformation on "line of contact". Correct functions are suggested. These correct functions contain the effect for the deformations with the distance from the free edge to the posiitons where a concentrated load acts on and where deformations are measured. There were applied to the contact between a finite width roller and a same width flat surface. The deflections and the load distribution were evaluated to make use of Sneddon's equation and the correct functions. The evaluatd results with these equations coincided with experimental results. And it becomes clear that the width of a gear tooth should be taken into consideration on the deflection when the width is narrow.
TL;DR: In this paper, a method for predicting the droplet transfer rate is proposed, which is expressed theoretically in terms of the duct height, the eddy diffusivity and scale of turbulent motion of droplet based on an analytical model, in which are introduced a diffusion equation for droplet concentration in the turbulent core region of duct flow.
Abstract: The liquid droplet transfer onto the duct wall was studied experimentally in the previous paper, part 1. In the present paper, a method for predicting the droplet transfer rate is proposed. The droplet transfer coefficient is expressed theoretically in terms of the duct height, the eddy diffusivity and scale of turbulent motion of droplet based on an analytical model, in which are introduced a diffusion equation for droplet concentration in the turbulent core region of duct flow and a new boundary condition taking into account the behavior of droplets near the duct wall. The ratios of the eddy diffusivity and scale of turbulent motion of droplets to those respective values of gas phase are estimated from Tchen's theory by substituting empirical data of turbulent energy spectrum of single phase gas flow. The trend of predicted values for the droplet transfer coefficient agrees well with the empirical results described in the previous paper when the effect of droplet concentration on the turbulence of gas phase can be neglected. A general semi-empirical equation for the coefficient including the effect of droplet concentration is also presented.
TL;DR: In this paper, the authors studied the deflection of a rack-shaped cantilever plate with finite width due to a concentrated load and established an approximate formula for defections.
Abstract: In this paper, the deflections of a rack-shaped cantilever plate with finite width due to a concentrated load are studied. The numerical solutions for the deflections obtained by applying calculus of finite differences to the basic differential equation, show a few similar characteristics on condition that pressure angles of rack-typed cantilevers are equal. An approximate formula for defections has been established to make use of these characteristics. This formula coincides with the numerical solutions and with the experimental results. The effects of the number of teeth of gear on the characteristics of deflections are discussed in comparison with experiment on a gear tooth profiled cantilever.
TL;DR: In this paper, a basic equation of air-lift pump performance is derived from a simple momentum equation, and frictional pressure drop in two-phase flow is expressed by means of liquid volume fraction of the mixture.
Abstract: A basic equation of air-lift pump performance is derived from a simple momentum equation. In the analysis, frictional pressure drop in two-phase flow is expressed by means of liquid volume fraction of the mixture, and slug flow is assumed in order to obtain the relationship between liquid volume fraction and flow rates of both phases. The results predicted by the analysis are compared with experimental data of other investigators as well as of the authors. Good agreement with experimental data is shown in the ranges of 25 mm≤D (inner diameter)≤100 mm, 4 m≤L (length of pipe)≤42 m and 0.4<σ (submergence ratio)<0.8. To give a clear explanation for pump characteristics, the efficiency of air-lift pump is subdivided into two components, the pipe efficiency and the ideal discharge efficiency. A procedure of a pump design is proposed.
TL;DR: In this paper, the authors performed experimental studies on influences of nozzle conditions such as thickness of nozzle wall or boundary layers on the inside and outside walls of a nozzle on the characteristics of jets in the main region.
Abstract: Concerning double concentric jets, the authors performed experimental studies on influences of nozzle conditions such as thickness of nozzle wall or boundary layers on the inside and outside walls of a nozzle on the characteristics of jets in the main region. And the following results are obtained. (1) In the main region, the dimensionless radial velocity profile fits the cosine curve independently of values of δ^-, λ and χ^-. (2) The velocity decay on the central axis and the intensity of turbulence are hardly affected by the value of δ^- for small values of λ. But for large values of λ, the tendency of velocity decay becomes remarkable and the intensity of turbulence is affected heavily by the wake behind the nozzle wall with an increase in the value of δ^-. (3) Values of ι^- and e^- vary in radial and axial directions and these values are different respectively in both cases of large and small values of λ.
TL;DR: In this paper, the relationship between the coefficient of drag and the Reynolds number on a sphere in the polymer solutions was studied experimentally through on the measurement of terminal velocity and the observation of flow about a falling sphere.
Abstract: The relationship between the coefficient of drag and the Reynolds number on a sphere in the polymer solutions was studied experimentally through on the measurement of terminal velocity and the observation of flow about a falling sphere. And then, the effectiveness of Stokes's law and Perry's curve for the concentrated polymer solutions (CMC & PED) in the range of low Reynolds numbers (less than 103) was examined using Re* instead of Re and the drag reduction of very dilute polymer solutions (PEO) in the range of high Reynolds numbers (more than 5×103) was confirmed. Besides, it was shown that such a drag reduction was characterized by two dimensionless numbers, Reynolds number (Re) and Weissenberg number (Rn*: Reiner-Rivlin model or Ne*: Combination model).
TL;DR: In this article, perfect Fourier series solutions for superharmonic vibrations in various piecewise-linear systems with viscous damping, and a stability criterion for these solutions utilizing Hill's infinite determinant are given.
Abstract: This paper deals with perfect Fourier series solutions for superharmonic vibrations in various piecewise-linear systems with viscous damping, and gives a stability criterion for these solutions utilizing Hill's infinite determinant. Resonance curves for superharmonic vibrations of the 3rd order and stability charts for vibrations of Type I are constructed. The results using analog computer are shown to confirm these curves and charts.
TL;DR: In this article, the authors theoretically analyzed the variation of the oil film thickness and the pressure distribution of hydrodynamic thrust bearings under periodical load and verified the results experimentally.
Abstract: With an increasing capacity of large marine engines, the axial vibration of a large ship propeller shaft becomes a new problem. In order to solve this, investigation of the dynamic characteristics of thrust bearings is necessary. The authors theoretically analysed the variation of the oil film thickness and the pressure distribution of hydrodynamic thrust bearings under periodical load and verified the results experimentally. In the theoretical calculation, two different ;methods were used. One of them is a strict method, in which the Reynolds equation is solved at every small time interval (nonlinear solution), and the other is an approximate method, using spring and damping coefficients of the oil film (linear solution). The results are: (1) The linear solution method can be applied up to a considerably large amplitude of load. (2) Phase delay of the oil film thickness against the load is large, which has been verified both analytically and experimentally.
TL;DR: In this article, the surface energy density (or the surface tension) of critical-sized droplets, which corresponds to the activation energy in chemical reactions, was evaluated utilizing the condensation point locus on the P-T plane.
Abstract: Refrigerant vapors were filled in the high pressure side of a shock tube, and measurements were made as the vapors condensed spontane usly through adiabatic expansion in the rarefaction wave. The experimental observations were analyzed on the basis of the classical nucleation theory, and for each of the test vapors, the surface energy density (or the surface tension) of critical-sized droplets, which corresponds to the activation energy in chemical reactions, was evaluated utilizing the condensation point locus on the P-T plane. It turned out that the estimated surface tension was consistently smaller than the macroscopic value for three kinds of refrigerants studied. In the case of methyl alcohol vapor, for which the expansion rate was varied over a wide range, the condensation locus was found to shift accordingly in agreement with the theoretical prediction. It was also shown that the droplet growth history could be inferred from the temporal change of the light transmission.
TL;DR: In this paper, the three-dimensional solutions for the stresses and displacements in a semi-infinite body having a spherical cavity are given for the case of a uniform pressure applied to the plane boundary and to the surface of the cavity.
Abstract: In this paper, the three-dimensional solutions for the stresses and displacements in a semi-infinite body having a spherical cavity are given for the case of a uniform pressure applied to the plane boundary and to the surface of the cavity. In analysis, the method of Boussinesq's two harmonic stress functions are used. The two stress functions are given by simple expressions of the cylindrical and spherical harmonics. The boundary conditions both on the face of the plane and on the surface of a cavity are satisfied with the aid of Hankel transform and the relations between the two harmonics. Further, numerical calculations are carried out for four different values of the radius of a cavity.
TL;DR: In this article, the authors used the maximum repeated shearing stress calculated from the combination of bending or twisting stress and frictional stress and concluded that the initiation of fretting fatigue cracks is due to the maximum repetitive shearing stresses.
Abstract: Fretting fatigue tests are carried out with various materials combinations, and the reduction rates of fatigue strength by fretting are obtained with an observation on the behaviors of frictional force. Stress analyses on the contacting surfaces are conducted elastically by using the maximum stress due to friction together with repeated stress applied on specimens, and the results are compared with the experimental results. The fatigue strength is reduced more remarkably by fretting under bending than under twisting and the damage is greater to materials combination with higher tangential stress. These results agree fairly well with the consideration where the fatigue cracks are initiated under the maximum repeated shearing stress calculated from the combination of bending or twisting stress and frictional stress. The strength reduction rate is, however, greater than the analytical one for specimens of aluminum alloy and for lower cycle frequencies. Although further studies should be made on the behaviors in fretting fatigue which are similar to those in corrosion fatigue, it may be concluded that the initiation of fretting fatigue cracks is due to the maximum repeated shearing stress.
TL;DR: In this paper, gear loss in relation to speed and torque was analyzed by measuring the temperature of the oil steeping test gears, and the variance in the data thus obtained was analyzed.
Abstract: This paper describes gear loss in relation to speed and torque. Loss of gears finished in various manners was obtained by measuring the temperature of the oil steeping test gears, and the variance in the data thus obtained was analyzed. Torque, speed and type of gears were considered as influential factors in this analysis. The analytical results show that speed is the most important factor to gear loss rate while torque has little influence compared with speed. Furthermore, it became clear that the relation between speed and loss rate is complex depending on the type of gear and torque while said relationship may be simplified if considered as the relation between speed and gear loss.
TL;DR: In this article, an analytical solution for floating-ring journal bearing and a theretical analysis of unbalance vibration of a rotor bearing system are presented, where theoretical solutions for fluid film force, friction coefficient and stifness and damping coefficients are derived.
Abstract: This paper presents an analytical solution for floating-ring journal bearing and a theretical analysis of unbalance vibration of a rotor-bearing system. Theoretical solutions for fluid film force, friction coefficient and stifness and damping coefficients are derived. The effect of a floating-ring journal bearing on unbalance vibrations of a symmetrical rotor-bearing system and some design recommendations for optimum bearing dimensions are discussed.
TL;DR: In this paper, experimental data of the condensate film thickness and the local heat transfer coefficient are presented for steam condensing in down flow inside a vertical tube, and the results indicate that the laminar sublayer thickness is considerably different from that of single phase full tube flow.
Abstract: Experimental data of the condensate film thickness and the local heat transfer coefficient are presented for steam condensing in down flow inside a vertical tube. On the basis of the data obtained, the relations between the condensate film thickness, local heat transfer coefficient, film Reynolds number of condensate and shear stresses at tube wall and vapor-liquid interface are investigated and compared with the theoretical predictions for tubulent and laminar film condensation. A brass tube with an inside diameter of 24 mm was used as the test tube. The ranges of variables covered by this experiment are: 40∼90m/sec for the inlet velocity of steam, 0.2∼0.8 for the exit dryness fraction and 500∼2000 for the condensate film Reynolds number. A prediction is also presented for the thickness of laminar sublayer from the experimental data of local heat transfer coefficient by assuming that the condensate film consists of two layers, a laminar sublayer and a turbulent layer. The result indicates that the laminar sublayer thickness of condensate film is considerably different from that of single phase full tube flow.
TL;DR: In this paper, the effects of the pump elements on the pump performance were investigated and two types of head capacity curves which depend on the fluid viscosity were classified by the vane angle and the dimension of flow channel.
Abstract: The authors carried out an investigation of the effects of the pump elements on the pump performance. The following conclusions are obtained ; (1) There are two types of head-capacity curves which depend on the fluid viscosity and they are classified by the vane angle and the dimension of flow channel. (2) The effect of clearance on the shut-off head is made clear with consideration of the vane angle, flow channel and fluid viscosity. (3) The shut-off head, maximum internal efficiency and torque dealt with in correlation to the dimensionless number based on vane angle, dimension of flow channel and fluid viscosity are systematically arranged. Also the shut-off head of radial vane type is ascertained with a widely changing number of vanes and sectional area of flow channel. (4) The head loss in the flow channel is determined taking into account the vane angle and the sectional area of flow channel.