Showing papers in "Jsme International Journal Series B-fluids and Thermal Engineering in 1973"
TL;DR: In this paper, the basic equations for plastic deformation of porous metals such as sintered metal powders or metal powder compacts are proposed, where the porous metal is assumed to be made up of a homogeneous metallic material and unformly distributed pores.
Abstract: The basic equations are proposed for plastic deformation of porous metals such as sintered metal powders or metal powder compacts. The porous metal is assumed to be made up of a homogeneous metallic material and unformly distributed pores. The following equations are obtained from the Levy-Mises equatioins, (de1-de2)/(σ1-σ2)=(de2-de3)/(σ2-σ3)=(de3-de1)/(σ3-σ1)=(3fdeυ)/(2σm/f)=(3deeq)/(2γσeq) where γ is the relative density of the porous metal, f a function of γ, the subscripts 1, 2 and 3 represent the principal directions, σm=(σ1+σ2+σ3)/3 and deυ=de1+de2+de3. The theory shows a good agreement with the experimental results for sintered copper powder compacts.
89 citations
TL;DR: In this paper, the authors studied the burnout phenomenon in the saturated nucleate boiling of water at atmospheric pressure on a horizontal 10mm dia. copper heated surface, where a small liquid jet was used to cause a forced collapse of the vapor masses generated periodically on the heated surface.
Abstract: Burn-out phenomena are studied for two special systems of boiling which are both realized in the saturated nucleate boiling of water at atmospheric pressure on a horizontal 10mm dia. copper heated surface.First, it is attempted by mechanical means to cause a forced collapse of the vapor masses which are generated periodically on the heated surface. In this case, burn-out heat flux qc increases, but the velocity of fluid movement concerned with the collapse of vapor mass is restricted so that the increase of qc is limited.Second, the heated surface is supplied with liquid by means of a small liquid jet. In this case, burn-out appears with a mechanism which is different from ordinary pool boiling. Splashing of liquid due to the violent effusion of vapor from the heated surface interrupts the part of supplied liquid in reaching the heated surface so that the quantity of liquid on the heated surface balances finally the heat flux, and burn-out occurs. For the burn-out of this type, qc can be increased steadily by increasing the velocity of liquid jet.
82 citations
TL;DR: In this paper, the authors investigated the mechanism of the energy dissipation and also the ways of theoretically calculating the damping ratio of the jointed cantibeam by considering experimental results of the characteristic of static micro-slip between the joint surfaces.
Abstract: The loss energy of a jointed cantibeam may be derived from a microscopic slip and a normal pressure on the interfaces. It is however very difficult to calculate theoretically the energy dissipation between the joint surfaces, because a characteristic of the micro-slip on the interfaces has not been fully clarified yet.In this study the mechanism of the energy dissipation and also the ways of theoretically calculating the damping ratio of the jointed cantibeam have been investigated by considering experimental results of the characteristic of static micro-slip between the jointed surfaces.From the results it is clarified that the damping ratio of the jointed cantibeam can be well calculated by using the equations proposed in this paper, and how the characteristic of micro-slip influences the behaviours of the damping ratio.
51 citations
TL;DR: In this article, the relationship between tangential force and relative slip displacement under fretting fatigue was analyzed by using a model of a spring system, and compared with the experimental results, and the correspondence of the damaged layer of a carbon steel due to fretting fatigues with the stress conditions near the contact surface was studied.
Abstract: The relation between tangential force and relative slip displacement under fretting fatigue is analyzed by using a model of a spring system, and is compared with the experimental results. And the correspondence of the damaged layer of a carbon steel due to fretting fatigue with the stress conditions near the contact surface is studied. When slip amplitude Δy is small, it is proportional to tangential force T because of elastic adhesion which exists within contact surfaces partly. Both the wave forms of T and Δy are sinusoidal. When Δy becomes so large that macro-slip occurs, T shows a peak value and then decreases with progress of cycles. The wave form of T is trapezoidal and that of Δy is not sinusoidal, agreeing well with the analytical results. The frequency effect appears under Δy showing macro-slip, coefficient of friction being smaller under higher frequency due to the lubricating action of more oxidized debris. The depth of the damaged layer due to fretting fatigue is measured in several tens of microns. This depth is nearly equal to the depth where the combined maximum repeated shearing stress reaches the fatigue strength of materials.
37 citations
30 citations
28 citations
TL;DR: In this paper, a linkage device has been developed for the measurement of piston temperatures in high speed engines with a high degree of accuracy and long durability, and the piston temperatures have been successfully measured under various driving conditions on ordinary roads by this device.
Abstract: A new linkage device has been developed for the measurement of piston temperatures in high speed engines with a high degree of accuracy and long durability. The piston temperatures have been successfully measured under various driving conditions on ordinary roads by this device. As a result of comparing these temperatures with the laboratory ones we reached the following conclusion : i) During driving, piston tmeperatures fluctuate, responding rapidly to changes in engine conditions. The temperatures change frequently and large over a range of 100°C, particularly on highways.ii) During acceleration, the longer the "knock" persists, the more the temperature rises. In this case, the highest temperature recorded is about 340°C.iii) Generally, the temperatures obtained nearly steady state conditions on the road agree well with those obtained in the laboratory.
23 citations
TL;DR: In this article, a plane turbulent jet reattached on an offset parallel flat plate for the nozzle has been studied by the law of analogy to mass transfer, where the technique of sublimation of naphthalene is used.
Abstract: Heat transfer to plane turbulent jet reattached on an offset parallel flat plate for the nozzle has been studied by the law of analogy to mass transfer. For the experiment the technique of sublimation of naphthalene is used. The flow development on an offset plate depends on shapes of bubbles induced due to separation and reattachment. The change of bubble shape occurs generally when the ratio of offset distance to nozzle height is 6.5. Considering such flow field, empirical formulae have been introduced for the following items. (1) Maximum Sherwood number in reattached region. (2) Mean Sherwood number in separated bubble region. (3) Local Sherwood number over the region of reattached wall jet. (4) The effect of reattachment by the curved jet on distribution of the local Sherwood numbers.
22 citations
TL;DR: In this paper, the limit of the applicability of boundary layer theory in the single-phase turbulent flow was examined by reviewing papers on this method, and it was estimated that the Reynolds number must not be smaller than 800.
Abstract: In analysing the heat transfer in vertical falling films it has been customary to apply the boundary layer theory in the single-phase turbulent flow. In this paper the limit of the applicability of this method is examined by reviewing papers on this method, and it is estimated that the Reynolds number must not be smaller than 800. Experiments on heat transfer were carried out with liquids of Prandtl numbers between 300 and 5500. By analysing the experimental data it is found that the equivalent eddy thermal diffusivity eH/υ is equal to 3 × 10-5(y+)3 for the stable wavy flow, while the order of the first term of the Taylor expansion of the eddy viscosity for the single-phase boundary layer is larger by one ; in other words e/υ is equal to (const.) x (y+)4. This difference indicates that, if the Reynolds number is small, the mechanism of the heat transfer in vertical falling liquid films differs largely from that in the flow Which has no free surface
21 citations
TL;DR: In this paper, an experiment on boiling heat transfer in a vertical open thermosyphon is performed, where tubes and annuli are used as the open thermo-yphons.
Abstract: An experiment on boiling heat transfer in a vertical open thermosyphon is performed. Tubes and annuli are used as the open thermosyphon. The latter consists of an unheated core and an externally heated tube. Data are taken using pure water by changing the diameter and the length of the heated tube, the diameter of the unheated core and the entrance temprature of the liquid. The heat transfer coefficient α is correlated with q0.4(Δts/Δt)0.9, where q is heat flux, Δts is excess wall temperature above saturation of the liquid, Δt is wall temperature minus entrance temperature of the liquid. It is also shown that the heat transfer coefficient is hardly affected by the length and the diameter of the heated tube. For the extremely small gap of the annulus, however, the heat transfer coefficient increases with a decreasing gap. The heat transfer coefficient in the thermosyphon is larger than that of pool boiling, but the critical heat flux is considerably smaller. Flow patterns in the open thermosyphon are observed and their relation with the heat transfer coefficient is discussed.
19 citations
TL;DR: In this paper, the authors made a test on erosion by means of resonant frequency of 22 kc/sec, and simultaneously took accurate measurements of half-value breadth both in the surface and in its innerface through Cobalt Kα radiation and of residual stress.
Abstract: Using specimens of SS41 carbon steel, authors made a test on erosion by means of resonant frequency of 22 kc/sec, and simultaneously took accurate measurements of half-value breadth both in the surface and in its innerface through Cobalt Kα radiation and of residual stress. Authors' conclusion is as follows. Both in an erosive surface and in its innerface, residual stress is attributed to compressive stress, after maximum residual stress has taken place in the surface, the weight loss of specimen remarkably increases; consequently there can be recognized a certain time rate in this test duration. The internal residual stress before starting of the weight loss of the test piece being compared with the one after starting, there occurs some change from maximum to minimum nearly at the same depth. The comparative test on half-value breadth at different amplitudes results in that in each period of operation the testing amplitudes relate not to the pressure in the collapse of each one of the bubbles but to the number of bubbles in the collapse.
TL;DR: In this paper, the coefficient of friction between vulcanized natural rubbers or polyurethane elastomers and metals is measured under the pressure up to 900 kg/cm2.
Abstract: The coefficient of friction between vulcanized natural rubbers or polyurethane elastomers and metals is measured under the pressure up to 900 kg/cm2. The effects of several factors on the coefficient of friction are examined and an experimental formula is derived from the experiment in which threaded metal bars are used as a model of metal surfaces. The pressure, the mechanical property of rubber and the geometry of metal surface are considered in the above formula. Moreover, the validity of applying the formula obtained by using screws to the surfaces of rolled sheets or drawn bars with microscopic asperities is discussed. The coefficient of friction decreases with an increasing applied pressure, but approaches a definite value in the range of high pressures. The definite values for the case of using soapsuds and powdered rosin are about 1/5 and 5 times the value for no lubricant respectively.
TL;DR: In this paper, the authors show that the existence of the fatigue limit in steel is due to the strengthening of the tip parts of the non-propagating micro-crack.
Abstract: The purpose of this paper is to make clear the reason why the fatigue limit and the coaxing effect exist in steel, using 0.13%C steel and copper specimens. The main results obtained are as follows. In 0.13%C steel specimens ; (1) The incipient fatigue cracks, revealed by light electro-polishing (1∼2μ) after 107 cycles under the stress repetitions of the fatigue limit of the specimen, exist in the ferrite not only at the surface but also in the inside and the tip parts of those cracks become 24∼34% harder than in the virgin state. (2) This incipient fatigue crack appearing by the stress of the fatigue limit is the starting point of fracture, when the specimen fails by a stress greater than the fatigue limit. In copper specimens ; (3) The tip parts of the incipient fatigue crack in copper, appearing after 107 cycles of the stress which corresponds to the fatigue strength for 2×107 cycles, do not become so hard than the ones in 0.13%C steel. These results show that the existence of the fatigue limit in steel is due to the strengthening of the tip parts of the non-propagating micro-crack.
TL;DR: In this article, a method is treated which predicts the low-cycle fatigue failure of a U-shaped bellows subjected to completely-reversed loading, with use of the solution procedure employing the finite difference technique proposed previously by the authors for the large deflection problems of elastic-plastic shells of revolution.
Abstract: In this paper, a method is treated which predicts the low-cycle fatigue failure of bellows subjected to completely-reversed loading, with use of the solution procedure employing the finite difference technique proposed previously by the authors for the large deflection problems of elastic-plastic shells of revolution. Namely, a procedure is discussed which estimates the low-cycle fatigue life, applying the plastic strain range under cyclic loading assessed by the elastic-plastic analysis to the Manson-Coffin equation. A U-shaped bellows subjected to deflection-controlled cyclic loading is taken as an example for the fatigue life analysis, and comparison is made with the corresponding experimental results to ascertain the appropriateness of the present method. Moreover, the fatigue lives predicted by other methods are compared with those by the present method, and fairly good agreement is recognized between the fatigue lives by the modified Langer equation which takes account of the strain concentration factor obtained from the elastic-plastic analysis and the experimental ones.
TL;DR: In this article, the authors experimentally examined the generation and decay of rotating noise and turbulent noise generated by axial flow fans by changing various factors, such as the suction pipe geometry, the location and the thickness of struts, and the combination of the number of impeller blades and struts.
Abstract: Noise generated by a fan consists of the rotating noise and the turbulent noise. These two kinds of noise have entirely different characters with respect to decay in an axisymmetric pipe. In this paper the generation and decay of these two kinds of noise are experimentally examined by changing various factors, such as the suction pipe geometry, the location and the thickness of struts, and the combination of the number of impeller blades and the number of struts. The rate of decay of the rotating noise is predictable and in most cases the noise quickly decreases in proportion to the distance from the rotor, providing that the number of impeller blades and the number of struts are properly chosen. Therefore, the noise observeda way from a low pressure axial flow fan is mostly the turbulent noise.
TL;DR: In this paper, the authors carried out an investigation of the pump performance using 18 kinds of impellers which combine six diameters from 94 mm to 180 mm with three vane angles 60°, 90° and 120° changing the dimensions of the flow channel and fluid viscosity.
Abstract: In order to make clear the scale effects of the regenerative pump with non-radial vanes, the authors carry out an investigation of the pump performance using 18 kinds of impellers which combine six diameters from 94 mm to 180 mm with three vane angles 60°, 90° and 120° changing the dimensions of the flow channel and fluid viscosity. The following conclusions are obtainded : (1) The influences of impeller diameter on the performance vary with the vane angle. (2) The relations between pump elements and coefficients of shut-off head, flow-rate, torque and maximum value of internal efficiency are made clear. Consequently, the authors give the outline of design method considering the effect of fluid viscosity. To facilitate the description, two examples by the present design method are given. The calculated values agree well with experimental results.
TL;DR: In this paper, a high-speed photographic study was made to reveal the mixture formation and combustion in a shallow-dish type engine with a multi-hole nozzle, and compared the photographs taken under various conditions have let to the following results.
Abstract: To reveal the mixture formation and combustion in a shallow-dish type engine with a multi-hole nozzle, a high-speed photographic study has been made. Comparisons of the photographs taken under various conditions have let to the following results. Under no swirl condition, various kinds of gas motion are produced in the flame in the piston cavity soon after ignition. They govern the subsequent state of combustion, finally affecting the air-utilization in the later stages of combustion, and they are dependent on the diameter of the nozzle-hole as well on the direction of injection. When a swirl is employed, the radial extension of the spray is considerably reduced with its intensity, thereby the subsequent spread of the flame being suppressed. Unless a sufficient penetration of the spray is assured, air-utilization is poor in the peripheral space, leading to the so-called overswirling.
TL;DR: In this paper, a prediction method of low-cycle fatigue strength was developed whereby the number of cycles to initiate a crack can be estimated for a notched specimen from the characteristics of the hysteresis loops of unnotched specimens and a few fatigue data of either notched or notched specimens.
Abstract: A prediction method of low-cycle fatigue strength has been developed whereby the number of cycles to initiate a crack can be estimated for a notched specimen from the characteristics of the hysteresis loops of unnotched specimens and a few fatigue data of unnotched or notched specimens. Good predictions were obtained for annealed 0.48% carbon steel notched specimens under completely reversed load. The prediction method can be applied to various materials, specimen shapes and loading modes. The plastic strain range Δep at notch root was computed by the finite element method and the Bauschinger effect was also taken into consideration. The method was compared with Langer's and the one based on Neuber's rule. Although it is difficult to predict by other methods that the number of cycles to crack initiation of notched specimens can be larger than that of unnotched specimens at high load level, the present method does not contradict this phenomenon.
TL;DR: In this paper, an axial load impact fatigue testing machine was designed and manufactured, which makes it possible to carry out a series of tests ranging from the ordinary fatigue test to the test under loads including some amount of impact load.
Abstract: An axial load impact fatigue testing machine was newly designed and manufactured, which makes it possible to carry out a series of tests ranging from the ordinary fatigue test to the test under loads including some amount of impact load. Using this machine, plain and notched specimens of 0.11% carbon steel were tested under fully reversed sinusoidal axial load and under impact fatigue load. It was observed that, under impact load, fatigue fractures occurred at the stress levels lower than the ordinary endurance limits for both of the specimens.
TL;DR: In this article, the vibrations of a circular plate with uniformly distributed load around the outer periphery are studied and the frequencies of circular plates with various boundary conditions are also obtained and the deflections, the inclinations, the bending moments and the shearing forces are shown in graphs.
Abstract: The vibrations of a circular plate with uniformly distributed load around the outer periphery are studied. The circular plate has a hole at the center and the profile is of an exponential curve. The frequencies of circular plates with various boundary conditions are also obtained and the deflections, the inclinations, the bending moments and the shearing forces are shown in graphs.
TL;DR: In this paper, an experimental investigation into vertical upward air-water two-phase flow was performed using a smooth tube and three spirally grooved tubes, all of which are about 13 mm in inner diameter and 8m in length.
Abstract: An experimental investigation into vertical upward air-water two-phase flow was performed using a smooth tube and three spirally grooved tubes. All the test tubes are about 13 mm in inner diameter and 8m in length. The experimental data on each test section include pressure drop, radial distribution of void fraction, cross-sectional mean void fraction, and mean film thickness in annular flow regime. The summary of the results is as folows : (1) The transition boundaries of flow patterns are very similar to those of smooth tube. (2) The pressure gradients do not always depend on the magnitude of relative roughness of test tube, but a ribbed tube, having the greatest relative roughness, shows the greatest values in pressure gradient. (3) The variation of grooves produces remarkable difference in radial distribution of void fractions. (4) Mean film thickness for grooved tubes become definitely greater than for smooth tube.
TL;DR: In this article, rotating bending and axial fatigue tests of plain and notched 7 : 3 brass specimens were carried out, and the results showed that the root radii of notches at the branch point ρ0 (branch point means the critical point for a non-propagating crack to develop) are about 0.6 mm for both cases.
Abstract: The rotating bending and axial fatigue tests of plain and notched 7 : 3 brass specimens were carried out.The main results obtained are as follows.(1) The characteristic in fatigue of notched specimens under rotating bending stress is similar to the one under completely reversed axial stress, and the root radii of notches at the branch point ρ0 (branch point means the critical point for a non-propagating crack to develop) are about 0.6 mm for both cases.(2) The relations of σw1/σw0 and σw2/σw0 (σw1 : limit stress for crack initiation, σw2 : limit stress for complete fracture in the range of non-propagating crack existing, σw0 : σw1 of plain specimens) to stress concentraiton factors α are almost the same in rotating bending fatigue of 7 : 3 brass and 0.13 % C steel.(3) In axial fatigue, the maximum stress repeated at a notch root at the crack initiation limit ασw1 becomes almost constant irrespective of mean stress, if the stress gradient χ is constant.(4) In axial fatigue, ρ0 increases as mean stress decreases. This means that σw2 increases as mean stress decreases.
TL;DR: In this paper, a linearized constant temperature hot-wire anemometer is designed and constructed which generates a voltage output directly proportional to instantaneous wind-speed from nearly zero to 150 cm/sec.
Abstract: The heat loss characteristics of the hot-wire probes placed normal to a horizontal wind are examined experimentally in the wind-speed range from zero to 150 cm/sec. The reproducibility of the characteristics is clearly shown at extremely low wire Reynolds numbers to which neither the empirical relation due to Collis and Williams nor King's law is applicable. Based on the examination, a linearized constant temperature hot-wire anemometer is designed and constructed which generates a voltage output directly proportional to instantaneous wind-speed from nearly zero to 150 cm/sec. Using the anemometer, practical problems related to the directional response and the effect of the proximity of a wall to the wire upno the reading are examined. An estimation is also given of the effect of velocity reversal upon the reading.
TL;DR: In this article, the planetary gear mechanisms were composed with two pair of gears, one pair with noncircular gears and the other with circular gears, and these mechanisms were analyzed as a function generator.
Abstract: The noncircular gears have been used in the flowmeters, pumps, etc., but they were used, for the mechanisms with nonuniform motion, to make use of the monotonous angular relations between the input and output axles by fitting them to the ordinary gear trains.In this paper, the planetary gear mechanisms were composed with two pair of gears, one pair with noncircular gears and the other with circular gears, and these mechanisms were analyzed as a function generator. Then, the mechanisms were classified into swing, swing and rotate, and intermittent and rotate motion, and the restrict conditions were obtained, and examples of synthesis with the displacement curves of practical use were shown. Furthermore, the mechanisms were produced by way of experiment, and by the experiment, it was shown that the noncircular planetary gear mechanisms with nonuniform motion make a function generator with good characteristic.
TL;DR: In this article, the authors investigated the general characteristics of such oscillations in a system possessing some non-linear characteristics, and then took up a typical case in which three forces act on a system having the nonlinear characteristics of a cubic function of the displacement.
Abstract: In a non-linear vibratory system subjected to several periodic external forces of different frequencies Ω1, Ω2…, ΩM, so-called combination oscillations of frequency Ω=|m1Ω1+m2Ω2+…+mMΩM|, (mj=±1, ±2, …) can occur, if Ω is close to the natural frequency of the system. In this paper we first investigate the general characteristics of such oscillations in a system possessing some non-linear characteristics. To carry on the investigation further we then take up a typical case in which three forces act on a system having the non-linear characteristics of a cubic function of the displacement, and discuss in detail the characteristics of the combination oscillations of frequencies Ω=|Ω1±Ω2±Ω3| induced in the system. Finally using an analog-computer we verify that these types of oscillations in fact occur.
TL;DR: In this paper, the authors used tubes and annuli as the channel of the open thermosyphon, which consists of an unheated core and an externally heated tube.
Abstract: Experiments on a heat transfer coefficient and a critical heat flux in a vertical open thermosyphon are performed. Tubes and annuli are used as the channel of the open thermosyphon. The latter consists of an unheated core and an externally heated tube. Pure water, ethyl-alcohol, normal-hexane, carbon-tetrachloride and sodium oleate aqueous solution are used as test liquids. Data are obtained with different lengths and diameters of the tube, diameters of the core and entrance fluid temperature of the thermosyphon. The experimental results are correlated on the basis of dimensional analysis and experimental expressioins are presented.