In this work, we present a comparison of the mechanical properties of 3D printed structures with respect to the printing orientation for 3D gel printer "SWIM-ER" and FDM (Fused Deposition Modeling) 3D printer with a result that the fracture surface of the 3D modeled object of the gel does not break along the stacked line, and the maximum stress at that time is the breaking strength. Also, the fracture surface of the 3D model of the ABS resin has broken along the stacked line other than 0 degrees, and the maximum stress at that time is the peel strength. The yield point can be observed at the 0 degree specimen, the maximum stress at that time is tensile strength. Moreover, while comparing both materials, we observed that the dependency in the stacking direction is weak in the 3D model of the gel, strong in the 3D modeled material of the ABS resin, and the dependence on the stacking direction is strongly influenced by the way of bonding the materials in stacking.
The purpose of this study is to investigate low cycle fatigue (LCF) and high cycle fatigue (HCF) strengths, crack initiation and growth behaviors of Ni based castalloy 246. LCF and HCF tests are conducted under load controlled conditions. As the result of the observation of etched specimen, the grain size is from 3 mm to 5 mm. And the microstructure is mainly composed of dendritic structure. Growth orientation of dendritic structure varies in every grain. The result of elemental analysis, Si and Ti are detected at dendritic boundary. The results of LCF test show that small cracks initiate at the first cycle, followed by the crack growth along slip direction. Observation of fracture surface reveals that small cracks originate at casting defect or dendritic boundary. The results of HCF, on the other hand, show that small cracks initiate from subsurface casting defect under Δσ ≦ 600 MPa, while fracture origin becomes surface under Δσ > 600 MPa. The result of HCF test after introducing small crack on the surface shows that small crack on the surface does not affect on the fatigue life and the location of crack initiation. As the result of EBSD, the crack initiation site is near grain boundary and the crack grows along slip plane.
The straight-bladed vertical axis wind turbine is one of the promising candidates for next-generation power sources because of its high efficiency, quiet operation and structural simplicity. Fewer wind turbines of this type have been manufactured and used so far compared with other types like the horizontal type. Therefore, further improvement in efficiency is essential in order to promote their widespread use. The purpose of this study is to better understand the influence of the blade profile of the straight-bladed vertical axis wind turbine on flow and aerodynamic performance and to improve wind turbine efficiency. Unsteady two-dimensional flow through a wind turbine with a symmetrical blade profile, the diameter of which was 3 m, was numerically computed with a commercial CFD code and the results were analyzed. A wind turbine with outward-cambered blades was then designed in order to increase the rotational force acting on the blade along with a wind turbine with inward-cambered blades for comparison. The computational results showed that the wind turbine with outward-cambered blades was better in performance than the ones with symmetrical or inward-cambered blades. Experiments using small wind turbine models, the diameter of which was 200 mm, were carried out in order to verify the computational results. The experimental results showed the same tendencies as the computational results in spite of the difference in scale, Reynolds number and blade number. The effects on flow and performance were also analyzed by additional computations performed with the same CFD code.
Simultaneous measurement of the velocity-gradient and fluctuating static pressure was carried out in a turbulent planar jet. We use a constant-temperature hot-wire anemometry and a miniature pressure probe for velocity measurement and fluctuating static pressure measurement, respectively. Two types of the combined probe are introduced for simultaneous measurement of the velocity-gradient and fluctuating static pressure. One consists of an X-type hot-wire probe and a pressure probe and the other consists of two I-type hot-wire probes arranged in vertical direction and a pressure probe. For improvement of the measurement accuracy, the responsivity of the pressure probe, the time-lag due to the spatial distance between the hot-wire probe and the pressure probe, and the attenuation of the velocity-gradient measurement due to the finite difference method, are corrected. In this paper, we compare the various statistics of the turbulent planar jet acquired using the combined probes and those acquired using hot-wire probe or pressure probe alone. Through the results, it is confirmed that the simultaneous measurements were well-performed in the turbulent planar jet expect for the outside of the velocity half-width. Further, it is revealed that the Pressure Rate-of-Strain Correlation, which appears in the Reynolds stress transport equation, is almost dominated by (p´/ρ)(∂u´2/∂x1) and (p´/ρ)(∂u´1/∂x2) barely contributes to the Reynolds stress transport in the cases of Re ≥ 10,000.
The present study investigates a swirl flow instability induced by a rotating cylinder between coaxial two disks as a model of a vaneless diffuser at zero flow rate. To begin with, the experiment and three-dimensional finite volume simulation were performed. The rotating cylinder was used to produce the swirl flow. Small vortices were generated from the cylinder surface. They were combing and forming one croissant-shaped toroidal vortex (CTV), which was rotating around the cylinder. Small vortices were separating from the CTV and flowing away from the cylinder. In order to investigate the cause of the swirl flow instability, a 2D stability analysis for an annular vortex street was performed. The annular vortex street became less unstable for the larger radial location and the fewer number of vortices. This implies that the vortices could be forming into one vortex as their radial locations increased. In order to validate the stability analysis, the vortex simulations were carried out. The vortices generated from the cylinder surface were forming into one cell as their radial locations increased. In order to validate the stability analysis and vortex simulation, the 2D finite volume simulation was performed. The vortices were generated from the cylinder surface. They were combining and forming one cell, which was rotating around the cylinder. The vortices were separating from one cell and flowing away from the cylinder. The frequencies of vortex rotation agreed in the experiment, the two and three-dimensional simulations. Therefore, it is considered that the 2D vortex transforms to the 3D CTV, similarly the Tayler vortex. Furthermore, all the results indicate that the 2D swirl flow instability causes the CTV, and the vortices combining to and separating from the CTV.
The water velocity field in a rectangular reservoir driven by a previously unexplored water streamer is investigated experimentally and numerically. Firstly, the velocity field on the water surface induced in a rectangular reservoir is estimated from trajectories of floating passive tracers. Secondly, the velocity at the several fixed points below the surface is directly measured with the aid of an electro-magnetic velocimetry. These measurements elucidate that the streamer activates an underwater circulation between the surface and the bottom in the reservoir. Additionally, a numerical simulation is examined to realise the induced three-dimensional flow below the water surface. The obtained results provide an evidence that the induced flow structure is three-dimensionally spiral, which is distinct from that induced by the water streamers traditionally utilized in aquacultural reservoirs. The investigated streamer may be utilized for the purpose to particularly enhance the underwater vertical mixing in aquacultural reservoir or purification plant.
Water spray is used for cooling suction air of gas turbine for power augmentation. Cooling efficiency depends on the spraying properties. The aim of this study is to investigate the spray characteristics and the influence of secular change in the spray nozzle. PDA (Phase Doppler Anemometry) measurements are conducted at each cross section in wind tunnel which is scale model of inlet duct. Pin type nozzles and a hole type nozzle are tested. Same type nozzles with different using period are also tested. The nozzles are new one and old one which is used 1750 hours before the spray experiments. The spray properties in high spatial-temporal resolution are provided by the PDA. As a result, the droplet size by a pin type nozzle has no change after 1750 hours. The data rate, velocity and flow rate decrease after 1750 hours due to increase of the passage resistance by filter clogged. Pin type nozzles have asymmetry shape in data rate distribution due to the existence of pin. The SMD distributions by pin type nozzles have flat shape in the measurement region. The SMD distributions gradually increase in the value from the center to outer in hole type nozzle. Droplet size dispersion at each measuring point for all nozzles are also evaluated by the experiment. Dispersion of diameter increase in from the center to outer in a hole type nozzle. Also cooling efficiency and the relations of particle density are evaluated. If the particle density is high, the cooling efficiency become small even if the particles have small diameter and high velocity.
It is important to improve spray characteristics of an energy conversion engine in order to reduce carbon dioxide and exhaust gas emission. The purpose of this study is to design and develop high-dispersion injection nozzle for direct injection Diesel engine. This paper describes about that effects of the measurement and the geometric shapes of nozzles on spray characteristics and design of the nozzle which is obtained more excellent spray characteristics. When the measurement, the geometric shapes and the internal structure of nozzle were designed the most suitable conditions, breakup length becomes approximately 10 % shorter and spread of spray i.e., spray angle becomes large about 30 %. Moreover, Sauter mean diameter obtained is about order of 10 μm which is smaller than that with the nozzle developed in the previous study.
A laser 2-focus velocimeter (L2F) was used for measurements of velocity and size of droplets in diesel fuel sprays. Diesel fuel was injected intermittently into the atmosphere by using a 8-hole injector nozzle. The diameter of the nozzle orifice was 0.112mm. The rail pressure was set at 65MPa by using a common rail system. The period of injector solenoid energizing was set at 2.3ms. The L2F had a micro-scale probe which consists of two foci. The focal diameter was about 3μm, and the distance between two foci was 20μm. The data sampling rate of the L2F system was markedly high as 15MHz. L2F measurement was conducted at 10mm downstream from the nozzle exit. Temporal and spatial changes in the velocity, size and number of droplets inside sprays were investigated. Spray images were taken by using a 180ns spark light source, and the scattered light intensity distribution and spray width were estimated. The scattered light intensity, the spray width and the number of droplets were oscillated several times in the injection period. The number of droplets at the inner region of the spray decreased and the one at the outer region of the spray increased, when the spray width increased. That is, many droplets fly to the outer region of the spray at the time when spray width is wide.
An experimental study has been carried out to clarify the effect of quantity of absorbed water on behaviour of single silica-gel particles in oil with dc electric field, as a basic research to augment adsorption. The progress of adsorption changes mass and physical properties of a silica-gel particle, and the change might influence the behaviour of the particle. The experiment is conducted under condition that the adsorbed material is only water, and the quantity of water is adjusted beforehand to prescribed value. Two electrode plates are horizontally set up 40 mm apart in silicone oil. Particle diameter is adopted of 2.7, 4.0 and 5.0 mm, and the range of applied voltage is 0 - 28 kV. The applied voltage is increased at approximately 2kV/min. Observation of behaviour of a silica-gel particle starts from resting condition on a lower electrode. As a result, a dried silica-gel particle does not begin moving even at the maximum voltage. For a silica-gel particle of water adsorbed, following four stages have been observed, excluding a very few exceptions; rise from the upper side of lower electrode to the upper electrode, bound and rest on the lower side of the upper electrode, descent to the lower electrode, and bound and rest on the lower electrode. The rest time on the electrode is not seen to a completely water-absorbed silica-gel particle. It is thought that the particle exchange the electric charge at the rest time. The applied voltage for the leave of a silica-gel particle from the lower electrode, rest time on each electrode, and bound height from each electrode are also shown.
To predict the combustion characteristic of auto ignition combustion in internal combustion engines, it is necessary to consider the inhomogeneity of the fuel, EGR and air in the mixture. In this research, a PDF (Probability Density Function) combustion model considering the influence of the inhomogeneity of mixture on the auto ignition combustion is developed. In our approach, the PDF of the injected fuel and the EGR gas is predicted by two-zone turbulent mixing model and only the PDF at the top dead center of the combustion stroke is used to calculate combustion characteristic to realize the reasonable calculation time for the control system design tool. The prediction model was validated by comparing with the experimental result for various injection timings and EGR ratios. It found that the model can qualitatively predict the combustion characteristics with reasonable calculation time.
The natural convective flow and heat transfer of air induced around an inclined row of heated horizontal cylinders have been investigated experimentally. The experiments were carried out with the ten-cylinders row placed in the plane of inclination angles θ=0°, 30°, 45°, 60°, 75° and 90° from horizontal. The cylinders in the row were heated with constant heat flux and their diameter d and gap G were varied as d=8.4, 14.4mm and G=3.6 to 20.6mm. The Nusselt numbers Nud from the cylinders in the row were measured. They showed maxima and minima for the horizontal and vertical rows, while intermediate Nusselt numbers were obtained for the inclined rows. Those Nusselt numbers were next converted to the gap-based Nusselt numbers NuG, and, then, rearranged with the non-dimensional parameter RaG*(G/d). The result showed that the Nusselt numbers NuG are predicted well with the parameter RaG*(G/d) for the whole rows of inclination angle from horizontal to vertical.
This paper presents the pressure drop prediction of BWR fuel assembly without experiment. To evaluate the core performance, pressure drop of fuel assembly is one of the key design parameters. The shape of fuel assembly is complicated and the spacer has a strong effect on pressure drop. Therefore, to obtain the pressure drop of fuel assembly, the experiments are needed. However, the experiments need a lot of time and money. In the authors' previous study, the friction coefficient and spacer loss coefficient under single phase flow condition were evaluated using CFD analysis and total pressure drop under two phase flow condition were predicted using these coefficients and verified by the data of the tight lattice bundle. The purpose of this study is to predict the pressure drop of BWR fuel assembly without experiments. The predicted pressure drop by the previous study's method was compared with the pressure drop data for full-scale high-burnup 8x8 fuel assembly covering the operating BWR conditions. The following conclusions are obtained; (1)The average and standard deviations of prediction accuracy (calculation/experiment) were 1.046 and 0.023, (2)The prediction accuracy of this method is almost same as that of the current BWR design method.
We have developed the evaluation method for two performance factors to design the thermal connector: Insertion force of thermal grease and thermal conductance. The thermal connector was comprised of a thermal plug and a thermal socket, and the thermal grease which was filled into the gap between the thermal plug and the thermal socket connected the thermal plug and the thermal socket thermally. Firstly, the insertion force was theoretically calculated using the Bingham plastic model for rheology characteristics of the thermal grease and the slip model on the surfaces of the thermal plug and the thermal socket. The calculated results were in good agreement with the experimental results. Secondly, the experimental results of the thermal conductance between the thermal plug and the thermal sockets at the first connection to the 20 times connection were -1 to +26 percent greater than the theoretical value. The reason why some experimental results exceed the theoretical results is the eccentricity between the thermal plug and the thermal socket. In addition, the filling status of the thermal grease in the gap was visualized by ultrasonic testing. The results after the 20 times connections showed there were some voids in the thermal grease and the area of voids was 4 percent of the heat transfer area. Therefore, the thermal conductance was mostly not influenced by the voids. Finally, it was found that the proposed methods to predict the insertion force and thermal conductance were reasonable.
This paper studies the condition of reducing knock intensity which is the pressure oscillation initiated by auto-ignition of the end gas. The knock intensity is thought to be decreased by suppressing the reaction rate of auto-ignition. In this study, the effect of the mixture dilution which decreases the reaction rate on the knock intensity was investigated by using a spark ignition engine. In the case of low dilution, knock was observed when the auto-ignition of the end gas occurred. When the dilution ratio was over 30%, there was the condition that the knock did not occur even if the end gas auto-ignited. The combustion with low knock intensity was observed in either case that dilution gas was inert gas or air. The knock intensity was shown as a function of the maximum temperature and the maximum pressure which affected the reaction rate although the knock intensity was affected by the composition of the mixture, load, ignition timing, auto-ignition timing of the end gas and heat release quantity of the auto-ignited mixture.
This study addressed a deflagration-to-detonation transition (DDT) process after interaction of the convex flame with a planar shock wave. High-speedvideo cameras and schlieren optical technique were utilized to observe the DDT as well as shock-flame interaction processes. A double-diaphragmshock tube was used to produce the shock wave, while the flame was produced by igniting a premixed gas of stoichiometric methane-oxygenat the observation section. Experiments were conducted by changing Mach number of the incident shock wave, Ms and a distance of flame front from the end wall, x0. As a result of schlieren photographs, flame propagation behaviors at initial stage were classified into four patterns, named as (a) coupling, (b) concave, (c) partial coupling and (d) convex type. The propagation patterns of flame were highly dependent on the initial position of flame front, x0. Under the experimental conditions, DDT was not observed when the flame had been propagated revealing (a) coupling (observed with the conditions of x0 > 110 mm) and (d) convex type (x0 < 50 mm). However, the DDT was observed following that the flame had been propagated revealing (b) concave or (c) partial coupling (50 < x0 < 110 mm). Furthermore, it was elucidated that DDT was typically caused through the following processes. (i) When the convex flame interacted with planar shock, the unburned gas was penetrated into burned gas inducing Richtmyer-Meshkov instability. (ii) The flame was highly accelerated at boundary layers behind the reflected shock. (iii) After accelerated flame propagated through the unburned shocked region, local explosion was occurred on the wall followed by detonation onset.
In this study, we discuss a problem to collect observation data with one mobile robot in extensive investigation field. When the measurement of observation data is carried out by the mobile robot, the setting of running-path and navigation are important for appropriate measurement. Usually reciprocating straight paths at even interval are employed to collect data with spatially uniform density. However it is possible that some area between the straight paths requires detailed measurement. The method proposed in this paper makes it possible that in ordinary situation the robot follows the straight path, in the proximity of the area with need of observation it leaves the straight path toward the area, after that returns to the preceding straight path. Recently the path-generating regulator (PGR) has been applied to a tracking problem along a straight passage for car-like robots. The PGR is a control method for a vehicle so as to orient its heading toward a tangent to one of the curves belonging to a family of path functions. In this paper, we append a property to the PGR tracking the straight passage to modify the target heading angle in accordance with necessity of observation and to realize the motion toward the area with need of observation. To confirm the efficiency of the proposed method, two types of simulations are performed. The first simulation shows how a level of necessity of observation and a range to the area changes the locus of the mobile robot. In the second simulation, the mobile robot is satisfactorily guided by the level of necessity of observation obtained from actual measured data in a survey site.
For seismic design of components, elastic response spectrum analysis, which is based on linear response using elastic response spectrum, is generally used as a dynamic analysis of multi-degree-of-freedom(MDOF) systems not only elastic response but also elastoplastic response. Elastoplastic response is different from elastic response due to nonlinearity of the system by yielding of components. Several researchers have proposed response spectrum analysis methods of nonlinear MDOF systems using equivalent linearized methods, which replace a nonlinear system to the linear system equivalent to the nonlinear system on the response. We developed a response spectrum analysis method using elastoplastic response spectrum and not replacing a nonlinear system to the linear system as a dynamic analysis method of nonlinear MDOF systems. This method is obtained from exact equations of motions by just two assumptions; no interaction between natural moods and modal combination rules. We verified this method was effective in the calculated 2-DOF systems. This method is also considered of value for interpretation on the response of nonlinear MDOF systems by spectrum modal approaches.
A seismic isolation system composed of a thick rubber bearing and an oil damper has been developed for Sodium-Cooled Fast Reactor. One of the advantages of the isolation system is the use of thick rubber bearings to ensure the longer vertical natural period of a plant, thereby mitigating seismic loads to mechanical components. Characteristics of thick rubber bearings have been confirmed through a series of tests. This paper focused on the aging properties of thick rubber bearings, such as basic mechanical properties and ultimate strength. An aging test of thick rubber bearings was conducted using 1/2-scale (800 mm diameter) and 1/8-scale (200 mm diameter) rubber bearings. Aging of the rubber bearings was reproduced using thermal degradation based on Arrhenius law, in which the target of aging periods was 60 years, plant life time. The hysteresis loops of the thick rubber bearings after aging were obtained through horizontal and vertical static loading tests, and the effects of aging were evaluated by comparison with the initial mechanical properties. In addition, for the purpose of further research, the effect of scale by aging was clarified to compare the mechanical properties between the 1/2-scale and 1/8-scale rubber bearings.
This paper describes about path planning for a root-cutting blade of an automatic spinach harvester. Automatic harvesters for spinach have not been widely used among farmers because mechanical harvesting easily spells bruises to stems and leaves. We have been developing the harvester which successfully harvests spinach without bruising stems and leaves. The path which blade moves in soil is very important in order to attain desired performance and to reduce the amount of soil which is pushed by the blade is the most meaningful factor for successful execution. In this paper, first, we discuss about a method to reduce the amount of soil and proposed a constraint equation for the method. Next, an appropriate path of the blade of the harvester is proposed by using the equation. The effectiveness of the proposed path is verified by numerical simulations based on the Discrete Element Method (DEM).
Axial thrust forces acting on an impeller of a diffuser type mixed flow pump and the behavior of the axial thrust generated by the vortex occurrence in a pump intake sump were studied. The thrust from distinct discontinuities, such as the hysteresis phenomenon, was measured from a pump's hydraulic performance. In pump partial load operation the axial thrust increases discontinuously because of the reverse flow at impeller inlet. Synchronous and non-synchronous components of axial thrust increase during the onset of reverse flow zones. A prediction method for static axial thrust was derived based on Oshima's theory, accounting for the pressure reduction at pump suction bell-mouth caused by a vortex. Qualitative comparison of the predicted results with the actual static axial thrust results measured during the experiment, showed reasonable similarities around pump best efficiency flow rate. The thrust was measured using a pump intake sump test apparatus in which both an air-entrained surface vortex and a submerged vortex could occur. The level of dynamic axial thrust is dependent on the pump intake sump water level and the dynamic axial thrust begins to increase when a full air core vortex occurs at the pump intake. When submerged as well as full air core continuous vortices occur, the axial thrust and the fluctuation of total pump head become abruptly large. The fluctuation of axial thrust becomes the highest when the impeller draws in a large air-drawing vortex, imposing a pressure fluctuation which generates not only a rotational speed but also nZ vane passing and low frequency components.
A vane used in a low pressure end of steam turbine is usually fixed to an inner shroud and an outer ring by welding both ends. In such a vane structure, the damping in loading operation is comprised of the material damping and the aerodynamic damping, because the structural damping is very small. In addition, steam turbine vanes are sometimes manufactured in a half-ring structure, where all vanes in a upper half and a lower half are connected by the shroud. In such a half-ring structure, the vane exhibits closely spaced natural frequencies of Toop (Tangential out-of-phase) modes, in which each vane in a half-ring vibrates like a fixed-fixed beam in a different phase. In such a steam turbine vane, the forced vibration and the self-excited vibration of Toop modes may become a serious issue. Therefore, in the design of the steam turbine vane, it becomes indispensable to evaluate the resonant response and the stability of Toop modes under the high loading condition. In this study, first, the vibration characteristics of steam turbine vane with a half-ring structure are studied by use of the results of FE analysis. Second, the reduced order model (the equivalent spring-mass model) of a half-ring structure is assembled, based on the results of FE analysis. Finally, the forced response analysis of the mistuned system of a half-ring structure is carried out, using the reduced order model and the Monte Carlo simulation. From these results, the vibration response characteristics of steam turbine vane with a half-ring structure are clarified.
In recent study, active thermography has reached a high status as an easy and speedy defects inspection method in a NDT field. This paper newly proposes a remote and non-contact NDT method using a sonic-IR for detecting and evaluating of fatigue cracks at runway girder of the overhead crane in the steel making plant. In this method, fatigue cracks are detected as localized high temperature areas caused by friction and collision at crack surfaces with an infrared camera, applying a high-amplitude ultrasonic vibration. In this paper, sonic-IR method is applied to remote and high-efficient crack inspection of the runway girder in the overhead traveling crane. Target crack located in high place can be detected using this method without setting up scaffolding for inspection. And the threshold of vibration amplitude to generate the sufficient heat for crack detection is clarified. Therefore the system to prevent missing the crack by unsuccessful vibration transmission from vibrator is developed applying monitoring the vibration.Time and cost saving inspection method in runway girder of the overhead traveling crane is carried out using this NDT technique.
In this article, we examined several longitudinal-sectional sizes of a silencer whose volume was limited by the thickness and aperture ratio of the ventilation door. We report the results of improvement in the sound attenuation properties of these shapes. As an evaluation method for the silencer, we measured transmission losses using an impedance measurement tube and calculated them on the basis of a theoretical analysis. The following results were obtained from the evaluation of the silencer using the measurement and calculation results and from the verification of the improved shape of a silencer and silencer array. For a side branch tube silencer with a 1/3 aperture ratio, assuming that it is installed into the ventilation door, we observed a side branch tube with an linear expanded longitudinal-sectional shape by improving the shape using the theoretical analysis of transmission losses. In addition, as a result of the experiment with a sample on the basis of the theoretical analysis, both the experimental and the theoretical analysis were in good agreement. Furthermore, the expanded shape of the longitudinal-section of the side branch tube decreased the frequency of the sound attenuation peak. It was found that a silencer with a combination of four of these silencers can be arrayed side-by-side in a ventilation door; this results in a flat transmission loss of more than 5 dB over a broad band.
In recent years, the demand for rocket launching has increased due to the development of space technology. However, using inexpensive rockets is not always possible. Although the cost of solid-propellant rockets is relatively reasonable, safely manufacturing a large amount of solid propellant is difficult, and the manufacturing process is disjointed. Therefore, safe and continues manufacturing of solid propellant is necessary. On the basis of the movements of the intestinal tract, we proposed that the movements required for transport and mixing of solid propellants are possible to achieve without the application of a large shear force. The peristaltic motion enables not only the mixing but also conveying even high viscosity slurry. By mimicking these intestinal movements, we have considered and developed the peristaltic pumping by driven artificial muscle as one of the candidates for the continuous and safety mixer. In this research, the mixing completeness of the composite solid propellant slurry by the peristaltic pumping mixer was estimated. The result showed that the mixer we proposed could mix the propellant slurry. In the propellant samples, these variances were sufficiently small. An appropriate combustion state as a solid propellant was confirmed.
This paper describes tip-over prevention control of a teleoperated excavator based on center of gravity (CoG) and zero moment point (ZMP) prediction. This method predicts a future CoG and ZMP when an operation input is given. This allows the determination of the risk of tip-over by the operation input before an excavator moves. When the risk is detected, the operation input to the actuator is modified or stopped automatically to prevent from tip-over. Future CoG and ZMP is predicted by computing the movement of a teleoperated excavator based on an approximate excavator movement model. The proposed method successfully demonstrates tip-over prevention via scaled model experiments of the hydraulic drive.
Nowadays, in vitro fertilization (IVF) of mammalian embryos is an essential technique in the reproductive technology and other related life science fields. However, the fertility rate by this technique is still less than 25%. Therefore, a novel in vitro fertilization method which obtains high fertility rate has been highly desired to the reproductive technology. In this study, we proposed and developed an in vitro embryo production device which allows three steps of sperm selection, fertilization and culture on a microdevice. To realize this concept, we integrated the sperm sorting function combining with swim-up and swim-down methods onto the device. To evaluate the device functions, sperm sorting experiment, in vitro fertilization experiment, and embryo culture experiment have been carried out. As results, we concluded that the device has ability to produce high quality embryos by integrating the sperm sorting function. This concept will open and enhance the management of in vitro fertilized embryos for assisted reproductive technology, livestock breeding, and fundamental stage research by further development.
Vibration characteristics of a flying head slider in hard disk drives at touchdown attract strong interest because head‒disk spacing must be decreased to less than 1 nm in order to increase recording density. This study first evaluates head‒disk interfacial force based on rough surface adhesion contact models and a simple air-bearing force model. Then, microwavinessexcited vibration of single-degree-of-freedom slider model at touchdown was numerically simulated in more detail than the previous study. It was found that the slider exhibits a MW-excited vibration having low frequency components of less than 100 kHz at touchdown and shifts to severe contact state near the boundary of static instability onset. When a small static unstable region is generated by decreasing air-bearing stiffness ratio, the occurrence of the low frequency spacing variation is interrupted by temporal flying state (loss of contact). When the static unstable region further increases by decreasing air-bearing stiffness ratio, the spacing variation with low frequencies can appear only at the beginning of contact and immediately jumps to a light contact state and then shifts to a perfect flying state during a long input power range and eventually jumps to a heavy contact state. These calculated results seem to correspond to the actual slider dynamic behaviors at touchdown in the inner, outer and middle diameter regions. The possibility of surfing recording is discussed from the analytical and experimental evidences.
The friction characteristics on sliding part between piston and cylinder in a swash plate type piston pump in which improvement of the power density is demanded affect the equipment performance and the efficiency. In this paper, targeting a straightly cylindrical piston and tapered pistons, the effects of geometric shape of the piston on the friction characteristics have been investigated based on both the results of friction force measurement using a model machine and the numerical calculation considering mixed lubrication. Moreover, the effectiveness of adopting each of the pistons to the swash plate type piston pump has been examined from view point of friction characteristics. The results are summarized as follows: (1) Optimum taper angle of the piston which can improve the friction characteristics will exist under severe lubrication conditions. (2) The degree of friction characteristics improvement can be formulated as a function of the Sommerfeld number which is one of important parameters to determine the bearing performance. (3) Adoption of tapered pistons may improve the friction characteristics under mild lubrication conditions. (4) The tapered piston will whirl widely in the cylinder than in the case of the straightly cylindrical piston, load carrying capacity due to squeeze effect of the fluid can be expected to increase.
Lightweight Al-Si alloy is expected as a substitute material for the cast iron of engine parts to improve fuel consumption of automobiles. In this study, the tribological properties of Al-Si alloys against diamond-like carbon (DLC) films were examined to comprehend the influences of Si particles on Al-Si alloy surfaces under lubricated with a fully formulated oil. Sliding tests were performed with a hydrogenated amorphous carbon (a-C:H) film coated steel cylinder against the five kind of Al-Si alloy disks with different Si contents. Sliding tests and surface analysis results showed that the friction coefficient of a-C:H/Al-Si tribo-pairs depended on the exposure height of Si particles on the Al-Si alloy surfaces rather than the area ratio of Si particles. The exposure height of Si particles plays important roles in determining the frictional properties of a-C:H/Al-Si tribo-pairs under lubrication with the fully formulated oil.
In order to clarify the reason that the multi-feeding is harder to occur in an overlap-type sheet separation mechanism than in a pressing-type, we examined the behaviors of the paper sheet in the both sheet separation mechanisms. The apparatus that handle paper sheets, such as copy machines, printers, and ATMs, are widely used in these days. These apparatus are equipped with sheet separation mechanism to make paper sheet separate one by one. The sheet separation mechanisms are classified roughly into two groups, one is a pressing-type and the other is an overlap-type. The pressing-type separation mechanism is widely used in copy machines, printers, and facsimile, because it is simple and low cost, however, its reliability is relative low because a multi-feeding is easily to occur. On the other hand, the overlap-type separation mechanism is used in apparatus that high reliability is required such as ATMs although the mechanism is complex and high cost, because a multi-feeding is hard to occur in this mechanism. However, the reason why the multi-feeding is hard to occur in the overlap-type sheet separation mechanism has not been clarified. First, we introduced the model and formulation that can calculate the resistance force and feed force acting on the paper sheets in the overlap-type mechanism. And, based on the calculation results of the resistance force and friction force between the paper sheets, we examined the behavior of the paper sheet. As a result, we found that, in the overlap-type sheet separation mechanism, when the piled paper sheets move between the feed-roller and the gate roller, a slippage caused by the resistance force that is proportional to the number of the piled sheet occurs between the piled paper sheet, and this slippage is the factor that is superior to the pressing-type sheet separation mechanism.
Manufacturing industry tends toward high-mix low-volume production in recent years. Therefore, in the field of machining, the ratio of preparation in the lead-time becomes higher because the preparation takes a great deal of time and labor to decide suitable machining method, allocate target parts, select cutting tools and generate tool paths. As a result, it is strongly required to develop a computer aided process planning (CAPP) system to shorten the preparation time and to generate NC program. Feature recognition has been considered as a key technology to develop a CAPP system, and a lot of researches have been tackling the technology for a long time. In authors' previous study, novel machining features for multi-tasking machine tools have been proposed. The machining features can correspond to several alternative machining methods. However, complex target shapes of practical mechanical parts have not been considered. In order to solve this problem, special shapes such as chamfer part and freeform surface are firstly approximated and machining features are recognized by simplifying machining primitives such as complicated groove or taper shape. The machining primitives are finally restored to original complex shapes for CAM system in this study. From the results of conducted case study, it is recognized that the proposed feature recognition method has a potential to deal with complex target shapes of practical mechanical parts.
Necessary conditions for usage of DLC coated mechanical seals were investigated by using ring on ring type sliding tests under various contact pressures and sliding speeds in dry and wet nitrogen. The wear mode of DLC coated SiC mechanical seal can be classified into two types by surface morphology of wear surface called ModeI with smooth surface that is useful as a seal and ModeII with relatively rough surface. The transition condition from ModeI to II is given by a critical μ2PV value, and show 0.025 under dry nitrogen and 0.070 under wet nitrogen. With the increase in PV value, arithmetic average roughness Ra decreases from 0.06 μm to 0.04 μm, and it leads to reduction of friction coefficient from 1.4 to 0.4. On the other hand, structural change of DLC films was not obtained within the condition of Mode I, and the friction was high. ModeI possibly has the desirable condition to DLC films for mechanical seal use. As a conclusion, the operation within critical μ2PV value range which depends on various conditions, and in addition, reduction of the friction coefficient in this range, achieve the increase of operating condition.
Recently, the miniaturization and multi-functionalization of electronic equipment have been demanded due to developments in IT. Therefore, the miniaturization and densification of the semiconductor package printed wiring boards (PWBs) have been more demanded. For the realization, the miniaturization of PWBs and fabrication of highly dense electrical circuit layers are also demanded. As a result, problems such as broken drill by the increase in aspect ratio and heat damage around the drilled hole are occurred in micro-drilling process of the PWB. A step feed drilling is considered to be effective as a solution to those problems However, it needs a high-speed reciprocating movement in short stroke to keep a drilling efficiency, and then causes residual vibration on machine tool table. In the present report, we propose a novel machine tool equipped with a counter balance mechanism using a left and right lead ball screw. This mechanism consists of a balance mass that moves in the Z-axis direction corresponding to the spindle movement to cancel a vibration force in linear direction at reciprocating movement. We construct a test stand to estimate the reducing effect of vibration force and to mode it. Moreover, we confirm the improving effect in high speed micro-drilling process with a proposed machine tool.
Process parameters in plastic injection molding (PIM) such as packing pressure, melt temperature and cooling time have a direct influence on the product quality and it is important to determine the optimal process parameters for the high product quality as well as the high productivity. This paper proposes a method to determine the optimal process parameters in the PIM for high product quality and high productivity. In particular, the variable packing pressure profile that the packing pressure varies through the packing phase is adopted as the advanced PIM. Warpage and cycle time are taken as the product quality and the productivity, respectively. Therefore, a multi-objective optimization of the process parameters using the variable packing pressure profile is performed. Numerical simulation in the PIM is so intensive that a sequential approximate optimization using radial basis function is adopted. It is found through the numerical result that the proposed packing pressure profile can improve both the warpage and the cycle time. Based on the numerical result, the experiment is also carried out. It is confirmed through the numerical and experimental result that the variable packing pressure profile is an effective approach for the warpage reduction and the short cycle time.
We construct a topology optimization method for two dimensional rarefied gas flow problems, based on level-set boundary expressions. The degree of rarefaction is expressed by the Knudsen number, which is the ratio of the mean free path and the characteristic length of the system. As the Knudsen number approaches 0 in the limit, flow behaviors can be described by Navier-Stokes equations and topology optimization methods for such flows have already been proposed. On the other hand, the governing equation for flows which have a large rarefaction is the Boltzmann equation and topology optimization methods for such flows have not been seen. This paper presents the topology optimization method for rarefied gas flows whose Knudsen number is approximately 1, aiming at an application for the design of flow channels in micromachines. We use the Bhatnagar-Gross-Krook (BGK) model of the Boltzmann equation and extend it to the entire design domain that includes both rarefied gas and solid domains. First, we briefly discuss the Boltzmann equation and the level set-based topology optimization method. Second, an optimization problem is formulated to address the design of flow channels that aim to maximize the flow velocity induced along a temperature gradient. Finally, several numerical examples demonstrate the validity and usefulness of the proposed method.
When visually impaired persons use general traffic facilities, they may face a lot of difficulties. Particularly, the accidents on the station platform may result serious injuries. One of the solutions is to install a platform door, which opens only when a train is at the station. However, the cost for the installation is very expensive. Also, if a different railroad companies use the same station, it usually cannot be installed. In this paper, we propose a safe walk support system at the station platform by sensor embedded intelligent white cane. Two functions will be realized by the intelligent white cane. It tells the direction of the platform even though a person lost a direction. It also senses a color on the ground and tells the position of the train door. We conducted experiments with subjects and confirmed the efficiency of the proposed system.
Hemiplegic patients often have reduced typing speed due to finger paralysis. Our motivation is to develop a keyboard that enables their typing speed to increase. For this purpose, we have developed a three-dimensional keyboard that reduces the distance that fingers move while typing. In this paper, our objective was to construct the finger model that combines the motion speed and muscle fatigue for design of keyboard that can be typed with fast motion speed and low muscle fatigue. In experiment, we measured the finger position using a magnetic 3D motion device and EMG when the participant pressed the proposed key. The experiment was carried out in a variety of the finger postures. We qualified the motion speed and muscle fatigue at each joint angle. Then, we weighted and combined two of the objective functions. We found out the Pareto solution and get an effective keyboard design straight. In the future, we verify the typing speed and finger muscle fatigue during typing the three-dimensional keyboard that is designed based on our finger model.
Tactile characters aid in providing information to visually impaired persons. The Japanese Standards Association enacted basic design methods for embossed tactile patterns in March 2011. However, data on the appropriate size of tactile alphabets are not necessarily enough available. The purpose of this study was to evaluate the influence of the size of a tactile alphabet on identification and to investigate the perceptible size for people without rich tactile experiences. The participants of this study were 15 young people and 15 old people who were unfamiliar with tactile characters intended for visually impaired people. They were asked to discriminate tactile alphabets of six different sizes by using their forefingers without the aid of eyesight. The results showed that the younger and older participants were able to discriminate the presented stimuli faster and more accurately as the stimulus size was increased. Concretely, when the size was 28 mm, each participants regardless of young or older groups could identify the tactile character accurately and quickly. In addition, a trend was seen in that the older group needed larger tactile alphabet sizes than the younger group. We determined the relationship between the tactile alphabet size and discrimination ability of younger and older people without rich tactile experiences.
The purpose of this study was to investigate the temperature behavior of sliding portions in the wear test of artificial joint materials using a hip joint simulator. We measured the concentrations of total protein in the lubricating liquids to determine whether they had an influence on the temperature of the fluids. Fluorescence microscopy was used to examine the relationship between the temperature of the sliding portions and the adsorbed state of the proteins. The results showed that the temperature of the sliding portions increased to more than 41°C during the running-in period, and it remained constant between 40 to 41°C after this period. However, it was necessary to exchange the lubricating liquids at regular time intervals to maintain the temperature of the sliding portions during prolonged wear tests. The exchange of lubricating liquids helped to maintain the concentration of total protein in lubricating liquids; however, the aggregate of the proteins increased at a temperature more than 40°C at the sliding surfaces. Consequently, it was considered that the adsorption of agglomerated proteins caused by the increased temperature of the sliding portions might influence the wear mechanism of artificial joints.