In this study, to evaluate the temperature dependence of the coefficient of thermal expansion (CTE) of multi-walled carbon nanotubes (MWCNTs) in the axial direction, the CTEs of aligned MWCNT reinforced epoxy composites are measured, and the axial CTEs of the MWCNTs are computed using the rule of mixtures. The mean diameters of the MWCNTs used in this study are 25 nm and 41 nm. The composite samples whose length is along the direction in parallel to MWCNT alignment are heated using a hot plate, and the length change is measured by a laser displacement meter. We demonstrate that the thermal contraction is observed in the composites, i.e. the CTEs of the composites are negative. The axial CTEs of both MWCNTs are calculated to be negative in the temperature range from -5‒85°C, and they tend to increase with the increasing temperature. The MWCNTs with the mean diameter of 41 nm possess larger negative CTE in the above temperature range compared with the MWCNTs with the mean diameter of 25 nm. The CTEs of the MWCNTs with the mean diameter of 25 nm and 41 nm are -1.1 ‒ 0.1×10-5 K-1 and -1.9 ‒ -0.8×10-5 K-1, respectively. These values are in reasonable agreement with those of the CNTs reported previously. The negative CTEs may be explained by out-of-plane atomic vibrations predicted by theoretical and numerical studies.
The criterion of micro-crack initiation on stronger, tougher steel, i.e., fail-safe steel, with an ultrafine elongated grain (UFEG) structure was studied through a combinations of numerical simulation and experimental observations and measurements. The test sample was machined from the rolled bar with 0° and 90° rotation along the rolling direction (RD). The static three-point bending test was conducted in a temperature range from 200 °C to -196 °C. The stresses near the initial notch were analyzed by three-dimensional finite element method. The conventionally quenched and tempered steel with a martensitic structure fractured brittlely with a peak bending loading. On the other hand, the developed steel did not fully fracture due to a lamella fracture even if load drops occurred during the bending test. The load drops are attributed to micro-cracks with normal to the loading direction (LD) or with an angle of 45° to the LD that occurred from near the initial notch root. When the crack orientation, i.e., LD is parallel to the RD, the developed steel showed a catastrophic fracture behavior. In the developed steel, the brittle fracture stress normal to the RD, σF⊥RD, was 3.2 GPa at temperature over -100 °C and 2.6 GPa at temperature below -170 °C. The σF of weak direction in the developed steel was 0.7 times lower than σF(QT) of the conventionally steel. When the effective grain size on fracture is assumed to be packet in the martensitic structure, the brittle fracture stress parallel to the RD, σF//RD, was estimated to be 6.2 GPa at temperature over -100 °C and 5.0 GPa at temperature below -170 °C. These values are 1.4 times as compared with the σF(QT), 1.9 times higher than the σF⊥RD regardless of the test temperatures. The anisotropic brittle fracture stress in the fail-safe steel is attributed to the microstructural features, and we would be able to control a fracture of the steel by designing microstructures.
Creep damage preferentially extends at a stress concentration portion in high temperature components such as steam turbine rotors. Therefore development of an accurate damage assessment method for creep damage process at the stress concentration portion under multiaxial stress states is necessary to maintain reliable operation. In this study, creep tests using a plain specimen and two kinds of round bar notch specimens with different notch radius on a CrMoV forging steel have been conducted to clarify effect of stress conditions on creep damage extension process. Three dimensional finite element creep analyses have been performed to discuss relation between the creep damage and stress conditions. Creep rupture time of the plain specimen is shorter than those of the notch specimens. Creep rupture time of the notch specimen with lower stress concentrate factor is longer than that with higher stress concentration factor. In the notch specimens, the maximum stresses occur at notch root at initial loading and portions of the maximum stresses gradually change to inside of the specimens with time due to stress redistribution. Triaxial tensile stress yields at the notch root sections with different distributions of the triaxiality factor depending on the notch radius. Void number densities at the maximum stress portion in the notch specimens are ten times larger than that in the plain specimen. The void growth simulation method developed previously was applied to predict the void number density under multiaxial stress states in the notch specimens. Distributions of the void number density from notch root to center of the specimen both in the notch specimens were quantitatively predicted by the void growth simulation method. An equation, which predicts change of void number density with time under a certain maximum stress and a triaxiality factor, was derived based on the void growth simulation under different multiaxial stress states.
A tip leakage flow is well known to have predominant influence on a loss generation in a compressor. An impeller for a transonic centrifugal compressor is generally composed of the main and the splitter blades to gain the choke flow rate. In this study, in order to clarify the individual influence of the tip leakage flows from the main and the splitter blades on the flow behavior in the transonic centrifugal compressor at design condition, the flows in the compressor at four conditions prescribed by the presence or the absence of the tip clearances of the main and the splitter blades were analyzed numerically. The computed results clarified a series of interactive influences of the tip leakage vortices on the flow field as follows. The tip leakage vortex from the leading edge of the main blade increased the incidence angle for the splitter blade by its blockage effect. The increased incidence angle generated the tip leakage vortex from the leading edge of the splitter blade and intensified the acceleration of the flow over the suction surface of the splitter blade. The accelerated flow produced the negative blade loading of the adjacent main blade by reducing the static pressure on the pressure surface of the main blade, which generated the tip leakage vortex appearing from the pressure side of the main blade. The tip leakage vortex from the leading edge of the splitter blade reduced the flow acceleration on the suction surface of the splitter blade by its blockage effect. As a consequence it strongly contributed to the reduction of the loss generation by suppressing the formation of the shock wave on the suction surface of the splitter blade and by decreasing the negative blade loading of the main blade.
When a train enters a tunnel, a compression wave is generated and propagates through the tunnel towards the other side of the tunnel portal, emitting a micro-pressure wave. The amplitude of the compression wave generated by a flat-fronted train is generally much larger than that by a streamlined train probably due to flow separation at the front end of the flat-fronted train. Flow separation at the front ends of flat-fronted trains of meter gauge railway lines results in increasing the aerodynamic drag and pressure fluctuations in tunnels, which may cause serious environment-related issues. Real train experiments have been conducted to explore pressure fluctuations in tunnels but details of spatial flow field around front end of cars are still unknown. In this study, model experiments for two varieties of rounded corners of the fronts of circular cylindrical trains entering a circular tube are carried out to visualize the unsteady flow with oil mist and tufts by using a high-speed camera as well as to measure the compression wave in the tube. It is shown that the pressure waves in the tunnel and the unsteady flows emitted from the tunnel entrance are considerably different between square- and round-ended trains. A vortex ring is generated by the round-ended train but not clearly by the square-ended train. A turbulent vortex ring may be generated by the square-ended train. The difference of amplitude of the compression waves generated by flat-fronted and streamlined trains can be attributed to the difference of structure of the jet flows generated by the trains.
The purpose of this paper is to analyze energy consumption and supply on a prefectural scale, and to visualize and compare the regional energy demand-supply distribution considering potential of renewable energy. The final energy consumption and the final energy consumption per capita are related to the industrial sector. Total final energy consumption is reported to be 13,297 PJ, of which 6,136 PJ is used for the industrial sector. In the residential and commercial sector, population is the most effective on the final energy consumption. On the other hand, final energy consumption per capita in residential sector is tied to the climate: cold areas like Hokkaido, Tohoku, and Hokuriku have larger consumption than other areas. Energy expenditure per capita in residential sector is also large in cold areas; for instance, 98,581 JPY/capita is spent for energy in Hokkaido. The energy supply system in Japan depends on thermal power generation that is large scale-centralized; Chiba has the largest thermal power generation estimated at 390 PJ. By contrast, thermal power generation in Yamanashi is the smallest in Japan estimated at 0.5 PJ. Renewable resources are widely distributed in Japan, but renewable energy supply which is calculated at 374 PJ is very small. Onshore wind power and solar power have enough potential, evaluated at 2,985 PJ, to substitute thermal power plants. This study indicates that development of local energy systems, especially local heat supply system, is important to introduce local renewable energy, and introduction of renewable energy leads to more balanced regional energy demand-supply distribution.
It is difficult to understand turbulent combustion, because the combustion process is very complex and unsteady. One of the useful parameters for discussion of the unsteady flame behaviors is the flame stretch rate, which is evaluated by local flame curvature and strain rate. In this study, we conducted simultaneous OH-PLIF/Stereo PIV measurements of turbulent premixed flames. Flame shape and flow field were obtained. Then, local flame curvature and strain rate were discussed. The turbulent flame was established by a cyclone-jet combustor for propane/air mixtures. The main jet velocity was Um = 10, 30 m/s, and the equivalence ratio was Φm = 0.75, 0.90. The equivalence ratio of the cyclone jet was the same as that of the main jet, but the velocity of the cyclone jet was the constant of 10 m/s. It was found that the variation of flame curvature was large when the main jet velocity was high. Difference between curvature convex to unburned gas and curvature convex to burned gas was relatively small. Frequency of larger strain rate was high when the main jet velocity was large and equivalence ratio was small. It is suggested that the local flame extinction could be caused by the large strain rate because the local flame extinction occurs more frequently. At all conditions, compared with the positive strain rate, the frequency of negative strain rate was high.
In order to evaluate the cooling performance of the porous metal fins, both the friction factor and heat transfer coefficient were taken into account. In this study, we compared six porous metal fins and four kinds of heat exchangers made of porous material. Moreover, we proposed a new model which predicts the cooling performance of the porous metal fins. Friction loss factor of porous metal fins became predictable in less than ±10% error by using effective cross-sectional flow area and Ergun coefficient in Forchheimer-extended Darcy model. Heat transfer coefficient of porous metal fins can be predicted within an error of 10% by our model. The predictive model has two assumptions. One is that the perimeter in the porous metal fin per cross-sectional area of porous metal fin is independent of the heights of fins and number of porous cells. Another assumption is that heat transfer coefficient of porous metal fin is also independent of the heights of fins and number of porous cells as long as the velocity is same.
Effect of fuel-air mixture diluted by inert gas on knock intensity was investigated by using a rapid compression and expansion machine. Dilution of fuel-air mixture decreased knock intensity. As the dilution ratio became high, increase in input heating value did not affect knock intensity too much although it shortened auto-ignition delay. Knock intensity is assumed to correlate with the pressure rising rate when the auto-ignition occurs. Knock intensity was shown as a function of the maximum pressure and the maximum temperature which affect the high temperature oxidation reaction rate.
To achieve precise temperature control, Peltier devices, which are also called thermoelectric coolers, are widely used. However, simulating the unsteady temperature history caused by the Peltier devices is difficult because the amounts of heat absorption and generation are affected by their temperature. The temperature dependence reportedly can be calculated using the quadratic equation of temperature and the typical temperature characteristic coefficients. However, as the temperature dependence varied among the manufacturers, the temperature characteristic coefficients had to be modified for each of the devices. We developed a technique to determine the temperature characteristic coefficients of the Peltier device automatically by using data assimilation. We integrated the particle filter, one of the data assimilation algorithms, into the thermal network method and enabled estimating the suitable temperature characteristic coefficients. To demonstrate the estimation, we evaluated a Peltier device. The constant current 1.0 A and its inverse current were applied to the sample device repeatedly, and the temperature of the control object fluctuated repeatedly between 40 °C and 90 °C was measured. The temperature change was simulated using the thermal network method with the typical temperature characteristic coefficients and the history was compared with the measurement results. The root mean square error of temperature between the measurement and the calculation results was 3.20 K. Then, we estimated the applicable value of the temperature characteristic coefficients by applying the particle filter combined with the thermal network model. When the estimated coefficients were applied to the thermal network model, the root mean square error of temperature decreased to 1.39 K.
The local heat transfer on a rotating cylinder was measured by Mach-Zehnder interferometer. The rotating cylinder was set in a restricted flow with narrow spaces by two horizontal plates. The two plates were made by copper or polycarbonate. The heat transfer was measured about both clockwise direction and counterclockwise direction. We observed flow pattern near the cylinder by smoke. Rotating Reynolds numbers were varied from 0 to 3000 and cross-flow Reynolds numbers were varied from 0 to 2000. The spaces between cylinder and plates were varied from 1 x 10-3m to 5 x 10-3m. The following results are obtained: When the spaces between rotating cylinder and flat plates are same as the displacement thickness on the plates, the heat transfer on the cylinder has best performance. The distributions of local Nusselt number were different from each other cases, however average Nusselt numbers were same values for the comparisons of the cylinder rotations and the plate materials. We have obtained empirical equation of heat transfer from the rotating cylinder with narrow spaces by two plates.
Spectral control of near-field radiation transfer by interference of Surface Plasmon Polaritons (SPPs) in pillar array structured surface made of nickel was investigated using a numerical simulation based on Maxwell’s electromagnetic wave theory. The electromagnetic field between two pillar array structured surfaces fixed in face to face with a vacuum gap of several hundred nanometers was obtained using a three dimensional Finite Difference Time Domain (FDTD) method and fluctuational electrodynamics (FED). The near-field radiation flux from a high temperature to a low temperature pillar array structured surfaces was evaluated through the summation of normal components of Poynting vector in any direction at the intermediate of the vacuum gap. Through the numerical simulation, it was clarified that the local maximum and the local minimum of near-field radiation flux were shown periodically with increasing height of pillar under the condition of a fixed vacuum gap, which was regarded as interference between the pillar height and an electromagnetic wave propagating in the channel between pillars. Moreover, the dispersion relation of the electromagnetic wave with interference in the channel between pillars is quite similar to the SPPs established in two semi-infinite smooth plates with a nanometer vacuum gap. As a result, it was concluded that the spectral control of near-field radiation transfer was achieved by interference of SPPs in the channel between pillars by tuning the height of pillar.
This paper presents an experimental and analytical investigation of the thermal characteristics in a layer of exothermic powder mixture that is utilized in body warmers, hot compresses, thermotherapy, etc. The research objective is to develop a manufacturing method that enables the exothermic temperature to be controlled in order to prevent cases of low-temperature burns. The exothermic powder mixture generally comprises metal powder, catalyst powder, and vermiculite particle absorbing some saline solution. The exothermic powder mixture is put into a mini-autoclave, and then placed in a constant temperature bath after the atmosphere inside the mini-autoclave has been replaced with pure oxygen. The degradation of oxygen pressure inside the mini-autoclave shows that the reaction rate of corrosion depends on the reaction temperature, the volume of the saline solution, and the conversion of iron powder into oxide, in addition to the ambient oxygen concentration; a correlation is suggested for the reaction rate. The variation over time of the temperature distribution in a layer of the exothermic powder mixture is evaluated analytically using this empirical correlation for the reaction rate, and compared with the experimental results. In the analysis, the mass, momentum, energy and oxygen component equations are solved numerically for a layer of the exothermic powder mixture, which is regarded as a porous medium. The analysis does not predict the temperature distribution accurately, but the analytical and experimental results are in accordance qualitatively.
In order to clarify the mechanism by which water adheres to the oxygen discharge side of the zeolite packed column composing a compact adsorption-type oxygen concentrator, the mass of a small amount of water absorbing to the column was measured by MRI (Magnetic Resonance Imaging). The zeolite particles used were Li-X type molecular sieve OXYSIV-700. The result of the MRI measurement showed that the mass of water adhering to the oxygen discharge side of the zeolite packed column increased almost linearly with the operating time of the oxygen concentrator. The experimental equipment comprised a thin zeolite packed column (inside diameter 8 mm, length 200 mm) and a thick zeolite packed column (inside diameter 30 mm, length 80 mm) connected in series. Even if the zeolite packed column had not reached the breakthrough point, water vapor contained in the gas passed through the thin zeolite packed column in the upper stream, and adhered to the thick zeolite packed column placed downstream. The amount of water absorbing to the thick zeolite packed column was about 1/150 as compared with that adsorbed to the thin zeolite packed column. This research showed clearly that the water adhering to the oxygen discharge side of a zeolite packed column is the water which passed through the column and reached the oxygen discharge side.
This paper deals with the flutter analysis of a rectangular sheet flexibly supported by a wire at the leading edge of the sheet subjected to axial fluid flow. The unsteady fluid force acting on the sheet surface is calculated by using Doublet-point method, which is based on unsteady lifting surface theory. The equation of motion of the sheet coupled with the wire is derived by employing the finite element method. Flutter velocity, frequency and mode are examined through the root locus of the flutter determinant of the system with changing flow velocity. Moreover we measure the flutter velocity and frequency. Flutter characteristic is clarified by comparing the analytical results with the experimental results. To organize the analytical and experimental results, we develop equivalent bending stiffness and torsional stiffness of the leading edge supported by the wire. Then the parameters of wire (tension, length, diameter and Young's modulus) are reduced in two dimensionless numbers (dimensionless equivalent bending stiffness and torsional stiffness). Moreover we organize the analytical and experimental results using these dimensionless numbers.
This paper proposes the steering characteristic compensation functions to adapt the driving situations by electric power steering (EPS). The desired compensatory handling characteristics are defined depending on the compensatory handling situations. Therefore, compensatory handling situations are divided into on center region, off center region and outside of off center region and discussed the influence of steering characteristic. In on center area, stick slip phenomenon is caused by combination of steering friction and high hand and arm system compliance with relaxed muscle condition. For this problem, torsion bar damping control is proposed and its effectiveness is demonstrated by simulation. In off center region, both steering feedback and low steering effort which are normally considered as trade-off are required. To solve this problem, structural damping which characteristic is Coulomb's friction increasing according to self-aligning torque is effective. Thus, structural damping compensation function is proposed by applying disturbance observer design technique and its feasibility is demonstrated by experiments. In outside of off center region, it is showed that the power assist characteristic function design contributes the driver recognition of tire grip condition by letting the driver estimate future torque based on linear tire characteristic.
Recently, we have faced on the problem such as increasing elderly people who have occurred accidents including solitary death and falling and so on at their houses. To deal with these problems, many researchers and companies are proposing and releasing the systems monitored by sensors for keeping them safety. However, conventional systems using sensors including cameras and microphones give little privacy. In order to solve the problems, we proposed and discussed the falling discrimination using sound information for watching elderly people. Proposed system expects the falling discriminations using acoustic features extracted from sound. For discrimination accurately, we focused on Spectrum gravity between subjects/things and flooring styles. The feature characterized and modeled as Spectrum ratio of delta power as dynamic parameter. Finally, experiments of two-class discriminations using feature parameters achieved to 96.83 % with dataset of unspecific conditions.
In this study, the optimal mechanical design method for fixed-pitch coaxial-rotor helicopter is proposed. The fixed-pitch coaxial-rotor helicopter has several advantages compared with other type helicopters. For example, it has great simplicity of the mechanisms, well maintainability, and well energy conversion efficiency, and so on. However, fixed-pitch coaxial-rotor helicopter has a drawback in forward flight named pitch-up phenomenon, and it causes a little cruise speed of the helicopter. To overcome such a problem, optimal mechanical design of the helicopter is required. The optimal design is based on the precise mathematical model and numerical optimization method. The mathematical model is derived by using Multi Body Dynamics (MBD) theory. The characteristics of the fixed-pitch coaxial-rotors are considered to the model by aerodynamics of the rotors. The mechanical parameters are examined to maximize the cruise speed of the helicopter. Particle Swarm Optimization (PSO), which is one of the population based stochastic optimization methods, is adopted as optimization method. The fundamental optimization of mechanical parameter is performed to show the validity of proposed optimal design method and to obtain the optimal mechanical parameters of fixed-pitch coaxial-rotor helicopter.
The change of lifestyle and medical environment has led to the increasing number of those suffering from lifestyle-related diseases in Japan. The extension of healthy period in lifetime is one of the most important goals of Japanese health policy. In this study, we proposed a new ankle supporter with C-shaped springs and embedded elastic elements in order to reduce the burden of an anterior tibial muscle, and make a clearance between a tip of toe and the ground. According to the results of the strength tests, the combination of the C-spring with 0.3 mm thickness and the elastomer with 70 % filling density performs the supporting torque of 3.7 Nm to the plantarflexion of ankle. In contrast, torques to the other directions were relatively small. In addition, according to the results of gait experiments for seven healthy young subjects, the proposed device reduced the muscle activation of the flexor in the initial contact and swing phase.
The demands for reduction of noise, vibration and harshness in the vehicle are getting increased in these years. In order to achieve the demands, the most efficient way is to reduce the input to the vehicle body. There are many investigations of the dynamic response of tire and suspension systems for reduction of the input from road surface to the vehicle body. Earlier studies presented improvement of the spectrum of roadnoise by the adjustment of tire - wheel system's eigenvalue. Thus, it is important to consider how to control the natural frequencies. In this paper, we present a new tire - wheel model for the prediction of natural frequencies below 200Hz using three-dimensional tire ring - wheel cylinder model. The ring represents the tread including belt, the springs represents the tire sidewall stiffness and the cylinder represents the wheel including the tire bead. The equation of motion of lateral, longitudinal and radial vibration on the tread are derived based on the assumption of inextentional deformation. Many of the associated numerical parameters are identified from experimental tests. Unlike most ring models, which only consider radial, circumferential mode, the presented model also predicts lateral bending mode. Impact tests have been conducted to confirm the theoretical findings. The results show reasonable agreement with the predictions.
Helmholtz resonators are used in many industrial products as devices for reducing low-frequency noise. An advantage of the Helmholtz resonator is that the structure is simple and applicable to low-frequency noise for its size. Further, an important feature is that the development costs and product costs are relatively low in actual product development. The optimum combination of the natural frequency and modal damping ratio of a Helmholtz resonator is dependent on the characteristic of the noise source. It is selected so as to minimize the sound pressure levels when the noise is stationary. In the case of a transient noise problem, the natural frequency and modal damping ratio is tuned for maximizing the modal damping ratios of the system consisting of the main system and a Helmholtz resonator. Noise reduction effects of Helmholtz resonators are generally predicted by 3D acoustic analysis. Recently, the effects are estimated by CFD at higher sound pressure levels exceeding 100dB, because they are greatly affected by eddies generated in the neck portion of resonators. However, there is no suitable method to predict the noise reduction effects of Helmholtz resonators that engineers can use easily in the early stages of design. This paper describes a simple method for estimating the optimum value of modal damping ratios of the acoustic system having a Helmholtz resonator. Here, two-degrees-of-freedom models similar to the mass-spring-damper models used in the design of tuned mass dampers are used. In addition, the differences between the optimum conditions of tuned mass dampers and Helmholtz resonators are described.
We demonstrated a high-speed human-robot cooperation task using a high-speed robot hand system consisting of a high-speed vision system, an image processing PC, a high-speed robot hand, a high-speed tactile sensor (only for measurement) and a real-time controller. In particular, our goal was to achieve a concrete task in which a board grasped by both a human subject and a robot hand is always kept horizontal by controlling the robot hand based on high-speed visual feedback using the vision system. We propose a basic strategy for appropriately achieving the task and discuss an image processing procedure for detecting the state of the board (position and angle). Also, we describe the inverse kinematics of the robot hand so as to keep the board horizontal, and we set limitations for the robot hand joint angles for avoiding an error action due to human error. Finally, we show experimental results for the human-robot cooperation task achieved using the high-speed robot system and our proposed method, and we compare the experimental results between low frame rate and high frame rate in terms of response time and reaction force detected by a high-speed tactile sensor.
This paper proposes a method to estimate the loaded static transmission error (STE) waveform by vibration measurement under operating load conditions of a gearbox. The proposed method is based on the understanding that vibration is determined by the loaded STE and frequency response function (FRF) of the gearbox. The loaded STE is calculated by dividing the measured vibration by the FRF. The FRF is derived by continuously combining the measured vibration response curves of mesh fundamental and harmonic frequency components with the calculated FRF by using a dynamic model of the gearbox. By employing parameter optimization for constructing a dynamic model that has the best fit with the measured vibration response curve, it becomes possible to accurately estimate the loaded STE. Because the objective function is multimodal, we solved this optimization problem by using a real-coded genetic algorithm (RCGA). The proposed method was performed on a single-stage helical gear vibration test rig. The estimated results are then compared to the calculated loaded STE by tooth contact analysis. This comparison shows good qualitative and quantitative agreement between the estimated and the calculated loaded STE waveforms. Our findings confirmed that the loaded STE can be estimated accurately by vibration measurement and that the effectiveness of the proposed method was verified experimentally.
The shaver is a popular electronic utility for male to cut their beard, hair and so on. It is roughly divided two shaving system as oscillating or rotating motion of an inner blade. The cutting hairs mechanism is also assumed that inner blade edge just cut hairs at the moment of contact between inner blade and hairs. However, the hairs were likely to pull into the shaver and a pulling force generated which we felt in use. The detail cutting motion and pulling force was observed and measured to clarify the differences between oscillation and rotation type by a high speed camera. Each shaving system showed same tendency that the inner blade penetrated to the hair at the first, then both the inner blade and hair moved together to the outer blade. Finally, the inner and outer blade cut the hair by scissor action with pulling force generation simultaneously. As regards oscillation shaver, it was indicated that the inner blade hit the hair several times before the hair was completely cut. The maximum pulling force was approximately 0.15 N and the average was 0.04 which was higher than rotation type of 0.13 N as maximum and 0.03 N as average. Finally, the relation between the inner blade speed and pulling force of rotating type shaver was investigated, and the rotating type showed lower pulling force generation nevertheless of its lower inner blade speed (1.18 m/s) than oscillation type (2.3 m/s).
Nowadays, a free-form surface, such as molding die surface, is required to be finished by reducing the environmental burden. Therefore, a novel polishing technology is needed with a less abrasive slurry,for the reduction of which a magnetic abrasive finishing method is attracting attention. However, it is well known that a conventional magnetic polishing method is unstable and insufficient to obtain the required surface roughness. In the present paper, we discuss the reasons causing instability in conventional magnetic polishing. We systematically investigate the magnetic pressure distribution characteristics and measure the pressing force distribution of the magnetic brush during machining. Furthermore, to observethe impact of an iron particle shape on the pressing force, we used steel balls (steel-ball brush) and abrasive slurry. Moreover, we compared this brush with a brush that uses iron powder paste (employed in the conventional magnetic polishing method). Thus, we determined the possibility of the wide range control of the pressing force by changing the shape and size of the magnetic material. The setting of the approach conditions should be sufficient because it could deteriorate the shape accuracy through very high pressure.
Brake squeals phenomena of the disc brake system for railroad cars were reproduced and were investigated in the test stands using a full-size brake rotor, a wheel, a floating caliper and a brake pad. Brake squeals of the disc-brake apparatus occurred at a low speed of 20 km/h or less, and the magnitude of brake squeals increased as the average braking force increases until it was saturated. Frequencies of the brake squeals exceeding the background noise of the test facility are 800 Hz, 2 kHz, 3.2 kHz, and 6.3 kHz. The largest squeal of 6.3 kHz was radiated from the leading side of the pad and the rotor, and coupled vibrations between the rotor and the pad were attributed to the self-excited vibration induced by the dry friction. To measure the vibrations of the rotating disc at the time of brake squeals, vibration measuring systems operating by wireless power supply were installed in the rotating axle. As a result, one-third octave band analysis of brake squeals at 6.3 kHz and at 3.2 kHz approximately coincides with the vibration of both the rotor and pad, and the coupled vibration tends to grow larger in the high friction coefficient range. Furthermore, these frequencies agree well with the natural frequency of the rotor examined using the scanning laser doppler vibrometer. The mode shapes and amplitude of rotor vibrations at the time of brake squeals are significantly affected by the number of bolts and their fastening positions to the wheel.
It is well known that the tooth surface accuracy greatly influences the vibration in gear meshing. The hypoid gear used in automobile differential has a complex shape, and the estimation of the contact conditions is difficult. Therefore we propose a estimating method of the tooth meshing contact conditions with a high response and high speed-camera thermography, based on monitoring the temperature distribution during meshing between the pinion and the gear. In the present report, we attempt to construct to a novel combined infrared image from the temperature data on the extraction line in each continuous shot thermal image, which is composed of temperature distribution on the tooth surface at the same time after tooth meshing. As a result, a proposed infrared image is found to be effective to estimate tooth meshing. Moreover, we develop a predicting method of tooth surface temperature by constructing a heat circuit network model, based on measured temperature on the tooth surface from a combined infrared image. Comparing calculating results with experimental ones, it can be seen that the constructed model is considered to be sufficient accuracy.
In our previous papers, we attempted to predict traction coefficient by combining oil film rheological models and heat conduction models. The rheological characteristic was considered by dividing rheological region in viscous and plastic. In addition, we formed a very tiny thin film sensor on rolling surface, and challenged to measure temperature change directly when the sensor passed through inside contact portion. But physical interpretation of shear flow transition between two rheological regions was still unclear. Since the plastic model was determined as empirical formula, its universality was also insufficient. In this paper, we define boundary continuity of shear flow transition between the two rheological regions in a new interpretation. Further utilizing this result, we propose a theoretical approach to determine the plastic model by using rheological parameters in viscous region. When the model is derived theoretically and if it could express physical phenomena as a function of actual temperature, we need accurate oil film temperature estimation. In that case, we show that it is effective to make the temperature prediction model in vicinity of contact portion. This is because the time constant of contact film thermal diffusion is small, it makes sense as an effective prediction of traction coefficient. Also by the thin film sensor measurement, the time constant is actually confirmed to be extremely small.
The impact sound and vibration significantly affect the usability of a golf club. Recently, a subjective evaluation of the golf club was carried out to determine the relationship between the sound of the impact and its auditory impressions, in which the impact sound of the golf club was improved. Then, the relationship between the impact vibration and the shot impressions that were transmitted to the hand was investigated, and efforts were made to improve the ability to differentiate the usability among the products. However, these research efforts independently investigate the impact sound and vibration. In this research, conditions favorable to the impact sound and vibration were studied in a subjective evaluation based on the semantic differential method to improve the impact sound of a golf club. Then, conditions were derived from the combination to enhance the comfort of the impact sound and its relationship with the impact vibration. Furthermore, the research considered whether the vibrations that were created during a comfortable impact sound enhanced the comfort of the impact sound. As the result, the following things were determined. The impression change was discovered when characteristics of the impact vibration changed. First, reducing the amplitude of vibrations in golf shafts can improve the shrillness, reverberation, and especially the cleanness of the impact sound. Reducing the decay of vibrations in golf shafts improves the reverberation, but impairs the cleanness and shrillness. Finally, higher frequency components of the impact vibration can homogeneously improve the cleanness, shrillness, and reverberation of impact sound impressions. Moreover, two conditions of the impact vibration that enhance the comfort of the impact sound are to reduce vibrations and reduce the amplitude of low frequencies.
Fibrils were isolated from rat tail tendons and the nanoindentation tests and tensile tests of these fibrils were performed in air (dry condition). In the nanoindentation test using atomic force microscope (AFM), the indentation depth and force of the AFM tip were determined by the force curve measurement. Elastic modulus was calculated from these data using Hertzian contact theory. In the tensile test, the both ends of the fibril were wound on to the tips of microneedles and the fibril was stretched to failure by moving the microneedle under dark-field observation. Elastic modulus was determined as the slope of the approximate line of the measured stress-strain relation. Elastic moduli measured by the nanoindentation tests and tensile tests were 0.97 ± 0.55 GPa and 0.90 ± 0.39 GPa (Mean ± S.D.), respectively. There was no significant difference between the two values. These results indicate that the elastic modulus of the sub-fibrils in the surface layers of fibrils may not be significantly different from that of whole fibrils in the longitudinal direction.
Tactile guide maps are well-known information support tools for visually impaired people. In a tactile guide map, area information is expressed by use of raised dot patterns and raised boundary lines. Tactile guide map designers must place spaces between these raised dot patterns and raised boundary lines so that tactile guide map users can easily identify the lines. However, there is a lack of quantitative data on the perceptibility of tactile guide map lines. In this study, we investigated the influence of the spaces between the raised dot patterns and raised boundary lines on the perceptibility of the tactile guide map lines. We made test pieces with seven different dot distances for dot patterns and five different space distances. The participants included 40 sighted people (20 younger and 20 older ones) as tactile guide map beginner users. The participants were asked to identify the direction of a line, which could be horizontal, vertical, diagonally left up, or diagonally right up. Based on these results, we found that the raised boundary lines were highly easy to identify when the distance between the raised dot patterns and raised boundary lines was greater than 5 mm. This knowledge will be helpful for tactile guide map designers.
The objective of this study is to optimize the design of thermoacoustic engines driven by LNG in order to exploit its unused energy at low temperature. LNG at 111K provides low temperature heat source while the environment has a role of high temperature heat source. The design variables such as regenerator channel radius, regenerator length, regenerator position, frequency and loop tube length were optimized based on Particle Swarm Optimization method in two cases of maximizing the acoustic power and the efficiency of energy conversion. In the optimization process the calculation of the acoustic field inside the regenerator and the buffer tube was simplified so that the temperature would have a given distribution. The comparison with the calculation assuming adiabatic condition verified that the proposed method was effective to derive optimal solution. It is also suggested that objective function needs to be estimated with the theoretical method to obtain precise value of the power generation. The optimization results indicate the strategies to design the thermoacoustic engine utilizing LNG. There is a clear trade-off relationship between the power generation and the efficiency. Consequently, it was found that the maximal power intensity of 1.9 MW/m2 with 4 m loop tube or the maximal efficiency of 52% with 2 m loop tube would be attainable. Based on the power intensity, the scale of the loop tube was estimated to generate 1 or 10 kW of acoustic power.
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