Nowadays, high frictional and low aggressive disc brake is required. For designing it, we have had to depend on empirical way because brake pad is complicated composite. We therefore attempted to optimize abrasion caused by abrasive which is one of the most important containing materials in brake pad. However, in general abrasion, high friction cannot provide low aggressiveness. In order to overcome this issue, we focused on degree of wear fab which has an effect on the ratio of wear coefficient to friction coefficient K / μ. In our previous (1st) report, by conducting scratch test with using 4 types of abrasives (CFP, FFP, AP1 and AP2), we clarified the effect of abrasive shape (open angle φ) on degree of wear fab ; degree of wear fab increased with increasing open angle φ except in FFP. Then we proposed small open angle abrasive for high frictional and low aggressive disc brake. This report, we conducted scratch test with using 7 disc materials as counter-part: SUS304, FC200, Pure Al, Pure Cu, Ti-Al-V, Ni-Cr-Fe and Al-Mg-Mn. Then we confirmed that in all disc materials degree of wear fab increased with increasing open angle φ, which strengthened our 1st report and we clarified the effect of property of disc material (toughness W) on degree of wear fab ; degree of wear fab decreased with increasing toughness W. Thus we proposed small open angle abrasive and tough disc material for high frictional and low aggressive disc brake.
Silicon (Si) wafers for electronic or photovoltaic devices are fabricated by slicing a Si ingot using mechanical slicing with a diamond wire. Recently, the slicing method without generating damage on Si surface has been strongly required because of the increasing demand of ultra-thin Si wafers. In this study, we have developed a novel machining method for Si grooving based on a wet chemical etching. In this method, Si was processed by the chemical etching in HNO3 and HF mixture combined with an abrasion effect of metallic wires that contains no abrasives. The extremely low kerf loss with approx. 100 μm was achieved by optimizing the composition of etchant. SEM observation showed that Si surfaces processed by the proposed method had no crack and tool mark contrary to the mechanical slicing. Furthermore, Raman microscopy exhibited that the proposed method generated no disordered layer on Si surfaces, whereas the mechanical slicing caused amorphous layers. Surface roughness was improved by adding CH3COOH to the etchant.
A rotating shaft is designed by comparing calculated stress for expected load with material strength. Because unexpected force is often applied to the shaft in an actual machine, the generated stress can be larger than the calculated one. Strain gauge method is generally applied rotating shafts by using a slip ring or telemetry. However measurement accuracy is decreased by electrical noise generated from motors in the machine. In the paper, the method of two-dimensional thermoelastic stress measurement was developed to determine fluctuating distribution of stress in the rotating shaft. Bending stress in the rotating shaft could be accurately identified by using inverse analysis with images taken from multiple positions of a thermographic camera. Validity and efficiency of the method were confirmed on the basis of numerical and the experimental results and the accuracy of the stress was also found to depend on reference temperature in the measurement.
In this study, for the matrix / fiber interface strength is investigated in the fatigue experiment for the glass-fiber reinforcing polycarbonate (GFPC). Here the effect of modified PC resin is discussed when Epoxy (EP) or Polydimethylsiloxane (PDMS) are blended into PC. The microscopic damage process and fracture surface is examined through the optical microscope and the scanning electron microscope. The EP and PDMS are found to improve the matrix / fiber interface strength since they may control crack propagation along the fiber. Tensile testing also shows that in modified PC the critical fiber length is quite shorter than the one in standard GFPC. Although the interface strength is improved, the fatigue lifetime of PC-PDMS is found to decrease because many crack tend to initiate and propagate around the fiber ends.
This paper describes evaluation methods of in-plane squirm buckling strength of bellows with thin wall reinforcing rings. Many bellows with thin wall reinforcing rings are used in the facilities of nuclear power plants. Bellows used in a vent pipe of the Mark-I type pressure containment vessel (PCV) is one of the examples. Bellows with solid reinforcing rings are not buckled due to internal pressure because deformation of bellows is restricted by the reinforcing rings. However, bellows with thin wall reinforcing rings might be buckled when it is subjected to high pressure exceeding design conditions. Buckling strength of the in-plane squirm mode is dominated by plastic collapse strength of convolutions, but buckling strength evaluation methods for bellows with thin wall reinforcing rings have not been proposed. Authors carried out parametric plastic collapse analyses for bellows with thin wall reinforcing rings, and examined simplified evaluation methods. Proposed evaluation methods were developed based on the formulae defined in Standards of the Expansion Joint Manufacturers Association (EJMA). Buckling strength of bellows with thin wall reinforcing rings can be evaluated using the effective thickness which is the same bending stiffness with the added thickness of bellows and reinforcing rings.
This paper presents general solutions for piezoelectric materials and anisotropic materials subjected to arbitrary loads at the boundary. General solutions are provided by using complex functions based on Lekhnitskii formalism. In the analysis, similarities of fundamental equation between piezoelectric materials and anisotropic materials are shown. By defining new similarity-based complex functions, expressions of mechanical and electrical quantities are derived by analogous form. It is shown that expression forms of electric displacement in piezoelectric materials are corresponding to those of out-of-plane share stress in anisotropic materials. And stress distribution, electric displacement distribution and coupling effect are shown by graphical representation from several analysis results.
There has been reported the occurrence of cracks in bolts in nuclear and thermal power plants. This paper proposes a new method for depth sizing of crack in bolts using ultrasonic phased array technology. The finite element method is used to predict sectorial views for various crack depths when a linear array transducer is used to inspect bolts. Numerical results show that a peak associated with the vicinity of crack tip can be observed in the curve of echo intensity versus refraction angle for deep cracks. The refraction angle with respect to this peak decreases with crack depth increasing, and it is larger than the refraction angle corresponding to central beam impinging the crack tip. Therefore, crack depth will be underestimated if it is determined directly from this peak observed in a sector view by ultrasonic phased array technology. To verify numerical results, experiments are performed for bolt specimens where EDM notches with different depths are introduced. Experimental and numerical results are in good agreement with each other. Based on the refraction angle associated to the peak, a new method for depth sizing of crack in bolts is proposed. Comparison between determined and actual depths shows that it is possible to determine a crack depth accurately from inspection results by proposed method.
This study aims to reveal the mechanism of electro-fusion joining of CFRTP composites using multiple Ni-Cr wires as resistance heating element. The materials used for electro-fusion joining test are unidirectional CF/PPS and woven CF/PPS laminates. The effects of electro-fusion condition such as applied voltage and fusion time, Ni-Cr wire spacing and PPS film thickness on the fusion behavior of CFRTP composites were investigated experimentally. The welding area and the joining strength were evaluated quantitatively by microscopic observation and single lap shear test. From the results of surface observation, it was shown that the welding area increased with increasing the applied voltage and fusion time, but thermal degradation and deformation were caused by excess conducting. It was also revealed that Ni-Cr wire spacing and PPS film thickness were significant parameters affecting on welding area and thermal degradation. The optimum electro-fusion condition could be obtained respectively for unidirectional CF/PPS and woven CF/PPS laminates because microscopic electro-fusion behavior was influenced by the fiber reinforcement configuration. Though the interlaminar shear strength (ILSS) is resulted in a marked improvement in the optimum electro-fusion conditions, ILSS was decreased significantly by inserting PPS film which can reduce the thermal degradation. Therefore the experimental results suggested that it is essential to avoid the thermal degradation of matrix polymer by heating of Ni-Cr wire.
This paper described the effect of friction welding condition on joining phenomena and tensile strength of ABS resin friction welded joint. When the joint was made with a friction speed of 4.2 s-1 and a friction pressure of 0.3 MPa, the temperature at the weld interface at a friction time of about 45 s or longer exceeded 130 ℃. That is, the temperature at the weld interface of the ABS resin friction welding exceeded the glass transition temperature of its resin. When the joint was made with a friction time of 60.0 s, it obtained approximately 67% joint efficiency. However, the joint efficiency decreased with increasing friction speed, and it also decreased with decreasing friction speed. The joint efficiencies with other friction pressures showed a similar change although the friction speed differed. When the joint was made with a friction speed of 2.5 s-1, a friction pressure of 0.3 MPa and a friction time of 180.0 s, it obtained over approximately 90% joint efficiency. However, the joint efficiency decreased with increasing friction time, and it also decreased with decreasing friction time. Furthermore, the joint efficiency increased with decreasing parallel part diameter of the joint tensile test specimen, and that achieved 95% joint efficiency. In conclusion, to obtain the higher joint efficiency, the joint should be made with opportune friction speed, friction pressure and friction time, and the friction welding should be completed when the whole weld interface became melting state.
In this paper, the new type lightweight structure by using truss core panel is proposed. By using general dynamic analysis software LS-DYNA and response surface optimization method to determine the optimal structure of proposed lightweight structure, the problem of bending during the crash is solved. And as the result, the optimal truss core lightweight structure is capable of absorbing crash energy more than that of the optimal honeycomb panel structure at the same mass. Furthermore, a theoretical analysis of the optimal truss core type lightweight structure is discussed. As a result, it is shown that lightweight structure by using truss core panel and optimization system for crash energy absorption are useful for lightweight structure design in wide industrial fields.
In this paper, the fracture problem of a piezoelectric material strip containing two coplanar cracks perpendicular to its boundaries is considered. The problem is solved for a strip that is suddenly heated from both the top and the bottom surfaces under static mechanical loading. In spite of many studies in the thermo-electro-mechanical fracture problem of a piezoelectric material strip with a crack, not much work has been done in the context of the crack contact problem. The main object of this paper is also to study the crack contact problem. By using the Fourier transform, the thermoelectromechanical fracture problem is reduced to a system of singular integral equations, which are solved numerically. The numerical results for the stress and thermal stress intensity factors are computed as a function of the normalized time and geometric parameters. For the cases of two embedded cracks and an embedded crack and an edge crack, the effect of the upper crack geometry on the fracture behavior of the lower crack are considered under the pure mechanical load and the pure thermal load, respectively. The following facts can be found from the numerical results. First, the stress intensity factor of lower edge crack under pure mechanical load monotonically decreases with increasing the upper embedded crack length. Second, absolute value of the stress intensity factor of inner crack tip under the pure thermal load increases with increasing the heating temperature. Finally, taking the crack contact into consideration, it is found that the edge crack in the strip under the heating process would be fully closed at some time after the thermal shock.
Fish eye failure that is unique fatigue fracture occurs in very long life region of high strength steel. The fatigue life of fish eye failure dominated ODA (Optically Dark Area) around the fracture origin. A granular looking area of ODA is visible close to the crack initiation, fatigue life of fish eye failure is almost exclusively spent in the propagating in ODA. To predict fatigue life of fish eye failure, therefore, it is important to know the formative mechanism ODA. In this study, fatigue test was performed under vacuum environment that simulates environment of subsurface failure. The observation of process when ODA is formed on the precrack tip was examined in order to make clear a mechanism of ODA formation. Fatigue crack growth rate has depended on maximum stress by range of ΔK ≤ 4MPa√m. Under the fixed maximum stress of value, initiated fatigue cracks became non-propagating cracks. Moreover, fractography results suggest that ODA is formed when internal crack is propagating extremely slowly.
The stress intensity factor can be applied as an evaluation parameter of crack growth under small-scale yielding conditions. Moreover, the stress intensity factor corrected by the plastic zone correction can potentially be used as an evaluation parameter of crack growth for small-scale yielding criteria or beyond these criteria. In the previous study, the plastic zone correction method for that purpose was proposed. The method focuses on the gradient of the stress intensity factor at the crack tip, incorporating the term into the correction formula. To investigate the applicability of the correction experimentally, fatigue crack propagation tests were conducted in this study using three types of specimens with different gradients. The results show that the crack growth rate increased when the gradient was large although the effective stress intensity factor range was the same. This indicates that the gradient of the stress intensity factor at the crack tip affects the stress state in the vicinity of the crack tip and the crack growth rate increases as the gradient increases. When the correction of the stress intensity factor was applied, the crack growth rate could be evaluated independently from the gradient of the stress intensity factor. The correction is applicable around small-scale yielding criteria or beyond these criteria, but is not applicable under sufficiently large-scale yielding conditions.
For assessment of structural integrity of operating welded structures, non-destructive evaluation of a crack propagation direction and a crack growth rate for each detected crack is demanded in in-service inspection. For crack propagation prediction, three-dimensional welding residual stresses have to be evaluated quantitatively by non-destructive techniques. Today, synchrotron X-ray diffraction and neutron diffraction are known as non-destructive measurement methods of residual stresses in the thickness direction. However, these higher energy diffraction methods cannot be used as on-site measurement techniques because they are available just in special irradiation institutions. In the bead flush method based on the eigen-strain methodology, inner residual stresses can be estimated by using released strains during removal of reinforcement of weld. But, it is impossible to apply this method to welded structures without excess metal such as friction stir weld and spot weld joint. In this study, welding residual stress distributions for whole structure are calculated by an elastic FEM (Finite Element Method) analysis from eigen-strains which can be estimated by an inverse analysis from residual strains just on surface. Here, residual strains on surface can be measured non-destructively by X-ray diffraction that is widely used as an on-site measurement application. Although it was difficult to estimate inner welding residual stresses accurately from residual strains just on one-side surface, solutions with higher accuracy could be obtained by using measured strains on the both top and bottom surfaces in butt-welded plate. Additionally, it was shown that estimation accuracy in this method was good enough when measured strains near the weld line were used as additional information for estimation.
This paper is concerned with numerical simulation on propagation behavior of three-dimensional detonations in square tubes. Influence on motion trajectories of high pressure region (shock triple points) due to the change of aspect ratio of tube is solved by a finite difference method which consists of the semi-implicit MacCormack method and Non-MUSCLE type TVD scheme in order to prevent numerical stiffness and Gibb's phenomena. Reaction mechanism utilized in this study is the Nagoya model constructed for the stoichiometric hydrogen and oxygen gas mixture. It was found from numerical results that distinction in propagation mode could be explained from the relation between the geometric form of the tube section and the behavior of triple points. Moreover, it was shown that the transition of the configuration and the mode of propagation might not be settled causing the aspect ratio of the section.
In a single wafer spin cleaner, the wafer is rotated at high speed to spin off ultrapure water and clean air is blown perpendicular onto the surface to dry the wafer. Interaction between the rotating wafer and blown air generates vortices and the recirculation flow due to the vortices may cause reattachment of contaminants on the wafer surface. Therefore, we experimentally investigated vortical structures and the conditions of their formation in a modeled cleaner by using particle image velocimetry (PIV). The model was a 330 mm diameter rotating disk in a 520 mm diameter cylindrical stationary housing. Laminar blown air was from the housing inlet onto the rotating disk. The rotating speed of the disk was changed up to 2000 rpm and the blown air rate was up to 3.0 m3/min. Our PIV data show that vortices were generated on the upper and lower sides of the disk near the outer edge and collided with each other to form a large one. Additional large scale vortices were observed on the housing wall for the rotating speed of the disk above 200 rpm. The scale of the vortices increased and their generation frequency increased as the rotating speed increased. This work also investigated the optimum blown air flow rate against the rotating speed of the disk to prevent from generating the vortices.
Effects of non-equilibrium plasma on combustion phenomena have been investigated in terms of the improvement of the ignitability and the enhancement of reaction rate of combustion. In this study, effects of dielectric barrier discharge (DBD) on methane/air laminar lean premixed flame were experimentally investigated. It is known that the properties of DBD are affected by characteristics of a power source. To understand effects of the condition of the electric power source of DBD, the peak to peak voltage and frequency of DBD were varied from 10 kV to 36 kV and from 200 Hz to 7 kHz, respectively. Results showed that the length of a lean premixed flame was shortened with DBD. It indicates that the laminar burning velocity was increased. To examine the mechanism of the enhancement of the laminar burning velocity, spectroscopy measurements were performed on the flame with/without DBD conditions. As a result, location of the flame zone, where the chemiluminescence of OH* and CH* was observed, was shifted slightly toward unburned side. In addition, it was found that the chemiluminescence of OH* and CH* steeply increased in a second DBD overlapped with the flame.
A lunar long duration method which utilizes a characteristic of a very low thermal conductivity of lunar regolith has been proposed. The principle of this method is to put heater in desired depth of the regolith and heat up the regolith layer during lunar daytime. Because of the very low thermal conductivity of regolith, stored heat in regolith propagates gradually and raises the surface temperature at cold lunar night. By this method, a lunar lander will be kept warm passively during cold lunar night. In this paper, a temporospatially small-scale experimental apparatus which simulate lunar surface environment was fabricated and thermal cycling condition and heater setting position was calculated by comparing lunar environment, and thermophysical properties of the lunar regolith and regolith simulant used in this work. The feasibility of a passive thermal control method with no electrical power during lunar night time was evaluated.
With pump-probe separated closed aperture Z-scan technique, nonlinear refraction can be detected and taken into account with transmittance signal of probe beam. Because the transmittance change induced by nanosecond pump pulse is temporal, temporal profile of probe pulse also changes with the thermal lens effect rising. In this study, a new concept for pulse shaping of nanosecond laser with thermal lens effect is discussed in terms of nonlinear optics. The rising of thermal lens effect in nanosecond regime is demonstrated by time-resolved measurement and theoretical model. Theoretical model that accounts for unsteady heat conduction and generation of acoustic wave in liquid sample shows good agreement with experimental results. As pump beam waist gets narrow, rising time of thermal lens effect becomes faster. It means drastic temporal change of transmittance is obtainable and controllable. Using this knowledge, temporal pulse-shaping of nanosecond laser pulse is tried in terms of pulse compression. It is shown that 7 ns pulse can be compressed by 30.0% in the present configuration theoretically. Also, experimental results show 32.2 ns pulse can be compressed by 21.7%.
Natural convective heat transfer from a horizontal array of heated circular cylinders to air has been investigated experimentally. The average heat transfer coefficients from the cylinders have been measured by varying the diameter d=8.4-20.4mm, the numbers of the cylinder N=1-14, and the horizontal spacing G=3.6-50.6mm between cylinders. The coefficients for fixed spacing G increase first with the number of cylinders from N=1 to 7, while they remained unchanged with further increase in N. Besides, the coefficients from the central cylinders of the array showed the identical values. The latter coefficients were, then, normalized with several non-dimensional parameters. The results depicted that the parameters, RaG*(G/d) or RaG(G/d), well predict the present Nusselt numbers, NuG, and their correlation equations were proposed. Moreover, based on the present correlations, optimum spacing to make the Nusselt numbers maximum was discussed.
We have developed the cooling unit for high-density packaging ICT racks by using the boiling heat transfer with the concept of transporting a heat generated from CPU into the outdoor atmosphere directly without exposure to air in the computer room. The aim of this paper is to evaluate the cooling and power saving performance of the cooling unit using the low height type thermosyhon installed in the 1U server and the heat exchanger cooled by the water from the outdoor chiller unit. First, we clarified some factors (tilt angle, flow passage length and cross sectional area of thermosyhon) influencing the cooling performance. Then we examined the power saving performance of this cooling system during operating 32 CPUs in the ICT rack and compared to the conventional system using the computer room air conditioner.
This paper proposes a feedforward controller for active suppression of contact force fluctuation between a pantograph and overhead contact line of a high-speed railway vehicle, assuming the use of a pneumatic actuator with low response speed. The proposed controller, designed to exploit the periodicity of the disturbance as a priori knowledge, consists of a phase-locked-loop-based synchronized harmonic generator and adaptive compensators to extract the periodic structure of the disturbance and to generate the appropriate input for disturbance cancellation. The synchronization condition of the phase-locked loop is clarified through a theoretical study, and a design of the controller that can cancel the sinusoidal disturbance with the frequency from 1 Hz to 10 Hz is presented. Numerical studies are carried out to examine the validity of the theoretical study and the performance of the controller. Experimental studies using an actual pantograph equipment show that the proposed controller can suppress the contact force fluctuation to 10 % of that without control at the frequency from 1 Hz to 10 Hz.
Vortices occur when gas flow passes through a duct with a tube bank of the heat exchangers, such as a gas heater and a boiler. Very high level sound called a “self-sustained tone” occurs due to the interference of the vortices and the sound field in the duct. There are many investigations concerning the generation mechanism and countermeasures of the self-sustained tones. However there are few investigations focusing on the behaviors of the pressure and the velocity in occurrence of the self-sustained tones. In the past, we experienced the failure of the fan blade used in the experiment. In this paper, the experiment was carried out to examine the behaviors of the pressure and the velocity in the duct with tube bank. As a result, the static pressure changes along the squared curve when the self-sustained tone does not occur. But it suddenly rises up when the self-sustained tone occurs and it is possible for this pressure rise to cause the blade failure due to the generation of the rotating stall. In addition, it was clarified that the flow velocity does not increase in proportion to the inverter frequency and its gradient decreases when the self-sustained tone occurs.
This paper deals with the response reduction effect by friction under 2-dof system. The friction behaviour is effective for dissipating seismic energy. Therefore, in recent years, the installation of an isolator and a damper with frictional element in industrial facilities has been investigated. In addition, the seismic response is reduced by the frictional vibration occurring between piping and support system. However, the seismic response of a 2-dof friction system depends on system parameters such as natural frequencies and the mass ratio of the structure by support. A great deal of time is required for non-linear analysis to obtain optimum system parameters. The present study deals with the “Response Reduction Map” for a 2-dof friction system. This map shows the area that the response magnification is less than 1 and less than the response of a linear system. Firstly, the response reduction map by actual seismic wave is shown. Secondly, the response reduction map by the artificial seismic wave calculated from the design spectrum is shown. Optimum friction forces for reducing the seismic response of 2-dof friction system can be easily obtained by this map without non-linear time history analysis.
For the passive vibration isolation system, a friction damper is advantageous at cost, a maintenance, etc. However, the conventional damper of constant friction force has performance limitations; the isolation characteristic declines when the friction force is large, while the resonant peak becomes large when the friction force is small. Furthermore, the displacement remains apart from the equilibrium position after the vibration diminishes. In order to overcome above drawbacks, this paper proposes a vibration isolation system equipped with a new linear friction damper where the magnitude of the frictional force increases proportionally to the relative displacement. This proportionality is achieved by combining a cylindrical block and a tilt lever supported with a leaf spring. When the cylindrical block moves and pushes the tilt lever, the normal force exerted by the leaf spring at the contact position increases. Thus, the friction force varies in proportion to the relative displacement between the tilt lever and the cylindrical block. The transient response and the displacement transmissibility are investigated by numerical simulation and experiments, confirming the effectiveness of the linear friction damper.
Recently pumps having magnetic bearings are used and developed. Although magnetic bearing motors have advantages of no friction loss, no lubrication and so on, they are not widely used because of their high cost and large size. To solve these problems, an axial self-bearing motor (ASBM) is proposed. The ASBM has functions of producing rotation torque and controlling axial position. It enables downsizing and reducing cost of magnetic bearings, but it cannot damp vibration of radial direction and tilting direction. It also cannot give a rotor high stiffness as to those directions. Therefore, we propose controlling tilt angle of rotor with the ASBM. In this paper, a structure of the ASBM and a design of the device are introduced, and experimental results are shown.
There are two principal methods to derivate motion of equation of robot manipulator, which are Newton-Euler (NE) method and Lagrange method. NE method treats each linkage as rigid linkage and it is possible to calculate internal force and torque not generating real motion of robot manipulator, which is a merit of NE method that Lagrange method does not have. So far, NE method has been applied to a robot of open-loop serial-linkage structure. However, the adaptation has been limited to a motion without contact of hand with environment. Although robot task based on contact with environment, for example assembly task, grinding task, is important, it is not formulated in the way of NE method. So, this paper proposes iterative calculation method for representing constraint dynamical motion of robot manipulator utilizing inverse dynamic calculation method-NE method, leading and enabling the forward dynamics calculation of constraint motions to be dealt recursively through proposed extended NE method for constraint motions, with no use of explicit representation of equation of motions. We applied this method to 2-linkage and 3-linkage manipulators and evaluated its validity by numerical simulations. Also, we calculated inertia force acting on each linkage during constraint motion and evaluated validity of those values.
In a jet engine, icing phenomena may occur primarily on the fan blades, the fan exit guide vanes (FEGVs), the splitter, and the low-pressure compressor. Accreted ice disturbs the inlet flow and causes large energy losses. In addition, ice accreted on a fan rotor can be shed from the blade surface due to centrifugal force and can damage the compressor components. This phenomenon, which is typical in turbomachinery, is referred to as ice shedding. The ice shedding phenomenon is very complicated because there are several unknown physical properties of ice, such as the ice density, the adhesion force between accreted ice and the wall, and the contact force between ice pieces. Moreover, although existing icing models can simulate ice growth, these models do not have the capability to reproduce ice shedding. In the present study, we developed an icing model that takes into account both ice growth and ice shedding. We validated the proposed ice shedding model through the comparison of numerical results and experimental data, which includes the flow rate loss due to ice growth and the flow rate recovery due to ice shedding. The predictive shedding time obtained using the proposed ice shedding model were in good agreement with the experimental data. Finally, we investigated the effects of ice growth and ice shedding on the fan performance.
Human ambition for design is to create objects that resonate with deep feelings. Recently, the field of design has been widened from static objects including pictures and architecture to dynamics object including music, animation and motion. In our previous study, we had proposed a method of designing a creative and emotional motion that might resonate with deep feelings. In this method, the motion is designed by blending motions which are called “base motions”. Base motions are based on motion of natural objects. In the present study, we focus on mimetic (reality-symbolic) words. Mimetic words express appearance and movements. These words can be understood as potential representations of those motions that are difficult to describe verbally. We attempt to create a database of base motions by focusing on mimetic words. First, we created a tool to obtain motion data by capturing a video of a natural object and extracting its movements. A total of 160 base motions were collected using the tool. Experiment 1 was conducted to classify mimetic words from the viewpoints of their similarities. Then, the representative word in each classified group was recognised as a head word of the database. Experiment 2 was conducted to relate each representative mimetic word to the base motion. As a result, a database of 160 base motions that were related to the corresponding mimetic words was constructed. Experiment 3 was conducted to examine generalities associated with evaluating the appropriateness of expressing each base motion with related mimetic words. Finally, a case study that used constructed database was conducted, and the feasibility of the database and the method was confirmed.
The conical involute gears have been applied to automotive parts such as FR-4WD transfer. To apply for automobile, high capacity, higher quietness and efficiency are required. However the tooth contact of conical gear pair is point contact, so the large ease off happens even though each tooth surface has no manufacture error. Also the tooth depth and thickness of conical involute gears change along the lead direction. These characteristics have to be considered for the tooth mesh analysis. We have already published the transmission error analysis and tooth surface durability analysis considering these peculiar characteristics. In this paper, we develop the mesh efficiency analysis and show the improvement method of mesh efficiency by tooth surface modification. From this investigation, it is found that the mesh efficiency of conical involute gears is better than same size cylindrical gears due to the peculiar ease off distribution.
The mechanism of the sideband phenomenon of planetary gear vibration that often occurs in a planetary gear set was clarified in connection with mesh phase differences. This sideband phenomenon is one in which the (Z-1) or (Z+1) order component level is higher than the mesh order (Z) component level. The notation (Z-1) or (Z+1) means the mesh order (Z) minus or plus one carrier revolution. An in-phase (IP) planetary gear set has no such sideband phenomenon. In a sequentially phased (SP) planetary gear set, this phenomenon occurs in transverse and tilting vibration of sun gear, carrier and ring gear. Which sideband, either (Z-1) or (Z+1), occurs depends on the relationship between the mesh phasing direction and carrier rotation direction. To verify this sideband phenomenon, we derived the formulae to calculate the translational forces in x, y and z directions and the rotational moments about these translation axes which act to sun gear, carrier and ring gear due to mesh forces at each mesh point.
Historically, fluidic devices such as switches, amplifiers, and oscillators, have an advantage, compared with electronic devices, in terms of maintenance-free operation and operating life. Therefore, prior to the great progress in electronic technologies that has occurred during the past several decades, the structure and function of fluidic devices were the subject of extensive research. In particular, the structures of these fluidic devices are often composed of complicated flow channel layouts. Recently, fluidic devices are again attracting significant attention, stimulated by progress in the development of MEMS technologies. In this study, to develop an energy-efficient structure for a MEMS-scale fluidic device, we apply a topology optimization method to an optimal design problem for a steady state incompressible viscous flow field. We use a level set-based topology optimization method incorporating the concept of the phase field method for the topology optimization so that clear boundaries between the solid and fluid domains are expressed in the optimal configurations. To define the topology optimization problem for a fluid regime, the expressions of the primary and adjoint problems are formulated concretely, to minimize viscous energy dissipation. Moreover, to ensure the intended design outflow rate at a designated outlet, the optimization problem includes an outflow rate inequality constraint in this paper. Following the concept of the standard adjoint variable method, a stable optimization process that satisfies the outflow rate inequality constraint is achieved. Two numerical examples, one for two-terminal and the other for multi-terminal flow, are provided to demonstrate the usefulness of the proposed level set-based topology optimization method.
Water driven stage is developed as a linear stage of the ultra-precision machine tool, especially, that is intentionally designed for the machining of small parts in size, such as optical mirrors and lenses. The water driven stage is mainly composed of a body of the stage and a table. The table is supported by water hydrostatic bearings and is driven by water hydraulic cylinder. Speed of the stage, determining the feed rate of the diamond turning, can be controlled by the flow rate into the water hydraulic cylinder. The paper deals with speed control of the stage. Mathematical models of the water driven stage and the proportional flow control valve are derived in order to design feedback control system. Performances of the designed feedback control system are verified via experiments and simulations. It is then verified that the steady state error is less than 0.5%. Step responses of the control system with a step input of the external load acting on the table are also tested, showing validity of the designed control system.
Sleep monitoring provides useful information for keeping a good health condition and detecting diseases. The monitoring system should not interfere with natural sleep, and be an existence that is almost unnoticed by the person being measured, to be used in daily life. We propose a method for unconstrained measurement of the lying posture, respiration and heartbeat of a person on a rubber-based tactile sensor sheet. The tactile sensor is soft, flexible, and thin, and is not uncomfortable for the person lying on it. To extract faint heartbeat signals from pressure detected by the tactile sensor, improvement of the S/N ratio by averaging oversampled data is needed. This process takes some time, and can be conducted at only a limited number of locations on the tactile sensor. The suitable locations for the heartbeat detection depend on not only the location but also the lying posture of the person on the sensor. In the proposed method, the lying location and posture are detected using a pattern recognition technique applied on pressure pattern obtained by the tactile sensor. The parameters in the pattern recognition are adjusted by using machine learning based on pressure pattern samples. In this paper, we describe the method for unconstrained measurement and report the experimental results.
Highway fatalities in Japan have been increasing over the past 3 years despite decline of traffic fatalities. Most of accidents on highway are caused by careless driving including drowsy driving. Therefore, a number of researches on detecting such drowsy driving have been carried out, and various detection methods have been proposed: steering behavior, heart rate, etc. Especially focusing on such drowsy driving detection, this paper proposes a model-based method evaluating driving behavior using driving data which can be measured with existing on-board vehicle sensors in terms of ease of implementation. The model-based method can eliminate influence of driving environment so it can potentially evaluate small change of driver state. According to the comparison between the actual driving data and the driver model, the error between them correlates with subjective driver drowsiness. As a result, this study exhibits the feasibility of the proposed method that it can detect the drowsy driving by using the driver models.
This paper describes the drivers steering behavior affected by the vehicle side slip angle during changing lanes. In order to investigate the influence of the sideslip angle to driver's steering behavior, driving simulator is employed to realize various vehicles with different side slip characteristics. We prepared three specifications, i.e. yaw rate and side-slip angle generate in the same direction, the opposite direction, and side-slip angle is kept to zero. In this study, we used two type second order prediction model. The one is the second order prediction by yaw rate and side-slip angle. Another one is the second order prediction by only yaw rate. And we discussed the effect of side-slip angle on the driver's forward prediction with compared the two prediction models.