This study aims to develop an eco-friendly fabrication method for micro-structured parts with high aspect ratio. To achieve this purpose, nanopowder printing (nPP) process was adopted to the plastic mold with microstructures produced by electrospinning nanofiber imprinting (ES-NFI) method. A novel method named as ES-NFI sacrificial plastic mold nanopowder printing (ES-NFI/nPP) was proposed and demonstrated in this study. Micro plastic molds were prepared by ES-NFI method using Si forms that have various micro-structures including line and space (L/S) pattern, multi-pillars and holes. The effects of aspect ratio in microstructure on the shape transcription were investigated by changing Si forms from 1µm to 50µm wide for 10µm high. Also the composition of paste materials made from TiO2 nano-sized powder and PEG water-soluble binder was varied for the optimization. It was shown from the experimental results that the sintered part with microstructures of 50µm wide for 10µm high could be formed soundly, and it was also desirable to use the paste materials with lower content of binder polymer in keeping adequate viscosity. It was confirmed that ES-NFI/nPP method was a useful method for fabricating the micro-structured parts in the mass production.
The market of care food is growing for aging society and the personal version of care food will be needed for improving a fun of meal. On this occasion, 3D printing technologies have been developed and are being applied for food creation. In the present study, we prepare food ink for the world-first 3D gel printer designed by our group. The hardness of food is one of the most important factors that influence the texture of food. So that the jelly foods made by the 3D gel printer is designed being soft and easy to chew. Here four kinds of jelly food samples are prepared by using agar and gelatin as gelation agents. The mechanical strength of the jelly foods is evaluated by a compression test for foods. We measured the hardness (maxmum stress) of the jelly foods and succeeded in the preparation of various jelly foods of 8 ~ 45kPa in hardness. The gelation of agar is possibly controlled by temperature change. Thus by using the temperature change, the jelly foods are easily printed by the 3D gel printer. We hope these printed jelly foods will make it possible for elder persons to enjoy their fun of everyday meal and improve the quality of life for the elder persons.
Torsion and bending fatigue tests of magnesium alloy AZ31were carried out to investigate the initial damage under high cycle fatigue. The crystallographic orientation of crystals in which slip lines were occurred was analyzed by using electron back scatter diffraction (EBSD). The slip line occurrence angle was then calculated based on a crystallographic slip system with the maximum Schmid factor and compared with the experimental results to examine the active slip system. The slip direction from the specimen surface was also calculated for crystals with slip lines and the relationship between the calculated direction and Schmid factor was investigated under both loading conditions. Schmid factor of crystals with slip lines becomes the maximum in basal slip systems and the calculated slip line occurrence angle agreed well with that obtained from the experimental results. Therefore, the basal slip system in which Schmid factor becomes the maximum is active in both loading conditions. Although the slip direction from the specimen surface was small value in the crystals without slip lines, the crystals with slip lines had relatively large values. This means that the slip direction also affects the initial fatigue damage. Slip deformation was activated by the in-plane maximum shearing stress in torsion condition. On the other hand, both in-plane and out-of-plane maximum shearing stresses were responsible for the slip deformation in bending condition. Particularly, the fatigue crack was considered to be initiated by the out-of-plane maximum shearing in small number of stress cycles, since the crack-induced crystals have large values of the slip direction from the specimen surface.
This paper deals with the effect of adhesion layer on the stress intensity factor for small edge interface crack in bonded plates under uniaxial tension or bending. In this study, the stress intensity factors of the small edge interface crack are analyzed by the crack tip stress method with varying the crack length, adhesive thickness and material combination. The stress intensity factor of the edge interface crack is controlled by the singular stress field at the interface free edge in adhesively-bonded joint without the crack when the crack is very small. The calculation shows that the normalized stress intensity factors of the small edge interface crack under uniaxial tension or bending are related to the ratio between the crack length and the adhesive thickness (a/h) and the singularity index λ at the interface edge without the crack. Then, it is found that the normalized stress intensity factors can be expressed as F1,2=C1,2(h/a)1-λ and the parameters C1 and C2 are constant values when a/h<10-3.
This study focused on non-destructive inspection of CFRPs using induction-heating thermography. To enhance the defect detectability, phase images constructed by Fourier transformation from conventional thermal images were used. The temperature images obtained using a CFRP specimen with artificial delamination included strong non-uniform temperature distribution caused by non-uniform heating by induction coil, and this distribution significantly disturbed the images of the inside defects. On the other hand, in the phase images, the influence of non-uniform heating was suppressed at certain frequencies, and the defects that could not be detected in the temperature images were detected. Analytical studies revealed that the phase at a location in the non-uniformly heated region periodically oscillated with a period that is reciprocal of the heating duration when the phase were calculated from the temperature data including both heating and cooling stages. Owing to this oscillation, phase contrast between the regions heated and unheated by the induction coils was periodically decreased, which means that the effect of non-uniform heating was periodically suppressed and that defects can be easier detected in the phase images.
In this paper, an intensity of singular stress field for a bonded cylinder is compared with the one for a bonded plate, which was obtained in the previous studies accurately. The analytical method focuses on the stress values at the interface corner edge obtained by performing FE analyses on the unknown and reference models which are subdivided by the same mesh pattern. It is found that this analytical method which is useful for analyzing the bonded plate cannot be directly applied to the bonded cylinder because the strain in the circumferential direction causes non-singular stress component affecting singular stress evaluation. In order to eliminate the non-singular terms, they are expressed explicitly from the interfacial continuity conditions and the stress-free boundary conditions at the interface corner edge. Since the intensity of singular stress field for the bonded cylinder cannot be controlled by Dundurs' parameter uniquely, the maximum and minimum values of the intensities of singular stress field are shown in the table and the chart according to Dundurs' parameter. There are cases where the intensity of singular stress field for the bonded cylinder is one and a half times as large as that for the bonded plate even if the practical materials are combined.
The elasto-plastic constitutive equation based on the concept of continuum damage mechanics was formulated for the niobium alloy (C103) which is used as a chamber material in a satellite's thruster. The existing theory was extended to deal with the creep fatigue behavior at the high temperature of 1500°C. Creep, tensile and creep fatigue tests (stress-controlled) were conducted with plate bar specimens made of the niobium alloy. The tests were conducted at 1500°C and obtained data were used to determine the material parameters employed in the constitutive equation. Time-strain curves and damage-evolution curves were also simulated and the validity of material parameters was confirmed by comparing calculated values with test results. Creep fatigue life analyses were also conducted and the results were compared with the experimental values. From the results, it is expected that the used constitutive equations and determined material parameters can predict the mechanical features and creep fatigue life for the niobium alloy at the high temperature.
Reactive centrifugal casting method could fabricate a Ni-aluminide/steel multilayer pipe. In this method, Ni powder is placed on a spinning steel pipe, and Al liquid was poured into the steel pipe. Then the Ni powder and Al liquid exothermically reacted and produced a composite layer consisting of Ni-aluminides on the inner surface of the steel pipe. The heat generated by the exothermic reaction melted the inner surface of the steel pipe and bonded the composite layer to the steel. In this study, fabrication of nickel/steel multilayer pipe by reactive centrifugal casting method is focused. However, during the above process, the Ni powder could move along the flow of the Al liquid. Moreover, sometime retained Ni powder was observed within the fabricated pipe, due to the lack of input heat. To overcome these shortcomings, in this study, Ni liquid as well as Al liquid was used for the reactive centrifugal casting method. Microstructure and ratio of joint region are studied. We focus on the effects of the pre-heating temperature and holding time, because these processing parameters can be easily controlled. Nickel layer and steel pipe are joined by the reactive centrifugal casting method under preheating-temperature from 700°C to 900°C. As preheating temperature increases, the ratio of the joint region is increased. Moreover, the ratio of the joint region is increased by heating the steel pipe under pre-heating temperature after the casting. Hence, it is found that the pre-heating and the heating after casting for the pipe are effective to join the nickel layer and the steel pipe.
As a series study which clarify the local stability at crack tip based on the positiveness of atomic elastic stiffness (AES), mode I type loading is applied on the periodic slab cell of bcc-Fe with single center crack and double cracks at the center and corner, by using molecular dynamics simulation. All the (010), (110) and (111) cracks shows propagation with cleavage cracking, under the condition of fixing the periodic cell length except in the loading direction. The (110) and (111) cracks show immediate fracture without remarkable plastic deformation, and it is found that the number of negative AES atoms at the stress-strain peak or the limit of crack propagation is almost constant despite of the different mechanical condition of crack array. The critical domain of negative AES for crack propagation is evaluated as about 40 and 25 atomic lines per crack tip, for the (110) and (111) cracks, respectively. The (010) cracks show dislocation emission and twin formation before cleavage cracking, and we can't distinguish the negative AES at the twin boundary and cleavage cracking, so that we can't define simple criteria as mentioned above. Finally we evaluate the eigenvalue of the AES as the further investigation of the unstable mode of the negative AES. It is natural that the emergence of negative 1st eigenvalue reflects the loss of positiveness of AES determinant; however, the (111) cracks show negative 2nd eigenvalue just after the stress-strain peak (single crack model) and just before it (double crack model). The atoms with negative 2nd eigenvalue are observed just at the tip of cleavage cracking as 1 or 2 atomic line in the first stage of unstable cracking; however, they are also observed in the various position, e.g. boundary of the local phase transformation, in the later stage toward the final fracture.
This work aims at developing a new cooling fan for vehicle engine. This fan can operate as a cooling fan at low vehicle speed. At high vehicle speed, however, the fan is rarely used as a cooling fan. Therefore the fan can be used as a wind turbine, which generates electric power. In the previous report we had confirmed the effect of S-Shaped blade profile on the wind turbine efficiency by CFD analysis and the experiments. The present paper reports the enhancement of wind turbine power by installing high solidity rotor on a vehicle. High solidity rotor can increase the wind turbine efficiency and receive more input power due to the increased rate of the rotor resistance to the total resistance through the cooling system, although the air flow rate through the system decreases. We confirmed by the estimation and the actual vehicle test that the high solidity rotor can regenerate more electric power than the original low solidity rotor.
A method to analyze pump dynamic characteristics by cavitation compliance, mass-flow gain factor and dynamic gain was evolved to analyze rotating cavitation, using one-dimensional multi-domain system analysis software. This analysis method was used to analyze one-dimensional phenomena such as surge phenomenon in the past. For example, POGO, which is an auto-oscillation where the thrust oscillation of rocket propulsion system including turbopumps is coupled with the natural frequency of the rocket structure, has been analyzed using this method. In the present study, cavitation compliance and mass-flow gain factor were divided and distributed in each flow path of an inducer and tried to evaluate the possibility of analyzing rotating phenomena such as rotating cavitation by this one-dimensional analysis method. Whirl motion of the rotor assembly was accounted for by variable flow area orifices which connect the next flow path. The areas of the orifices are changed harmonically and the oscillation phase of each orifice is given according to the number of the blades. The variation of leakage flow rate through the tip clearances of each blade is simulated by the motion of the variable flow area orifices. With the evolved analysis model, effects of various parameters on the eigenvalues of the system were investigated. Analysis results showed that there existed rotating phenomena and agreed with inducer test results qualitatively.
The experimental and CFD analysis were conducted to investigate the relationship between stall and leading-edge vortex (LEV) in a centrifugal compressor with vaned diffuser. The LEV is distinct from the separating vortex of the diffuser leading-edge and passage vortex of the diffuser. The LEV is made up of two longitudinal vortices. It is produced by the accumulation of vortices caused by the velocity gradient of the impeller-discharge flow. According to the experimental results, both the impeller and diffuser rotating stalls occurred at 55 and 25 Hz during off-design flow operation. Both stall cells were existed only on the shroud side of the flow passages, which is very close to the source location of the LEV. Additionally, the intensity and scale of the diffuser stall fluctuation are much larger than those of the impeller stall fluctuation. Therefore, the unsteady behavior of the LEV may play an important role in the inception of the rotating stall. According to the CFD results, the size of the LEV doesn't change, and the LEV is comparatively stable in the designed flow operation. On the other hand, the LEV develops and forms a huge flow blockage within the diffuser passages during off-design operation. Therefore, the LEV may be considered to be one of the causes of the diffuser stall in the centrifugal compressor.
We experimentally and numerically investigated large-scale structures formed by vortices in a single wafer spin cleaner. The Q-criterion identified the vortices developed in the cleaner as the flow regions with positive second invariant of the velocity gradient tensor obtained by both the PIV and LES. The time-series two-components PIV data shows that small-vortices were clustered near and under the edge of the rotating disk and were periodically emanated from there to the housing wall of the cleaner. The emanation frequency was increased with increasing in the angular velocity of the rotating disk. Three-dimensional LES reveal that six longitudinal vortices were spirally developed from under the edge of the rotating disk to the housing wall. This structure stably rotated slower than the disk speed. Fourier analysis of the LES data agreed with that of the PIV data. This supports that the passages of the stable spiral vortices on the PIV measurement region resulted in the periodical emanation of the clustered small-vortices observed in the PIV. Such a very large-scale spiral structure will induce reattachment of contaminants on the wafer surface, and should be destructed for development of much higher efficient cleaner.
In order to improve the pour point of palm oil biodiesel, palm oil 2-butyl ester (P2BE) was made from palm oil and 2-butanol by transesterification. As a result, the pour point of P2BE is -2.5 °C and it is lower than that of palm oil isobutyl ester (PiBE), 0 °C. The combustion characteristics and exhaust emissions of P2BE were investigated using a DI diesel engine, and were compared with that of palm oil 1-butyl ester (PBE), palm oil methyl ester (PME) and JIS No.2 diesel fuel (gas oil). The thermal efficiency of P2BE is almost the same as that of the other test fuels. Although the HC, CO and Smoke emissions of P2BE are slightly higher than that of PiBE, PBE and PME, these are lower than that of gas oil. It is concluded that P2BE is a good alternative diesel fuel.
Flame-wall interaction is an important phenomenon on combustors. Especially, the influence of wall on the flame characteristics in small scale combustors becomes larger than that on normal scale ones because of their large surface-to-volume ratio. In this study, the influence of surface reaction and heat-loss on radical distributions and heat release rate of propane-air mixture is investigated using numerical simulation. A two-dimensional slit burner between two parallel plates is modeled. The distance between the plates is changed, and the profiles are obtained for both active wall, which is considered surface reaction causes radical quenching, and inert wall conditions. As a result, it is found that heat release rate for active wall condition is smaller than that for inert wall condition while the reactant consumption rate is the same for active and inert wall conditions. It is because that the radical which distribute widely near the wall like OH is quenched by surface reaction before be used in gas phase reaction. Thus, the blow off distance for active wall with high wall temperature condition is larger than that for inert wall condition. For low wall temperature condition, since the influence of surface reaction is negligibly small as compared with that of heat-loss, the distance is the same value for active and inert wall conditions.
The objective of this research is to investigate the ignition and the combustion characteristics of polyethylene film in a high temperature field. Polyethylene was inserted in a high temperature chamber. The polyethylene was used as a film-type. 4 mm, 5 mm, 6 mm, and 7 mm square of polyethylene were used. Polyethylene inserted in the chamber was melted and formed the droplet during the ignition delay time, and after ignition, polyethylene was burned along with the puffing by the pyrolysis. For the 4 mm film size, polyethylene has ignition limit at 850 K surrounding temperature. Ignition delay time on various surrounding temperature was based on the Arrhenius law. However, ignition delay time for various surrounding temperature has two tendencies. On the other hand, combustion time of the polyethylene has different tendency from ignition delay time. As the surrounding temperature increases, the burning time became longer. This has influence on the amount of polyethylene remained at the ignition without pyrolysis during the ignition delay time. In a high surrounding temperature, large amount of polyethylene was left during the ignition delay time, and combustion time was longer than when the surrounding temperature was low. The temperature history of polyethylene for various surrounding temperature had approximately the same tendency during ignition delay period.
The safe and precise landing control method of planetary exploration spacecraft is indispensable to achieve its missions. However, the landing methods used in previous missions have some problems such as high complexity. To improve them, the authors' have focused on the momentum exchange principles and adopted momentum exchange impact dampers (MEIDs) that absorb the controlled object's momentum to extra masses close to the object. This extra mass is called damper mass. Some kinds of MEIDs have been introduced; for example, this paper shows Upper-MEID (U-MEID) that launches the damper mass upward, Lower-MEID (L-MEID) that drops the damper mass downward, and Generalized-MEID (G-MEID) consisting of U-MEID and L-MEID. The authors' previous paper shows the effectiveness of G-MEID. The purpose of this paper is to introduce its improved version called G-MEID-A (G-MEID-Advanced). G-MEID-A can realize downsizing of the damper mass and more effective momentum exchange by tuning of momentum exchange timing. Simulation investigation verifies that the G-MEID-A has some advantages against the rebound reduction of the spacecraft and robustness against some variable conditions.
With the development of the modern vehicle industry, research and development of intelligent transport system has been undertaken. As an active safety feature, there is a need to develop a system with an appropriate steering and braking operation for accident avoidance. In this study, it is assumed that an automatic vehicle, which runs on the highway, encounters an obstacle in distance of collision by braking without steering operation. Our study aims to find operations that the vehicle can perform to avoid an obstacle by a combination of steering and braking. This paper proposes a method to generate operating waveforms using an immune algorithm (IA) that can generate plural quasi-optimum solutions. CarSim (Mechanical Simulation Company), which possesses full vehicle dynamics with 27 degrees of freedom, is adopted as the vehicle model in our study. Inputs for this model include wheel steering angle and brake pressure. Operation waveforms are generated by linear interpolation through designated data points. Real number type IA, which is coded real number expression, is adopted in order to find data points. The efficacy of the proposed method is verified through an emergency avoidance simulation using CarSim. The simulation result demonstrates operation patterns to avoid an obstacle; in addition, real number type IA is shown to perform better than conventional binary type in a search performance of the solution.
Transfer Path Analysis (TPA) has been conducted in order to improve the noise and vibration quality of mechanical structures. However, the force identification in the TPA is still challenging problem and its accuracy has to be improved. The Matrix Inversion Method and the Apparent-Mass Matrix Method are approaches for force identification. The Matrix Inversion Method estimates the excitation force by the product of an inverse matrix of accelerance and a vector of actual operational acceleration. It is known that the Matrix Inversion Method is very sensitive to measurement noise especially at the resonance. Apparent-Mass Matrix Method has been recently proposed, which provides more accurate results than the Matrix Inversion Method. However, these methods are still insufficient in accuracy, and improvement of identification accuracy is required. This paper proposes a new force identification method by using strain measurement. The method estimates the force using the Strain Frequency Response Function (SFRF) instead of acceleration or Apparent-Mass Matrix. The SFRFs are more strongly affected by higher-order modes than accelerance FRF. Therefore, we considered that more accurate force identification can be obtained by using SFRF than the conventional method. A numerical simulation and a vibration experiment are conducted to compare the results by the proposed method with the conventional method.
We analyze backlash occurrence mechanism of a no-backlash drive control technique in which two motors drive a load axis, as one is for a plus direction and another is for a minus direction, into the simulation and the experiment. We derive a condition that the backlash occurs easily when the load inertia is more than the driving system inertia, and that the backlash becomes hard to occur when the load inertia exceeds a certain value. We conclude that the condition to be the easiest to cause the backlash is that, a natural frequency of the driving system is equal to a natural frequency of the load, where the former natural frequency is calculated from the motor inertia, the gear ratio and stiffness of the drive line and the latter one is calculated from the load inertia and stiffness of the drive line. In this condition, Gramian, which measures the contribution of each natural frequency to the input/output (the position reference / the transmission torque of the gears between the driving axes and the load axis) also becomes the maximum. Since these two natural frequencies are practically determined by mechanical dimensions regardless of the controller gain, we need to separate these natural frequencies in mechanical design of the no-backlash driving system.
In this research, a mobile robot system moved by intuitive gesture instructions using the flick motion is suggested. The flick motion is commonly used in operating smart phones and involves sudden and rapid motion of the hand. One of the aim of this research is to move the robot quickly using this flick motion. At first, a flick motion is measured and the characteristic of the movement is analyzed. Next, a model to move a mobile robot in response to flick movement is proposed. In the model, the velocity of the hand is converted into virtual force, and the virtual force moves an object with virtual mass and viscosity. Another aim is introduction of a mechanism automatically switching the flick instruction and the following instruction. For the purpose, the switcher using the neural network is learned in advance to distinguish between the movement of the flick instruction and the following instruction. The experiment was conducted to examine the usefulness of the proposed system. As the results, flick instructions and following instructions were changed automatically and were able to operate a robot to the aim position comfortably.
Actuator rate saturation has characteristics to increase the phase lag of the system and it can be one of the factors that destabilize the motion control system for a higher control response. We propose a new control method that can stabilize the system with rate limited actuators. First, it is shown that the actuator rate limited characteristics causes control systems to be unstable using both describing function analysis and nonlinear simulations. Next, the proposed method using linear actuator reference model is described. It can avoid the rate saturation of actuators to improve the phase lag characteristics. Then, the effectiveness of proposed method is demonstrated through stability analysis and nonlinear simulations.
This paper introduces a novel direction-of-arrival (DoA) technique based on phase differences of electromagnetic waves. In detail, design and implementation issues for the DoA directional sensing are described, towards providing an efficient solution to mobile robot target tracking for various applications. What is the most important aspect from the practical point of view is how to realize accurate measurements of the bearing from an electromagnetic spot source. For the purpose, a DoA estimation model is proposed using a minimum number of antennas. Another focus lies in the implementation of an in-house DoA detection prototype considering the simplicity and generality of hardware configurations. This paper explains details of a purpose-built, cost-efficient solution ranging from the estimation model design to its hardware implementation suitable for autonomous robot navigation. Experimental results show that the proposed method for the DoA estimation and its hardware prototype can be considered quite satisfactory in an indoor environment.
This paper presents an application of equivalent non-Gaussian excitation method for the response analysis of systems subjected to non-Gaussian random excitation with an asymmetric probability distribution. The non-Gaussian excitation is prescribed by the probability density function and the power spectrum. The excitation is governed by the Itô stochastic differential equation. Moment equations for the response can be derived from the stochastic differential equation for the excitation and the equation of motion of the system. However, the moment equations are generally not closed due to the nonlinearity of the diffusion coefficient in the stochastic differential equation for the excitation even though the system is linear. In the previous paper, equivalent non-Gaussian excitation method was developed to obtain a closed set of the moment equations. It was demonstrated that for obtaining the variance and kurtosis of the response, the method is applicable to the case of the symmetric non-Gaussian excitation with a wide range of the kurtosis and bandwidth. In this study, equivalent non-Gaussian excitation method is utilized to analyze a linear system subjected to non-Gaussian random excitation with extended generalized Gaussian distribution. The probability distribution can express a variety of asymmetric non-Gaussian distributions with the quite different skewness and kurtosis. The results are compared with those obtained by Monte Carlo simulation. The application in the present paper shows that the method can accurately estimate not only the variance and kurtosis of the response but also the non-zero skewness caused by the asymmetry of the excitation.
This paper presents semantic grasping of everyday objects using a knowledge model. The knowledge model of an everyday object describes the structure of the object and information on how to manipulate it. Information on the structure of an object includes component parts of the object in terms of simple shape primitives to provide geometrical information and the connections between parts. Some everyday objects have movable connections between parts, so their kinematic attributes are described for those connections. The manipulation knowledge of the object includes the grasp areas and approach directions for the intended tasks. The grasp areas and approach directions are mapped on to the 3D point cloud data of the target using the geometrical information which is described in the knowledge model when the 3D point cloud data of the target and the intended task are given. Fine grasps suitable for the intended task are generated by performing a grasp planning. In the grasp planning, the system selects the appropriate operation according to the kinematic attributes of the objects and evaluates the efficiency for the task. We conduct experiments on semantic grasping for picking task and opening the lid of two types of container using the knowledge model and show the feasibility and the efficiency of our approach.
This paper describes a new automatic balancer that uses magnetic fluid and magnets. The new automatic balancer has a structure for magnetic fluid to levitate magnets used as balance weights, involving the shifting of magnets to correct imbalance. The friction coefficient for the movement of the balance weights is therefore an important factor for the performance of balance correction. A prototype was fabricated to confirm that the balance correcting characteristics are improved by improving this friction coefficient, through an experiment. The automatic balancer of the new structure was confirmed by the experiment, to reduce the friction coefficient relevant to the movement of the magnets at low speeds. The automatic balancer using magnets and magnetic fluids was confirmed to reliably correct the imbalance as it features low friction coefficients and reduces generated vibration to 19% in average. Such results made it apparent that the new automatic balancer offers a superior balance correcting performance.
The position sense of a human body is a basis for performing various body motions, especially high-speed. Therefore, the mismatch of the position sense generates the lack of performance , for example , in case of immersive interfaces so called “Telepresence ”and sports motion . In response the authors have been researching on the method using AR-Limb which aims to adjust or control the human position sense. However, the current research only discussed the update through static measurement and the measurement through dynamic motions was out of scope. Therefore, this paper introduced the method to measure the state of position sense during the actual motion, and evaluated the effect of update of position sense on the body motion. As an experimental result, it was verified that the body motion was completely effected by the update of position sense.
This paper presents an industrial application for an air type anti-vibration apparatus based on the consideration of difference between its apparatus and a velocity sensor. The former apparatus has the function to attenuate the vibration on the isolated table transmitted from the floor. The later sensor detects mechanical vibration. Then, they have mutually different functions. However, both feedback control systems look alike, namely, these have a velocity feedback to add damping and a weak position feedback to maintain the equilibrium state. However, in case of the anti-vibration apparatus, the velocity feedback is constructed by using absolute acceleration signal. While, in case of its feedback for the velocity sensor, relative velocity signal through the differentiation of the relative displacement is used. Consequently, when the velocity feedback gains are increasing, the frequency responses have mutually different shapes. Then, by modifying the velocity feedback from the absolute acceleration on the isolated table to the relative acceleration between the isolated table and the floor, the anti-vibration apparatus can easily change to the velocity sensor itself. In the case of velocity sensor-like air type anti-vibration apparatus that suffers long period earthquake ground motions, the relative displacement between floor and isolated table can be reduced and then its apparatus becomes robust against earthquake ground motions in terms of mechanical collision.
The effectiveness of a dynamic absorber for self-excited vibration, such as parametric resonance, has been known for several years. However, in the case of self-excited vibration, the operating mechanism of a dynamic absorber is still poorly understood. In this paper, two simple and fundamental models with two degrees of freedom (DOFs), that is, a single-DOF parametric excitation system with one dynamic absorber, are considered and the operating mechanism is investigated from the viewpoint of the energy balance. As an analytical tool to clarify the operating mechanism, a new type of complex modal analysis is developed for accurately evaluating the energy for each mode. By applying the new method, the damping matrix can be diagonalized exactly in addition to the mass and stiffness matrices, and the equation of motion for a multi-DOF system can be converted into modal equations for a single-DOF system in the form of real second-order differential equations. Using approximate solutions obtained from the modal equation, the energy generated due to parametric excitation and that dissipated due to damping can be estimated accurately. The results show that the appropriate decentralization of the excitation energy to each mode and the increase of the dissipation energy, caused by the dynamic absorber, play dominant roles in the stabilization of the system, and the effects of the dynamic absorber on the stabilities of two models differ from each other. In addition, the very effective optimization procedure of the dynamic absorber is formulated based on the different effects. The validity of the analytical results is verified by comparing with very accurate numerical results.
CONWIP (Constant Work in Process), which is a simple pull production control method keeping WIP (Work in Process) of a whole production line constant, has been considered a better alternative to Kanban in some ways. However, CONWIP involves a trial-and-error process to determine the appropriate constant WIP level by commonly employing MVA (Mean Value Analysis) for its performance measure estimation. This trial-and-error approach with the recursive nature of MVA might prohibit industries from widely implementing CONWIP in practice. This paper proposes a new simpler approximate solution of CONWIP by focusing on the bottlenecks in the system. The precision of the proposed approximation method is evaluated by simulation. It is found that the proposed method tends to outperform MVA by far, particularly in the range of relatively small process variability. In addition, a practical method determining the appropriate level of WIP is proposed to maximize TH (throughput) based on the current system performance. Moreover, through the formulation incorporating the influence of process variability such as machine failures, practical implications are derived to accommodate CONWIP to situations such as unstable production ramp-ups or overseas productions where Kaizen could not be readily expected.
The oil film flow in large journal bearings usually transits from laminar flow to turbulent one with increase in shaft speed. This paper presents a new turbulent THL (thermo-hydrodynamic lubrication) model based on the low-Reynolds-number k-ε model to predict the performance of such bearings, while conventional turbulent THL models are based on the mixing length theory. The static performance of a four-pad tilting pad journal bearing of a real size is predicted with the new turbulent THL model and the predictions are found to agree well with the measurements presented in the open literature, including the temperature inflection characteristics of maximum pad surface temperature, a hump increase of minimum oil film thickness corresponding to the temperature inflection with shaft speed and also a steep increase of friction loss resulting from the transition to the turbulent flow of the oil film with increase in shaft speed. The new turbulent THL model is also shown to give the predictions comparable with those with the conventional turbulent THL model. However, the program developed by applying the new model is found to give the predictions surely, when compared with the one applying the conventional model. It is concluded that the new turbulent THL model can replace the conventional one in designing the turbulent journal bearings.
A tsunami is caused by a large coastal earthquake. We devise the foldable tsunami pod on which evacuees can get, when tsunami is approaching. The 3D model for the foldable ellipsoid body is generated by FEM software “LS-PREPOST”. We perform a numerical simulation, and confirm the safety by von Mises equivalent stress and Head Injury Criterion (HIC). As the result of the 1st simulation, it is proved that the initial model is weak to the impact force from rigid wall and obstacles and can be strained in the central part. On the other hand, an occupant hits against the inner side of the wall and can be injured. So, a seat and upper and lower bars are added to the initial model. Von Mises equivalent stress for the modified model is decreased, however is still over the ultimate strength of the 1st simulation. While, HIC value is decreased largely which is much less than the HIC safety level. This is because an occupant isn’t hit by the internal wall for an occupant restraint system. Moreover, we optimize the form and property for a tsunami pod on condition of its mass is minimized by uncoupled analysis. Finally, we confirm the validity of the optimal model by an original condition of coupled analysis.
The conical involute gears have been applied to automotive parts such as 4WD transfer. The conical gear pair has characteristic large ease-off and this is equivalent to meshing of cylindrical gears which has large crowning for lead direction. Consequently, the trochoidal interference is thought to be caused because of tooth stiffness reduction. In this study, to clarify the influence of the tooth flank modification on the tooth surface damage, tooth surface endurance test with several tooth flank modification forms is experimented. As a result, the gear pair with crowning for tooth profile direction and reverse crowning for lead direction can extend the pitting fatigue life because of the edge load reduction of tip or root.
In order to evaluate nitrogen and sulfur behavior during carbonization, carbonization experiment with bio-dried sludge was conducted in a horizontal lab-scale reactor and rotary kiln. Bio-dried sludge dried by using fermentation was used as the carbonization material. Carbonization temperature was changed from 573 to 1173K, and the effect of steam introduction on the elements behavior during the carbonization process was revealed. Nitrogen in the bio-dried sludge decomposed linearly with rising treatment temperature, and more than 90% of nitrogen decomposed at the 1173 K temperature. Sulfur in bio-dried sludge decreased slowly with increasing treatment temperature, but the decreasing ratio was insignificant against the carbonization temperature. Around 70 % of sulfur remained in the char after the carbonization at 1173 K. Sulfur behavior was changed when the steam was introduced during the carbonization. Sulfur content in the char was decreased significantly.
This paper describes a vibration reduction system that can minimize the vertical vibrations of the human body in a vehicle. This system can control the mechanical properties of the seat cushions and seat back cushions, such as the spring constants and damping coefficients. In previous study, it was estimated a vibration model considering vibrations transmitted from the bottom of the seat and the footrest, and vibration reduction effects of the human body was examined by using this model. However, vibrations transmitted from vehicle body have a frequency characteristic affected by the sprung mass, unsprung mass and engine. Therefore, it is necessary to investigate vibration reduction effects by a model including vehicle system. The purpose of this paper is to clarify the vibration reduction effects for the driver by controlling mechanical properties of the seat. In this study, we design a vibration model of an occupant-seat-vehicle system and a numerical analysis system, and examine the feasibility of the vibration reduction system based on the vibration model of the occupant-seat-vehicle system. Further, a numerical analysis with an optimized algorithm is carried out to calculate the magnitude of vibrations transmitted to the human body. The feasibilities of both the vibration model and numerical analysis system were confirmed by comparing the results of the occupant-seat system between the numerical analysis and the measurement. The vibration reduction system successfully reduced vibrations from the seat to the human body by the analytical results using ISO 8608:1995. In addition, analytical results clearly show differences of the vibration reduction between the model with the steering wheel and the model without the steering wheel.
A railway collision at a level crossing of the Hakodate line of JR Hokkaido occurred on January 29, 2010. The details of this accident can be obtained in the railway accident investigation report published by the Japan Transport Safety Board. Based on this railway accident investigation report, numerical simulations of the level crossing collision were conducted in order to investigate a correlation between the injury rate of passengers and the deceleration history during collision. New modeling methodologies and initial conditions derived from accident details were adopted and also in order to obtain accuracy of numerical simulations, analysis models of the cab end structure and the interface structure between cars in the train were validated by quasi-static compression tests. Since the numerical simulation shows good correlation in the deformations of the cab structure and a situation of scattered parts of the railway obstacle, this paper finally demonstrates the deceleration history of each car body of the relevant train set in the level crossing collision. In regards to the maximum value of the integration of the deceleration history: MID, it was found that 7.4m/s occurs at the leading car, which had the most injuries, and it appears that exceeding 4m/s results in increase of rate of injuries above 50%. Regarding injury parameters, values at forward facing seats are lower than the half of the criteria of FMVSS208 but values at the seat of the fore end of the cabin exceed the criteria. It is estimated that injury parameters at the seat of the fore end of the cabin are within the criteria if MID is kept under 6m/s.
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