日本機械学会論文集
Online ISSN : 2187-9761
ISSN-L : 2187-9761
最新号
選択された号の論文の26件中1~26を表示しています
材料力学,機械材料,材料加工
  • 澤田 祐子, 越前谷 大介
    2019 年 85 巻 875 号 p. 18-00505
    発行日: 2019年
    公開日: 2019/07/25
    [早期公開] 公開日: 2019/07/09
    ジャーナル フリー

    A large quantity of engineering plastics are used in electric industrial products. It is necessary to estimate the life of the product made of engineering plastics because of its shorter life and lower strength than some of ceramics or metals. Polybutylene terephthalate is one of the hydrolyzed engineering plastics. Their test pieces were submitted to accelerated stress test of elevated temperature and humidity. Their strength was evaluated by three-point bending test. It was found that the strength degradation was related to water vapor pressure, temperature and retention time. It was possible to estimate the time required for strength degradation in service environment.

  • 古巣 克也, 尼子 龍幸, 中川 稔章, 浜辺 勉, 青木 典久
    2019 年 85 巻 875 号 p. 19-00053
    発行日: 2019年
    公開日: 2019/07/25
    [早期公開] 公開日: 2019/07/09
    ジャーナル フリー

    In this paper, the equations of in-plane and out-of-plane displacements, in-plane stress distributions, and Mises stress of the rectangular plate after buckling are composed using the well-known buckling deflection shape, based on the plane stress state and the effective width theory by Karman. Equations of in-plane displacement and stress distributions are obtained from the large deflection theory, and the maximum value of out-of- plane displacement is derived by use of Karman’s theory. The composed equations are compared with results of the finite element method (FEM) with shell elements. The boundary condition used in FEM is that the in-plane displacement of both long side edges is unconstrained. As a result, the following conclusions were obtained. Among the composed equations, the out-of-plane displacement amplitude and the in-plane compressive displacement are close enough to FEM computation results. Three in-plane stresses near the both long sides show slightly different distributions between composed equations and FEM results. The normal stress distribution of the FEM result fluctuates near the both long side edges, although that distribution by the composed equation indicates the intermediate value of the FEM result, and it was found that the maximum compressive stress appearing at both sides is lower than the one by the FEM result. On the other hand, the Mises stress distribution and its maximum value were close to the FEM results. As factors of these differences, it is considered that the in-plane deflection of the both sides and the out-of-plane displacement shape at larger load are different from the shape used in this paper.

流体工学,流体機械
  • 山出 吉伸, 加藤 千幸, 長原 孝英, 松井 純
    2019 年 85 巻 875 号 p. 19-00072
    発行日: 2019年
    公開日: 2019/07/25
    [早期公開] 公開日: 2019/06/27
    ジャーナル フリー

    The origin and formation mechanism of a submerged vortex and an air-entraining vortex have been fully clarified by large-eddy simulation (LES) that used approximately 2 billion hexahedral elements with maximum resolution of 0.255 mm and was applied to the internal flows of a model pump sump. The model pump sump is composed of a 2,500 mm-long water channel of rectangular cross section with a width of 300 mm and a water depth of 100 mm and a vertical suction pipe with a 100 mm diameter installed at its downstream end with an offset of 10 mm from the centerline of the rectangular channel. At the upstream end of the channel, a uniform velocity of 0.37 m/s is given. LES with different wall boundary conditions have revealed that the origin of a submerged vortex is the mean shear of the approaching boundary layers that develop on the bottom and side walls of the pump sump. From detailed investigations of LES computed for a long time period of 16 seconds have revealed that deviation of the mean flow that approaches the suction pipe triggers conversion of the axis of the vorticity that was originally aligned to the lateral direction in the approaching boundary layers to that aligned to the vertical direction. The local acceleration of the vertical flow stretches the afore-mentioned vertical vortex, which results in formation of a submerged vortex. The separated flows downstream of the suction pipe generate vertical vorticity, and forms an air-entraining vortex when such a vortex is sucked into the suction pipe. Computations with a different bellmouth height and a different water-surface height have supported the above mentioned origin and formation mechanism of these vortices.

熱工学,内燃機関,動力エネルギーシステム
  • 天寅 喬文, 渕端 学
    2019 年 85 巻 875 号 p. 18-00399
    発行日: 2019年
    公開日: 2019/07/25
    [早期公開] 公開日: 2019/06/27
    ジャーナル フリー

    In recent years, NOx and soot contained in the exhaust gas of diesel engines become problems. Currently they are elutriated by exhaust gas aftertreatment devices, which make the engine system more complicated. Therefore, we focused on emulsion fuel, which is known as one of the simultaneous reduction technology of NOx and soot. Although emulsion fuels are generally characterized by its water content, some literatures report that the effect on the diesel engine performance could not be controlled by the water content properly. Therefore, we focused on dispersed water droplet diameter as the other factor. In this study, we prepared emulsion fuels of different water droplet diameters and investigated the exhaust gas and power performance of a diesel engine with these fuels. The emulsion fuels consist of light oil, water and surfactant. We added 2.0 vol% of surfactant whose HLB value was adjusted to 6.0 to light oil. The water content was 10 and 15 vol%. We prepared emulsion fuels of three different mean dispersed water droplet diameters. The test fuel was 6 types of emulsion fuel (3 kinds of dispersed water droplet diameter, water content 10 and 15 vol%) and light oil. The diesel engine used in our experiment was of air-cooled, single-cylinder, jerk pump driven direct injection type. The displacement is 320 cc. We measured in-cylinder pressure, ignition delay, exhaust gas emission (NOx, Soot and CO) and power performance (Output power and Thermal efficiency). We found a relationship between the Sauter Mean Diameter of dispersed water droplets (DS.M.D.) and each parameter. The smaller DS.M.D. is, the more the NOx and soot are reduced. On the other hand, the bigger DS.M.D. is, the higher the output and thermal efficiency are.

  • 糀谷 喜久, 佐藤 稜汰, 齋藤 広海, 石井 大二郎, 及川 昌訓, 高木 靖雄, 三原 雄司
    2019 年 85 巻 875 号 p. 18-00427
    発行日: 2019年
    公開日: 2019/07/25
    [早期公開] 公開日: 2019/06/27
    ジャーナル フリー

    The authors have proposed a new combustion process called the Plume Ignition Combustion Concept (PCC), in which a plume of the hydrogen jet is spark-ignited just after hydrogen is injected to accomplish combustion of a plume of rich mixture. With an optimal combination of injection timing, ignition timing and controlled jet geometry, this combustion process markedly improved thermal efficiency by reducing cooling loss which is an essential element to be reduced for improving thermal efficiency in hydrogen engine. In this study, in order to evaluate the cooling loss in hydrogen engine, characteristics of local cooling loss of PCC combustion are evaluated by measuring heat flux in two locations, one in the leading location and the others in the trailing location in the combustion chamber. As a result, it was found that local cooling heat flux in the leading direction of the jet injected showed extremely high level compare to trailing direction and spatially averaged cooling loss of the combustion chamber in injection angle of 15° of PCC combustion. By enlarging injection angle to 25°, thermal efficiency was improved and local heat flux in the leading direction is also mitigated. This result indicated that capturing local heat flux, especially in the leading direction of the injected jet, is a key to improve thermal efficiency.

  • 鄭 載勳, 佐藤 進, 小酒 英範
    2019 年 85 巻 875 号 p. 19-00068
    発行日: 2019年
    公開日: 2019/07/25
    [早期公開] 公開日: 2019/07/04
    ジャーナル フリー

    In order to reduce the heat loss of diesel combustion, it is important to clarify the effect of in-cylinder flow on heat transfer to the chamber wall.The experiments were conducted using the rapid compression machine (RCM) equipped with heat flux sensors fixed on chamber wall to measure local instantaneous wall temperature to investigate the effect of swirl flow on the local heat transfer in diesel flame.Injection angle of single hole nozzle and swirl were controlled to investigate the correlation of spray flame and in-cylinder flow characteristics on heat transfer to the chamber wall.The results show that, the local heat transfer at the impinging point was suppressed because of decreasing local flame temperature with reverse swirl. On the other hand, local heat transfer was increased by forward swirl with local flame temperature rises. The exponent of Reynolds number in the empirical equation of Nusselt number was decreased by the reverse swirl than without swirl. Meanwhile, the exponent of Reynolds number was increased by the forward swirl than without swirl.

機械力学,計測,自動制御,ロボティクス,メカトロニクス
  • 前川 智史, 井上 喜雄, 園部 元康, 菅野 直紀
    2019 年 85 巻 875 号 p. 18-00355
    発行日: 2019年
    公開日: 2019/07/25
    [早期公開] 公開日: 2019/07/05
    ジャーナル フリー

    The energy efficiency of the conventional flow control of hydraulic systems using the pressure loss of throttle valves, which are widely used in construction machinery, is very low. If the switching inertance hydraulic system which is a kind of PWM control hydraulic system is used, a significant improvement in energy regeneration efficiency can be expected. The aim of this study is to develop a new analysis method which can consider the elasticity of oil and the influence of mass of the hydraulic cylinder and the structure in a typical hydraulic system which is more complex than the electrical PWM control system, and can help to understand the mechanism of energy regeneration and the effect of parameters on energy regeneration efficiency. A flow response analysis method is developed using the modal analysis method with approximate theoretical equations which can help to understand the effect of parameters. Next, a new definition of energy regeneration efficiency is proposed. Some calculations are carried out using the proposed response analysis method and definition of efficiency, and the mechanism of the energy regeneration in a typical hydraulic system is clarified and the effects of parameters on energy regeneration efficiency are noted.

  • 網干 光雄, 田中 博文
    2019 年 85 巻 875 号 p. 18-00426
    発行日: 2019年
    公開日: 2019/07/25
    [早期公開] 公開日: 2019/07/05
    ジャーナル フリー

    Rail corrugation is a phenomenon in which roughness patterns of approximately regular wavelengths are formed on the rail running surface by trains running, and causes the vibration and the noise. Therefore, in this paper, we analyze the amplification factor of roughness amplitude using a model that takes into consideration the interaction between the track and the vehicle, and clarify the growth mechanism and the wavelength determination mechanism of the rail corrugation. As a result of the theoretical analyses, it is indicated that the essential factors of growth of the corrugation are (1) interference of rail wave motion between the front and the rear wheels of a bogie of the vehicle, (2) anti-resonance phenomenon of the elastic support of the track system, (3) anti-resonance phenomenon of the total system of the track and the vehicle, and (4) anti-resonance phenomenon of the vehicle system. In addition, as a result of examing the rail corrugation measured on the commercial lines, it is confirmed that the causes of the corrugation occurrence are the above mentioned (1),(2) and (3) factors, and that the measured wavelengths almost agree with the theoretical values.

  • 富岡 隆弘, 瀧上 唯夫, 秋山 裕喜, 相田 健一郎
    2019 年 85 巻 875 号 p. 18-00453
    発行日: 2019年
    公開日: 2019/07/25
    [早期公開] 公開日: 2019/07/05
    ジャーナル フリー

    This paper presents an analytical method for in-plane and out-of-plane coupled vibration in thin curved panels. To treat such vibrations simply, a structure consisting of the combination of straight and curved beams is proposed and the connecting conditions of these beams are satisfied by means of artificial springs introduced at their joints. Firstly, the strain energy of the curved beam is derived based on a shell theory, and the validity is checked by comparing the modal characteristics with those obtained by beam theory. Then the straight and curved beam coupled system (SCBS) is introduced. The analytical procedure to derive the equation of motion of the SCBS is described in detail. Numerical result shows that the SCBS can successfully express the coupling effect between roof-floor relative vertical displacement and side panel’s lateral deformation. As some numerical examples, vibration responses for the different bending rigidities and loss factors in the SCBS are calculated. The influence of the loss factors in the curved beams is observed upon the vibration response of the floor section, particularly in the motion with large relative displacement between roof and floor.

  • 山本 武志, 菅原 佳城, 坂間 清子
    2019 年 85 巻 875 号 p. 18-00455
    発行日: 2019年
    公開日: 2019/07/25
    [早期公開] 公開日: 2019/07/08
    ジャーナル フリー

    Cables connected to mechanical systems enable efficiently power supply to the system and also enable high speed communication even in a poor communication environment. But it is not easy to control position and attitude of such mechanical systems with cables or tethers, because tension and inertia of the cables become disturbances, which greatly affect the behavior of the mechanical system. However, there is not enough studies on the control of such a mechanical system with cable. In this study, the cable is expressed by absolute nodal coordinate formulation (ANCF) which is one of the nonlinear finite element methods. The control system design method using the ANCF model has not been established and there are few research examples. Control law is derived by the use of the special feature of obtained model, that is inertia matrix of the system is constant. By applying coordinate transformation utilizing the feature, a controller design problem for mechanical system with cable is converted to that for mechanical system which consists of only rigid body, and the derive controller achieves low calculation cost. The proposed method controls the mechanical system so that the influence of the tether is compensated. Furthermore, in order to achieve the proposed control law, state variables of the cable are estimated by Kalman filter. Numerical analyses are carried out for evaluation of the proposed method.

  • 霜島 和明, 原 謙介, 山浦 弘
    2019 年 85 巻 875 号 p. 18-00462
    発行日: 2019年
    公開日: 2019/07/25
    [早期公開] 公開日: 2019/07/08
    ジャーナル フリー

    In this paper, we analyze the behavior of the chain by the analytical method of the multibody dynamics. For this system, there are two problems in the conventional method. One is the description of rotation for the rigid body. It leads to high nonlinearity and singularity caused by rotation. The other is the calculation efficiency due to the degree of freedom increases. In this research, in order to solve these problems, we introduces ”Rotation update equation”, which uses an incremental rotation for describing rotation matrix. This method doesn’t use the rotation angle in the equation, therefore the problems are mentioned improved. It can also reduce the calculation time, too. Moreover, this study introduces the normalization of the equation of rotation with the time step. It enables us to reduce the times of iteration procedure. This research compares the calculation results by the proroposed method with the results obtained from the experiment using the ball chain. Furthermore, we compare the experimental result and the analysis result by constructing an experimental equipment. From the above, we verified the validity of the proposed method.

  • 松原 真己, 森川 行生, 伊勢 智彦, 河村 庄造, 古屋 耕平
    2019 年 85 巻 875 号 p. 19-00062
    発行日: 2019年
    公開日: 2019/07/25
    [早期公開] 公開日: 2019/07/08
    ジャーナル フリー

    Computer-aided engineering is widely used in mechanical engineering to analyze the noise- and vibration-related performances of components and assemblies. Recently, extremely fine meshes of the body structure and large number of degree-of-freedom (DOF), in a finite element model (FE model) with increased CPU power, have been used to run simulations in high-frequency regions and to improve the accuracy of the simulations. This FE model is better suited for studying the effects of changing physical parameters, such as material stiffness and structural details, thereby facilitating a detailed analysis of the vibration behavior. Moreover, with an FE model, it is difficult to develop effective countermeasures against noise and vibration because of the increasing number of modes in unit intervals of frequency. For this type of problem in high modal density regions, earlier studies have explored several mode-grouping methods based on similarity of mode shapes. The overall mode shapes are similar in groups but dissimilar in parts. On comparison of two mode shapes, it is observed that the vibration behavior of dissimilar parts is similar to that of a mass damper. If the structure parts that behave like a mass damper can be extracted, we can use the design theory of tuned mass damper for designing structures. This study presents extraction of structure parts that behave like a mass damper. This proposed method uses mutual modal kinetic energy distribution and extracts anti-phase area by two different modes. The main system is defined as the in-phase element, the subsystem is defined as the anti-phase element. In the case that the natural frequency of the subsystem is very close to that of the main system, it is found that the height of the resonance peak decreases.

  • 草刈 亮輔, 恩田 知弥, 山田 就策, 黒田 洋司
    2019 年 85 巻 875 号 p. 19-00064
    発行日: 2019年
    公開日: 2019/07/25
    [早期公開] 公開日: 2019/06/13
    ジャーナル フリー

    In the conventional intersection recognition method, shape information is used. In order to recognize an intersection composed of roads divided by grass and asphalt, it is necessary to distinguish them. There is almost no difference in shape between grass and asphalt. For this reason, it is difficult to distinguish them by the method using shape information. Therefore, we use reflection intensity by LiDAR to distinguish grass and asphalt. In this paper, we compare the reflection intensity of the ground surface at points where distances from LiDAR are equal. The appropriate threshold for distinguishing materials of the ground is dynamically calculated for each distance using Discriminant Analysis Method. We accumulate the drivable region using the dynamically calculated threshold value in chronological order taking the relative movement amount into account. We add probabilistic processing to the drivable region accumulated in chronological order to extract more stable drivable region. Finally, an intersection is detected by combining the drivable region extracted using the reflection intensity and the drivable region extracted using the shape information. Intersection detection method uses Toe-Finding Algorithm. In order to show the usefulness of our method, we compare our method with two method, Partition Line Method and the proposed method unaccumulated the drivable region.

  • 尾崎 亮太, 黒田 洋司
    2019 年 85 巻 875 号 p. 19-00065
    発行日: 2019年
    公開日: 2019/07/25
    [早期公開] 公開日: 2019/06/13
    ジャーナル フリー

    This paper presents a real-time 6DoF localization method which corrects accumulative error by estimating relative poses to building walls for mobile robots in urban areas. This method exploits a fact that most of all artificial walls are built vertically. It estimates poses by not only an inertial sensor but also real-time SLAM and observations of normals from point-cloud of artificial walls for estimating absolute poses in the gravity coordinate system. Those three types of poses which are estimated by each way are combined by extended Kalman filter. To evaluate the proposed method, outdoor experiments with an actual robot were performed. They show the method keeps correcting accumulative error while the robot moves. The other experiments show how the method suppresses influence of non-vertical planes.

  • 飯田 浩貴, 池 勇勳, 梅田 和昇, 大橋 明, 福田 大輔, 金子 修造, 村山 純哉, 内田 吉孝
    2019 年 85 巻 875 号 p. 19-00069
    発行日: 2019年
    公開日: 2019/07/25
    [早期公開] 公開日: 2019/06/13
    ジャーナル フリー

    This paper proposes a method that fuses two kinds of stereo measurements using a fisheye stereo camera. A stereo measurement method can be divided into two types: binocular and motion stereo. Generally, the accuracy of long range depends on the baseline of the camera. In case of the binocular stereo, the direction of the baseline is horizontal. Its size is small due to the convenience of installation conditions. By contrast, in the case of the motion stereo, the direction of the baseline changes depending on the direction of the camera motion. For example, the direction of the baseline is the optical axis when a stereo camera is mounted on a vehicle or a mobile robot that drives in the forward direction. When the speed is high such as in driving, its baseline becomes larger as it becomes the moving distance between frames. Therefore, between the two stereo measurements there are differences in the magnitude of the baseline and the uncertainty of the position in the image. In addition, the area-based approach is used for binocular stereo and the feature-based approach is used for motion stereo at the time of corresponding point search. So, robustness against false matching is different. In this paper, we try to fuse the two stereo measurements in order to realize more accurate range image generation. A method, which restricts the disparity search range using the reference disparity map and a bilateral-like filter, which is a weighted averaging are proposed for fusing the two stereo measurements. The proposed methods are verified by experiments in indoor and outdoor environments.

  • 遠藤 玄, 髙田 敦, 堀米 篤史
    2019 年 85 巻 875 号 p. 19-00075
    発行日: 2019年
    公開日: 2019/07/25
    [早期公開] 公開日: 2019/06/13
    ジャーナル フリー

    The decommissioning of the Fukushima Daiichi Nuclear Power Plants is a national urgent problem in Japan. The distribution and characteristics of the fuel debris inside the nuclear reactor must be investigated to safely retrieve them. This study describes a 10 m-long articulated manipulator for investigation inside the primary container vessel. We employed a coupled tendon-driven mechanism and a gravity compensation mechanism using synthetic fiber ropes to design a lightweight and slender articulated manipulator. After discussing the basic principle and control algorithm, we focus on the detailed mechanical design of a prototype model. We confirmed its feasibility through basic motion experiments.

計算力学
  • 根岸 秀世, 雨川 洋章, 間庭 和聡, 小原 新吾, 羽山 誠, 董 大明
    2019 年 85 巻 875 号 p. 19-00086
    発行日: 2019年
    公開日: 2019/07/25
    [早期公開] 公開日: 2019/06/11
    ジャーナル フリー

    Grease lubrication in ball bearings is one of key technologies to reduce energy consumption and enhance lifetime in design of spacecrafts as well as general industrial machineries. From a view point of grease lubrication design, it is crucial to understand grease macro flow phenomena in ball bearings taking into account non-Newtonian property of grease. In the current study, grease macro flow phenomena were investigated based on experimental and numerical works as a preliminary study. Grease dam breaking was defined as a benchmark problem and its collapsing phenomena were experimentally observed. As for the numerical work, a basic algorithm to simulate non-Newtonian grease macro flows was developed based on the explicit MPS (Moving Particle Simulation) method coupled with Bingham pseudoplastic fluid model. The observed grease dam breaking behavior was simulated by the developed numerical approach and the numerical results showed a good agreement with the corresponding experimental data.

  • 金野 圭祐, 山下 拓三, 磯部 大吾郎
    2019 年 85 巻 875 号 p. 19-00107
    発行日: 2019年
    公開日: 2019/07/25
    [早期公開] 公開日: 2019/06/19
    ジャーナル フリー

    To stably operate electronic equipment such as computers and networking devices is essential to the current information society. They should be stably operated even when they are being subjected to seismic excitations. The computers and other devices are often mounted to a framework called a rack by using some screws when they are operated. In this research, we developed an effective numerical code to analyze the seismic behaviors of mechanical structure with bolted joints such as the rack. The numerical code was developed based upon the adaptively shifted integration (ASI) - Gauss technique, which is a finite element scheme that provides higher computational efficiency than the conventional code. Loosening mechanism of bolted joint was considered by employing a bearing-surface slip frequency dependent model. We carried out a seismic vibration test of a rack on a shake-table and simulated with three types of numerical simulation models. The screw elements were not considered in the first numerical model. The screw elements were considered in the second numerical model; however, the loosening mechanism of bolted joint was not considered. In the third numerical model, both the screw elements and the loosening mechanism were considered. Each numerical result was validated by comparing with the shake-table test result. Consequently, the numerical result of the third model agreed best with the test result. These results suggest that it is necessary to consider the loosening mechanism of bolted joint when analyzing the seismic behaviors of mechanical structure with screws.

設計,機素・潤滑,情報・知能,製造,システム
  • 梶田 大毅, 榎本 敦子, 堤 大輔, 諸貫 信行
    2019 年 85 巻 875 号 p. 18-00491
    発行日: 2019年
    公開日: 2019/07/25
    [早期公開] 公開日: 2019/06/21
    ジャーナル フリー

    To accommodate highly-mixed variable-volume assembly production, a human-robot cooperative production line utilizing a robotic cell is promising. A robotic cell is equipped with an industrial robot of which motion plans can be switched depending on the product variation. The motion plans should be switched quickly as possible on the demand from market, but the planning is one of the time-consuming tasks. This study aims to develop an automatic planning method for assembly motion using the geometric constraint conditions on 3D CAD data of the products. It was found that reduction of planning work-time by 61% can be achieved compared with the manual planning method.

  • 岡本 竜也, 梅原 徳次, 野老山 貴行, 村島 基之
    2019 年 85 巻 875 号 p. 19-00071
    発行日: 2019年
    公開日: 2019/07/25
    [早期公開] 公開日: 2019/06/13
    ジャーナル フリー

    Among DLC (Diamond-Like Carbon), ta-C (tetrahedral amorphous Carbon) coatings have been applied to improve fuel efficiency in automobile engines. Furthermore, it has been reported that a ta-CNx (tetrahedral amorphous Carbon Nitride) coating showed more than 50% lower friction coefficient in base oil lubrication compared to ta-C coating. On the other hand, the low friction mechanism of the ta-CNx coating has not been clarified. From the previous research, low friction mechanism of the ta-CNx coating in oil lubrication is considered that the increment of oil film thickness in accordance with increasing the oiliness of the transformed layer is important. However, the effects of oil film thickness and oiliness of the transformed layer on friction coefficient have not been quantitatively clarified, because oil film thickness and oiliness of the transformed layer have not been measured during friction. Therefore, in this research, the objective was set to clarify the low friction mechanism of the ta-CNx coating in oil lubrication by in-situ observation with reflectance spectroscopy, and oil film thickness and physical properties (polarizability, chemical bonding fraction) of the transformed layer was measured by in-situ observation with reflectance spectroscopy. Using in-situ observation with reflectance spectroscopy, film thickness, refractive index n and extinction coefficient k can be measured during friction test. And polarizability and chemical bonding fraction of the transformed layer were estimated from refractive index and extinction coefficient. From in-situ observation with reflectance spectroscopy, low friction mechanism of the ta-CNx coating in oil lubrication was proposed as shown below. The transformed layer was formed during friction and the polarizability of the transformed layer increased in accordance with decreasing C-Csp2 bonding fraction of the transformed layer, and PAO4 oil molecules were physically adsorbed on the transformed layer. As a result, oil film thickness increased and low friction occurred.

  • 数仲 馬恋典
    2019 年 85 巻 875 号 p. 19-00109
    発行日: 2019年
    公開日: 2019/07/25
    [早期公開] 公開日: 2019/06/28
    ジャーナル フリー

    Recently, wave-powered electrical generators, using double-cones moving on circular rails, have been proposed. Rotational motion of the generator’s hull, induced by waves, is changed into the rotational and translational movement of either a rigid magnetized double-cone, rolling on divergent-convergent circular rails, or a double-cone geared motor-generator, rolling on concentric circular rails. However, if such generator is not directly floating on the water waves of random direction, period and height, but it is placed inside of the hull of a ship, the movement of the double-cone is one-directional and dictated by the rolling period and amplitude of the ship’s hull. In such case, divergent-convergent straight rails resembling an O letter might be more efficient than the circular rails. In this work, the optimal design conditions of such a mechanism are examined. Concretely, the O-rails are fixed on the hull of a ship, which is excited to roll along its longitudinal axis, by using a pendulum. Movies of the double-cone moving on the O-rails were shot, and the total travelling time was determined through the slow motion processing of the movies, for various values of the inclination angle of the hull, and energies introduced into the system by the pendulum. Optimal geometry of the O-rails was decided in order to maximize the kinetic energy of translation of the double-cone. Apparent spring constants and damping ratio for the oscillatory movement of the double-cone were experimentally found and validated by a theoretical model. Experimentally observed optimal length of the pendulum arm, to maximize the total traveling time of the double-cone, was justified by a two degree of freedom vibration model of the test rig.

  • 丘 華
    2019 年 85 巻 875 号 p. 19-00150
    発行日: 2019年
    公開日: 2019/07/25
    [早期公開] 公開日: 2019/06/25
    ジャーナル フリー

    From the machining center (MC) user’s point of view, the author proposes a practical approach to estimating the trajectory errors of a circular arc interpolation cutter path produced by the NC servo characteristics for a target MC in this paper. Firstly, a simple and convenient acceleration/deceleration procedure model is given for describing the behavior of the servo axes in an interpolation motion of circular arc segments. This model contains two parameters whose value is necessary to be identified by experiments. The first is the time constant of the servo axes and its value can be easily determined from the radius reduction in circular motion trajectories corresponding to different radius and feed rate. The second is a timing parameter to define the time interval of the acceleration and the deceleration procedures between two interpolation segments, and its value can be readily identified from a measured trajectory of two circular arc cutter path. Based on the model and an assumption, in which the motion of each segment is independently performed, a concise and efficient simulation algorithm to calculate a cutter path trajectory composed of many circular arc segments in detail is developed. Comparison results of the simulated cutter path trajectories with the measured ones and the contours of work pieces machined under the same motion condition sufficiently demonstrate the effectiveness and reliability of the proposed approach. Therefore, as a useful tool, the approach is applicable to beforehand estimating the influence of the NC acceleration/deceleration motions on cutter path accuracy or judging the motion conditions for the machining purpose without performing an actual machining test with the machining center.

生体工学,医工学,スポーツ工学,人間工学
  • 長谷川 純爾, 久保田 直行
    2019 年 85 巻 875 号 p. 19-00059
    発行日: 2019年
    公開日: 2019/07/25
    [早期公開] 公開日: 2019/06/21
    ジャーナル フリー

    From worldwide statistical data of whiplash injuries in the rear-end impact accidents, females have been found to be at a higher risk than males and the reason for the same is an ongoing research topic. First, we created finite element model of the head and neck of a 50th %ile Japanese adult female (JAF50) by scaling an existing 50th %ile (JAM50) male model. The activity level of neck muscles before a rear-end impact was determined using the L36 of DOE method, which held a neutral posture of the head with the relaxed muscles under 1G condition. Subsequently, the head and neck behaviors of both the models were validated using the volunteer's rear-end impact test data. Comparing both the results using a new index (S - θmax), which measured the S-shape deformation of the neck during rear-end impacts, the model results were found to have the same trends as that of the volunteer's test data. JAF50 had a higher (S - θmax) value than JAM50, which means that a female neck undergoes larger S-shaped mode than a male. This index value difference between the genders was due to the difference in their muscle forces while maintaining a neutral posture of the head. This difference in the muscle forces, however, was not proportional to only the head mass ratio of the two genders. As a result of the investigation of the underlying reason, the neck muscle force ratio of each gender at the neutral position was roughly related to mass ratio × neck column cross-sectional area ratio × neck length ratio. If the ratio (female to male) of neck circumferences was 3: 4, the female muscle force could be nearly twice less than that of a male. We also estimated the muscle activity for each gender assuming the same (S - θmax) = 15 ° at the rear-end impact of Δ V = 5 km/h. It was found that a female's muscle activity is about twice that of a males for the same rear-end impact conditions.

交通・物流
  • 風間 晃輝, 道辻 洋平, 丸茂 喜高
    2019 年 85 巻 875 号 p. 18-00419
    発行日: 2019年
    公開日: 2019/07/25
    [早期公開] 公開日: 2019/06/19
    ジャーナル フリー

    This study evaluates the effectiveness of a driver assistance system at signalized intersections by using an incident database. The research target is in the incident scenes of a vehicle and crossing pedestrians in which the vehicle proceeds straight to the signalized intersection. The evaluation of the effectiveness for the driver assistance system has three steps. Firstly, incident scenes for the crossing pedestrian during an amber traffic signal are extracted from the incident database by visual observation. Next, the extracted incident scenes are classified according to the behaviors of both the vehicle and the crossing pedestrian, and the location of the incident. Finally, assuming the driver follows the driver assistance system, the extracted incident scenes are analyzed as to what extent the incident could be prevented based on numerical simulation where the vehicle moves following the decision of the system whether continuing forward or stopping. For cases that the driver tries to enter the intersection despite the amber signal and being able to stop by the stop line, the driver assistance system is supposed to prevent the incident effectively. For cases that the crossing pedestrian does not obey the pedestrian traffic signal, the driver assistance system is found not to be effective. However, if both the driver and crossing pedestrian obey their respective traffic signals, the driver assistance system can prevent the incident effectively in many cases.

  • 真木 康隆, 曄道 佳明, 山本 勝太, 池内 健義
    2019 年 85 巻 875 号 p. 19-00003
    発行日: 2019年
    公開日: 2019/07/25
    [早期公開] 公開日: 2019/06/19
    ジャーナル フリー

    We firstly executed bench tests of a bogie having the wheelset with a wheel flat installed on the roller rig. A wheel flat of 75 mm was prepared on the wheel tread and the front edge of the wheel flat was rounded by the grinding work. By making the radius of the front edge large, the maximum vertical acceleration of an axlebox decreased in the speed range less than 50 km/h compared with the one in case of the smaller front edge radius. The speed corresponding to the peak value of the maximum vertical acceleration of the axlebox shifted from 30 km/h to 80 km/h. Moreover, the peak value of the maximum vertical acceleration was larger than the one in case of the wheel flat edge without grinding work. To grasp and clarify the mechanism of the collision of the rotating wheel against a roller rig after descent leaving the roller rig, we built a simulation model and validated it by comparing the simulation results with the experimental ones, and the following were shown. The expansion of the radius r1 of the front edge of the wheel flat resulted in shitting of the spot of leaving the roller rig to the front side away from the front edge of the wheel flat. The shifting of the spot to leave the roller rig ahead makes the rear edge of the wheel flat collide against the roller rig at high speed, and then, a larger impact force is generated. Larger edge radii of r1=r2=429 mm nearly to the wheel radius, however, have the remarkable effect on decreasing the vertical acceleration of axleboxes in the whole operating speed range.

  • 後藤 健太郎, 村山 英晶
    2019 年 85 巻 875 号 p. 19-00034
    発行日: 2019年
    公開日: 2019/07/25
    [早期公開] 公開日: 2019/06/19
    ジャーナル フリー

    The Lean Automobile is a minimalistic tilting personal mobility for urban transportation with the suspension device equipped with a mechanism which converts driver’s actuation force into lean moment. We proposed it as a solution for the urban traffic problems and conduct study of it aiming for societal implementation. Since the most distinctive feature of the Lean Automobile among the other micro mobilities is its lean control method that is enabled by the unprecedented suspension device, we need to focus on the lean motion dynamics in order to verify the feasibility of the lean control left in the hands and feet of the driver. In this paper the process and outcomes of the feasibility study based on the calculations of transient characteristics and the simulations of lean motion is discussed. A newly developed dynamic model which describes the tilting vehicle with the suspension device equipped with the mechanism generates lean moment is used for the calculations and simulations. Through the study we find out the conditions to stabilize weave mode along with the differences between multiple lean control tactics that is allowed by the distinctive suspension device, therefore we get the prospect that there is multiple tactics to stabilize the Lean Automobile’s lean motion along with avoiding rollover.

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