日本機械学会論文集
Online ISSN : 2187-9761
ISSN-L : 2187-9761
早期公開論文
早期公開論文の12件中1~12を表示しています
  • 矢鍋 重夫
    論文ID: 23-00278
    発行日: 2024年
    [早期公開] 公開日: 2024/04/17
    ジャーナル オープンアクセス 早期公開

    The process of a trough stepping into a wrinkle during web transfer is simulated by FEM commercial software. Two models are employed. The first one consists of a web and four cylindrical rollers, while the second one has a curved axis roller instead of a cylindrical roller to prevent wrinkles. After applying tension to the web, a roller is inclined and then the web is transferred by a roller rotation, if necessary, the curved axis roller is bent before tilting. The main outcomes are as follows. (1) As the trough of the web reaches the inclined roller and flattens at the inlet of the roller, a CD compression stress of the web increases due to slippage of the flattening and accumulates there. A wrinkle occurs when the maximum CD compression stress exceeds a critical value. The value increases with MD strain calculated by tension and Young’s modulus. (2) The wrinkle tends to occur when the MD strain is smaller or when the roller tilt angle and coefficient of friction are larger. (3) A boundary of the wrinkle occurring area is shown by a figure with the axes of the MD strain and the roller tilt angle. (4) The wrinkle is prevented from forming when parameters of the curved axis roller are suitably selected. There was a case where the wrinkle doesn’t occur for a large area of a bent direction angle ranging from -90° to +45°. (5) Spreading or shrinking of the web on the curved axis roller can be qualitatively illustrated by considering both the vector distribution of the roller surface velocities and the expansion or contraction of the bent arc of the roller.

  • 山下 義隆, 佐藤 宏紀
    論文ID: 23-00313
    発行日: 2024年
    [早期公開] 公開日: 2024/04/17
    ジャーナル オープンアクセス 早期公開

    Overhead contact lines (OCLs) are subjected to longitudinal displacement due to factors such as temperature changes and external force. Excessive longitudinal displacement may prevent the tension balancers from performing their proper tension adjustment function. It is therefore important to develop a method for calculating the longitudinal displacement of OCLs and to make it possible to predict the longitudinal displacement in response to changes in temperature and external forces. This paper presents a model to represent the longitudinal displacement of OCLs on a curved track installing tensioning devices and hinged cantilevers at each support point and proposes calculation methods to find the equilibrium points of the longitudinal displacement of the OCL. Furthermore, the validation of the proposed calculation methods was confirmed by scale model tests.

  • 中井 一馬, 榎並 祥太
    論文ID: 23-00321
    発行日: 2024年
    [早期公開] 公開日: 2024/04/17
    ジャーナル オープンアクセス 早期公開

    In order to enhance the safety of passengers in the event of the railway accident, it is important to identify the risk to the passengers. The seated passengers have a risk of getting injured due to collision with seats in front of them. The severity of injury depends on the structure of the seat types. There are a lot of types of the seats, for example a rotating and reclining seat and a walkover seat. However, the study compared the injury risk between these seats have not been reported. The purpose of this study is to investigate the effect of seat types to passengers’ injury through a series of physical sled tests. The rotating and reclining seat for normal car and green car in express train, and the walkover seat in suburban train were used for a comparison in this research. The experiment results showed that the measures to the lower seat back are effective for reducing the severity of injury of passengers seated in the rotating and reclining seat, that the measures to the seating face are effective for reducing the severity of injury of passengers seated in the walkover seat, and that the design of the footrest are also important for the measures.

  • 皮籠石 紀雄, 永野 茂憲, 中村 祐三, 仮屋 孝二, 岩本 竜一, 小林 祐次
    論文ID: 24-00007
    発行日: 2024年
    [早期公開] 公開日: 2024/04/17
    ジャーナル オープンアクセス 早期公開

    The work affected layer of shot peened maraging steel was examined and fatigue properties of the steel were investigated under rotating bending in relative humidity of 25 % and 85 %. Shot peening produced a grain refinement in the surface layer with about 50 μm in depth of a specimen and a phase transformation to austenite structure was measured on the specimen surface, in addition to hardening and formation of compressive residual stress. Especially, the thin surface layer showed a nano-size structure in the work affected layer. Fatigue strength and its humidity sensitivity were improved by shot peening. The fatigue fracture process was occupied by the initiation and propagation of a surface crack in the electro-polished specimens. On the other hand, fracture mode in the shot-peened specimens smoothly changed from the fracture controlled by the propagation of many surface cracks originate at dimples yielded by shot peening at high stress levels to the combined fracture accompanied the propagation of an internal crack originated from a subsurface defect of a specimen with the surface crack propagation simultaneously with decreasing in the stress level. A definite internal fracture controlled by a propagation of an internal crack was not confirmed until around 107 cycles. In relation to the change in fracture mode stated above, fatigue life increased with decreasing in the stress level monotonically, that is, the shape of S-N curve of the shot-peened specimen did not show a duplex curve which was observed in many surface-treated steels. In all of the macroscopic fracture surfaces, a ring-shaped flat area was observed at the surface layer of the shot-peened specimens and the depth of the area nearly corresponded to the thickness of the fine-grained layer. No or little effect of humidity on the above-mentioned results was confirmed.

  • 黒坂 隆太, 加藤 孝憲, 牧野 泰三
    論文ID: 24-00010
    発行日: 2024年
    [早期公開] 公開日: 2024/04/17
    ジャーナル オープンアクセス 早期公開

    This study aims to evaluate shear-mode crack propagation rates under rolling contact fatigue (RCF) in railway wheel steels. Presently, no standardized evaluation method has been established for shear-mode crack propagation under RCF. In this study, twin-disc-type RCF tests were conducted on railway wheel steels with artificial defects, alongside finite element analyses (FEA) simulating these tests. The RCF test results indicated that the cracks initiated from the leading side of the defects propagated inward, while those initiated from the trailing side propagated toward the surface. The stress intensity factor (SIF) calculations revealed that cracks initiated from the leading side of the defects propagated through a mixed modes I and II, whereas cracks initiated from the trailing side propagated exclusively in Mode II. Additionally, crack propagation rates on the trailing side of the defects were higher than those on the leading side, attributed to a larger Mode II equivalent SIF range on the trailing side compared to the leading side. These results suggest that the FEA results corresponded to those of the RCF tests. Therefore, the relationship between the RCF crack propagation rate and shear mode SIF range could be evaluated by combining twin-disc-type RCF tests using test specimens with artificial defects and FEA.

  • 山本 茂, 松田 尚大, 森下 瑛心, 髙木 山河, 堀川 徳二郎, 山崎 之博, 宇治川 弘人
    論文ID: 23-00051
    発行日: 2024年
    [早期公開] 公開日: 2024/04/03
    ジャーナル オープンアクセス 早期公開

    In a hot strip finishing mill, an unstable lateral steel strip movement called strip walking causes the strip to crash into side guides placed at the entrance of the stand mill, resulting in a tail pinch where the strip is pressed into a folded state. Therefore, strip walking should appropriately be suppressed to prevent tail pinches, requiring adequate strip steering control. To this end, various strip steering control methods have been proposed. Among them, model predictive control, which explicitly considers the motion of a steel strip and constraints on the actuator’s speed, is expected to be of great practical use. However, the disadvantages of this control are that the model’s accuracy affects control results, state variables must be estimated, and its optimization computation is time-consuming. Hence, this paper proposes a method to overcome such disadvantages by adopting a model describing adequately strip walking, model predictive control using discretized inputs, and a deadbeat current observer to estimate state variables. Subsequently, we demonstrated the effectiveness of the proposed method using several numerical simulations together with setting discrete values for the discretized inputs and setting weights in the cost function to be minimized in the model predictive control. In conclusion, it is clarified here that the selection of a set of discretized control inputs, which maximize the leveling speed in minimum time and the proper selection of weights in the evaluation function are crucial for the practical use of model predictive control to prevent strip walking.

  • 畠山 貴充, 千田 有一, 種村 昌也
    論文ID: 23-00226
    発行日: 2024年
    [早期公開] 公開日: 2024/04/03
    ジャーナル オープンアクセス 早期公開

    This paper presents an analysis of the motion of a motorcycle at high-speed using a motorcycle dynamics model that considers the compliance of the frame components. Several motorcycle nonlinear dynamics models have been proposed in previous studies and in the industry. However, these models do not consider the compliance of the frame components, which affects the maneuverability and stability of motorcycles. Moreover, there is not any researches that analyzes the effect of such compliance on motorcycle dynamics in a domain that includes turning. In this paper, we derive a nonlinear dynamics model of a motorcycle that takes into account the compliance of the frame components and analyze the effect of such compliance on the vehicle body motion during high-speed straight riding and turning. For the dynamics model, the Kane’s equation is constructed based on multi-body dynamics analysis. In conclusion, we demonstrate that the compliance corresponding to the lateral torsion of the front forks is the most dominant factor in improving stability in the high-speed region, both in straight riding and in turning.

  • 鈴木 秀忠, 吉田 一也, 高橋 徹, 新部 純三
    論文ID: 23-00275
    発行日: 2024年
    [早期公開] 公開日: 2024/04/03
    ジャーナル オープンアクセス 早期公開

    In recent years, the demand for lighter and more compact equipment has been increasing due to reduce product manufacturing time and the viewpoint of environmental load. Therefore, further lightweighting is demanded with the ball screw. The ball screw has step shape on both ends of shaft. Therefore, the lightweighting method of drilling to center of ball screw shaft makes it difficult to significantly reduce weight due to the thicker wall thickness to secure the strength of the shaft end. The lightweighting method devised is to form the step shape of the shaft end by swaging process to have a structure with a large space inside, which enables a significant weight reduction. The appearance and surface roughness of the lightweight ball screw shaft does not differ from that of conventional shaft. The weight of 0.70 kg is 0.55 times that of the conventional shaft, which enables a significant weight reduction. In the rotary bending fatigue test, the fatigue limit decreases with the ratio of wall-thickness, but the allowable torsional stress of the conventional shaft is satisfied. The axial rigidity is approximately 0.76 times that of the conventional shaft, which is smaller due to the reduction of the area moment of inertia in the hollow structure. The maximum torque is 0.02 Nm, satisfying the specified value of ±0.41 Nm. The torque fluctuation ratio is ±5 %, satisfying the best accuracy grade of ±15 %. The quietness is equivalent to number of revolutions above 2100 and improve at number of revolutions below 1000. Vibration characteristic is on the high-frequency side of resonance frequency in bending vibration, which increases the allowable rotational speed by approximately 1.2 times.

  • 松浦 健児
    論文ID: 24-00041
    発行日: 2024年
    [早期公開] 公開日: 2024/04/03
    ジャーナル オープンアクセス 早期公開

    To quantify the underseal pressure characteristics of an evolved 2 mm thick apex seal, the pressures under the apex seal and in the leading and trailing working chambers were measured using a cantilevered eccentric shaft single rotor engine equipped with a multichannel slip ring. A theoretical model that treats the vicinity of the apex seal as a labyrinth passage was applied to calculate the underseal pressure from the measured leading and trailing working chamber pressures and the flow coefficients for flow into and out of the underseal volume were adjusted so that the underseal pressure matched the measured value. These flow coefficients were used to study the effects of rotational speed, underseal volume, and apex seal clearance on the underseal pressure. In addition, since the combustion pressure rise near top dead center acts on one flank of the rotor and deflects the eccentric shaft to move the flank away from the inner surface of the rotor housing at high load, causing the leading and trailing apex seals to move outward in the seal slots. It has been proposed to improve sealing in these regions by making the rotor housing inner surface partially convex inward or outward from its basic shape to control the radial movement of the apex seal. A new underseal model with isothermally varying volume was introduced to the previous model, which showed that the modified rotor housing is effective in increasing the underseal pressure.

  • 濱本 芳徳, 梅沢 修一, 浅野 恭一, 酒井 泰地
    論文ID: 23-00311
    発行日: 2024年
    [早期公開] 公開日: 2024/03/28
    ジャーナル オープンアクセス 早期公開

    Dry storage of adsorbent reactors after contaminated water treatment in decommissioning contributes to reducing the risk of contamination spread. In general, the drying process of wet particles involves the simultaneous heat and mass transfers in the particle bed, and the thermal flow becomes complicated. In this study, a simulation model considering the physis involved in the bed, such as the structure of the vessel, the distribution of the initial moisture content, and the resistance of heat and mass transfer, was presented. Predictive calculations of the temperature and moisture content in the drying bed in full-diameter vessel were then performed. In addition, the reproductions of the temperature and the amount of evaporation were confirmed by comparison with the actual measurement results. This model was useful for examining heating methods and predicting drying time. Approximately 100 hours after the start of heating, the adsorbent in contact with the inner surface and bottom of the steel container was dried, and it was thought that it is possible to prevent moisture from coming into contact with the container even during long-time storage. Furthermore, by appropriately setting thermal boundary conditions on the top surface of the packed bed, it was able to improve the prediction accuracy of local moisture content.

  • 奥井 健斗, 多田 直哉, 上森 武, 坂本 惇司, 榊原 圭太
    論文ID: 24-00008
    発行日: 2024年
    [早期公開] 公開日: 2024/03/28
    ジャーナル オープンアクセス 早期公開

    In recent years, environmental concerns have led to a demand for sustainable materials, and natural rubber (NR) reinforced with cellulose nanofibers (CNFs) has been attracting attention as one such material. When CNFs are added to NR, the elastic modulus is greatly improved. This is considered to be caused by deformation constraint of NR by reinforcing CNFs. On the other hand, it is known that there exists a region around reinforcing fibers where the rubber is tightly connected to the surface of fibers, which is called bound rubber. The volume fraction of the bound rubber is usually measured by swelling tests using organic solvent. In this paper, we focused on the relationship between the tensile properties of NR reinforced with CNFs and the volume fraction of bound rubber. Firstly, cyclic tensile tests were performed using plate specimens of CNF-reinforced NR and the effect of reinforcing CNFs on the tensile properties of CNF-reinforced NR and their change with loading cycles were investigated. Then, the swelling tests were conducted for similar specimens and the volume fraction of the bound rubber was evaluated. It was found from a series of experimental results that tensile deformation resistance of NR increased largely by adding 5 phr (4.8 mass%, 3.2 vol.%) of CNFs but that this increase decreased from the second loading cycle. Moreover, a clear relationship was found between the tensile deformation resistance of CNF-reinforced NR and the volume fraction of bound rubber. These results suggest that the tensile deformation resistance of CNF-reinforced NR can be evaluated by swelling tests.

  • 小林 潤也, 中沢 信明
    論文ID: 23-00324
    発行日: 2024年
    [早期公開] 公開日: 2024/03/22
    ジャーナル オープンアクセス 早期公開

    In recent years, Japan's declining birth rate and aging population have become serious problems. Under such circumstances, there is a concern about the shortage of caregivers in elderly care facilities, especially when looking after residents. Therefore, the introduction of camera-based monitoring systems in elderly care facilities could help reduce the burden on caregivers. However, caregivers may feel averse to being captured by surveillance cameras, so there is an issue of privacy. Our proposed solution to this problem is a camera-based monitoring system that focuses only on the feet of pedestrians. The purpose of this research is to extract gait features from videos in which only the pedestrian’s feet are visible by image processing and to classify young and elderly people using these features. First, the obtained gait feature image was converted into a flat feet image, which was generated by Otsu's binarization to extract the foot region that was completely in contact with the ground. Next, the heel position was estimated from the flat feet image and converted from the image coordinates to world coordinates using a perspective projection model. Finally, using the calculated heel position and estimated heel-strike and toe-off frames, gait features such as step length, stride length, gait cycle, and gait velocity were obtained. T-tests revealed significant differences in the step and stride lengths between young and elderly people. In addition, the gait velocity of elderly people tends to be lower than that of young people. These results support the findings of previous studies. Furthermore, a support vector machine was used to evaluate the classification accuracy for young and elderly people. According to the cross-validation results, the present system achieved an 82% accuracy.

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