Transactions of the JSME (in Japanese)
Online ISSN : 2187-9761
ISSN-L : 2187-9761
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Special issue on new developments in the field of design and systems engineering 2021
  • Yoshihiro SEJIMA, Hiroki KAWAMOTO, Yoichiro SATO, Tomio WATANABE
    2021 Volume 87 Issue 903 Pages 21-00187
    Published: 2021
    Released: November 25, 2021
    [Advance publication] Released: October 20, 2021
    JOURNAL FREE ACCESS

    Pupils give favorable impressions to humans depending on their size. Focusing on effects of the pupil size, various pupil sizes were evaluated using human images as stimulations in previous researches. However, it is difficult to express an extreme pupil size in a face image due to a limited area of eyes. In addition, the evaluation of pupil size itself is hard because impressions in human images are formed depending on not only the pupil size but also other facial parts. In order to evaluate impressions of the pupil size itself, it is desirable to extract only the pupil and exclude other facial parts. In this study, we analyzed impressions on various pupil sizes that combined the dilation / contraction using two kinds of pupil expression media that have been developed so far. In the analysis, the impression evaluation obtained by the SD method was factor-analyzed. As the result of factor analysis, three factors were extracted: acceptability, reliability, and curiosity. Acceptability and reliability factors had a certain peak, and curiosity factor was proportional to the pupil size. These analysis results demonstrated that a certain dilated area of pupil could form a favorable impression regardless of pupil expression media.

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  • Kotaro YOSHIDA, Hidefumi WAKAMATSU, Yoshiharu IWATA, Takahiro KUBO
    2021 Volume 87 Issue 903 Pages 21-00201
    Published: 2021
    Released: November 25, 2021
    [Advance publication] Released: November 16, 2021
    JOURNAL FREE ACCESS

    A method to design the function of the brassiere cup shape as developable surfaces and its developed shape using Gaussian Process Regression is proposed. A developable surface, which is generated by sweeping a straight line along a three-dimensional curve, can be seen many products such as ships, buildings, clothes, and so on. The shape has not only its aim which can be formulated but also that which cannot be formulated such aesthetics. In this paper, we focus on a brassiere cup. A brassiere cup is composed of several patterns and the cup shape is designed by repeatedly making paper cup model and then checking its three-dimensional shape. For improvement of design efficiency of brassieres, such trial and error must be reduced. The difficulty of the design process is caused by the function of a brassiere cup. Its function, such as to enhance woman’s breast size, et.al., is difficult to formulate and unclearly correlated with its three-dimensional cup shape. In this paper, we propose a method to support the design of the three-dimensional shape of a cup and its developed shape by machine learning when the cup shape and quantitatively evaluated value of its function are given as a set of data. First, we formulate the cup shape as developable surface using differential geometry. Then, we propose the method to extract the attribute from the three-dimensional cup shape based on the differential geometry and a predictor of an output value for its attribute using Gaussian Process Regression. The validity of the method is confirmed by a numerical experiment regarding the evaluated value using its volume and size. Finally, we propose a method to design the cup shape using this predictor. We experimented whether our proposed method can output the approximate cup shape when the evaluated value of the cup is given.

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  • Jin-Xing SHI, Masatoshi SHIMODA, Shinobu SAKAI
    2021 Volume 87 Issue 903 Pages 21-00203
    Published: 2021
    Released: November 25, 2021
    [Advance publication] Released: September 17, 2021
    JOURNAL FREE ACCESS

    Lure fishing is a special fishing method that using artificial fishing lures as fish baits and has become more and more popular all over the world. Vibration lures are a regular item among fishing lures that perform vibration action in the water for baiting fish. In the present work, to enhance the vibration behavior of vibration lures with a real analytical condition, we propose a free-form optimization method for fundamental frequency maximization design problem of solid structures considering initial stress and apply it in shape optimization of vibration lures. We use the fundamental frequency (i.e., the 1st order) eigenvalue as the objective function and maximize it subject to a weight constraint. As the optimal results, the fundamental frequency eigenvalue of a vibration lure made of Zinc could be enhanced to 2.20 times as much as its initial value under initial stress conditions induced by water pressure and tractive force of fishing line, while the mass of the optimal shape satisfied the mass constraint during the optimal design process. As a comparison, we also perform a design optimization of the vibration lure without considering any external loading, whose fundamental frequency can be also enhanced over 2 times as much as its initial value.

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  • Tamotsu MURAKAMI, Tatsuya KURE, Yuta MATSUNAGA
    2021 Volume 87 Issue 903 Pages 21-00207
    Published: 2021
    Released: November 25, 2021
    [Advance publication] Released: October 01, 2021
    JOURNAL FREE ACCESS

    Recently in the field of design, it is becoming more important to generate innovative ideas of "what to create" at early design stage than ideas of "how well to make". Ideation informatics to enhance idea generation by adding systematicity and exhaustiveness of information technology to human intuition should be a prospective approach to the problem. In this research, a ten sentence pattern model is proposed as a computable description of function and user experience (UX) at early design stage as a fundamental technology for ideation informatics by extending the English basic five sentence patterns. An XML format is designed to add semantic information to words, phrases, and sentences described in the ten sentence pattern model by using concept dictionary, i.e., concept identifiers of EDR electronic dictionary and synsets of Japanese WordNet, and software to calculate their semantic similarity is implemented in Python. Then, based on the knowledge of cognitive neuroscience that "human creation does not create something out of nothing, but the memory of the past is the basis of creation", a database of functions and UXs of existing products and services is prepared as an extension of human memory. Using the database, experiments to coming up ideas for solving problems related to the new coronavirus. From the obtained results, the effectiveness and possibility of the proposed method are confirmed.

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  • Kazuo YONEKURA
    2021 Volume 87 Issue 903 Pages 21-00212
    Published: 2021
    Released: November 25, 2021
    [Advance publication] Released: October 18, 2021
    JOURNAL FREE ACCESS

    Research on shape generation using machine learning has been widely conducted, and two-dimensional laminar flow airfoils are treated as a benchmark problem. When learning airfoil shapes using variational autoencoders (VAEs), it is known that the results obtained by ordinary VAE (N-VAE) and hyperspherical VAE (S-VAE) differ significantly. The difference is attributed to the fact that the standard normal distribution is used as the prior in N-VAE and the vMF distribution is used in S-VAE, but quantitative comparison of the latent space of both has not been conducted. In this study, we quantitatively compared how the data are embedded in the latent space of both VAE models. It is shown that data with different trends are embedded near each other in N-VAE, while data with similar trends are embedded near each other in the latent space of S-VAE. The difference can be explained by the difference in KL divergence and data characteristics. The NACA airfoil data is used in the present study, and the dataset is not normally distributed, which is usually the case with other data in mechanical design. S-VAE is suitable in such a case.

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  • Takashi OYAMA, Teruaki ITO
    2021 Volume 87 Issue 903 Pages 21-00218
    Published: 2021
    Released: November 25, 2021
    [Advance publication] Released: October 26, 2021
    JOURNAL FREE ACCESS

    The speed-accuracy trade-off in motor tasks is well-known. An error within a movement can increase with the speed of the movement. Fitts’ law formulizes the relationship between speed and accuracy. Several studies have confirmed the validity of Fitts’ law in various types of motor tasks. However, the reason why this law can provide a good regression of the movement duration on the speed and accuracy of the movement has not been clarified. In this study, the influence of the dynamic parameters of arms, the magnitude of the signal-dependent noise, and a criterion of movement smoothness on the Fitts’ law was investigated to gain insight into the speed–accuracy trade-off. Computer simulations of a reciprocal arm movement task were examined. Moreover, it was attempted to interpret the speed–accuracy trade-off by mathematically approximating a human arm as a mass–damper system. Consequently, it was revealed that positive viscosity did not affect the motor control based on the Fitts' law, whereas negative viscosity prevented obedience to the law.

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Solid Mechanics and Materials Engineering
  • Hideki SEKINE, Hiroshi SHIRAHATA
    2021 Volume 87 Issue 903 Pages 21-00114
    Published: 2021
    Released: November 25, 2021
    [Advance publication] Released: October 29, 2021
    JOURNAL FREE ACCESS

    The shape optimization of joining interface profile is performed for maximizing the tensile load carrying capacity of scarf jointed plates of dissimilar materials. On the basis of the two-dimensional theory of elasticity, we first examine the stress singularity at an edge of joining interface, and elucidate the disappearance of stress singularity for the ratio of shear moduli of dissimilar materials G1/G2 and the intersection angle θ* between the joining interface and the surface of scarf jointed plate. The region of the disappearance of stress singularity is represented in the θ*?G1/G2 diagram. After the examination, we formulate the shape optimization problem of joining interface profile for maximizing the tensile load carrying capacity of scarf jointed plate under the constraint that the stress singularities disappear at the both edges of jointed interface. The two-dimensional boundary element method with quadratic isoparametric boundary elements of joining interface is used for the stress analysis of scarf jointed plates of dissimilar materials, and the optimum shapes of jointed interface profile are determined by solving the optimization problem using the method of feasible directions. As the results, it is found that the enhancement of the tensile load carrying capacity of scarf jointed plates of dissimilar materials can be achieved by slight modification of planar joining interface profile.

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  • Masayuki KAMAYA, Hideo MACHIDA, Kiminobu HOJO
    2021 Volume 87 Issue 903 Pages 21-00149
    Published: 2021
    Released: November 25, 2021
    [Advance publication] Released: November 04, 2021
    JOURNAL FREE ACCESS

    A procedure for application of finite element analyses (FEAs) for the limit load assessment was investigated for the fitness-for-service code for nuclear facility by the Japan Society of Mechanical Engineers. The current code prescribes the equations to obtain the limit load for pipes. FEAs were carried out for various geometrical conditions and their results were compared with the limit load obtained by the equations. It was shown that the FEAs derived unconservative limit loads for pipes with a circumferential crack. The stress triaxiality near the crack tip, whose effect is not considered in the limit load equations, increased the failure load. On the other hand, the limit load equation for pipes with an axial crack predicted conservative burst pressure because the equation was originally developed for wall-thinning. The comparison with the failure tests using cracked pipe revealed that FEAs predicted accurate bust pressure for pipes with an axial crack whereas they made unconservative prediction of failure bending load for pipes with a circumferential crack. It was suggested, for plastic collapse assessment of pipes under bending load, the flow stress for the elastic-perfect-plastic stress-strain curve should be multiplied by 0.84 to the average of yield strength and ultimate strength, which is used for the current code. On the other hand, the flow stress prescribed in the current code is applicable to the assessment for pipes subjected to internal pressure or tensile load.

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  • Kosuke TOKIHIRO, Ryogo KAWAI, Yu KUROKAWA, Yousuke IRIE, Hirotsugu INO ...
    2021 Volume 87 Issue 903 Pages 21-00177
    Published: 2021
    Released: November 25, 2021
    [Advance publication] Released: October 18, 2021
    JOURNAL FREE ACCESS

    The technique of rapid evaluation of fatigue limit using infrared camera is beneficial because it not only allows the fatigue limit to be obtained in a short time and at low cost, but also it makes possible to detect the location of fatigue damage in real structures. In this technique, the fatigue limit is determined based on the temperature evolution with the load amplitude. Several data processing methods have been proposed so far to determine the fatigue limit, but no definitive method has been established yet. In this study, three data processing methods are proposed, namely, a method of selecting pixel to evaluate the temperature evolution, a method of excluding inappropriate data using adjusted R-square, and an approximation function to represent the relationship between the temperature evolution and the load amplitude. As a result, these methods are applied to experimental data and proved to be accurate and reliable enough compared to the existing methods. Experimental data were obtained for double edge notched specimens of type 304 stainless steel. The second harmonic amplitude of temperature was adopted as the characteristic value of temperature evolution for estimating the fatigue limit.

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Fluids Engineering
  • Atsushi KAGAWA, Yoshihide SUWA
    2021 Volume 87 Issue 903 Pages 21-00185
    Published: 2021
    Released: November 25, 2021
    [Advance publication] Released: October 13, 2021
    JOURNAL FREE ACCESS

    The visualization system has been developed to control the fluidity of the excavated soil in the chamber of the EPB shield in real time during the shield advance. For further improvement of the visualization system, agitation tests of the fluid sand mixing with CMC aqueous solution as a thickening material or rheological form to enhance fluidity have been carried out to clarify its flow property. It was confirmed by the tests that the agitating flapper torque of the fluid sand decreased with the increase of the number of flapper rotations. It is assumed that above-mentioned phenomenon was caused by the friction in-between the sand particles. Therefore, the fluidity property of the fluid sand is not exactly same as the general viscous fluid materials. It is, however, useful to evaluate this phenomenon in a numerical formula using the power-law model for the flow property in which shear stress decreases with the increase of the shearing deformation rate, and to apply the formula to numerical analysis, if the analysis is able to simulates the fluid sand behavior with high accuracy. As a result of the agitating tests, the formulas based on power-law model applied negative value to the power index was proposed to evaluate the flow property of the fluid sand.

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  • Shunichi MIZUKAMI, Takahiro KIWATA, Takaaki KONO, Toshiyuki UENO
    2021 Volume 87 Issue 903 Pages 21-00229
    Published: 2021
    Released: November 25, 2021
    [Advance publication] Released: October 26, 2021
    JOURNAL FREE ACCESS

    To develop the power generation system using iron-gallium alloy, we focus on the transverse low-speed galloping vibration for a D-section prism and a rectangular prism with a critical depth section of less than the side ratio D/H ≈ 0.6 (where D is the depth of the prism in the flow direction and H is the height of a prism normal to the flow direction) which vibrates at a reduced velocity Vr lower than the resonant velocity. The free vibration test using a plate spring was carried out in the water tunnel to investigate the effects of the angle of attack and the vibration direction on the vibration characteristics. The vibration direction I of the prism is the same as the longitudinal direction of the prism. The vibration direction II of the prism is the same as the transverse direction to flow. The power generation experiment using the iron-gallium alloy also was carried out to investigate the effects of angle of attack on the energy harvesting. The D-section prism with the side ratio of D/H = 0.23 for the vibration direction I vibrates at a wide range of angle of attack in comparison with the other prisms. The maximum electric power using a D-section prism with D/H = 0.23 is 26 mW at Vr = 3.56.

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  • Kenta SUZUKI, Motoshi SUZUKI, Tomohiro YOSHIDA, Takashi FUJIMOTO
    2021 Volume 87 Issue 903 Pages 21-00251
    Published: 2021
    Released: November 25, 2021
    [Advance publication] Released: November 09, 2021
    JOURNAL FREE ACCESS

    In order to understand motion mechanisms of slippers in swash plate type piston pumps, the analysis flow combining multi-body dynamics and the oil-film analysis was constructed. In the modeling, it is possible to consider the slipper deformation due to the oil film reaction force and the contact with the retainer. This analysis evaluated the effects of elastic deformation of the slipper, discharge pressure, and hydraulic oil temperature on the slipper behavior, and clarified the following. (1) When the slipper is located on the high-pressure side of the pump, the oil-film gap to swash becomes wider in the entrance direction of slipper’s sliding surface. As a result, the gap becomes wedge shape and dynamic pressure is generated. The slipper floats due to this dynamic pressure combined with the static pressure. (2) The slipper tilt angle becomes larger and the flying height is smaller in calculation by considering the elastic deformation of the slipper. This makes it possible to safety evaluate the gap. (3) Changes in discharge pressure and hydraulic oil temperature have a great influence on the behavior of slippers.

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Thermal, Engine and Power Engineering
  • Kakeru NANJO, Ryusei OKUYAMA, Eriko MATSUMURA, Jiro SENDA
    2021 Volume 87 Issue 903 Pages 21-00131
    Published: 2021
    Released: November 25, 2021
    [Advance publication] Released: October 20, 2021
    JOURNAL FREE ACCESS

    In recent years, with the depletion of fossil resources, there is a need to further improve the thermal efficiency of diesel engines. In order to improve the thermal efficiency of diesel engines, it is necessary to realize rapid combustion. The combustion process in diesel engines is greatly affected by spray characteristics and depends on air fuel mixture characteristics. Therefore, it is necessary to grasp the detailed spray characteristics in mixture formation process. In the past, many studies on the spray characteristics in mixture formation process have been reported. For example, Nishiura et al experimentally evaluated the effect of fuel injection pressure, nozzle hole diameter, and ambient density on the spray characteristics (Nishiura and Inoue ,2019). However, most of the previous reports have evaluated the spray characteristics using the total time averaged over a quasi-steady period for the physical quantity. Thus, the temporal and spatial variability of the spray and the large-scale vortical structure have not been sufficiently investigated. In this study, the turbulent intermittency phenomena in diesel sprays were investigated by using sheet scattered light imaging, focusing on the large-scale vortex structure that affects the formation mechanism of the diesel spray mixture. The intermittency of the diesel spray was investigated by applying the analysis method used for clarifying the phenomenon of turbulent intermittency in free jet flow to the analysis of the diesel spray. In this experiment, the effects of injection pressure on the intermittent behavior of the diesel spray were investigated.

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  • Ryota YORIFUJI, Shin’ya OBARA
    2021 Volume 87 Issue 903 Pages 21-00208
    Published: 2021
    Released: November 25, 2021
    [Advance publication] Released: October 20, 2021
    JOURNAL FREE ACCESS

    Since plants with a high biomass conversion efficiency of light energy consume less energy and require shorter cultivation periods, it is expected that plant factories can have more output with less energy. However, there have been few studies on the biomass conversion efficiency of light energy in various cultivated plants, and this agricultural engineering field is still unexplored. If the amount of energy consumed by a plant factory can be obtained from the biomass conversion efficiency of light energy, the plant types that can be grown in a plant factory and the economic efficiency of the plant factory can be clarified. In this study, we determined the amount of light energy required for plant cultivation by measuring the wavelength distribution of sunlight and plant-growing light-emitting diodes. Also, we investigated the light to biomass conversion efficiency (LBE) from the amount of heat generated by the biomass of cultivated plants. The LBE was also used to analyze the payback period of plant factories so as to estimate the profitability of various cultivated plants. However, since the market price of plants varies with the selling season, it is necessary to clarify the biomass conversion efficiency while taking into account the annual air conditioning energy consumed by plant factories. The biomass conversion efficiency by light and air conditioning energy (BELA) is the energy conversion efficiency based on the input values of light energy and air conditioning energy and the output value of the biomass calorific value of cultivated plants. In this study, a new method for economically determining the plant types that can be cultivated using BELA was proposed.

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Dynamics & Control, Robotics & Mechatronics
  • Ryota OZAKI, Yoji KURODA
    2021 Volume 87 Issue 903 Pages 21-00098
    Published: 2021
    Released: November 25, 2021
    [Advance publication] Released: October 18, 2021
    JOURNAL FREE ACCESS

    This paper presents a real-time self-attitude estimation method which utilizes the clues to the direction of the gravity hidden in images and structures of the environments. In the proposed method, the angular velocity is integrated using a gyroscope, a camera-based method estimates the gravity direction, and a LiDAR-based one also estimates the gravity direction, respectively. These estimations are integrated using the EKF (extended Kalman filter). The camera-based gravity direction estimation uses a DNN (deep neural network) which learns the regularity between the gravity direction and the landscape information. By learning the regularity, the proposed DNN can infer the gravity direction from only a single shot image. The DNN outputs the mean and variance to express uncertainty of the inference. The LiDAR-based gravity direction estimation extracts vertical planes from the surrounding environment measured by the LiDAR, and outputs the gravity direction based on their normals. By using both the camera and the LiDAR, more robust and accurate estimation can be achieved. To show the DNN can estimate the direction of gravity with uncertainty expression, static validations on test datasets are performed. Dynamic validations are also performed to show the proposed EKF-based method can estimate the attitude in real time. These validations are performed in both simulator and real world to compare the proposed method with conventional methods.

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  • Yosuke KOMATSU, Takashi YAMAMOTO, Daiji KATSURA, Keisuke YAMAKAWA, Hid ...
    2021 Volume 87 Issue 903 Pages 21-00140
    Published: 2021
    Released: November 25, 2021
    [Advance publication] Released: October 26, 2021
    JOURNAL FREE ACCESS

    Quantitative evaluation of uncertainty in acoustic properties is an essential issue to improve product quality. The acoustic properties of porous materials, such as sound absorption coefficient, are affected by variations in microstructure and material properties during manufacturing. In particular, the microstructure uncertainty significantly affects the variation of the sound absorption coefficient, and a trial-and-error approach using prototypes is necessary for its evaluation. This study proposes a method to obtain the probability distribution of the sound absorption coefficient by combining the homogenization method with the probabilistic approach under the microstructure uncertainty. Defining the porosity and the homologous deformation of the unit structure as random variables, the probability distribution of the sound absorption coefficient was calculated using the homogenization method and the Monte Carlo simulation or perturbation method. The result by the perturbation agrees well with the Monte Carlo simulation result, and the uncertainty of the sound absorption coefficient can be evaluated with our proposed method. Using the method developed in this study, the effect of microstructure variation on the sound absorption properties of porous materials by simulation can be predicted. Our method can contribute to the development of new sound-absorbing materials.

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  • Yuki KAGA, Toshio MORITA
    2021 Volume 87 Issue 903 Pages 21-00162
    Published: 2021
    Released: November 25, 2021
    [Advance publication] Released: November 04, 2021
    JOURNAL FREE ACCESS

    This study aims at realization of multiaxial load compensation mechanism capable of adjusting compensation force in any position. By using a load compensating mechanism on an articulated manipulator, it is pointed out that the gravity of the manipulator and the object can be fully compensated regardless of those position. This mechanism reduces the energy consumption while operating and makes it possible to easily move the weightless manipulator. The purpose of this study is to clarify a design theory of a novel load compensating manipulator with the following three performance requirements. (Performance A) Since the load of the object is not uniquely determined, the compensating force can be adjusted without external energy inflow. (Performance B) Since the position of the object to be grasped is not uniquely determined, the compensation force can be adjusted in multiple positions. (Performance C) Since the picking work requires multiple degrees of freedom, it is possible to adjust the compensation force with multiple axes. For this purpose, a constant-torque spring and a transmission are used to enable adjustment of the compensation force in any position (Performance A and B), and differential gears are added to them due to enable easy multi-axis operation (Performance C). In order to evaluate the feasibility of the proposed design theory, the testing machine equipped with a constant-torque spring, a transmission for bicycles, and a differential gear for three-wheeled motorcycles are constructed to realize the theory. As a result, the error rate of the compensation force is less than 9%, and the standard deviation is less than 0.8 Nm when the compensation force is adjusted in 10 different positions. These results indicate that the proposed theory and the mechanism embody a multiaxial load compensation function that can adjust the compensation force in any position.

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Computational Mechanics
  • Masayuki ARAI, Kazushi YAYOI, Iori YAMAZAKI
    2021 Volume 87 Issue 903 Pages 21-00165
    Published: 2021
    Released: November 25, 2021
    [Advance publication] Released: October 29, 2021
    JOURNAL FREE ACCESS

    Heat transfer in media is generally characterized by the empirical heat conduction law which was proposed by Fourier. However, the application of this empirical law to the problem of fast transient heat transfer such as a pulsed laser heat is not available, which is an important engineering problem. A heat conduction equation that considers about the time delay in the heat flux has been proposed to overcome such problem. In addition, Load and Shulman attempted to extend the heat conduction equation coupled with thermoelastic deformation. In this study, a nonlinear partial differential equation for the coupled problem of heat waves and thermoelastic waves with time delay was derived. Furthermore, temperature and thermal stress analysis was performed on the one-dimensional bar problem based on the finite-difference time-domain method. As results obtained in this study, thermal wave split into two peaks and propagated along the bar by considering the coupled thermoelasticity effect in the heat conduction equation. The elastic wave caused by the thermoelasticity effect also propagated. However, it was found that the peak stress in elastic wave was relaxed as the coupling effect being stronger.

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Design, Machine Element & Tribology, Information & Intelligent Technology, Manufacturing, and Systems
  • Kana SAWAI, Yutaka NOMAGUCHI, Kikuo FUJITA
    2021 Volume 87 Issue 903 Pages 21-00055
    Published: 2021
    Released: November 25, 2021
    [Advance publication] Released: October 18, 2021
    JOURNAL FREE ACCESS

    Structural analysis of customer data such as purchase history and customer attributes is expected to be effective for designing the products that are appropriately adapted to requirements of individual customers. This paper proposes a structuralization method of customer requirements for configure-to-order products with the customer data analysis and the design structure matrix (DSM). In the method, association rule mining is applied to order reception data for extracting structural relationships among customer requirements. The extracted association rules are transformed into a customer requirements DSM, which can be used as the input to the clustering method for the multi-domain matrix across customer requirements, physical functions and entity structure. A case study of an industrial three-axis linear-type robot is demonstrated. The customer requirements DSM generated by the proposed method is compared with the one generated without using association rule mining. Its results show the effectiveness of the proposed method.

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  • Takeshi YAMAMOTO
    2021 Volume 87 Issue 903 Pages 21-00209
    Published: 2021
    Released: November 25, 2021
    [Advance publication] Released: October 26, 2021
    JOURNAL FREE ACCESS

    A high speed electric motor with a small reducer and high power transmission efficiency realizes a powertrain system with high power density because electric motors can be miniaturized to increase the rotational speed. The transmission performance and behavior of meshing gears or traction drive transmission elements with a high-speed reducer have not been clarified at such high rotational speeds due to experimental difficulty. Therefore, a high-speed transmission tester was designed and built to enable experiments at 50,000 rpm, without the use of special motors or measuring instruments, by increasing the speed using the ratio of the test roller or gear radii. The measurement results almost agree with the known values and trends, confirming that this tester can be used to perform measurements at high speed. Because the traction coefficient and transmission efficiency do not decrease drastically at high rotational speed, discontinuity was not found in the mechanism of traction expression. At high rotational speed and low torque, a traction drive has a higher transmission efficiency than that of gears, and this is more pronounced at higher rotational speed. At low speed and high torque, gears are more efficient. Therefore, this study demonstrates that gears are suitable as transmission reduction elements below 25,000 rpm, and traction drives are suitable for rotation speed reduction above 25,000 rpm.

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  • Akitoshi TAKEUCHI
    2021 Volume 87 Issue 903 Pages 21-00238
    Published: 2021
    Released: November 25, 2021
    [Advance publication] Released: November 04, 2021
    JOURNAL FREE ACCESS

    The generation state of the pressure for partial water-repellent (slip) type flat thrust bearings with high/low slip parts was examined with experiments and infinite width bearing approximation. In this bearing, water-repellent (WR: high slip), weak water-repellent (WWR: low slip) and hydrophilic (HP: non-slip) regions were alternately arranged in the slip direction, and the pressure to support the load was generated by discontinuity of shear flow rate in each region. The measured pressure in slip direction increased in the water repellent side (static contact angle of water droplet θ≒110 °) and weak water repellent part (θ ≒80 °), and it decreased in the hydrophilic side (θ≒10 °). And this pressure distribution in circumferential direction was close to quadrangle and it increased almost in proportion to the load. The pressure distribution differed greatly depending on the slip length in low slip part (e.g. WWR), it became a quadrangle having a maximum pressure at the boundary of the non-slip part (e.g. PH). For example, the pressure distribution became close to a triangle when the slip length in low slip part was long close to the slip length in high slip part (e.g. WR). Whereas, it became a quadrangle close to a trapezoid when low slip part had the short slip length. For the bearing with large angle φWWR in low slip part, the generated pressure and the difference in generated pressure at each load was lower. Especially, generated pressure decreased when φWWR approached the maximum angle (60° in this experiment) because high slip and non-slip areas became extremely narrow. Incidentally, the effect of slip length in high slip part on the load capacity was remarkable, but the influence of slip length in low slip part was hardly observed.

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  • Kazushi YOSHIDA, Yujiro HISATOMI
    2021 Volume 87 Issue 903 Pages 21-00246
    Published: 2021
    Released: November 25, 2021
    [Advance publication] Released: October 20, 2021
    JOURNAL FREE ACCESS

    A new paper sheet feeding mechanism using a friction force owing to electrostatic adhesion is proposed to realize long-term reliability and reduction in maintenance work. In this mechanism, friction force owing to electrostatic adhesion of an electrostatic pad acts as a resistance force to make paper sheets separate successively instead of a friction force of rubber parts used in the conventional feeding mechanism. The electrostatic pad with comb-type electrodes and whose upper surface is coated with an insulator with high wear resistance generates the resistance force. First, the width of the electrode and the spacing between electrodes of the electrostatic pad that generate a large electrostatic adhesion at the lowest possible voltage are determined from an experiment using the evaluation electrostatic pad. Then, the feed force acting on the first and the second paper sheets, and the resistance force owing to the electrostatic pad are measured by pulling the paper sheets in the separation mechanism. Furthermore, the performance of the paper sheet feeding mechanism is measured while changing the value of the voltage applied to the electrostatic pad. Consequently, it was found that the paper sheets could be accurately fed successively by adjusting the applied voltage to an appropriate value.

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Bio, Medical, Sports and Human Engineering
  • Shimpei AIHARA, Kai ISHIBE, Rikushi SABU, Hiroyasu IWATA
    2021 Volume 87 Issue 903 Pages 21-00214
    Published: 2021
    Released: November 25, 2021
    [Advance publication] Released: November 09, 2021
    JOURNAL FREE ACCESS

    Small inertial sensors having low cost and simple structure have recently been developed owing to improvements in microelectromechanical systems. Therefore, inertial sensors are being widely used in various sports for quantitative measurements and athletes’ evaluation. However, no wearable device has been specifically designed to capture karate movements such as punching, blocking, and kicking, and these movements are being recorded manually in the field of karate training. Automated recording and identification of karate movements using wearable sensors can lead to improved training and performance, therefore we developed an identification method for various karate movements using inertial sensor data. First, we created a dataset of karate movements by acquiring measurements from 22 karate players at the karate club of Waseda University. Their competitive levels were wide-ranging, from Japanese local competition level to international competition level. Inertial sensors were attached to five parts of each participant’s body (right hand, left hand, right foot, right leg, and waist), and basic karate movements (reverse punch, upper block, and front kick) were performed by each participant for measurement. Then, we established the dataset containing inertial sensor data paired with the correct karate movement label. Next, we designed a deep learning network based on long short-term memory and trained the network using part of the dataset. We evaluated the network using leave-one-out cross-validation, obtaining the F1-scores of 0.90 for right reverse punch, 0.89 for left reverse punch, 0.88 for right upper block, 0.86 for left upper block, 0.90 for right front kick, and 0.90 for left front kick. In addition, the micro-average of the F1-score was 0.89. Therefore, high identification accuracies were achieved for all types of karate movements.

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Transportation and Logistics
  • Keisuke NAGATA, Tomohiro OKINO, Jun-ichi TAKANO
    2021 Volume 87 Issue 903 Pages 21-00117
    Published: 2021
    Released: November 25, 2021
    [Advance publication] Released: October 22, 2021
    JOURNAL FREE ACCESS

    Although the number of accidents at level crossings in Japan has been decreasing annually, there is still possibility of such accidents to occur due to wrong-way entry. Therefore, it is essential to study the crashworthiness of rail vehicles in level-crossing accidents. Given that there are many possible collision scenarios for such accidents, it is useful to perform a comprehensive analysis of these scenarios. To investigate the crushing characteristics of a double-skinned aluminum-alloy car body structure for a conventional railway line, we conducted impact compression tests. The impact condition compresses the overall specimen's end face (overall compression condition) and part of its end face (local compression condition). The results of the impact compression tests were as follows. Buckling was the main cause of failure in the overall compression condition, whereas shear crushing was the main cause of failure in the local compression condition. Finite Element Method (FEM) analysis was also conducted in which several material rupture laws were used and compared with the test results. No appropriate solution could be obtained when the equivalent plastic strain was used as a threshold, whereas the results of analyses using the ESI-Wilkins-Kamoulakos (EWK) model showed good agreement with those of the experiments in both compression conditions.

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  • Kazuma NAKAI, Tomohiro OKINO, Shota ENAMI, Keisuke NAGATA
    2021 Volume 87 Issue 903 Pages 21-00181
    Published: 2021
    Released: November 25, 2021
    [Advance publication] Released: October 20, 2021
    JOURNAL FREE ACCESS

    It is important to enhance the safety of the railway passengers on board in the event of a collision accident. The railway vehicle standard in European countries and the U.S. set the framework for structural crashworthiness design. On the other hand, an evaluation method for the crashworthiness design of railway vehicles has not been established yet in Japan. Our objective is to suggest the safety index for the railway vehicles in which longitudinal seats are arranged. The severity of passenger’s head injury was estimated in a level crossing accident scenario, including the horizontal collision position to a dump truck, the collision angle, the vertical collision position and the load weight of the dump truck by using numerical simulation. The correlation between the severity of injury of an Anthropomorphic Test Device (ATD) model and the safety index, integral of deceleration waveforms, mean deceleration waveforms and maximum waveforms which occurs on the railway vehicles at the time of collision with a dump truck were verified. It was found that the integral of deceleration values during an integration time timp had the highest correlation with the injury values of ATD. We suggested the integral of deceleration and the critical values of the second-furthest away from the bench-end partition as an evaluation method for the crashworthiness design of railway vehicles.

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  • Takahiko ONO
    2021 Volume 87 Issue 903 Pages 21-00211
    Published: 2021
    Released: November 25, 2021
    [Advance publication] Released: October 13, 2021
    JOURNAL FREE ACCESS

    As a road pavement assessment tool, this paper presents an equation to estimate the vibrational ride comfort of local fixed-route buses from the international roughness index (IRI) and the bus speed. Before construction of the equation, all the needed data was collected as big data: The bus data such as acceleration, speed and position have been collected with the built-in accelerometer and GPS sensor of a smartphone for about 100 days on three national routes. After the measurement, according to ISO2631-1, the ride comfort was quantified as a running r.m.s of the frequency-weighted acceleration on a passenger seat. The IRI was measured every 10 meters with the Class 3 method. It was observed that the ride comfort was weakly correlated with the speed and moderately correlated with the IRI. For the large and the medium buses, two estimate equations were constructed in the form of a function with arguments of the bus speed and the IRI. Their parameters were determined by applying the data fitting technique to the collected big data. The estimate equations give the correlation coefficients of 0.70 to 0.79 and the root mean squared errors of 0.08 to 0.13 m/s2 between the mean values of the measured ride comfort and their estimates on the 10-meter road segments.

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  • Takatoshi HONDO, Shoya KUNIYUKI, Takayuki TANAKA, Mitsugi SUZUKI, Hisa ...
    2021 Volume 87 Issue 903 Pages 21-00253
    Published: 2021
    Released: November 25, 2021
    [Advance publication] Released: October 21, 2021
    JOURNAL FREE ACCESS

    Instrumented wheelsets are widely utilized in the railway industry for the purpose of the measurement of the wheel-rail interaction force. In the conventional instrumented wheelset, the measurement accuracy of the lateral force is reduced due to the bending moment induced by the wheel load. The authors have proposed a new configuration of the instrumented wheelset to reduce the influence of the wheel load on the measurement of the lateral force. This proposed configuration utilizes the shear strains of the wheel web as a measure of the lateral force. This paper describes the accuracy verification of the proposed configuration under the wheel rotating condition. The single-wheelset roller-rig tests are carried out and the test results show that the proposed method can reduce the influence of the wheel load even under the rotating condition.

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