Transactions of the JSME (in Japanese)
Online ISSN : 2187-9761
ISSN-L : 2187-9761
Advance online publication
Showing 1-34 articles out of 34 articles from Advance online publication
  • Kazumasa IKEDA, Toru YAMAZAKI
    Article ID: 20-00279
    Published: 2020
    [Advance publication] Released: October 27, 2020
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    In the automobile industry, quietness has been pursued with electrification and vehicle weight has been reduced for longer traveling distance. In design of component products to be mounted on vehicles, “low noise” and “weight reduction” have been also required. In order to realize them, it is important to approach sound characteristics in initial design stage and detail design stage. In the initial design stage, parts layout, material and rough dimensions are designed to decrease “average” of noise level. In the detail design stage, accurate dimensions and detailed shapes are designed to suppress noise peaks. These are called “two-step design”. Especially, analytical SEA (ASEA) is a suitable technology for the initial design because it provides results by using only theoretical equations without 3-D models. However, it has hurdles to be a practical process. One is a constraint of ASEA that accuracy of results can be kept high only in high frequency range. In this paper, we proved theoretically and practically that initial design using ASEA was effective even in low frequency range.

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  • Takahiko ONO, Soichiro YOSHIMURA, Yuki SHIMIZU
    Article ID: 20-00223
    Published: 2020
    [Advance publication] Released: October 22, 2020
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    To improve patient safety in ambulance transport service, this paper proposes a new method for finding an optimal route of an ambulance depending on the disease or injury of a patient. Three transport cases are considered in this paper: Heart disease (HD), hemorrhagic cerebrovascular accident (HCVA) and fracture/dislocation (Fx/dx). The route optimality is measured with three evaluation functions. The first function evaluates an elapsed time from the scene of an emergency to a hospital. The second evaluates a blood pressure variation induced by the acceleration/deceleration motion of an ambulance. The third evaluates a compression load acting on the back of a patient due to the centrifugal force. They are calculated by applying the traveling model of an ambulance to the three-dimensional road network. The optimal route is selected in two stages. First, the candidate routes are found by solving the multiobjective optimization problem of minimizing the three evaluation functions. If the completely optimal solution (route), which minimizes the three functions simultaneously, is found, the selection process is finished. Otherwise, obtain the Pareto solutions to go to the second stage, in which a preference solution is selected from the Pareto solutions depending on the disease or injury of a patient. In the numerical example, the route selection is shown for HD, HCVA and Fx/dx. For the reference sake, the real routes of the ambulance recorded in Hiroshima City and the shortest routes obtained by Google Maps Navigation are also presented and compared to each other.

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  • Fumio ITO, Hiroto SATO, Yuki MANO, Manabu OKUI, Taro NAKAMURA
    Article ID: 20-00052
    Published: 2020
    [Advance publication] Released: October 21, 2020
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    This paper introduces a two-degree-of-freedom pipe selection mechanism using contraction and extension unit composed of single tube and a T branch experiment of an in-pipe mobile robot equipped with this mechanism. Household piping is used for gas transportation to each household. If the pipe is cracked or corroded due to long-term use, it becomes difficult to supply a stable gas. Therefore, inspection of household piping is necessary. The existing methods require a lot of time for the inspection or it is difficult to inspect the entire pipeline. Therefore, in this study we developed an inspection robot for home piping using a mobile robot. To date, the robots proposed have been able to bend in the direction along the pipeline, as the tip of the robot passively bends when passing through the curved pipe. However, at the branch pipe, there is no mechanism that actively bends the tip of the robot, and the pipe cannot be selected and moved in a specific direction. Therefore, this paper proposes the application of a small pipe selection mechanism combining a ball-point pen knock mechanism and a wire bending mechanism to an in-pipe mobile robot using the pressure difference of a single tube.

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  • Naoto TAKEBE, Yuichiro SUEOKA, Hiro SHIGEYOSHI, Yasuhiro SUGIMOTO, Koi ...
    Article ID: 20-00095
    Published: 2020
    [Advance publication] Released: October 21, 2020
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    In general, small robots can operate in narrow spaces, and large robots can traverse over rough terrains. Although a few robots with adjustable wheel diameter have been developed, they require multiple actuators for rotating the wheels and changing the wheel diameter. This paper proposes a wheel robot that can adjust the wheel diameter according to the wheel rotation. The robot uses a centrifugal force-aided diameter adjustable mechanism; the wheel diameter is expanded/contracted by a circular pantograph via the centrifugal force. Thus, the wheel diameter can be changed depending on the drive of the wheel. We adopt the circular pantograph mechanism to maintain the round shape of the wheel during expansion and contraction. We conducted experiments with the developed robot and found that the wheel diameter appropriately changes with the wheel acceleration and deceleration. The results show that the proposed mechanism improves the performance when climbing a step and operating in a narrow space. Further, the robot also had mechanical flexibility, which helps reduce the impact when facing a step. These characteristics could be achieved because the wheel was passively and adaptively deformed according to the running environment.

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  • Toru TSUMUGIWA, Shinya KADOTA, Ryuichi YOKOGAWA
    Article ID: 20-00121
    Published: 2020
    [Advance publication] Released: October 21, 2020
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    It is important to elucidate the lower limb motion based on the activation of lower limb muscles during pedaling to improve pedaling performance of cyclists. In previous studies, although the activation of these lower limb muscles has been investigated by a surface electromyogram (EMG), the evaluation of muscle contraction during pedaling has not been conducted. Muscle contraction refers to the muscle activation state accompanying a change (stretching / shortening) of the muscle length, and the exerted muscle strength and the status of muscle fatigue have complicated relationships that are difficult to be clarified. The purpose of this study is to propose a novel method to evaluate the muscle contraction during pedaling. Muscle contraction characteristics were analyzed to elucidate the pedaling motion based on relationships between muscle length variation (stretching / shortening) and contraction velocity and the strength of muscles. In the experiments, cyclists were instructed to perform their pedaling technique at two pedaling rates (cadence: 80–90 and 110–120 rpm). EMG signals were recorded from rectus femoris (RF), biceps femoris (HAM) and gastrocnemius (GAS). Pedal force was measured by a power meter (Pioneer Inc.). Furthermore, the lower limb motion during pedaling was measured using a 3D motion capture system. In addition, the muscle length model of the lower limb was constructed based on the Hill–Stroevo model to identify the lower limb muscle length during pedaling. The experimental results show that the proposed system evaluates the muscle activation and contraction during pedaling as well as the pedaling skill based on the muscle contraction. The analysis results of the muscle contraction show the importance of the hamstrings activation state during the pedaling motion.

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  • Shota ASAHI, Ayaka MATSUI, Satoshi TAMURA, Satoru HAYAMIZU, Ryosuke IS ...
    Article ID: 20-00020
    Published: 2020
    [Advance publication] Released: October 20, 2020
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    In this paper, we propose a method to predict the failure of factory equipment by machine learning architectures using vibration data. We design the model so that we can predict robustly the failure of the equipment in advance. We use a Gaussian Mixture Model (GMM), a machine learning architecture, to calculate abnormality value which is used for the decision whether the state of the equipment is normal or abnormal by thresholding. We also use Long Short-Term Memory Autoencoder (LSTM-AE), one of the structures of the deep learning algorithm, for feature extraction. LSTM-AE model learns both spatial and temporal patterns which are difficult to capture with conventional machine learning algorithms. We conducted the prediction experiment using vibration data obtained from actual mechanical equipment, to confirm our method can predict the failure more robust than conventional methods. From this experiment, we found that the abnormality value tended to exceed a threshold value before the actual failure, indicating that the failure can be predicted in advance by our method. Besides, when compared with conventional methods, we found that the transition of abnormality and the accuracy of failure prediction were almost the same in all cases, but we also showed that the proposed method has superiority on robustness compared to conventional methods about the transition of abnormality and the setting of the threshold.

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  • Takahiro MORISHITA, Takamoto ITOH, Naoto KASAHARA
    Article ID: 20-00225
    Published: 2020
    [Advance publication] Released: October 20, 2020
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    This study investigates an effect of inelastic non-proportional preloading on failure life in a followed high cycle fatigue for two steels, SUS316 stainless and Mod.9Cr-1Mo steels. Preloading tests were conducted using a servo controlling hydronic multiaxial fatigue testing machine which can apply an axial loading and torsional loading. Two types of loading paths under strain controlled were employed: a push-pull loading and a circle loading. The circle loading is the non-proportional loading in which axial strain ε and shear strain γ have 90-degree difference. Using the specimens fatigued in the inelastic preloading test, high cycle fatigue tests were conducted by a rotating bending fatigue testing machine. Based on the obtained results, effects of inelastic proportional and non-proportional preloading on the failure life in high cycle fatigue is discussed. The high cycle fatigue life for SUS316 stainless steel such as the materials of which crystal structures are FCC was increased due to cyclic hardening depending on inelastic non-proportional preloading. On the other hand, the life for Mod.9Cr-1Mo steel which has BCC was reduced by the cyclic softening induced by the preloading.

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  • Hitoshi MORITOKI
    Article ID: 20-00277
    Published: 2020
    [Advance publication] Released: October 20, 2020
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    For judging whether two stresses maintain objectivity between different frames, appropriate criterion needs to be used. The criterion, c*u= cuQ: Σ*= QTΣQ has been normally used, but it was found that it did not have the ability to judge the essence of objectivity. Getting over the deadlock for judging quality of objectivity, the comparison of stress values is indispensable between frames under an identical stress tensor. As a result of examining the difference of stress values, the essential criterion for objectivity σCpq=σBpq+DMσBpq, DσCpq=DσBpq was given. It is shown that Jaumann stress increments DJσpq is not recognized as an objectivity stress increment. Even in such an environment, there are some proposals that DJσpq should be replaced instead of Dσpq in constitutive equations. Then, the spin included in DJσpq gives stress a fluctuation depending on the induced spin, which was presented in this manuscript.

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  • Shingo SHIMAZAKI, Qinzhong SHI
    Article ID: 20-00287
    Published: 2020
    [Advance publication] Released: October 20, 2020
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    Ground acoustic tests using stationary acoustic environments have been conducted to verify spacecraft resistance design against the transient random acoustic load during launch. Traditionally, a stationary acoustic test spectrum has been derived from a kind of short-time Fourier transform performed on transient random acoustic load, being enveloped. The envelopment, however, inevitably results not only in an excessively conservative spectrum, but also in the innate disparity between stationary and transient-random acoustic environments in their vibro-acoustic responses, diverting them from exhibiting equivalency for design verification. Furthermore, an excessively conservative spectrum forces unnecessary cost increase upon product design. One solution proposed in this paper is a method based on a vibro-acoustic single degree of freedom model, to derive the stationary acoustic environment condition with equivalent maximum load and cumulative fatigue damage of vibro-acoustic structure as in transient random acoustic environment condition, using extreme response spectrum and fatigue damage spectrum. The application of this method to actual flight acoustic data during launch demonstrates that it outweighs the conventional method in environmental resistance of structures with reduced conservative margin.

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  • Takahiro MORISHITA, Takamoto ITOH, Naoto KASAHARA
    Article ID: 20-00224
    Published: 2020
    [Advance publication] Released: October 14, 2020
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    In a pressure vessel, a heat exchanger and a junction piping where cold and hot water are mixed, temperature fluctuation yields multiaxial stress and random amplitude loading conditions. In most cases, the loading becomes non-proportional loading in which directions of principal stress and strain are changed in a cycle. Fatigue lives under the non-proportional loading are reduced depending on non-proportionality of loading path. In this paper, cyclic deformation under multiaxial loading simulated thermal fatigue is discussed based on the test results and a method of fatigue life evaluation under complex multiaxial random loading is presented. T-shaped loading, in which reversed torsion loading with static tension (tension T-shape loading) or compression (compression T-shape loading) followed push-pull in a cycle, is used as the simulated loading in the junction piping. Fatigue lives under T-shaped loading depend on the number of the reversed torsion loading. The fatigue life is increased due to increase in the number of the reversed torsion loading which leads to relaxation of loading non-proportionality. The fatigue lives under compression T-shape loading is shorter than that under tension T-shape loading. The reason is effect of mean stress, which the mean stress in push-pull under compression T-shape loading is shifted to tension due to static compression stress relaxation by reversed torsion loading. Modified IS-method, which takes into account of mean stress by using centroid of loading path, is proposed to represent the reduction in non-proportionality and the stress relaxation in T-shape loading.

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  • Yoshihiro SATO, Jan Hendrik ELM, Jens VIEHÖFER, Jan-Welm BIERMANN, Nob ...
    Article ID: 20-00008
    Published: 2020
    [Advance publication] Released: October 13, 2020
    JOURNALS FREE ACCESS ADVANCE PUBLICATION

    In the previous reports, a methodology for estimating noise radiation including airborne noise from a mechanical system under the operational condition by component test of a certain active subsystem using the in-situ blocked force approach, which is normally used for estimating only structure borne noise, was proposed and verified by numerical simulations of noise radiation from a cantilever rectangular plate. This paper describes experimental verification of the proposed methodology by application to rattle noise from a column type electric power steering system (EPS) for a vehicle. Therefore an EPS corresponds to the active subsystem and the other parts such as vehicle body correspond to passive subsystems. At first, a method of measuring rattle noise from an EPS under the operational conditions, i.e., running tests with a vehicle, was established. Since it is possible to apply the in-situ blocked force approach also to vehicle running tests and to estimate rattle noise, the measured and estimated rattle noises under an identical operational condition were compared and validity of the proposed methodology was confirmed. Next, a component test bench which enables to reproduce vibration behavior of an EPS under the operational conditions was developed, and rattle noise under an operational condition was estimated by means of the proposed methodology using both vibration accelerations measured with this component test bench and vibro-acoustic transfer functions measured with the vehicle under a static condition. Finally, the proposed methodology was verified by comparing the estimated and measured rattle noises under the operational condition. The proposed methodology is expected to replace time-consuming operational tests of a whole mechanical system to simple component tests of the active subsystem.

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  • Yuji ISHINO, Takeshi MIZUNO, Masaya TAKASAKI, Daisuke YAMAGUCHI
    Article ID: 20-00015
    Published: 2020
    [Advance publication] Released: October 13, 2020
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    A first-order-reset element (FORE) controller is modified to adjust the vibration attenuation characteristic of a magnetic suspension system. The proportional-derivative (PD) feedback control is the simplest control method of stabilizing magnetic suspension systems. In the PD-controlled system, restoring force is produced with the proportional element and damping effect is produced with the derivative element. Meanwhile, a feedback control using a FORE has been proposed to stabilize magnetic suspension systems. The FORE replaces a linear integrator built into a first-order low-pass filter by a non-linear integrator. The proposed controller can stabilize a magnetic suspension system with one element. The restoring force and damping effect are generated simultaneously. However, the two effects could not be adjusted separately. To adjust the vibration attenuation characteristic, the FORE controller is modified to adjust the transition value at reset. The characteristics of the modified controller are studied through numerical analysis. Then the effectiveness of the modification is demonstrated by several simulations and experiments.

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  • Tatsunori HARA, Masafumi HAMANO, Haruka CHINO, Takaomi SATO, Yusuke KA ...
    Article ID: 20-00192
    Published: 2020
    [Advance publication] Released: October 13, 2020
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    In the context of recent servitization of manufacturing characterized by IoT, Big data, and AI, we require a data-driven front-loading design of product with service. This paper proposes a design method of service system that encourages co-creation using a structural framework called TriCyPSS (Triple Cycles for Product Service System) from the viewpoints of service chain and continuous provision among client business, my business, and partner business. This paper shows a case study according to the method’s procedure and details notations using a system modeling method called i* (eye-star). Using them, we clarify value in use brought by the service chain and continuous provision as well as data utilization and information circulation. Finally, this paper employs the method together with business planning methods and tools for practical use.

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  • Shigeo YANABE, Shigeru NAGASAWA
    Article ID: 20-00219
    Published: 2020
    [Advance publication] Released: October 13, 2020
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    Surface winding processes are simulated up to 49-70 laps by means of a FEM commercial software. The simulation model is composed of a flexible web with linear-isotropic nature, rigid core and rigid drum (or rigid two drums and a rider roll). Stress distributions of wound rolls, tension (tangential stress) change during winding and layer slippage are investigated. The main results are as follows. In case of single-drum surface winding, the roll stresses become larger as a friction coefficient between web layers, nip load, drum diameter or a line tension increases, or Young’s modulus decreases. Poisson’s ratio has little effect. The roll stresses depend on not only WIT (increased tension of the outermost layer due to the nip load), but a decreasing rate of tension at a web point during winding, and they have a cross relation with a value obtained by integrating a web tension varying curve from the start point where the web enters the roll to the end of winding. In case of two-drum surface winding with differential drum speeds, the web tension varies complicatedly at three nip zones and is larger between the rider roll and the second drum. The tension of the outermost layer decreases with increase in the roll diameter. The slippage occurs as the outer web layer pulls the inner in the roll rotational direction and is larger at the outer web layers. When speeds of the two drums are equal, the first drum drives the roll and the tension is larger between the second and the first drum. The slippage is the same as the differential drum speed case in the range of 2/3 of the roll thickness, but in the rest range, the slippage occurs in the opposite direction.

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  • Akitoshi ITO, Jinghuii LI, Yusuke MAEDA
    Article ID: 20-00028
    Published: 2020
    [Advance publication] Released: October 12, 2020
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    Today, offline programing is available on industrial manipulators and used in many factories. However, the absolute accuracy of robots is insufficient due to manufacturing and assembly tolerances, thus it is necessary to perform kinematic calibration in advance. Most of existing calibration methods require a large amount of measurements just to calibrate a robot. In addition, when programing the robot offline, it is also important to perform motion planning for safe and efficient operations. Appropriate motion planning enables the robot to move along the optimal route taking obstacle avoidance and cycle time reduction into account. For this purpose, the accurate measurement of the environment around the robot is required, but existing methods require a lot of work and time. Therefore, in order to reduce the time and effort required for kinematic calibration and environmental mapping, we developed a SKCLAM (Simultaneous Kinematic Calibration, Localization And Mapping) method, in which kinematic calibration and environmental mapping are performed simultaneously for a manipulator with an RGB-D sensor attached to its hand. In this study, in order to improve the accuracy of the SKCLAM method, we introduced checkerboard patterns. We verified the SKCLAM method with checkerboard patterns in both a virtual environment and a real environment. The results showed that the effectiveness and some limitations of our current implementation.

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  • Issei YAMAZAKI, Kazuhiko HIRAMOTO
    Article ID: 20-00059
    Published: 2020
    [Advance publication] Released: October 12, 2020
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    Mechanical snubbers and inertia mass dampers are known as vibration control devices that have inertia mass elements and generate the inertial resistance force. By adding the devices with the inertia mass elements to piping systems, we aim to reduce various responses of the piping systems during earthquake events. In this study, we propose a design method to optimize design parameters of mechanical snubbers installed on a single cross section beam (continuum model) piping system to achieve good dynamic responses of the beam while maintaining the structural integrity of the beam and the supporting device. A performance index considering various specifications related to mitigation of responses of the piping system for earthquake disturbances and the economic cost for installation of devices with some inequality constraints is defined. Design parameters to optimize the performance index are the number and the model size (capacity) of the mechanical snubbers, the value of the inertia mass and the placement of each snubber. The performance index is optimized with a genetic algorithm. A simulation example shows that we could search the optimal design parameters that show the good performance on vibration suppression while satisfying the considered constraints.

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  • Aya ABE, Haruki YASHIRO, Ichiro HAGIWARA
    Article ID: 20-00126
    Published: 2020
    [Advance publication] Released: October 12, 2020
    JOURNALS FREE ACCESS ADVANCE PUBLICATION

    If the octet truss core, which is a space filling structure of half regular octahedrons and regular tetrahedrons, has excellent sound insulation characteristics, the possibility of using the octet truss core is sufficiently widened. From this fact, we have studied to obtain sound insulation characteristics of the flat plate and the plate with single core using acoustic tube by the finite element method (FEM) with high accuracy. The calculation of sound insulation performance by FEM was limited to the qualitative study so far. For example, the correction is required due to the difference from the theoretical value, and the magnitudes of the correction values differ depending on the test pieces. In this study, we considered the incident wave and compared the sound insulation calculation result by the FEM calculation using the non-reflective boundary at the rear end of the sound receiving room with the theoretical calculation. As a result, both calculation values were almost the same. Therefore, it can be said that when the magnitudes of the incident wave and the reflective wave are almost equal, a quantitative study is possible. Taking advantage of this fact, in this paper the sound insulation characteristics of the plate with single core are compared with that of flat plate, and the effects of the sound insulation characteristics by the aspect ratio of the core are examined.

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  • Kunihiko ISHIHARA
    Article ID: 20-00250
    Published: 2020
    [Advance publication] Released: October 12, 2020
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    In heat exchangers like a boiler, as a tube bank is set in a duct the alternative vortices occur behind a tube bank and the vortex shedding frequency increases with the flow velocity when the boiler is operated. High level sound is suddenly generated when the vortex frequency comes close to the acoustic natural frequency of the duct. The high level sound keeps the frequency and the amplitude constant even if the flow velocity increases in the case of small acoustic damping due to the self-excited mechanism. This is generally called the self-sustained tone and the factory is forced to stop the operation due to the complaints of the neighborhood. The effective countermeasure is required in the design stage. In general, the baffle plate is inserted in the tube bank but it is difficult to treat it, especially to the duct with plural tube banks. Then the other effective countermeasures are keenly anticipated. The author has many studies concerned to the clarification of the generation mechanism and the countermeasures and their effects. In recently, it is clarified that the perforated plate suppresses the high level sound. The author has a question what is the relation between the suppression effect of the perforated plate and the dimension ratio. Then in this paper, the acoustic experiments will be conducted by using the three different sizes of the ducts and perforated plates. The acoustic damping obtained by these experiments and analyses is compared. As a result, it was clarified that the acoustic damping ratio becomes smaller with larger of dimensional ratio.

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  • Masato MIYOSHI, Shixian LIU, Akira OKADA, Akihito HOSHIMA, Masatoshi K ...
    Article ID: 20-00213
    Published: 2020
    [Advance publication] Released: October 09, 2020
    JOURNALS FREE ACCESS ADVANCE PUBLICATION

    Demand for high precision machining of complicated shapes has recently increased with the miniaturization of mechanical and electronic products. Therefore, further development of fine wire electrical discharge machining (EDM) technology using a thin wire electrode has been also requested. However, there might be a limit in improving the machining performance of fine wire EDM using conventional wire only by optimizing discharge pulse conditions and gap control. Therefore, it is essential to develop a new type of thin wire electrode for further improvement of wire EDM performance. In this study, high-zinc-content brass (γ-phase brass) coated steel core wire as a new type wire electrode was trially made to improve the machining stability. In wire EDM, zinc content of wire surface would contribute to rapidly cool down the gap by the evaporation due to its low boiling point. However, the surface of γ-phase brass coated wire tends to become rough in the heat treatment process of the wire. Thus, another type of the γ-phase brass coated wire with smoothed surface was also made by an extra finish drawing. The wire EDM characteristics using these wires were compared with those using conventional brass coated steel wire. Furthermore, the distribution of spark locations during process was evaluated by high-speed observation to investigate the influence of γ-phase brass and the surface roughness of wire. As a result, the cutting speed using the γ-phase brass coated steel wire with smoothed surface is faster than that using conventional wire because of uniform distribution of spark location.

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  • Jiaqing ZHU, Terutake HAYASHI, Syuhei KUROKAWA
    Article ID: 20-00220
    Published: 2020
    [Advance publication] Released: October 07, 2020
    JOURNALS FREE ACCESS ADVANCE PUBLICATION

    For poly-dispersed nanoparticles, which have more than two peaks on their particle size distribution (PSD), it is important to determine the mean particle diameter and their dispersion at each peak in a liquid. Dynamic Light Scattering (DLS), that is one of a typical nanoparticle sizing method, has difficulty to determine the several peaks in the PSD for the poly-dispersed particles. On the other hand, Image analysis methods (IA) can distinguish the peak for both the primary particle and secondary particle in the PSD of poly-dispersed particles accurately. However, IA is a time-consuming method and it is difficult to apply the measurement of the PSD due to the requirement of measuring the large number of particles, one by one. The particles in the liquid are transferred to a substrate in air when observing the particle to measure their size and the size distribution. In this procedure, some particles usually aggregate with surrounding particles. It causes the difference between the PSD for dispersed particles in liquid and that of the particles on the substrate. In this study, we suggest a novel particle sizing method using “Nanoparticle chip”, that is nanoparticles grid on the substrate to maintain the poly-dispersed condition in the liquid, to develop IA for measuring the poly-dispersed particles in liquid. The dispersed condition of the particle on Nanoparticle chip can be kept from the condition in liquid when the particles are transferred to the substrate in air. Therefore, measuring the PSD on Nanoparticle chip is equal to measure the PSD in the liquid. In this paper, in order to verify the feasibility of the nanoparticle sizing using Nanoparticle chip to measure the PSD for poly-dispersed particles in the liquid, we performed a fundamental experiment to fabricate the Nanoparticle chip and to determine the PSD for poly-dispersed particles. In this report, it is reported that the PSD for the poly-dispersed particles, which is the mixture of 152nm particle and 498nm particle, using Nanoparticle chip.

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  • Sho SAKATAYA, Hayato YOSHIOKA, Shingo TAJIMA, Hidenori SHINNO
    Article ID: 20-00207
    Published: 2020
    [Advance publication] Released: October 06, 2020
    JOURNALS FREE ACCESS ADVANCE PUBLICATION

    The generation of burrs is unavoidable in most cases of mechanical machining. Leaving the burrs on the workpieces may cause various problems, thus the deburring process is necessary. Deburring process requires exclusive tools, and the tools are difficult to apply the workpieces with complicated shape. Laser machining is noncontact process thus it does not cause the deformation of workpiece and tool wear. Especially, fiber laser beam can be transmitted by flexible optical fibers so that it is easy to handle. The purpose of this study is to clarify the processing condition for achieving desired chamfering width with fiber laser. A series of experiments were performed by providing fiber laser beam to ferrous block’s right angle edge. In the experiments, the assist gas direction, the laser power, the processing speed, and the beam diameter were defined as processing parameters. Experimental results confirmed that defocused fiber laser beam can apply to chamfering ferrous materials. It also became clear that processing time can be shorten by processing fiber laser chamfering with higher laser power and higher scan speed. In addition, the results confirmed that the chamfering width is controlled by altering processing parameters as the input energy per unit time and unit volume are kept constant. Furthermore, the burrs on right angle edge can be removed by fiber laser, and the shape of deburred edge becomes rounded.

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  • Hideo TAKINO, Hiroki YAGAMI, Toshiju KUNIBE
    Article ID: 20-00217
    Published: 2020
    [Advance publication] Released: October 06, 2020
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    Ion beam etching is effectively used for the fabrication of high-precision optics. The main application of ion beam etching is to figure large optical surfaces to correct shape errors remaining on polished surfaces. To figure small or medium-size optical surfaces, the generation of an ion beam with a smaller diameter and a higher ion current is required. In this study, we designed a magnetic lens with quadrupole magnets using neodymium magnets to obtain an ion beam with a small diameter. The magnetic lens is installed between the outlet of an ion gun and a chamber, which enables the trajectory of the ion beam in the chamber to be changed. The trajectories of the ion beam and the ion particle distribution on a workpiece surface when a doublet or a triplet magnetic lens was used were simulated. Simulations were also conducted for ion beams with large and small emittances entering a magnetic lens. In the simulations, the ion beam without a magnetic lens was approximately 30 mm in diameter on a workpiece surface. The simulations showed that the doublet magnetic lens can converge the ion beam on a workpiece surface to an area of approximately 6 mm × 10 mm when the emittance is small. However, this lens is less capable of converging the ion beam in one direction when the emittance is large: the ion beam was converged to an area of approximately 6 mm × 27 mm on a workpiece surface for the large emittance. On the other hand, the triplet magnetic lens can converge the ion beam for both large and small emittances: the ion beams with large and small emittances converged to areas of approximately 4 mm × 4 mm and 10 mm × 5 mm, respectively.

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  • Takahito IGAWA, Aimi NAGASAWA, Hideo TAKINO, Shin UTSUNOMIYA
    Article ID: 20-00208
    Published: 2020
    [Advance publication] Released: October 01, 2020
    JOURNALS FREE ACCESS ADVANCE PUBLICATION

    To realize carbon fiber reinforced plastic (CFRP) mirrors, the high-precision polishing of an epoxy resin surface, which is the reflection surface of such mirrors, is required. To polish the surface with high quality, it is necessary to know the polishing characteristics of epoxy resin. However, unlike acrylic resin, there are few studies in which the polishing characteristics of epoxy resin were investigated. In this study, we polished test pieces of epoxy and acrylic resins in the same single batch under various conditions, and compared their removal rates. For this purpose, a new polishing technique that enables the simultaneous polishing of different materials under the same conditions was developed. We also evaluated the surface roughnesses for both resins before and after polishing. As a result, we found that the removal rate of epoxy resin was approximately 90% lower than that of acrylic resin under the polishing conditions using alumina abrasive grains and a suede pad. The roughness of the resulting epoxy surface was 4.76 nm RMS, which satisfies one specification of optics used in a space telescope.

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  • Kohei MAKINO, Makoto MIWA, Kohei SHINTANI, Atsuji ABE, Yutaka SASAKI
    Article ID: 20-00177
    Published: 2020
    [Advance publication] Released: September 30, 2020
    JOURNALS FREE ACCESS ADVANCE PUBLICATION

    Computer Aided Engineering (CAE) is indispensable for vehicle design to reduce the development cost; however, its computation time is a heavy burden when tuning design parameters. In this respect, several studies have been carried out for replacing CAE with machine learning-based surrogate models. In this paper, we propose a novel neural sequence network-based surrogate model for CAE using Recurrent Neural Networks (RNNs), which are neural networks that treat sequences such as temporal sequences. Our target task is the NCAP Fishhook test to evaluate vehicle dynamics of the rollover propensity. We propose a machine learning model with a sequential model to calculate the response of the NCAP Fishhook test from vehicle parameters such as tire and suspension characteristics. Our model reduced the error in approximately 10% for the NCAP Fishhook test dataset, which is generated with CAE, compared to that of the baseline neural network model with multi-layer perceptrons (MLPs). Furthermore, to improve performance and stability, our model has the following task-specific characteristics: (1) the skip connection, (2) the hybrid loss, and (3) the scheduled sampling. We confirmed that the skip connection reduced errors in the additional ablation study. Our experiments showed that the sequential model is effective as a surrogate model for CAE, and we also find that there is still room for the improvement regarding the dataset and the model because the accuracy is not saturated with the current dataset.

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  • Katsushi FURUTANI
    Article ID: 20-00197
    Published: 2020
    [Advance publication] Released: September 30, 2020
    JOURNALS FREE ACCESS ADVANCE PUBLICATION

    Electrochemical discharge machining (ECDM) is a machining method for inorganic insulators. When a tool electrode is fed at a constant rate, the removal rate is often decreased due to enlarging the gap length between the tool electrode and workpiece. In this paper, the effects of the applied voltage, which is a changeable condition during ECDM, and the initial gap length between the tool electrode and workpiece on the current waveforms and machining performance were experimentally investigated. Soda lime glass was machined with a tungsten electrode in NaCl solution. Plenty amount of bubbles were generated below an applied voltage of 45 V, and the removal amount was large. Though discharge strongly occurred over 50 V, the removal amount was small. With an increase of the applied voltage, lower frequency components of the current measured during ECDM were decreased. The initial gap did not affect the current waveforms. The mixture of long and short pulses accelerated removal at a low applied voltage. The phenomena around the tool electrode such as the bubble generation and discharge were distinguished by the principal component analysis (PCA). After a series of current pulses was divided into 12 periods, their statistical parameters were calculated, and the frequency components were calculated by the first Fourier transform. In both the cases, the applied voltage was distinguished by the PCA. The principal components obtained from the statistical parameter performed as essential parameters.

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  • Yuta INABA, Shuoxun LI, Atsushi YAMAGUCHI, Akira OKADA
    Article ID: 20-00205
    Published: 2020
    [Advance publication] Released: September 28, 2020
    JOURNALS FREE ACCESS ADVANCE PUBLICATION

    In current mechanical machining technology, it is not easy to form an internal space shape inside a metal workpiece through a small-diameter entrance hole only by removal process. On the other hand, EDM is one of thermal machining methods that removes the material by the high temperature of discharges, and the tool electrode does not contact to the workpiece. The machining force acting on the electrode is very small. Therefore, it is highly expected that internal space shape may be machined if an optimum electrode structure can be designed. This study proposes a new internal space machining method by EDM using a revolution ball electrode consisting of a vertical rotation rod, a tilting rod, and an electrode ball. Experimental results show that the tilting angle between the vertical rotation rod and the tilting one can be changed by the rotation speed, and the electrode ball position can be controlled. Then, machining of some axially-symmetric spacial shapes, such as cylindrical shape and spherical one into a zinc alloy workpiece was succeeded. In addition, machining of internal space shapes by simultaneous two-axis control of the tilting angle and Z coordinate of electrode was possible. Therefore, this method has high possibility to create axially symmetric spatial shapes inside the metal.

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  • Satoshi KITAYAMA, Sara HASHIMOTO, Masahiro TAKANO, Yusuke YAMAZAKI, Yo ...
    Article ID: 20-00161
    Published: 2020
    [Advance publication] Released: September 04, 2020
    JOURNALS FREE ACCESS ADVANCE PUBLICATION

    As weldline that is formed when two or more flow fronts meet has an influence on not only the appearance but also the strength of a plastic product, it is important to reduce it as much as possible. It has been reported that a high injection velocity is effective to the weldline reduction, but results in short shot. In addition to the weldline reduction, high productivity is always required in plastic injection molding. Thus, short cycle time is much preferable. For weldline reduction and short cycle time without short shot, this paper adopts variable injection velocity and variable packing pressure. Both profiles are unknown and it is difficult to determine them simultaneously. To determine both profiles, a bi-objective design optimization problem is constructed and the pareto-frontier between the weldline reduction and the cycle time is identified. Sequential approximate optimization using radial basis function network is used to identify the pareto-frontier with a small number of simulations. Based on the numerical result, the experiment is carried out to examine the validity of the proposed approach.

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  • Kotaro YOSHIDA, Hidefumi WAKAMATSU, Eiji MORINAGA, Takahiro KUBO
    Article ID: 20-00169
    Published: 2020
    [Advance publication] Released: September 03, 2020
    JOURNALS FREE ACCESS ADVANCE PUBLICATION

    A method to design a developable surface and its developed shape 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. Although it is important to design the surface in case that designers give some constraints, its design process is not automated because of the difficulty of its modeling. Especially, cloth products are required to design not only their three-dimensional shapes but also their developed shapes. Therefore, we aim to propose a method to design the surface satisfying some constraints and its developed shape. As an example, we assume that some constraints are related to the control points of a curve in a developable surface. In this paper, it is revealed that the direction of a generatrix can be determined geometrically when a pair of three-dimensional curves are given. Moreover, in order to obtain a steadier shape, not only this condition but also the potential energy of the surface should be considered. From the above, we formulate optimization problems, upon this design process, which have different objective functions: one is the condition of a developable surface and the other is its bending energy. We compared and examined bending energies and maximum principal curvatures obtained by two different optimization problems. In order to verify our proposed method, we performed an experiment and confirmed its validity.

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  • Hideki TAKEZAWA, Shogo TOYAMA
    Article ID: 20-00212
    Published: 2020
    [Advance publication] Released: September 03, 2020
    JOURNALS FREE ACCESS ADVANCE PUBLICATION

    It is difficult to machine permanent magnets by traditional machining because of brittle-material and magnetic force, but EDM can machine permanent magnets easily. However, because magnets have a Curie point, the reduction in the magnetic flux density may occur in EDM where the machined surface becomes high temperature. In previous studies, when 1 mm removal machining was performed for the cylindrical neodymium magnet, the magnetic flux density decreased in the region of several millimeters directly below the machined surface. When the magnet internal temperature was measured individually for several depths, the region where the magnetic flux density decreased was up to about the upper temperature limit. In this study, to improve the accuracy of temperature measurement, three points were measured simultaneously. In addition EDM was performed for the magnet with different initial magnetizing ratio before machining, and it was made efforts in EDM characteristic of the machining. As a result, in spite of the same discharge conditions, it was found that the magnet internal temperature during machining varies greatly due to the difference in initial magnetizing ratio. From the classification of the discharge state, it was found that these differences were affected by the reattachment of the debris to the magnet.

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  • Itsuki HATANO, Eiji MORINAGA, Hidefumi WAKAMATSU
    Article ID: 20-00160
    Published: 2020
    [Advance publication] Released: August 28, 2020
    JOURNALS FREE ACCESS ADVANCE PUBLICATION

    In recent years, with globalization in industry, there is a concern about increase of defects caused by using products in unexpected ways. To solve this problem, a method to predict such defects in the products in advance in the design stage has been proposed, in which behaviors of the products and physical phenomena are represented by Petri net. However, in order to achieve a more accurate prediction, it is necessary to consider topological information of components of the products. In this research, we aimed to represent topological information of elements of an electric circuit, and to make it possible to detect defects in cooperation with the method of the previous research. By modeling each element in an electrical circuit by Petri net and connecting them each other following the connection state of the circuit, it is possible to build a model that represents topological information of the circuit. And, two types of the model can check whether there is a closed circuit and which element the current flows through. In addition, by integrating them and the conventional model and reflecting the information in the circuit to the conventional model, more accurate defect detection can be performed. The effectiveness of the method was shown by case studies using simple circuit examples.

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  • Shun KOBAYASHI, Mitsunobu FUJITA, Takao MORI, Junji SUGIMOTO, Akihiro ...
    Article ID: 20-00163
    Published: 2020
    [Advance publication] Released: August 26, 2020
    JOURNALS FREE ACCESS ADVANCE PUBLICATION

    Automobile repair options include three types: new, rebuilt, and reused parts. Both rebuilt and reused parts are manufactured from used parts, so environmental impact and cost are lower than new parts. However, rebuilt parts need more manufacturing processes than reused parts for overhaul, so they need more environmental impact and cost than reused parts. Therefore, compared with new, rebuilt, and reused parts, product value is high in order new, rebuilt, and reused parts, but environmental and economic performance are high in inverse order. Hence, it is difficult for automobile users to evaluate which repair option is high adaptability for them over the entire lifecycle of an automobile. Besides, the adaptability may change depending on the difference of user’s intension. This paper proposes adaptability assessment method of automobile repair options in terms of product value, environmental impact, and cost. Product value of automobile parts is assessed by distributing product value of an automobile to each part. Environmental impact is calculated by life cycle assessment method. Cost is calculated by life cycle costing method. Proposed method is applied to the automobile engines as a case study and shows that users who emphasize environmental and economic performance have high adaptability to reused parts, and users who do not emphasize them have high adaptability to rebuilt parts. This paper discusses that automobile recycled parts have higher performance than new parts in terms of product value, environmental impact, and cost.

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  • Yusuke TSUTSUI, Nao YAMADA, Yuya MITAKE, Yoshiki SHIMOMURA
    Article ID: 20-00194
    Published: 2020
    [Advance publication] Released: August 06, 2020
    JOURNALS FREE ACCESS ADVANCE PUBLICATION

    The market circumstances around the manufacturing companies have changed due to several factors, including globalization, commoditization, and advanced innovation. This condition triggers the manufacturing companies to reconsider the competitive advantage of their value propositions and to promote their change not only their product but their closed business models. In regard to these circumstances, Open Business Model (OBM) is attracting attention as a new concept that replaces the closed business model which depends on the company’s own resources. OBM is a business model realized by sharing resources and collaborating with external partners. If the companies can transform their business model to OBM, they can receive several benefits such as long-term profits through providing new customer value, diversifying risks due to uncertainty in the market environment, and shortening the development period for products and services. Responding to this expectation to OBM, many researchers make a study related to this concept. However, existing research on OBM is limited to its advantages and comparison with similar concepts. Thus, it is difficult to design OBM in actual design activities. For this background, this study aims to support OBM design with high openness and proposes a design tool composed of the design templates and the procedure to use them. A proposed tool was applied to the OBM design workshop, and the application result confirmed usefulness and direction for improvement of this tool.

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  • Yoshinori NISHIO, Yang LIU, Nagato ONO, Masatoshi SHIMODA
    Article ID: 20-00046
    Published: 2020
    [Advance publication] Released: July 31, 2020
    JOURNALS FREE ACCESS ADVANCE PUBLICATION

    In this paper, a density-based topology optimization of a shear panel damper made of low yield steel has been carried out to improve the deformation ability. A minimization problem of maximum cumulative equivalent plastic strain (CEPSmax), which is an index of the deformation ability of the shear panel damper, is formulated subject to a constraint of volume. The optimization process consists of the following steps. Firstly, the finite element analysis with isotropic/kinematic hardening model is adopted to simulate the cyclic elasto-plastic behavior instead of experimental approach, and the numerical solutions are evaluated by comparing with previous experimental results. After that a density-based topology optimization is applied to obtain the optimal material layout, and investigate the relationship between the maximum CEPS and the total absorbing energy during the optimization process. With the topology optimization method, the objective function can be substantially decreased to improve the deformation capacity of the shear panel damper. The optimization results for each volume constraint value are also compared. Finally, based on the results of the topology optimization, a detailed shape is obtained by using the response surface methodology combined with the design of experiment technique.

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  • Jin-Xing SHI, Masatoshi SHIMODA, Shinobu SAKAI
    Article ID: 20-00128
    Published: 2020
    [Advance publication] Released: July 27, 2020
    JOURNALS FREE ACCESS ADVANCE PUBLICATION

    Because of its extremely high strength-to-weight ratio and specific elastic modulus, carbon fiber reinforced polymer (CFRP) has been widely employed in aerospace, automotive, sports equipment, civil engineering, and so on. Commonly, composite structures made of CFRP are manufactured as plates or shells, which are weak in noise and vibration due to their thin thickness and light weight. Hence, developing new design optimization methods for the enhancement of the vibration behavior of CFRP composite structures, especially in the lower frequencies, is very important and popular among scholars. In the present work, we aim to develop a free-form optimization system and apply it for optimizing the shapes of CFRP plate/shell structures considering the fiber orientation to maximize their fundamental frequencies under the volume constraint. This shape optimization system composed of vibrational eigenvalue analysis, derivation of shape gradient function, velocity analysis, and shape update, is implemented with a finite element method code and in-house program. We employ the method of Lagrange multiplier and the material derivative method to derive the shape gradient function considering the repeat eigenvalues, and adopt the H1 gradient method in the velocity analysis to achieve the “free-form” of CFRP shells. By considering different fiber orientations of CFRP plate/shell structures, we perform two simple numerical design examples using the developed free-form optimization system. The optimal results show that the smooth optimal shapes can be obtained, and the fundamental frequency of CFRP in each design example can be significantly enhanced from 1.73 to 4.60 times as much as its initial value after the free-form optimization.

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