Transactions of the JSME (in Japanese)
Online ISSN : 2187-9761
ISSN-L : 2187-9761
Volume 86, Issue 886
Displaying 1-21 of 21 articles from this issue
Solid Mechanics and Materials Engineering
  • Takumi NAKAMURA, Yuko ARAI, Tomohisa KOJIMA, Tomoaki TSUJI
    2020 Volume 86 Issue 886 Pages 19-00388
    Published: 2020
    Released on J-STAGE: June 25, 2020
    Advance online publication: June 02, 2020
    JOURNAL FREE ACCESS

    If we use wood as a structural material, we can reduce carbon dioxide emissions. In Japan, houses have been made by wood traditionally and wood is used as a structural material such as pillar and beam. In order to use wood as a structural material, a joint is necessary. The shapes of these traditional joints are determined empirically and used without any analytical evaluation such as stress analysis. Therefore, stress analysis is necessary in order to use such joints efficiently. In this study, we make stress analysis of the gooseneck joint, which is one of the typical joints in Japan. The strain distributions of the joint are measured, and the stress distributions are obtained by digital image correlation method (DIC). We also simulate the gooseneck joint subjected to tensile load by using FEM. A male part and a female part are contacted in the joint region. Comparing FEM results to DIC results, the validities of both results are confirmed. Moreover, we propose the formulae to obtain the joint stress concentration factor by using the FEM results. The optimum shape, which gives the least maximum stress under uniaxial loading, is obtained by using the proposed formulae.

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  • Michihiro KAWASHITA, Takayuki SHIMODAIRA, Takayuki OHNO, Akio HOSHI, K ...
    2020 Volume 86 Issue 886 Pages 19-00396
    Published: 2020
    Released on J-STAGE: June 25, 2020
    Advance online publication: May 26, 2020
    JOURNAL FREE ACCESS

    In the hydraulic excavator, the bellows exhaust pipe connects the engine and the exhaust gas post-processing device and is exposed to thumping vibration from the engine and the body. In order to ensure the reliability of the pipe under such harsh conditions, we developed a technology for evaluating the fatigue life of the bellows. First, in order to get the appropriate fatigue life curve of the bellows, the fatigue tests of bellows were conducted. In the fatigue tests, we judged that a fracture had occurred when a crack was detected in either the outer layer or the inner layer of the bellows. The cracks in the outer layer were detected by the change of strain measured with axial strain gauges installed on the outer layer, and the cracks in the inner layer were detected by the change of the internal pressure of the bellows. A fatigue life curve was derived from the fatigue test results by using the method of least squares. Next, the resonance endurance test (repeat cycles: 107) of the bellows exhaust pipe was carried out with the actual machine, and the derived fatigue life curve was verified using the endurance test results. In order to verify the fatigue life curve, the endurance test results were plotted on the stress limit diagram obtained from the derived fatigue life curve. In the stress limit diagram, failure and non-failure of the bellows were mixed at the boundary of the proposed curve. From this result, it became clear that the derived stress limit diagram can evaluate the fatigue life of bellows.

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  • Ken HIKASA, Takashi SUMIGAWA, Shuhei TANAKA, Ryota KANEKO, Takayuki KI ...
    2020 Volume 86 Issue 886 Pages 19-00398
    Published: 2020
    Released on J-STAGE: June 25, 2020
    Advance online publication: May 26, 2020
    JOURNAL FREE ACCESS

    The purpose of this project is to examine the notch sensitivity to the strength of a mechanical metamaterial comprising a periodic arrangement of snapping units. A unit cell of the metamaterial consists of two centrally connected wavy-shape segment (a snapping segment and a bearing segment). Since the unit cell possesses two stable deformation states in a certain load range, the nominal strain is rapidly increased by snap-through instabilities (snap-through deformation) when the applied load reaches a critical value. In the tensile experiment of specimens comprised of 30×30 unit cells under quasi-stick conditions, the cells on a certain row snap, and this results in a macroscopic load drop. As the applied deformation increases the snap-through deformation propagates to the adjacent cell. The cells snap through row-by-row with relatively small increases and decreases, until fracture occurs in the specimen. This process brings about a large macroscopic ductility of the metamaterial. Subsequently, a center-hole notch is introduced into the specimen and tensile experiments are performed. Although the snap-through deformation preferentially occurs at the notch root, it propagates to the other cells row-by-row without fracture because a stress concentration at the notch root is relaxed by the snapping. The snapping metamaterial possesses low defect susceptibility and high embrace as a structural material.

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  • Nao-Aki NODA, Xi LIU, Yoshikazu SANO, Kosuke TATEISHI, Biao WANG, Yuto ...
    2020 Volume 86 Issue 886 Pages 19-00413
    Published: 2020
    Released on J-STAGE: June 25, 2020
    Advance online publication: May 29, 2020
    JOURNAL FREE ACCESS

    In industrial fields, the bolt-nut connection is widely used and unitized as an important machine component. In the previous studies, a bolt-nut connection with slight pitch difference was considered towards realizing anti-loosening performance and high fatigue strength through axisymmetric finite element method (FEM) as well as experiment. Also by applying three-dimensional FEM, the nut screwing process was analyzed to obtain the prevailing torque Tp confirming anti-loosening performance. In this study, the tightening and untightening processes after the nut touched the clamped body are analyzed through 3D FEM as well as experiment. The FEM results are in good agreement with the experimental results. The clamping force and tightening torque relationship under the pitch difference is compared to the normal nut. Then, the behaviors of the pitch difference nut in tightening and untightening process is discussed by varying the pitch difference. For the normal nut, the equation of clamping force and tightening torque relation in the untightening process is clarified by FEM. Since the nut untightening property after the nut tightening is more important to prevent the nut self-loosening, the loosening resistance torque TRu is newly defined in this process. It is found that with increasing the pitch difference the loosening resistance torque TRu increases. The large loosening resistance torque TRu suggests that the pitch difference nuts have good anti-loosening performance.

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  • Kazuma SHIMIZU, Hiroto SHOJI, Taichiro KATO, Hiroyasu TANIGAWA, Mitsur ...
    2020 Volume 86 Issue 886 Pages 19-00438
    Published: 2020
    Released on J-STAGE: June 25, 2020
    Advance online publication: May 26, 2020
    JOURNAL FREE ACCESS

    Weibull stress criterion based on the “Local Approach” is applied for rational brittle fracture assessment of steel components taking account of the plastic constraint effect on fracture resistance. Once the cumulative distribution of critical Weibull stress is identified for the material itself, that is Weibull shape parameter m as a material constant independent of size/shape of components, loading mode and temperature, fracture toughness can be corrected to the fracture resistance of structural components on the basis of the Weibull stress criterion. On the other hand, a miniature fracture toughness specimen is useful for evaluating the toughness of local area of the component and limited material such as irradiated test sample. Then, this study focuses on developing a method for identification of shape parameter m of critical Weibull stress distribution using miniature specimens. Two types of miniature 3PB (3-point bend) specimen with thickness B=1.65mm that has different crack depth are used to identify the m-value. The m-value determined from the two types of miniature specimen is found to be almost the same as that obtained from normal size specimens with thickness B=15mm, whereas both testing are conducted at different temperature. It is demonstrated that the fracture toughness of the steel at the other temperature can be precisely corrected to the fracture resistance of the cracked component with lower crack-tip plastic constraint by means of the m-value identified from test results for two types of miniature specimen.

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  • Kiyohiro ITO, Toshikazu MURAMATSU, Masayuki ARAI
    2020 Volume 86 Issue 886 Pages 20-00060
    Published: 2020
    Released on J-STAGE: June 25, 2020
    Advance online publication: June 04, 2020
    JOURNAL FREE ACCESS

    Johnson-Cook (JC) flow stress model is widely used in computer aided engineering (CAE) for simulations of car crash and machining behaviors. The JC parameter C, which is a material constant in the model associated with strain rate dependency, is usually identified by a split-Hopkinson bar method. However, a huge equipment is required for this method to achieve an appropriate test condition. Therefore, the JC parameter C is expected to be estimated by a simpler method. In this study, an estimation method of the JC parameter C based on a high-velocity impingement test with a solid sphere, which is called EJCC, was developed. The fundamental equation in the EJCC was theoretically derived based on the energy conservation during impingement process, which was previously reported by our research group. Using the EJCC, the JC parameter C can be easily estimated with a depth of indentation obtained by the impingement test and the other JC parameters identified by a quasi-static tensile test. The quasi-static tensile test, the high-velocity impingement test and a high-speed tensile test were conducted to identify the JC parameters A, B, n and estimate the JC parameter C on three ductile metallic materials. As a result, the JC parameter C estimated by the EJCC was in good agreement with that obtained by the high-speed tensile test irrespective of materials and impingement velocities. Consequently, it was demonstrated that the EJCC can appropriately estimate the JC parameter C on ductile metallic materials.

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  • Shingo TAMAGAWA, Saki SHIMIZU, Teruhisa MIHARA, Yuya OIKAWA
    2020 Volume 86 Issue 886 Pages 20-00065
    Published: 2020
    Released on J-STAGE: June 25, 2020
    Advance online publication: June 02, 2020
    JOURNAL FREE ACCESS

    This study aims to develop the switch and crossing for a single line operation at the double track section. First, the authors design and produce the simplified structure of the switch and crossing for passenger trains which can be installed without the cutting of the existing rails. Secondly, we test the fatigue durability of the front end of the structure by rolling fatigue test device. As a result, the sufficient durability is verified under the condition that the design use period is one month and the total annual axle loads are 1.0×108 kN. Thirdly, we perform the running test of the motor car on the product installed at the test track and confirm that the motor car can pass over the structure at the maximum speed 15 km/h. Fourthly, we perform the vehicle running simulation based on FEM and confirm the running safety of the structure from the point of view of the stress generated at the components, the derailment coefficient and the decrease ratio of wheel loads. Finally, we test the fatigue durability of the specimen and conclude that the welding part of the turn rail and bed plates, the spring for turning rails and rail fastenings have a practically sufficient durability.

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Thermal, Engine and Power Engineering
  • Yukiko FURUHASHI, Takashi TAKIGUCHI, Shuichi OHMORI
    2020 Volume 86 Issue 886 Pages 19-00357
    Published: 2020
    Released on J-STAGE: June 25, 2020
    Advance online publication: May 19, 2020
    JOURNAL FREE ACCESS

    When severe accident occurs in nuclear power plant, radioactive iodine would be emitted from reactor pressurized vessel to primary containment vessel (PCV). The emitted iodine is basically trapped into the suppression pool water in ionized condition. However, it is assumed that the gaseous iodine might be re-volatilized from the water in suppression pool chamber by the irradiation effect. The iodine volatilizing behavior is said to be affected by irradiation and pH control of the pool water. In this study, volatilizing behavior of inorganic/organic iodine with pH control under gamma-ray irradiation is evaluated, based on simulated actual plant environments. It is confirmed that the pH control to alkaline environment is effective to the inhibition of re-volatilization of inorganic/organic iodine. It is also confirmed that the emission behavior of organic iodine gas is mainly due to the reaction between the epoxy paint of gaseous phase in PCV inner wall and volatilized inorganic iodine gas with irradiation effect. Under non-irradiation, emission of inorganic iodine was extremely low, and almost no emission was detected in the inorganic iodine. Moreover, it is assumed that the existence of inorganic iodine and hydrocarbon radical compound emitted from epoxy paint component leads to the emission of organic iodine.

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  • Takeshi YASUNAGA, Yasuyuki IKEGAMI
    2020 Volume 86 Issue 886 Pages 19-00383
    Published: 2020
    Released on J-STAGE: June 25, 2020
    Advance online publication: May 19, 2020
    JOURNAL FREE ACCESS

    Ocean thermal energy conversion (OTEC) is a system to convert the thermal energy stored as the vertical temperature gradient in the ocean into the electricity. The authors have proposed a theoretical thermodynamic model using a reversible heat engine to calculate the available thermal energy, exergy, normalized thermal efficiency and exergy efficiency in OTEC based on finite-time thermodynamics. In an OTEC system, the available power will be a balance of the performance of component, such as heat exchangers, turbine/generator, pumps and a working fluid. Thus, the performance of each component has a significant effect on net power production as the efficiency of heat engines driven by low temperature difference is theoretically low. This research develops the conventional OTEC theoretical model, and to calculate the theoretical net power of OTEC considering irreversibility in the heat engine, heat exchange process and fluid flow of heat sources using a coefficient of irreversibility in the heat engine and the effectiveness of heat transfer to apply optimum operation or design optima. The theoretical performance calculated by the model compared with the 30 kW OTEC experimental results in two cases of configurations with different types of plate heat exchangers and units. Consequently, the performance of the thermodynamic model and the experimental results show good agreement using the experimental heat exchanger performance and the irreversibility of heat engine in the thermodynamic model, therefore, the results verified the effectiveness of the novel model.

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Dynamics & Control, Robotics & Mechatronics
  • Tomohiro WATANABE, Kojiro IIZUKA
    2020 Volume 86 Issue 886 Pages 19-00263
    Published: 2020
    Released on J-STAGE: June 25, 2020
    Advance online publication: June 04, 2020
    JOURNAL FREE ACCESS

    Purpose of our research is to improve the movement performance of small leg typed rovers using effects caused by vibration propagation. When the loose ground is given vibration, there are two effects. One is to increase density of the loose ground, and the other is to increase sinkage of legs. If the density of the ground is increased by vibration/stop, the rovers are not easy to slip. This means that the shearing strength becomes large since the loose ground is given effect of vibration/stop. Moreover, when the sinkage of legs are increased, the supporting force becomes large. The difference of ground before and after vibrating are confirmed by implemented some experiments such as measurement of shearing strength, sinkage and earth pressure. As results, the value of shearing strength and sinkage of leg were increased after vibration. Also, the value of earth pressure was increased after vibration. Furthermore, these effects given by vibration/stop are confirmed using multi-legged rover. In experimental results, walking distance of proposed rovers with vibration was longer than one without vibration. From theses experimental results, we could get knowledge that the method using vibration/stop was very effective for the leg typed rovers.

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  • Eiji SUZUKI
    2020 Volume 86 Issue 886 Pages 19-00345
    Published: 2020
    Released on J-STAGE: June 25, 2020
    Advance online publication: May 19, 2020
    JOURNAL FREE ACCESS

    There are the conveying machines utilizing vibration which can transport the various parts of engineering products in succession. When the body to be carried has the axisymmetric shape like an ellipsoid, it does not need to vibrate the conveying machine, and the ellipsoidal body itself can roll down the stationary tilted track automatically. But it will continue to accelerate in speed and we cannot avoid the bump due to the over-speed at the goal. The author designed to prevent the over-speed rolling motion of this ellipsoidal body by setting the vertical walls on the both sides of the slope through the slight collision there. This way leads to simplify the complicated vibrating mechanism and further to decrease the consumption of power and the emission of noise & vibration. The most important subject for realizing this simple conveying system is whether rolling and colliding motions of the body are sustained spontaneously or not. The purpose of this research is to clarify the behavior of the self-excited motion which this ellipsoidal body continues to roll down the tilted slope through the repetitious collision with the walls. The author analyzed this motion of the body as three dimensional descending movement of the rigid body without a fixed point. From this analysis, he could confirm the continuous rolling and colliding motions which were also observed in the experiments.

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  • Kenta MORI, Takumi INOUE, Ren KADOWAKI
    2020 Volume 86 Issue 886 Pages 19-00381
    Published: 2020
    Released on J-STAGE: June 25, 2020
    Advance online publication: May 15, 2020
    JOURNAL FREE ACCESS

    Heat sealing is a packaging technique by means of welding of seal materials with heating and compression, and is widely used for hermetic seal of foods and medical supplies. However, a defect of the heat sealing, for example a “pinhole”, caused by small wrinkle on the sealing film or jamming by contaminants occasionally arises. In order to enhance the reliability of heat seal products, this study proposes a nondestructive technique to detect such a small defect in the heat seal by utilizing coincidence effect of airborne ultrasound. In the proposed method, a bending wave with sufficient amplitude is excited by the coincidence effect, and this bending wave appears as a traveling wave on the heat seal. This traveling wave is sensitive to the defect in heat seal and shows apparent phase lags compared with defectless heat seal. Therefore, defect in the heat seal is detectable by observation of the phase lags in the traveling wave. Arrangement of ultrasound transmitter and receiver is important for the proposed technique in order to observe the phase lags efficiently. Traveling wave plays an important role to detect the defect in heat seal, so that the airborne ultrasound inspection without the coincidence effect is unavailable because the traveling wave is not generated. Validity of the proposed technique is demonstrated through experiments and numerical simulations.

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  • Yasutomo KANEKO, Kazushi MORI, Tatsuya FURUKAWA
    2020 Volume 86 Issue 886 Pages 19-00404
    Published: 2020
    Released on J-STAGE: June 25, 2020
    Advance online publication: May 15, 2020
    JOURNAL FREE ACCESS

    To develop turbomachinery blades with high reliability, it is indispensable to verify the natural frequency, the damping, the resonant stress, etc. under operating condition, and utilize these data in the mechanical design of a new blade. BTT (Blade Tip Timing) and the telemetry system have been widely used to measure the modal parameters of turbomachinery blades. In measurement of the modal parameters of blades in rotation, it is well known that the mistuning phenomena make the identification of modal parameters difficult. Namely, because, in a mistuned bladed disk, responses of many vibration modes are superimposed, it becomes difficult to correctly identify the natural frequency and the damping of each vibration mode. This is one of the critical issues to be overcome for developing blades with high reliability. Recently LSCF(Least-Squares Complex Frequency-Domain)method has been proposed as an effective method for identifying the modal parameters from complicated frequency responses. This method was also applied to derive the modal parameters of a bladed disk from the frequency responses expressed by travelling wave coordinates. In this paper, the validity of the LSCF method is verified by numerical simulations, where the modal parameters of mistuned bladed disks are identified from the frequency responses consisting of many vibration modes. In addition, the accuracy of the conventional half power method used in identifying the blade damping is researched.

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  • Taichi MATSUOKA, Nagato AIZAWA
    2020 Volume 86 Issue 886 Pages 19-00405
    Published: 2020
    Released on J-STAGE: June 25, 2020
    Advance online publication: May 19, 2020
    JOURNAL FREE ACCESS

    Vibration suppression devices, such as a semiactive damper, are common use for vibration reduction. In general, many of them have a controllable flexibility, damping and friction. The authors have developed variable inertia damper by using Magneto-Rheological (MR) fluid with a long by-pass pipe in previous study. In this study a new type vibration suppression device, which is having variable moment of inertia by using the MR fluid, is developed. The MR fluid is filled into the flywheel, and magnetic field is applied to the flywheel by electromagnets. The moment of inertia of the flywheel is depended on own weight and a radius of gyration. If the radius of gyration is changed because ferrite particles of the MR fluid are clustered when magnetic field is applied, the vibration suppression device can have a variable moment of inertia effect. In order to confirm the effect, a prototype vibration suppression device was manufactured, and resisting force characteristics of the device were investigated. To confirm validity of the vibration reduction, vibration tests of one degree-of-freedom system with the vibration suppression device were carried out by a shaking table. From the experimental results, the peaks of response acceleration and displacement decrease about 1/2 in case with the vibration suppression device, and also cut 5 % by the inertia effect under earthquakes. Finally, feasibility study and the effect of variable moment of inertia for vibration suppression were confirmed.

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Design, Machine Element & Tribology, Information & Intelligent Technology, Manufacturing, and Systems
  • Ikuo TANABE, Sayaka OHTA, Satoshi TAKAHASHI
    2020 Volume 86 Issue 886 Pages 19-00389
    Published: 2020
    Released on J-STAGE: June 25, 2020
    Advance online publication: June 08, 2020
    JOURNAL FREE ACCESS

    In the 21st century, as it is important to produce products with care for protecting the earth, a producer must carefully give attention on the energy conservation issue, save resources and reduce waste which pollutes environment. On the other hand, in case of a machine tool, much quantity of oil and electrical energy was used for smooth drive, high accuracy and long tool life. This is large problem for protecting the earth. Therefore, in this research, the cutting fluid with lower coefficient of friction focused on the controlling of cutting heat was developed and evaluated. The lubrication technology using polymer and small grains mixed in the strong alkaline water was firstly investigated for lower coefficient of friction. Then optimum condition for the proposed cutting fluid was investigated and decided in the several experiments. Evaluations for the cutting property through a CNC lathe machine performance and the environmental impact for the cutting fluid with lower coefficient of friction by using simple LCA was lastly analyzed. It is concluded from the results that; (1) The lubricant of the proposed cutting fluid which mixed the strong alkaline water with polymer and small graphite grains has coefficient of friction 0.13, (2) Accuracy of the machine tool was very good and the tool life was very long in spite of wet cutting, (3) The cutting fluid was excellently eco-friendly.

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  • Hidenori MURATA, Hideki KOBAYASHI
    2020 Volume 86 Issue 886 Pages 19-00390
    Published: 2020
    Released on J-STAGE: June 25, 2020
    Advance online publication: June 08, 2020
    JOURNAL FREE ACCESS

    Ensuring sustainable consumption and production patterns is one of the United Nation’s sustainable development goals (SDGs) for 2030. To achieve this, it is necessary for product development to consider not only reducing the environmental burden from a product life cycle but also satisfying human needs. The authors have proposed locally-oriented sustainable product design, which aims to improve the sufficiency of human needs and reduce the environmental impact by reflecting the regionally specific conditions in product development. For this purpose, a systematic approach for connecting fundamental human needs and the product development process, called the living-sphere approach, has been proposed. This approach uses a framework of fundamental human needs proposed by Max-Neef. The point of this approach is that product structures are connected to satisfiers. This study aims to propose a modeling method from a product to satisfiers in a living-sphere. In this study, we focus on reverse engineering and laddering method. By combining these bottom-up methods, we propose a modeling method from product structures to satisfiers. In a case study, we selected Japan as a target region and a rice cooker as an example. The result shows a possibility of this method for an evaluation of sufficiency, on the other hand, also shows the necessity of improvement of extracting regional requirements.

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  • Ikuo TANABE, Takehiro SUZUKI, Satoshi TAKAHASHI
    2020 Volume 86 Issue 886 Pages 20-00001
    Published: 2020
    Released on J-STAGE: June 25, 2020
    Advance online publication: May 26, 2020
    JOURNAL FREE ACCESS

    Recently many products with high quality, high dignity, high confidence, multipurpose and originality in innovation technology were developed. Now everyone still desires the higher properties for several products. Therefore, in this research, the material optimization technology for small structures was developed and evaluated. The some small structures were desired for miniaturizing, weight saving and energy saving in the products. The concept of “material optimization” is a new and general idea. This material is the composite type. The material optimization technology regarding Young’s modulus, density, coefficient of linear expansion, specific heat and thermal conductivity was spread in this research. The calculation models for the properties were firstly cleared. The manufacturing method for small structures with the desired properties was also developed. Then the small structure with the material optimization were calculated through a newly developed program and were made by the new manufacturing method. The small structure with the material optimization was manufactured and evaluated. It is concluded from the results that the technology was very effective and useful for development of a new composite material with several hybrid properties.

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  • Kunitoshi KAWANO, Daisuke IBA, Koichiro URIU, Hidekatsu NODA, Hiroki I ...
    2020 Volume 86 Issue 886 Pages 20-00026
    Published: 2020
    Released on J-STAGE: June 25, 2020
    Advance online publication: May 15, 2020
    JOURNAL FREE ACCESS

    In a hobbing process, many factors bring pitch, profile, and helix deviations to hobbed gears, and it is generally difficult to identify which factors cause the deviations. Therefore, a system that allows causal factors to be determined is required especially in the after-sales service of the hobbing machine manufactures. In the present study, a hobbing-machine-diagnosis system is being developed. Artificial intelligence will be employed in the system to easily determine the cause of deviations that occur in hobbed gears. The development of the system requires a lot of learning data for artificial intelligence. The data should be obtained in various conditions. However, collecting data from real cutting is almost impossible because of cost and time, so that hobbing simulation was carried out. The hobbing simulation has already been developed by many researchers. But those simulations are not enough for manufacturers of hobbing machines to evaluate problems in the machines. In addition, the conventional tooth profile/helix deviations diagrams are not appropriate for images used in artificial-intelligence systems, because they include redundant data. In the present paper, therefore, a network graph representing the correlation between every two teeth were discussed to examine whether the graph can be used as data for artificial-intelligence systems. As a result, an image of the network graph could be suitable for the system and could enable its data size to be reduced.

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  • Yohei TANNO
    2020 Volume 86 Issue 886 Pages 20-00036
    Published: 2020
    Released on J-STAGE: June 25, 2020
    Advance online publication: June 08, 2020
    JOURNAL FREE ACCESS

    In this paper, a new method for estimating the axial tension of each bolt after the hydraulic tightening, and an appropriate structure for the hydraulic tightening have been proposed. A hydraulic tensioner is frequently used to tighten the pressure vessels by the bolted joints. The hydraulic tensioner can apply higher value and lower variation of the axial tension than the torque tightening. However, the axial tension remaining in the bolt after the hydraulic tightening is less than the initial tension by the hydraulic load, and the ratio of the residual tension to the initial tension, the effective tensile coefficient, is the most critical factor to tighten the pressure vessel securely. Some estimation methods of the ratio considering the stiffness of tightening parts have been proposed. However, there are no previous studies that verified the theory, the characteristics and the appropriate structure for the hydraulic tightening using various bolts, such as a stud bolt, a through bolt and a two-nuts bolt. In this study, we developed some new equations for estimating the effective tensile coefficient of each bolt by considering the compliance at each part of the bolted joint. Then the analysis method of the hydraulic tightening for each bolt was developed by using a finite element model simulated the joint process with the hydraulic tensioner. In addition, we evaluated the effective tensile coefficient of each bolt by the analysis and considered improvement measures of that. As a result, it was clarified that the analysis method and the equations could estimate accurately the effective tensile coefficient and the coefficient of the two-nuts bolt was the highest of the three bolt types. It was confirmed that the coefficient could be improved by locating the foot close to the bolt and reducing the diameter of the bolt-hole.

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Bio, Medical, Sports and Human Engineering
  • Masahiro YONEDA, Kanji FUKUDA, Mitsuhiko IKEBUCHI, Yu INOUE, Michimasa ...
    2020 Volume 86 Issue 886 Pages 20-00080
    Published: 2020
    Released on J-STAGE: June 25, 2020
    Advance online publication: May 20, 2020
    JOURNAL FREE ACCESS

    The purpose of this study is to investigate the gait improvement for lame patients based on the gait quality index estimated by the spectral analysis results of trunk acceleration. The gait quality index (GQI) is defined as the power spectrum ratio of the total value up to 10 Hz to that of the fw component in the vertical direction where fw is the pace frequency. The hemiplegic patients, patients after total hip arthroplasty, patients with femoral fractures, patient with anterior cruciate ligament injury and Parkinson's disease patients were selected in this study. Dynamic load factor (DLF) corresponding to the vertical walking force is also calculated using power spectrum density for time history trunk signals measured by the accelerometers. When the correlation between DLF and GQI was plotted, it was found that the gait quality index GQI was clearly improved (numerically reduced) for all lame patients as the increase of DLF due to the improvement of the gait. Based on these results, it was confirmed that the value of GQI in the vertical direction was the useful index in order to evaluate the gait improvement for all lame patients.

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Environmental and Process Engineering, Safety
  • Yosuke UEKI, Hiroaki AMAKAWA, Ippei NUMATA, Atsuki SANDO, Makoto NAKAS ...
    2020 Volume 86 Issue 886 Pages 20-00042
    Published: 2020
    Released on J-STAGE: June 25, 2020
    Advance online publication: May 18, 2020
    JOURNAL FREE ACCESS

    A variety of health assessment technologies for mechanical systems utilizing time-series sensor data has been developed and are recently being applied to the maintenance work as a solution to the predictive maintenance. A majority of these technologies are the condition-based way which premises the existence of condition monitoring sensors such as accelerometers for the vibration monitoring of rotating mechanical elements. In the present study, authors suggested a load history-based methodology for identifying a descriptive and stochastic model of the useful life of mechanical systems to realize the predictive maintenance under constraints of sensing conditions. The methodology (Damage-based survival analysis, DbSA) was based on a parametric survival analysis by the maximum likelihood estimation assuming the Weibull distribution of the useful life. A random variable of the probability distribution was converted from the elapsed time to cumulative value of a function of time-series sensor data and parameters of this function were optimized to minimize the dispersion of the probability distribution by the particle swarm optimization. DbSA was applied to a historical record of a clogging problem in a strainer in a chemical plant and its time-series process data to demonstrate the usefulness. An identified damage-based lifetime model exhibited less than 50% smaller dispersion (coefficient of variance) compared to the timed-based probability distribution. In addition, an identified function composed of the process data implied an effect of the impurity generation to the clogging problem. If the identified model was applied to a dataset which was not used to the model identification, it was indicated that 3 of 8 cloggings were occurred when the damage-based failure probability was more than 50% although the time-based probability did not reach to this level at any time.

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