Mechanical Engineering Journal
Online ISSN : 2187-9745
ISSN-L : 2187-9745
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Recent Advances in Materials and Processing 2018
  • Hironori TOHMYOH
    2019 Volume 6 Issue 3 Pages 19preface1
    Published: 2019
    Released: June 15, 2019
    JOURNALS FREE ACCESS
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  • Yoshinao KISHIMOTO, Yukiyoshi KOBAYASHI, Toshihisa OHTSUKA, Akira MATS ...
    2019 Volume 6 Issue 3 Pages 18-00471
    Published: 2019
    Released: June 15, 2019
    [Advance publication] Released: February 08, 2019
    JOURNALS FREE ACCESS

    Multi-material structure is expected to be the main scheme to construct automobiles. Many methods have been studied to properly fix or bond dissimilar materials. The fixing by the bolts and nuts is one of the primary fixing methods, and has the advantage of easy assembly and disassembly. The interfacial stiffness of the bolted joints is lower than the stiffness of the base materials and varied by the clamping force of the bolts and nuts, because the micro asperities formed on the interfaces just contact each other. The contact analysis by using the surface profile of the interfaces in microscale is one of the accurate estimations. However, the estimation method of the interfacial stiffness in macroscale is also necessary for the in-situ evaluation. This study has developed an estimation method of the interfacial stiffness by the inverse analysis of the clamping force and the natural frequency of the structure. The inverse analysis algorithm introduces the mathematical model of the interfaces in which the contact of the surfaces is assumed to be the contact of the elastic asperities whose peak heights obey the Gaussian distribution. The hammering test was conducted by using the specimen which consisted of the steel plate and the aluminum alloy plate joined by the bolts and nuts. Moreover, as the contact analysis, the finite element method simulated the contact of the asperities formed on the interfaces by using the surface profile of the interfaces. The results showed that the proposed method could estimate the interfacial stiffness which reproduced the natural frequency of the specimen subjected to the clamping force of the bolts and nuts. The interfacial stiffness estimated by the proposed method was comparable to that calculated by the contact analysis.

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  • Hironori TOHMYOH, Kanta YAMAGUCHI
    2019 Volume 6 Issue 3 Pages 18-00509
    Published: 2019
    Released: June 15, 2019
    [Advance publication] Released: February 12, 2019
    JOURNALS FREE ACCESS

    This paper treats the Joule heat welding of thin Pt wires having various diameters. Joining of fine-scale materials, such as micro- or nanowires, has been essential to create advanced materials systems. Joule heat welding is one of the suitable way for this purpose. It has been reported that thin wires were welded together under the supply of constant direct current, and the welding condition was sensitive to the thermal boundary conditions around the wires under the current supply, which was affected by the heat transfer from the wire surface to the ambient and the heat conduction at the ends for the current supply. The diameters of thin Pt wires were 0.8-20 μm, and the current required to cut the wire by Joule heating was investigated. The temperature of the wire having the smaller diameter was easily increased by Joule heating, and this became remarkable with increasing the slenderness ratio, i.e., the ratio of the diameter to the length for current supply. An index related to the temperature of the wire under the current supply was introduced to describe the thermal boundary conditions around the wire. The behavior of the index against the diameter was approximated by the exponential functions, and the thermal boundary conditions around the wires having various diameters became predictable. Finally, the validity of the thermal boundary conditions determined and predicted in this study was verified by conducting the experiments to cut and weld the wires by Joule heating.

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  • Ryo MATSUMOTO, Takuma KAGECHIKA, Hiroshi UTSUNOMIYA
    2019 Volume 6 Issue 3 Pages 18-00523
    Published: 2019
    Released: June 15, 2019
    [Advance publication] Released: February 21, 2019
    JOURNALS FREE ACCESS

    Influence of stepwise ram motion, one of practical ram motion controls of servo press, on shape and dimensional accuracies of forged billet was investigated in cold cup forging process by the finite element analysis. In the process with stepwise ram motion, the billet inserted in the container was forged by the punch with upper ram of press, and the punch was operated with repetition of advance and pause modes. Following four stages were analyzed; (i) forging, (ii) removal of the punch from the forged billet, (iii) ejection of the forged billet from the container by the knockout punch and (iv) air cooling of the forged billet. In the analysis, the shape and dimensional changes of the inner wall of the billet during the four stages were investigated with several stepwise ram motions under the same forging duration. It is found that repetition of the punch advance with short stroke reduces heterogeneity of the temperature and stress distributions, so that the shape and dimensional accuracies of the inner wall of the forged billet were improved. The results of the finite element analysis were confirmed to be qualitatively agreed with the results of forging experiment on a link-type servo press.

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  • Tatsuya KIMURA, Hinako OZAKI, Michimasa UDA, Yoshio HASEGAWA, Akiko KO ...
    2019 Volume 6 Issue 3 Pages 18-00543
    Published: 2019
    Released: June 15, 2019
    [Advance publication] Released: March 04, 2019
    JOURNALS FREE ACCESS

    Research and development of SiC/SiC composite materials as structural members of aerospace engines is progressing. In order to manufacture SiC/SiC composites with excellent high-temperature characteristics, the SiC fibers which have high mechanical properties at high temperature are necessary; thus, further development of SiC fibers is considered a critical issue. In addition, the development of low-cost SiC fibers is necessary for the practical application of SiC/SiC composites. Here, the low-cost SiC fibers can be fabricated by dry spinning method. In the dry-spinning method, the raw material, Polycarbosilane (PCS) is dissolved in an organic solvent and the solution is spun at room temperature. As high-molecular-weight Polycarbosilane is prepared in advance, the infusible process conventionally required in the melt-spinning method is not required. In this study, to evaluate the differences among dry-spun SiC fibers fabricated under various conditions, monofilament tensile tests were conducted. Examination of the fracture surface and elemental analysis of arbitrary cross-sections were then performed to investigate the effects of the fabrication conditions. The tensile strength results indicated that defects were suppressed by excluding low-molecular-weight components and that heat treatment between 1300°C and 1500°C resulted in the maximum strength. Weibull analysis revealed that the dry-spun fibers exhibited lower tensile strength but smaller variation of fiber strength than that of the melt-spun fiber because the dry-spun fibers were more homogeneous. However, evaluation of the crystallinity indicated that the interference pattern derived from the crystal was unclear in the dry-spun fibers but clear in the melt-spun fiber. Therefore, it was suggested that the dry-spun fibers exhibited lower crystallinity than the melt-spun fiber. In addition, the dry-spun and melt-spun fibers exhibited similar C/Si ratios, whereas a large amount of oxygen was detected on the surface of the dry-spun fiber relative to that on the surface of the melt-spun fiber. Further improvement of the mechanical properties is expected upon increasing the molecular weight of the raw material and improving the microstructure.

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  • Ippei TANAKA, Takumi NISHIMIYA, Gaku OHGITA, Yasunori HARADA
    2019 Volume 6 Issue 3 Pages 18-00547
    Published: 2019
    Released: June 15, 2019
    [Advance publication] Released: February 26, 2019
    JOURNALS FREE ACCESS

    Carbon nitride has noteworthy properties including high hardness levels. If the c-C3N4 or β-C3N4 structure can be synthesized, then hardness levels higher than that of diamond can be obtained. It is important to clarify the effect of ion impact on the growth of crystalline carbon nitrides on the synthesis of super-hard carbon nitrides. The ion beam-assisted deposition (IBAD) technique provides independent control over parameters, such as ion energy, temperature, and arrival rate of the atomic species during deposition. In this study, we investigated the structure and composition of a carbon nitride film prepared using graphitic carbon nitride as the evaporation source for the IBAD. The graphitic carbon nitride was formed into a pellet by press molding. The film deposited without nitrogen ion beam was obtained by evaporation using the pellet molded at 200 °C and 300 °C as the evaporation source. An amorphous carbon nitride film was obtained by IBAD using g-C3N4 as the evaporation source. The main chemical bonding in the carbon nitride film changed from C-N=C to C-C by varying the acceleration voltage of the nitrogen ion beam. Accordingly, the hardness of the film was increased. The hardness of the film at an acceleration voltage of 500 V was 23 GPa. This is due to the breaking of the CN bond by the ion beam, depending on the acceleration voltage of the ion beam.

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  • Chandrasekaran GURUNATHAN, Rajappa GNANAMOORTHY
    2019 Volume 6 Issue 3 Pages 18-00548
    Published: 2019
    Released: June 15, 2019
    [Advance publication] Released: March 07, 2019
    JOURNALS FREE ACCESS

    Wear is the major mode of failure in machine components made out of polymer and its composites. The low thermal conductivity of the polymer causes heat accumulation near the contact surface and the resulting thermal softening accelerates the wear. In this research work, an attempt is made to enhance the thermal conductivity and wear resistance of the polymer composite using the network reinforcement. Two different composite specimens were prepared with an equal quantity of reinforcement with different geometric form - one with discrete particles and another with the interconnected network. The thermal conductivity and tribological properties of the composites were measured. In particle reinforced composite, the presence of low thermal conductive matrix between the discrete particles act as a barrier for heat conduction and does not enhance the thermal conductivity considerably. In the case of network reinforced composite, the three-dimensional continuity provides an effective heat transfer path and increases the thermal conductivity significantly. The reinforcement in the form of network reduces the wear significantly compared to discrete particle form. The struts in the network reinforcements enhance the strength and arrest the removal of material from the surface.

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  • Keisuke NAGATO, Nana TAKAHASHI, Yuki YAJIMA, Eisuke SHIMIZU, Masayuki ...
    2019 Volume 6 Issue 3 Pages 18-00553
    Published: 2019
    Released: June 15, 2019
    [Advance publication] Released: May 27, 2019
    JOURNALS FREE ACCESS

    Laser-assisted thermal imprinting (LATI) is a promising high-throughput direct replication method for micro- or nanostructured films. In LATI, only the surface of the mold is heated by laser irradiation and the surface of the polymer is heated by heat transfer; subsequently, the polymer surface lowers its viscosity and fills into the micro- or nanostructures of the mold. After the laser irradiation, the imprinted polymer surface is cooled by heat conduction to the inside of the film and mold immediately after the micro- or nanostructures are replicated. Therefore, not only a short cycle time but also low energy consumption in the imprinting process can be realized. However, the mechanism of heat conduction and polymer flow in the microstructured mold in LATI has not been clarified. In this study, we performed model experiments and simulations of heat conduction to determine the approximate time schedule of heat conduction in the polymer and the flow of the polymer. In the model experiments, we found that the replication speed of scanning irradiation was much higher than that of spot irradiation in spite of the same power density. It was found that the partial contact was decreased in scanning irradiation and the polymer flow easily occurred. This is because the surface profiles were different depending on the filling method. In spot irradiation, the surface exhibited a concave shape owing to the surface tension between the polymer and mold surface; meanwhile, in scanning irradiation, the surface exhibited a convex shape owing to pushing pressure.

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  • Kazuki HORIKIRI, Tetsuro YANASEKO, Isao KUBOKI, Hiroshi SATO, Hiroshi ...
    2019 Volume 6 Issue 3 Pages 18-00556
    Published: 2019
    Released: June 15, 2019
    [Advance publication] Released: February 25, 2019
    JOURNALS FREE ACCESS

    This paper describes the fabrication of a metal matrix piezoelectric composite using surface-oxidized nickel fiber as the internal electrode. Piezoelectric ceramics, which have excellent piezoelectric properties, are widely used as energy conversion materials. However, their application is limited by their brittleness. To solve this problem, a metal-core piezoelectric ceramic fiber/aluminum composite has been developed by using the interphase forming/bonding method. Here, a piezoelectric ceramic is reinforced by embedding it in an aluminum matrix, and this process causes the piezoelectric ceramic to have better mechanical properties than a bulk ceramic. However, this composite has some serious disadvantages considering that it cannot be designed to possess arbitrary piezoelectric properties because the metal-core piezoelectric fiber is formed by the extrusion method, so that the sectional shape cannot be arbitrarily changed. In this paper, a metal matrix piezoelectric composite using a surface-oxidized nickel fiber as the internal electrode is proposed. This composite provides design flexibility in that its piezoelectric property can be changed by varying the size and materials of the composite. The fabrication procedure of this composite consists of three steps: oxidation of the internal electrode, molding and sintering of the piezoelectric ceramic, and embedding of the piezoelectric ceramic into the metal matrix. The proposed composite is fabricated under optimized oxidizing and molding conditions. An impact test is performed on the fabricated composite, and the output voltage is measured. The test results indicate that the composite is capable of generating piezoelectricity. Overall, the study results substantiate the validity of the concept and fabricating method of the proposed composite.

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  • Syunsuke MURAOKA, Reiichi TOKUMOTO, Yuki NAKAYAMA, Takashi TOMINAGA, M ...
    2019 Volume 6 Issue 3 Pages 18-00561
    Published: 2019
    Released: June 15, 2019
    [Advance publication] Released: March 19, 2019
    JOURNALS FREE ACCESS

    This study investigates the effects of interface edge configuration on the stress distribution near the edge of a ceramics/metal joint system interface using numerical thermal elastoplastic analysis. Finite element bonded dissimilar models were employed, which consisted of an elastic material to represent the ceramics and an elastoplastic material in the case of the metal. In this finite element method (FEM) study, it was assumed that silicon nitride and nickel were bonded at high temperatures and cooled slowly. The thermal elastoplastic behavior on the free surface of the ceramic side near the edge of the interface was determined numerically. The dependence of thermal elastoplastic behavior on geometrical interfacial configuration was also clarified numerically using FEM models with various interface edge configurations. Results of the numerical analysis were compared with the dependence of practical tensile bonding strength on the interface edge angle of a silicon nitride/nickel joints system bonded at 780°C, with the same interface shape as that of the analytical model. The practical tensile bonding strength was improved by setting the optimum interface shape. The optimum interface shape was obtained by determining the effects of the interface wedge angle on practical tensile bonding strength. Results of thermal elastoplastic analysis for the FEM model and fracture patterns suggest that an appropriate interface shape can reduce thermal residual stress near the interface edges on the ceramic side.

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  • Muniandy NAGENTRAU, Abdul Latif MOHD TOBI, Saifulnizan JAMIAN, Yuichi ...
    2019 Volume 6 Issue 3 Pages 18-00562
    Published: 2019
    Released: June 15, 2019
    [Advance publication] Released: April 24, 2019
    JOURNALS FREE ACCESS

    The rapid age growth in most of the developed countries leads to application of artificial joints such as knee joints and hip joints. The properties of titanium alloy such as light weight, high strength and good biocompatibility make it a suitable material for wide usage as artificial joints. However, titanium alloy cannot directly adhered with human bone; thus, bonds or coating are required. Plasma-sprayed hydroxyapatite (HAp) is widely used as a coating to bond artificial Ti-6Al-4V implants with human bone. The contact slip mainly occurs at the HAp-Ti-6Al-4V interface which also known as possible delamination interface in hip joint artificial implant. The coating fretting fatigue delamination condition can lead to contact slip at HAp coating-Ti-6Al-4V interface which will accelerate HAp coating fretting wear behavior. This paper presents the influence of normal loading, fatigue loading and delamination length on contact slip distributions at HAp coating-Ti-6Al-4V interface through finite element based methodology. A simple FE contact configuration model consist of contact pad, HAp coating and Ti-6Al-4V substrate is examined under static simulation. The predicted results revealed that lower normal load with higher maximum fatigue loading condition could promote more contact slip distribution. The contact slip is also increased with increasing delamination length. The induced contact slip can accelerates fretting wear behavior of HAp coating.

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  • Reiichi TOKUMOTO, Syunsuke MURAOKA, Takashi TOMINAGA, Masayoshi TATENO
    2019 Volume 6 Issue 3 Pages 18-00566
    Published: 2019
    Released: June 15, 2019
    [Advance publication] Released: April 05, 2019
    JOURNALS FREE ACCESS

    The focus of this study is to clarify the effects of an interface-edge shape on the bonding strength of a ceramics/metal joint. Each silicon nitride-to-nickel joint plate with an arc-shaped free-surface edge was prepared using wire-electric discharge machining after a bonding process. The interface-edge shape was characterized by defining an interface-edge angle as the configuration angle between the interface plane and tangential line at the arc edge of the bonded interface. The dependence of the bonding strength on the interface-edge angle was experimentally verified in the silicon nitride-to-nickel joint with an arc-shaped free surface of the interface edges. The result shows that enlarging or reducing the edge angle from a right angle improved the bonding strength because it reduced the residual stress near the interface edges in the ceramic side. Setting a suitable interface-edge condition using a secondary-bonding process produced the highest strength in a ceramics/metal-joint system. The free surface of the interface edges removed by the secondary-machining process was very smooth. Secondary machining can improve the surface integrity and redistribute the stress concentration because of the removal of the gap at the interface edges. This study demonstrates that secondary machining can be effective for improving the bonding strength.

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  • M.J. Mohammad FIKRY, Shinji OGIHARA, Vladimir Vinogradov
    2019 Volume 6 Issue 3 Pages 19-00003
    Published: 2019
    Released: June 15, 2019
    [Advance publication] Released: March 07, 2019
    JOURNALS FREE ACCESS

    Digital Image Correlation (DIC) is a non-contact method to analyse the deformation of materials that can measure displacement or strain behaviour during tensile loading. In this study, DIC is used to measure the deformation of cross-ply carbon fibre reinforced plastics (CFRP) laminates and for the detection of damages in them. The objective of this study is to measure the deformation around the damages in cross-ply CFRP laminates by using the DIC system from both width and thickness directions. For this purpose, thick CFRP [04/9024]s and thinner [0/906]s laminates were tested. In cross-ply laminates, usually a straight transverse crack will initially occur in 90 degree ply followed by the following damages such as delamination, fiber fracture, and etc. To start, straight transverse cracks are induced in the laminates by using an artificial crack method. Then, X-ray radiography is used to detect the location of the straight cracks in order to be used for DIC observation to examine the strain distribution around the existed cracks. The DIC observation from the surface of the laminate around the cracks area clearly showed how strain is distributed from one crack to another adjacent crack. From the result, secondary mode damages of matrix cracking such as oblique and curved cracks can also be observed and are being discussed in this paper.

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  • Keiichi SHIRASU, Itaru TAMAKI, Go YAMAMOTO, Toshiyuki HASHIDA
    2019 Volume 6 Issue 3 Pages 19-00012
    Published: 2019
    Released: June 15, 2019
    [Advance publication] Released: February 01, 2019
    JOURNALS FREE ACCESS

    Aligned MWCNT/epoxy composites made with the three types of the multi-walled carbon nanotubes (MWCNTs) with different thermal annealing temperature have been prepared, and the tensile tests and thermal expansion tests of the composites in the MWCNT alignment direction were conducted to evaluate the effects of crystallinity of MWCNTs on the mechanical and thermal expansion properties of aligned MWCNT reinforced epoxy composites. Additionally, the coefficients of thermal expansion (CTEs) of the MWCNTs in the axial direction were computed by using the Young's modulus of the MWCNTs and the CTE of the composites in Turner's model. The annealing temperatures of the MWCNTs were 2400°C and 2900°C. It was shown that the thermal annealing of MWCNTs was effective for improving the crystallinity of the MWCNTs, while it had no major effects on both tensile strength and Young's modulus of the composites. This is mainly because the thermally annealed MWCNTs themselves possessed almost comparable nominal tensile strength (~4-5 GPa) and Young's modulus (~200 GPa) compared with the as-grown MWCNTs. On the other hand, we demonstrated by thermal expansion testing that the thermal contraction of the composites in the nanotube alignment direction was observed by the addition of MWCNTs. All the MWCNTs possessed negative CTEs and the CTEs tend to become more negative with increasing annealing temperature. This is probably because of a decrease in the number of small defects (vacancies and Stone-Wales defects) and intershell cross-linking defects associated with sp3 carbons, and an increase in the sp2 carbons owing to the high-temperature thermal annealing.

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  • Go YAMAMOTO, Tomonaga OKABE
    2019 Volume 6 Issue 3 Pages 19-00020
    Published: 2019
    Released: June 15, 2019
    [Advance publication] Released: April 24, 2019
    JOURNALS FREE ACCESS

    The accurate tensile strength prediction of unidirectional carbon fiber-reinforced plastic composites (UD composites) requires approximate determination of the stress concentration on surviving fibers around a fiber break point. Here the stress concentrated on the intact fiber surface was determined by implementing double-fiber fragmentation tests in combination with a spring element model (SEM) simulation. The double-fiber fragmentation composites and the UD composites were elaborated with a T1100G-type carbon fiber and epoxy material, and tested to validate the proposed prediction method. The size scaling results, implementing a bimodal Weibull distribution for the statistical distribution of fiber strength, coupled with the results of the SEM simulation, designed to take into account the surface stress concentration, were reasonably consistent with the experimental data on the tensile strengths of the UD composites. Then, the proposed strength prediction procedure was applied to investigate the effects of the bimodal Weibull scale and shape parameters on the tensile strength of the UD composites. It was revealed that the degree of stress concentrated on the surface of fibers can be changed by modifying the bimodal Weibull shape and scale parameters. However, the carbon fiber with an improved scale parameters of 20% displayed enhancement to the composite strength by factor of ~1.07, and with an improved shape parameters of 20% showed enhancement by factor of ~1.04, indicating that the degree of enhancement in the tensile strength of the UD composite was limited.

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  • Putita KATESRIPONGSA, Tatiya TRONGSATITKUL
    2019 Volume 6 Issue 3 Pages 19-00038
    Published: 2019
    Released: June 15, 2019
    [Advance publication] Released: April 23, 2019
    JOURNALS FREE ACCESS

    This work focused on a fabrication of smart membranes using a novel grafting method comprising of plasma peroxide technique together with microwave-assisted polymerization. PNIPAm, thermo-responsive polymer, both with and without crosslinker, were grafted onto porous Nylon-6 membranes. Key parameters for grafting including the microwave irradiation time, output power, and monomer concentration have been investigated. Characterizations using scanning electron microscope (SEM) and Fourier-transform infrared spectroscopy (FTIR) revealed that the PNIPAm have been successfully grafted onto the surface both on the top surface of the membrane and the surface inside the pores. Irradiation time of 10 min under 800 w were found to be an optimum condition which gave the highest yield of 10 wt%. For both the linear and crosslinked PNIPAm-grafted membranes, the highest grafting yield was obtained from using 3 wt% of NIPAm monomer solution. Because of this fast fabrication time and environmentally friendly method, new smart gating membranes can be produced which will help providing an ever-better performances transport control of gas and liquid for various fields including medical and packaging applications.

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  • Kouta WAKUI, Naoto OHTAKE
    2019 Volume 6 Issue 3 Pages 19-00046
    Published: 2019
    Released: June 15, 2019
    [Advance publication] Released: March 26, 2019
    JOURNALS FREE ACCESS

    In order to realize light weight structure with multi-materials, this research applied ultrasonic joining method for dissimilar joining. As the joining members, aluminum alloy and CFRTP, CFRP using thermoplastic as base resin are selected because of their specific strength. By using ultrasonic joining system which generates maximum stress amplitude on joining plane, this stress fluctuation by ultrasonic application promote plastic flow in aluminum alloy. As a result, the plastic flow at interface remove resin of the CFRTP matrix, and the exposed carbon fibers are embedded in the Al alloy. Those mechanical interlocking at the interface enabled this dissimilar joining. Focusing on those effects caused by ultrasonic, we examined conditions that show high joining strength. By preparing specimens under various conditions, discuss relationship between joining conditions and joining strength by a series of cross tensile strength test. Moreover, the series of experiments with changing ultrasonic application time revealed that this joining method has the most suitable processing time, 0.8 s, and excess processing decrease its joining strength. Finally mechanism of this joining method has been discussed with the results of joining interface observation. And it was confirmed that carbon fibers embedded into Al alloy by plastic deformation form mechanical interlocking between carbon fiber and Al alloy.

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Solid Mechanics and Materials Engineering
  • Yoshinao KISHIMOTO, Yukiyoshi KOBAYASHI, Toshihisa OHTSUKA, Motoi NIIZ ...
    2019 Volume 6 Issue 3 Pages 18-00123
    Published: 2019
    Released: June 15, 2019
    [Advance publication] Released: May 14, 2019
    JOURNALS FREE ACCESS

    The surface texture formed by the micro asperities on the surface of the solid members induces the stiffness reduction of the structure constructed by screws and bolts. In recent years, the fixing by screws and bolts is one of the primary fixing methods to construct multi-material structures, and the fixing state such as the interfacial stiffness at the clamped part is required to be evaluated for the proper fixing. The interfacial stiffness affects the total stiffness of the structure and is dominated by the surface texture and the clamping force. Especially, the standard deviation of the asperity peak heights and the homogenized elastic modulus collectively named as the surface texture parameters mainly determine the interfacial stiffness. This study has developed an estimation method of the surface texture parameters by the inverse analysis of the hammering test data, and numerically investigated the basic behavior and the estimation error of the inverse analysis for the establishment of the methodology to find the limitation of the proposed method against the disturbance in the hammering test data. In the investigation, a theoretical limitation of the inverse analysis has been derived by the linear approximation, and a numerical simulation which is the same approach as the Monte Carlo simulation has been performed by using a bolted joint model consisting of two plates joined by the eight sets of the bolt and nut. From the results of the numerical simulation, the followings were summarized: 1) The recalculation error of the natural frequency subjected to the clamping force is as large as the disturbance in the hammering test data. 2) The sensitivity of the homogenized elastic modulus is much smaller than that of the standard deviation of the asperity peak heights in the inverse analysis. 3) The theoretical limitation of the linear approximation can qualitatively predict the estimation errors of the surface texture parameters.

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  • Hung Anh LY, Hirotsugu INOUE
    2019 Volume 6 Issue 3 Pages 18-00451
    Published: 2019
    Released: June 15, 2019
    [Advance publication] Released: April 12, 2019
    JOURNALS FREE ACCESS

    The rapid evaluation technique of fatigue limit using infrared thermography has been developed during the past 30 years. In this technique, the fatigue limit is evaluated on the basis of the temperature evolution associated with cyclic loading. However, this technique is still not reliable enough because the temperature evolution has not been verified quantitatively very well. In previous studies, the authors conducted numerical analysis to simulate the temperature evolution. The results of fatigue limit evaluation were compared fairy well with experimental ones. However, the temperature evolution was significantly larger compared to experimental results due to adiabatic assumption. In this paper, heat conduction within the specimen is taken into account in order to conduct more realistic simulation of temperature evolution. The results are compared quantitatively to those obtained in experiment. The fatigue limit obtained from simulation is compared with those determined by Wöhler method and thermography experiment.

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Thermal, Engine and Power Engineering
  • Jun YOSHIDA, Eito MATSUO, Yasuyuki TAKATA, Masanori MONDE
    2019 Volume 6 Issue 3 Pages 18-00388
    Published: 2019
    Released: June 15, 2019
    [Advance publication] Released: April 15, 2019
    JOURNALS FREE ACCESS

    This paper introduces a new hydrogen refueling system with a micro-scale hydrogen turbo-expander that enables us to replace a conventional low temperature refrigerator. From the process simulation of hydrogen refueling to the tank of a typical Fuel Cell Vehicle (FCV), the system is thermodynamically verified to be capable of refueling 5 kg-H2 within 3 minutes by the direct expansion in the micro-scale hydrogen turbo-expander. For the realization of this new concept, a process design approach of a high pressure hydrogen refueling system with the micro-scale hydrogen turbo-expander is described. In this process design, a turbine-compressor type is adopted to the micro-scale hydrogen turbo-expander unit, and an extracted power from the turbine side is consumed as a compressor power which is equipped on the opposite side of the turbine rotor. As a consequence of the thermodynamic analysis and simulation for the proposed system including the turbo-expander with adiabatic efficiency around65 %, it reveals that the new system provides some significant advantages compared with the conventional process. From a feasible investigation of this system, several advantageous features such as 1) high energy conservation, 2) compactness, 3) initial cost and operation cost, and, 4) system expandability (modification for shorter time refueling) are also described when it is compared with the existing system.

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Dynamics & Control, Robotics & Mechatronics
  • Hiroyuki FUJIWARA, Kazutoshi YANAGIHARA, Osami MATSUSHITA, Osamu TOKUD ...
    2019 Volume 6 Issue 3 Pages 18-00481
    Published: 2019
    Released: June 15, 2019
    [Advance publication] Released: May 01, 2019
    JOURNALS FREE ACCESS

    These days, centrifugal compressors and other industrial turbomachines tend to be faster, downsized, and reduced in cost. If a technology can be established for operation of machines over higher critical speed using an active magnetic bearing, the number of impellers per casing can be increased, allowing downsizing and cost reduction of trains. In this study, experimental equipment of a flexible rotor supported by active magnetic bearings was developed to carry out experiments as a step toward developing the technology. The following results were obtained, (1) Mass distribution in designing flexible rotors allows adjustment of the critical speed by design. (2) With the modal balancing method under higher critical speed, the sixth critical speed was passed through, the world's first achievement of this.

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Computational Mechanics
  • Yoshinori SHIIHARA, Shoki TANAKA, Nobuhiro YOSHIKAWA
    2019 Volume 6 Issue 3 Pages 18-00363
    Published: 2019
    Released: June 15, 2019
    [Advance publication] Released: April 10, 2019
    JOURNALS FREE ACCESS

    The peridynamics is a particle methods considered superior to the finite element method in describing fracture phenomena since fracture can be simply expressed as bond breaking between the peridynamics particles. The Non-Ordinary State-Based (NOSB) peridynamics is a variant of the particle method which allows us to implement constitutive laws as in the finite element method. To maintain its computational accuracy, parameters used in the peridynamic simulations needs to be optimized through parameter searches, hence the peridynamics requires a fast quasi-implicit algorithm which allows to directly compare the results to the one obtained by the finite element method. The FIRE algorithm is such an algorithm well examined through molecular dynamics studies and is easy to implement existing explicit algorithms. The objective of this study is to describe the details of the implementation of the FIRE method to the peridynamic elastic and elasto-plastic computational codes and the effectiveness through the comparison with another quasi-static algorithm, the energy based relaxation method. The computational results show the effectiveness of the algorithm and some examples of the parameter search in simple problems such as elastic and elasto-plastic deformation analyses and a stress analysis near a crack.

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Transportation and Logistics
  • Kei KITAHARA, Keisuke KAZAMA, Hiroshi MOURI
    2019 Volume 6 Issue 3 Pages 18-00386
    Published: 2019
    Released: June 15, 2019
    [Advance publication] Released: May 15, 2019
    JOURNALS FREE ACCESS

    This study aims to develop a new steering system that can help increase the ease of driving and reduce the driver's mental workload during low-speed driving. First, the problems associated with low-speed driving were investigated. It was found that the act of changing the steering grip is one of the major factors that increase the workload. Therefore, it a new steering system, which eliminates the need of changing the steering grip, should be developed. A preliminary lab experiment was conducted to determine the specifications for the new steering system. Resultantly, it was found that hassle-free low-speed driving can be performed by changing the directions of the driver's arm motions and form of the steering grip, which are the characteristics of a conventional steering system. Therefore, we decided the bar type steering as a proposal system which changed them. A driving simulator experiment was conducted to compare the differences between conventional steering system and the proposed steering system. It was also found that the proposed steering system has a lower driver gain and higher time constant in comparison with a conventional steering system. The proposed steering system enables a hassle-free driving experience, even with a low steering ratio. Finally, an experiment with test subject drivers in a real car was conducted to evaluate the compatibility between the proposed steering system and real car. Furthermore, it was found that the proposed steering system was easy to drive with, even for drivers with no previous driving experience.

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  • Takuma ITO, Satoshi NAKAMURA, Kyoichi TOHRIYAMA, Minoru KAMATA
    2019 Volume 6 Issue 3 Pages 18-00558
    Published: 2019
    Released: June 15, 2019
    [Advance publication] Released: May 31, 2019
    JOURNALS FREE ACCESS

    In this study, we aim to develop a new upgrading method of digital map content for automated driving on nationwide public roads. In general, a dense waypoint map based on a digital map is necessary to realize precise motion controls of intelligent automobiles. However, current preparation methods for digital maps have two problems for practical use on public roads in wide areas: the size of the map data for onboard storage and the monetary and human resources for manual mapping processes. To solve these problems, in our previous study, we proposed a new digital map called “LeanMAP,” which consists of elementary information about the road, and also proposed an upgrading method of its contents from the level of car navigation map to the level of quasi-precise map. Furthermore, in this study, we propose another upgrading method based on a virtual trajectory to reduce the number of resources necessary for the mapping process to as low as possible. First, we propose a lateral transcription method that generates a virtual trajectory of an adjacent lane. Although three or more driving data items are necessary in order to upgrade the LeanMAP contents in the previous method, the proposed method in this study requires only one item of driving data. Then, to evaluate the accuracy of the dense waypoint map based on the elemental information upgraded by the proposed method, we conduct an initial evaluation using actual driving data on a public road. As a result, we confirm that the proposed system satisfies the target value of less than 1 % lateral error. From this result, we confirm the feasibility that our proposed system can reduce the cost and manual operations of mapping a precise digital map.

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