Mechanical Engineering Journal
Online ISSN : 2187-9745
ISSN-L : 2187-9745
Advance online publication
Displaying 1-31 of 31 articles from this issue
  • Satoshi KOBAYASHI, Kotono YANAGISAWA, Toshiko OSADA, Tetsuya MORIMOTO
    Article ID: 23-00203
    Published: 2023
    Advance online publication: June 02, 2023
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION

    In this study, we aim to investigate the effect of galvanic corrosion on the mechanical properties of aluminum-CFRP adhesive joints. Aluminum-CFRP, aluminum-aluminum, and CFRP-CFRP adhesive joint specimens were prepared. Subsequently, the specimens were subjected to accelerated aging treatment in a salt spray environment, and the tensile shear adhesive strength, the transition of the failure surface and the deposition state and the components of corrosion products with aging time were quantitatively evaluated. As a result, in aluminum-CFRP adhesive joints under the salt spray, galvanic corrosion of the aluminum substrate occurred within 24 hours, and the adhesive-adherend interfacial strength decreased significantly compared to aluminum-aluminum and CFRP-CFRP adhesive joints. In addition, the failure mode of aluminum-CFRP adhesive joints changed from the mixed failure of interfacial failure, cohesive failure, and fiber tear failure to interfacial failure. Furthermore, it was found that the deposition amount of Al2O3 increased under the influence of the salt spray environment.

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  • Yucheng LI, Chiaki KOGA, Yuki HIRATA, Hiroki AKASAKA, Hiroyasu KANETAK ...
    Article ID: 23-00088
    Published: 2023
    Advance online publication: May 30, 2023
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    Diamond-like carbon (DLC) films had been formed as a surface treatment for intracorporal device for decreasing the coefficient of friction. DLC film showed significant stability without being damaged during acid immersion and high-pressure steam sterilization. However, bacteria that adhere to medical devices lead to the induction of infectious diseases associated with therapeutic actions. Therefore, maintenance of a hygienic surface condition has been strictly required. This study demonstrated the fabrication of DLC films (gas source: CH4), which incorporated Cu (Cu-DLC). The Cu-DLC films were synthesized on a Si (100) substrate via plasma-enhanced chemical vapor deposition and magnetron sputtering. The surface morphology, microstructure, element contents, wear resistance, hardness, and antibacterial properties of the films were experimentally analyzed. Cu particles were considered not uniformly distributed in the DLC film, they embedded in DLC films formed a three-dimensional structure led to higher roughness. The Cu-DLC exhibited wear resistance and higher hardness compared to Cu. After inoculation, Cu-DLC films showed higher antibacterial activity against E. coli than pure DLC. It is expected that the hygienic films with excellent mechanical properties demonstrated in the present study will be utilized in various medical and industrial sectors.

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  • Masayuki ISHIHARA, Yuto NAKADA, Yoshitaka KAMEO
    Article ID: 23-00096
    Published: 2023
    Advance online publication: May 30, 2023
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    For safe and sound utilization of the applications made of polylactic acid that output an electric signal to an intended mechanical input within an undesirable thermal environment, the transient thermoelectroelastic field is investigated for an infinite cylinder with D symmetry subjected to shear stress as an intended mechanical input and temperature as an unfavorable thermal environment. By use of the analytical technique constructed previously, the field quantities are represented in terms of the elastic, piezoelastic, and thermoelastic displacement potential functions and the electric potential function, and the governing equations for these functions are presented. Then, the analytical solutions of the transient and non-axisymmetric field quantities are obtained using the Fourier and Laplace transformations with respect to the axial coordinate and time variable, respectively, and the Fourier expansion with respect to the circumferential coordinate. Subsequently, numerical calculations are performed to investigate the field due to the shear stress or temperature. As a result, the structures of respective fields are elucidated and the effect of thermal disturbance on the output signal to mechanical input is investigated quantitatively, both of which illustrate the significance of transient and three-dimensional analysis.

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  • Shun YOSHINO, Kazuhisa ABE, Kazuhiro KORO
    Article ID: 22-00300
    Published: 2023
    Advance online publication: May 28, 2023
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION

    This paper presents a frequency-domain analytic solution of mathematical expectation for bogie-track dynamic interaction problems in which a random roughness on the railhead is considered. To achieve this, the Floquet transformation is applied to the coupling system consisting of a bogie and an infinite track. Due to the periodicity of the sleeper spacing, the present problem is reduced to that in a representative track unit. Transformed solutions are expressed by Fourier series in the unit cell. The unknown Fourier coefficients are then obtained from infinite simultaneous equations. In the present formulation the vibration reaction due to the roughness is described in terms of the response function of the bogie-track coupling system and the power spectrum density (PSD) of rail roughness. The track dynamic nature which is independent of the roughness is represented by the former. To validate the derived solution, comparison with time-domain numerical solution is carried out. Furthermore, based on the developed frequency-domain method, two kind of pad damping model given by a constant loss factor and viscous damping are compared through evaluation of the expected value of energy spectrum density (ESD) of rail vibration and the PSD of wheel acceleration. Finally, influence of track structure such as the dynamic equivalent stiffness of rail pad and that of under-sleeper pad on the expectation of ESD of rail vibration and the PSD of wheel acceleration is examined.

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  • Tetsuta MATSUMURA, Toshikazu FUJINO, Tatsuhiro JIBIKI, Katsumi IWAMOTO ...
    Article ID: 23-00047
    Published: 2023
    Advance online publication: May 28, 2023
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION

    The purpose of the present study is to clarify the effect of surface texturing on lubrication characteristics of a sliding surface under reciprocating motion and to develop design guidelines for surface texturing in order to obtain lower friction. To achieve this purpose, the lubrication characteristics of a sliding surface with dimple-shaped texturing during reciprocating motion are numerically analyzed by solving the Reynolds equation. The effects of texturing are compared with those of no texturing under various operating conditions as determined from the sliding speed, viscosity coefficient of the lubricant, and surface pressure, and the placement and dimensions of the texturing that result in lower friction are evaluated. The results show that in the oil film pressure distribution generated by the slider without texturing, friction loss is reduced by applying texturing at the location where the maximum value of this oil film pressure occurs. In this case, under the conditions analyzed in the present paper, the texturing reduces friction loss by 5 to 7%.

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  • Shozo KAWAMURA, Sara ITO, Masami MATSUBARA, Daiki TAJIRI
    Article ID: 23-00091
    Published: 2023
    Advance online publication: May 28, 2023
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION

    In this study, we proposed a structural health monitoring and diagnostic method for layered structures using the force identification of approach. This method belongs to the primary diagnosis one, and its purpose is to identify the location of abnormality quickly after abnormality detection. A feature of this method is that the displacement change caused by an abnormality in the structure is considered by applying additional force to the normal structure. In the early stage of abnormality, the stiffness of a certain layer will change, so the local additional force is identified, and the accuracy of the reconstructed displacement change is estimated. In the diagnosis of an actual structure, the actual vibration characteristics may differ from those obtained by the mathematical model. We also proposed a method for predicting the frequency response function in the abnormal state based on the difference between the actual measurement and the mathematical model in the normal state. First, we considered a five-layered structure as a numerical example and validated the proposed method. When we applied the method to three types of abnormal conditions, we found that the abnormality could be diagnosed correctly. Next, we constructed an experimental model of a five-layered structure and verified the applicability of the proposed method. We created a type of abnormal condition and showed that the abnormality could be diagnosed correctly. As described above, the validity and applicability of the proposed method were clarified.

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  • Haoran GENG, Masafumi MIYATAKE, Qingyuan WANG, Pengfei SUN, Bo JIN
    Article ID: 22-00360
    Published: 2023
    Advance online publication: May 23, 2023
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION

    The timetable of urban rail greatly affects its daily energy consumption. To improve the utilization of renewable energy between trains using timetabling has become an effective way to reduce energy consumption. Previous studies ignore or simplify the modelling of traction power supply network, which failed to accurately describe the flow of energy between trains through the power network. This paper proposed an optimisation method of energy efficiency timetabling considering the power flow of traction power supply network. First, an urban rail transit DC traction network model is established, and the current-vector iterative method is used to characterize the energy consumption. Then, a train timetable optimisation model is proposed to minimize the total energy consumption of the traction network system by adjusting the dwell time and section running time. The genetic algorithm is used to solve the optimisation problem. Finally, simulation result shows that the proposed method can accurately characterize the energy flow and effectively reduce the total energy consumption of the urban rail transit.

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  • Dejie SUN, Shijie ZHU, Kazuhiro OHYAMA, Muneaki KURIMOTO
    Article ID: 23-00077
    Published: 2023
    Advance online publication: May 23, 2023
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION

    Dielectric elastomer generator (DEG) could harvest electrical energy from cyclic deformation by changing the capacitance of dielectric elastomer (DE). Due to its advantages of light weight and high energy density, DEG has great development potential in the utilization of renewable mechanical energy. A key bottleneck restricting the development of DEG is the charge leakage phenomenon, which can reduce the DEG energy density. In this work, the effect of the charge leakage phenomenon on DEG energy density was investigated based on experiments and theoretical simulations. The results showed that with the increase of bias voltage and transverse pre-stretching ratio, the DEG energy density of quadrangular and triangular harvesting cycle first increased and then decreased, and the maximum experimental energy densities of the DEG with transversely restrained configuration were 120 mJ/g and 187 mJ/g, respectively. In addition, a simulation method for calculating the DEG energy density based on charge leakage model was proposed to quantitatively analyze the influence of charge leakage on DEG energy density. The simulation results showed that the energy density of the quadrangular harvesting cycle could be significantly improved by decreasing the charge leakage of the DE film.

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  • Byunghyun CHOI, Akemi NISHIDA, Tadahiko SHIOMI, Manabu KAWATA, Yinshen ...
    Article ID: 23-00026
    Published: 2023
    Advance online publication: May 19, 2023
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION

    The basemat uplift is a phenomenon that the bottom of the basemat of a building partially rises from the ground due to overturning moments and vertical motions during earthquake. The degree of the basemat uplift can be indicated using a ground contact ratio which is defined as a ratio of the contact area of the bottom of the basemat to its entire area. The problem is that, at a large earthquake, the basemat uplift becomes large, so-called low ground contact ratio state, and the basemat falls resultant to recontact between the basemat and the ground, and large acceleration response occur on the floor of the building. It is a crucial aspect in the seismic evaluation of a nuclear facility building. It affects not only structural integrity of the building but also the response of the equipment installed in the building. However, the building behavior under the low ground contact ratio state lacks sufficient study. In this study, we conducted seismic response analyses for the building using a three-dimensional finite element model and simulated shaking table experiments focused on the basemat uplift and confirmed the validity of this analysis method. Since the basemat uplift is a strong non-linear phenomenon, we conducted computer simulations under the same analysis conditions with three different analysis codes, namely E-FrontISTR, FINAS/STAR, and TDAPIII, and compared the results. We investigated the influence on the structural response caused by the difference of the adhesive force of the basemat and the bearing ground at the low ground contact ratio state. In addition, we studied the influence of numerical parameters to the structural response through sensitivity analyses. This paper reports the analysis results and the insights obtained from our investigations.

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  • Suguru ISHIDA, Masataka IJIRI, Toshiko OSADA, Satoshi KOBAYASHI
    Article ID: 23-00031
    Published: 2023
    Advance online publication: May 19, 2023
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION

    In this study, we will report the efficiency of hybrid filler for the mechanical properties and the thermal conductivity of Polyamide-6 (PA6) composite. One of the ways to improve the thermal conductivity of the composite is to add fillers to the matrix, but the excessive filler causes the composite to form aggregation and void. They make the mechanical properties and thermal conductivity decline. As the solution to this problem, to use of hybrid filler is expected to realize the lower filler content of composite with keeping the properties. However, the most efficient ratio of hybrid filler is unclear. In this study, PA6 and filler were composited using a twin-shaft melt-mixing machine. A manual injection molding machine was then used to produce test specimens for thermal conductivity measurement and tensile test specimens. Thermal conductivity was measured based on the laser flash method. The structure of the composite was also investigated by fracture surface observation after tensile testing. It is revealed that two types of fillers were composited with PA6 to obtain higher thermal conductivity than that of a single filler with the same filler content. This is because the different shapes of the two fillers made the thermally conductive path.

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  • Satoru MAEGAWA, Hiroki INAGAKI, Xiaoxu LIU, Fumihiro ITOIGAWA
    Article ID: 22-00254
    Published: 2023
    Advance online publication: May 17, 2023
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION

    This study demonstrates that the robustness of friction dampers can be enhanced by using the positive velocity dependence of the kinetic friction force. First, we show that the kinetic friction coefficient can be reduced under extremely low sliding velocity conditions by using oleyl acid phosphate (OLAP) as an additive to the lubricant on the sliding surfaces between bronze-filled polytetrafluoroethylene (PTFE) and steel. Next, based on the results of the numerical simulations, we show that the use of a sliding surface with a positive velocity dependence of the friction coefficient is effective in improving the vibration reduction ability of the friction dampers. Finally, our findings are demonstrated through a simplified experiment.

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  • Shun TAKASE, Takahiro YAMAZAKI, Chiemi OKA, Junpei SAKURAI, Seiichi HA ...
    Article ID: 23-00074
    Published: 2023
    Advance online publication: May 17, 2023
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION

    As the application areas of MEMS (microelectromechanical systems) expand, more advanced functions and performance are being demanded from MEMS. To meet these demands, materials with various functionalities such as mechanical strength and shape memory, which are difficult to achieve with Si-based materials alone, are being used in MEMS. When applying new materials to MEMS, it is essential to establish micromachining techniques and control internal stresses in the same way as for Si-based thin films. In this research, a method for measuring the internal stress of thin film structures formed by microfabrication technology was developed. The thin film structure sample to be measured is in the form of a beam with fixed ends. The uniaxial strain due to internal stress is measured using a micro spring, and the internal stress is calculated. A process for fabricating a device that realizes the novel measurement method was devised and the device was fabricated. The microfabrication technique used was a reverse lift-off process, which can form thin film structures with rectangular cross-sections and uniform film thickness. Thin film metallic glass, an amorphous alloy with higher strength and lower Young's modulus than Si-based materials, was used as the new material to be measured. Using the developed measurement method, the internal stress change of the thin film was measured as a function of annealing temperature. As a result, it was confirmed that the internal stress of the thin film changed from the compressive direction to the tensile direction with increasing annealing temperature. The internal stress values measured by the novel method were compared with those measured by Stoney's equation, and the two measurement methods were close, demonstrating the usefulness of the new measurement method.

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  • Koki MIMURA, Kenta SUGIMURA, Tatsumi KAWAFUCHI, Kiminori WASHIKA, Mune ...
    Article ID: 23-00076
    Published: 2023
    Advance online publication: May 17, 2023
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION

    Dump trucks are widely used in the construction industry. When sand is discharged from a dump truck bed, the friction with the bed causes sand to remain on the bed. Therefore, it is desirable to develop a technology to adhere low-friction fluororesin to the steel plates of a truck bed. This study develops a technique for directly joining dissimilar materials, namely steel and polytetrafluoroethylene (PTFE), using one-sided seam welding and investigates the effects of heat input and pressure conditions on joining quality. The joining conditions that affect joining quality are examined. The results show that tensile shear strength tends to increase with increasing heat input. Furthermore, it is found that the amount of PTFE deformation and the fracture morphology during tensile testing change with roller pressurization. For a one-sided seam welding machine, the anchor effect occurs between the electrodes with roller pressurization but does not occur without roller pressurization. It is also found that the type of anchor effect (dense or dispersed) depends on whether roller pressure is applied. Furthermore, it is suggested that the amount of deformation of PTFE during tensile testing is different caused by the different form of occurrence of the anchor effect. It was assumed that the fracture morphology of PTFE changed as the amount of deformation increased during the tensile test, approaching the elongation limit of PTFE. Furthermore, when the rollers were cooled to increase the cooling function of the rollers, the number of anchors was found to be lower than when the rollers were not cooled. This result suggested that the thermal contraction of the PTFE during cooling causes the PTFE in the concave area to peel off. From these results, it is assumed that the reason for the dispersed anchor effect is due to the influence of heat removal by the roller pressurization.

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  • Takahiko KURAHASHI, Kengo TAKEUCHI, Towa KOIKE, Masayuki KISHIDA, Yuki ...
    Article ID: 23-00090
    Published: 2023
    Advance online publication: May 17, 2023
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION

    This paper describes the visualization of defect regions in a structure via hammering test that employs the level set type topology optimization based on the concept of the phase-field method. In this study, the residual between the calculated displacement and the observed displacement is defined as the performance function, with the identification problem of defect regions being formulated based on the adjoint variable and finite element methods. Numerical experiments were performed to investigate the effect of the regularization parameter, the number of observation point, the evaluation equation of convergence and the application of the weighted gradient. Consequently, it was found that the number, position and size of defect can be adjusted using the regularization parameter τ. In addition, it was seen that if the number of observation points and the evaluation equation in the iterative computation of topology update are appropriately given, the identified defect topology is close to the exact defect topology. Furthermore, it was found that defect topologies can be more accurately identified by applying weighted sensitivities.

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  • Yukihiko OKUDA, Zuoyi KANG, Akemi NISHIDA, Haruji TSUBOTA, Yinsheng LI
    Article ID: 22-00370
    Published: 2023
    Advance online publication: May 09, 2023
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION

    The influence evaluation against projectile impacts has attracted much attention for the safety assessment of nuclear-facility buildings subjected to projectiles, such as tornado missiles or aircraft. Many experimental studies have been reported on the impact resistance of reinforced concrete (RC) structures. Based on these results, many empirical formulas for penetration depth, scabbing limit thickness, and perforation-limit thickness have been proposed for the local damage evaluation. However, most formulas were derived from impact tests based on normal impact to target structures using rigid projectiles that do not deform during impact. Therefore, this study develops a local damage evaluation method considering the rigidity of projectiles and oblique impacts that should be considered in realistic projectile impact phenomena. Specifically, we focused on scabbing, defined as the peeling off the back face of the target opposite the impact face, and conducted impact tests on RC panels to clarify the scabbing limit by changing the impact velocity in an oblique impact. The effects of the projectile rigidity and oblique impact on the scabbing limit were investigated based on the test results. This work presents the test conditions, equipment, results, and the scabbing limit on the local damage to RC panels subjected to oblique impacts.

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  • Masafumi TAZUKE, Tsuyoshi MIYAKOSHI, Atsushi HOSOI, Koji MICHISHIO, Na ...
    Article ID: 23-00089
    Published: 2023
    Advance online publication: May 09, 2023
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION

    The objective of this study was to experimentally evaluate the fatigue limit of 90° unidirectional carbon fiber reinforced plastic (CFRP) laminates. The very high-cycle fatigue properties of the specimens were evaluated using ultrasonic and electromagnetic fatigue testing machines. Ultrasonic fatigue tests were conducted to obtain the fatigue properties under the giga-cycle regime. The specimen geometry was designed to resonate at 20 kHz, the specimen consisted of CFRP laminate and a metal tab to connect to the horn end of the testing machine. Additionally, the free volume of the matrix material, namely, epoxy resin, of the CFRP laminates was evaluated using the positron annihilation method. A slit was introduced in the specimen surface to identify the location of damage development, which facilitated the free volume measurement by positron microscopy. The obtained S-N curves reveal that failure did not occur at strain levels lower than εmax = 0.75% at the slit tip for all specimens up to N = 1.0 × 109 cycles. The free volume measurement for a specimen set above the threshold strain level revealed that the free volume increased in size and decreased in amount as the number of cycles increased. The test results revealed that the opposite trend existed below the threshold, which suggests that a fatigue limit may exist.

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  • Yukihiro IGUCHI, Daisuke KAWASAKI, Satoshi YANAGIHARA
    Article ID: 22-00460
    Published: 2023
    Advance online publication: April 22, 2023
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION

    Basically, decommissioning of nuclear facilities is a project that does not generate new profit because it is carried out with the reserve funds from operation, etc. Therefore, its cost should be minimized with optimization by shortening the process and minimizing the waste, etc. Meeting the requirements of exposure risk (safety) also affects the optimization. In this study, we decided to integrate these evaluation methods to develop a comprehensive optimization evaluation method. In this study, we established an average process for the current decommissioning plans of Japanese nuclear power plants and developed a cost evaluation method including sensitivity analysis. As a result of examining the feasibility of the deferred dismantling strategy using the above calculation method, it became clear that although there is a reduction in disposal and dismantling costs due to the natural decay of radioactive materials, the maintenance and management costs during the safe storage period account for a large proportion of the costs, and for this reason, immediate dismantling is unconditionally advantageous, at least in Japan. The components of optimization described above are naturally subject to various uncertainties and risks. For example, there are regulatory risks, and the location of waste disposal site is subject to social acceptance, so there is a great deal of uncertainty. In the future, these factors will be incorporated into the evaluation and studied, and the optimal strategy for decommissioning and what kind of uncertainty should be focused on will be clarified quantitatively.

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  • Toshiya FUKUZAKI, Kiyoshi KINEFUCHI, Yutaka UMEMURA, Koichi OKITA, Hit ...
    Article ID: 23-00015
    Published: 2023
    Advance online publication: April 21, 2023
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION

    Vapor cooling shield is a key technology for long-term cryogenic propellant storage in space. Cooling channels with a triply periodic minimal surface embedded inside are expected to improve its cooling performance. Herein, a cooling channel with a triangle cross-section embedded gyroid structure, a type of the triply periodic minimal surface structure, was additively manufactured. The pressure drop and heat transfer performances of the channel were experimentally measured using liquid nitrogen vapor. Furthermore, in addition to the gyroid-embedded channel, three channels with different cross-sections were fabricated for comparison: circular, triangle, and triangle with a step/groove on the bottom. The gyroid-embedded channel exhibited unique characteristics, with a thermal conductance that was approximately 40% higher than that of the channel with a simple triangle cross-section, but an excessive pressure drop of approximately 50 times higher than that of the other cross-sections. This denotes that strong vortex and turbulence and the flow separation cause excess pressure drop in the gyroidembedded channel. The pressure drop characteristic of the gyroid-embedded channel against the Reynolds number completely differed from that of the other channels, and the pressure drop of the gyroid-embedded channel can be estimated assuming analogy with particle packed beds.

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  • So UENO, Wataru OHNISHI, Takafumi KOSEKI
    Article ID: 22-00310
    Published: 2023
    Advance online publication: April 19, 2023
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION

    A “personalized guidance system” has been gathering attention as a service for railroad users that utilizes information and communication technology to guide passengers to the most appropriate train to board. In addition to commuters, there are also some private users who are willing to accept a delay in arrival at their destination if they can avoid congestion, and especially in recent years when infectious diseases are spreading, there are passengers who strongly desire to avoid congestion. The purpose of the individual guidance system proposed in this study is to provide individual guidance that meets the individual requirements of each passenger by classifying passengers into matrix groups according to their disutility for early and late arrival and for congestion, and by reflecting the behavioral characteristics of individual passengers in the guidance. Authors compared the results of two methods used by the system to assign trains to passengers: the “incremental assignment method,” in which passengers are assigned to trains one by one in a certain order, and the “user equilibrium method,” in which all passengers choose the best route for themselves. Authors also proposed an index to quantify passengers’ trust in individual guidance systems, and evaluated the passenger disutility and distrust caused by the guidance systems through an urban rail model. The results showed that when the order in which passengers are assigned to trains is random, both the overall disutility of passengers and their distrust of the guidance system are reduced, and that the disutility of passengers who are assigned to trains earlier is greater. This study confirmed that a guidance method that is easy to implement in society can reduce both overall disutility and individual trust to some extent, but it also revealed that passengers who make decisions early in the process can suffer greater disutility.

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  • Yutaka HAMAGUCHI, Pongsathorn RAKSINCHAROENSAK
    Article ID: 22-00361
    Published: 2023
    Advance online publication: April 19, 2023
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION

    Semi-trailers have the advantage that the maximum load capacity is large. However, there are some problems that high driving skill is required because it is necessary to perform unique steering during turning or backward driving. This paper proposes a path planning and tracking algorithm for autonomous parking of semi-trailers. The path planner determines the parking path to the target parking position in accordance with the given parking environment including obstacles. Furthermore, the steering control system is desinged to handle the path tracking and stabilize the hitch angle. The proposed path planning method and tracking control are both unique in that it focuses on the vehicle’s terminal state at the target parking position, and finds the solution in the time-inverse order of the actual driving sequence. The parking simulations is performed and the effectiveness of the proposed method is verified.

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  • Hiroki SUWA, Yasunori YUSA, Takashi KUBOKI
    Article ID: 22-00462
    Published: 2023
    Advance online publication: April 19, 2023
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION

    This study proposes a parallel parametric analysis approach, in which parametric analysis for a local shape, such as a hole, is automated and parallelized. For the automation, the present approach is based on an s-version FEM, namely, the coupling-matrix-free iterative s-version FEM. In this method, the hole can be detached from the mesh of the global structure. This feature overcomes a difficulty in generating a mesh with a hole, particularly together with a crack for fracture mechanics analysis. Moreover, the parallelization is implemented by Message Passing Interface (MPI). In the present approach, a large number of analyses for different hole positions are performed in parallel. In each analysis, the hole position is changed using the s-version FEM. Then, this approach was applied to numerical examples of stationary crack problems, namely, a plate with an edge crack and a V-bending die with a circular surface crack. Both examples had a hole, the position of which was the parameter of the parametric analysis. In each numerical example, changes in stress intensity factor of the crack for different hole positions were investigated. It was numerically demonstrated that some hole positions decreased the stress intensity factor of the crack. Moreover, our approach achieved high speedup and parallel efficiency in a strong scaling test.

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  • M. J. Mohammad FIKRY, Vladimir VINOGRADOV, Shinji OGIHARA
    Article ID: 23-00079
    Published: 2023
    Advance online publication: April 19, 2023
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION

    An understanding of damage mechanisms induced by drop-off plies in tapered composite laminates is crucial. This study investigated the mechanical properties and damage behaviors of asymmetric tapered unidirectional carbon fiber-reinforced plastic laminates. Damage observations of laminates with simultaneous tapered and staggered tapered structures under monotonic and cyclic tensile loads were done by an optical microscope and X-ray radiography. Based on the results, matrix cracks in the resin pocket and delamination occurred earliest in the simultaneous tapered specimen due to a greater stress concentration in a single large resin pocket in the structure. Intralaminar damages in the staggered tapered specimen with a shorter step spacing occurred mainly in the lower dropped ply as there was a more significant interaction between the neighboring steps in the specimen. The drastic decrease in the stress concentration after the occurrence of damages in the neighboring step(s) then suppressed the occurrence of intralaminar damages in the upper dropped ply. This is in contrast to the specimen with a longer step spacing where the intralaminar damages occurred in both dropped plies due to the distributed stress distribution. Delamination propagated between the dropped plies and continuous (belt and core) plies for both staggered laminates regardless of the length of the step spacing at higher applied stress levels. The results showed that internal ply-drop configuration and step spacing in staggered tapered structures contribute to significant differences in the mechanical properties and damage behavior in the laminates.

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  • Karrar H. AL-WAELI, Rizauddin RAMLI, Sallehuddin Mohamed HARIS, Zulian ...
    Article ID: 22-00450
    Published: 2023
    Advance online publication: April 15, 2023
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION

    A “Stroke” is a neurological disease due to poor blood flowing to the brain, resulting in body cell death. It is ranked second as the most common cause of death globally. The “World Health Organization” estimates that about 15 million people suffer a stroke annually. Most stroke survivors have gait disorders, and most patients cannot walk without assistance. Physiotherapy is crucial for stroke patients to recover and maintain their mobility, functionality, and well-being. In the last 20 years, the replacement of physiotherapists with wearable robotics has become essential due to the developing technology, the need for economic growth, and the challenging health circumstances around the world, such as the COVID-19 pandemic recently. Lower Limb Exoskeleton (LLE) represents the solution for stroke patients under such circumstances, though its performance is a critical challenge paid attention to in the industry. This challenge has motivated the researchers to investigate the application of gait rehabilitation. This review presents and discusses the developments in the control system of LLE over the last decade. It also explores the limitations, new directions, and recommendations in LLE development according to the literature.

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  • Haruka SASA, Jeehwan SHIN, Atsushi HOSOI, Makoto KITANO, Hiroyuki KAWA ...
    Article ID: 23-00027
    Published: 2023
    Advance online publication: April 15, 2023
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION

    The effect of electropulsing on the extrusion due to persistent slip bands (PSBs) and the defects in PSBs was investigated. To extend the service life and improve structural safety, technology is needed to repair fatigue damage such as cracks and dislocations directly. It has been shown that electropulsing of damaged metallic materials delays fatigue crack initiation and extends fatigue life, but the detailed mechanism of this has not been explained. When cyclic strain is localized into a PSB, the PSB forms lamella, thin walls that contain rich dislocation, and thick channels that contain poor dislocation. The cyclic plastic strain within a PSB causes extrusions and intrusions, called persistent slip markings, to appear on the surface. Cracking is initiated at the tip of the intrusion. Fatigue tests were performed using an electromagnetic force fatigue testing system while applying electropulsing every 2000 cycles to polycrystalline copper. The extrusion height before and after electropulsing was observed through atomic force microscopy. The resulting extrusion growth was slowed by the electropulsing. Polák’s model was applied to examine the effect of electropulsing on the extrusion growth. When the vacancy concentration reaches a steady state in the channel and electropulsing is performed, the vacancies migrate and are assumed to be annihilated at the matrix or walls. Therefore, the vacancy concentration in the PSB decreases with electropulsing. The decrease in vacancy concentration in the PSB is thought to suppress the extrusion growth until the vacancy concentration reaches a steady state again.

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  • Hayato NAKATANI, Yuichi HATANAKA
    Article ID: 23-00069
    Published: 2023
    Advance online publication: April 06, 2023
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION

    Flow drilling screw (FDS) is a novel joining technique that enables high-speed joining of dissimilar metals with one-shot process of hole machining, female thread forming and fastening from one side. The damage after FDS process and its effect on joint strength and fracture behaviour near the screw by load-bearing tests for FDS joints between aluminum alloy and carbon fibre reinforced thermoplastics (CFRTP) are evaluated. Cross-sectional observation after joining process reveals that delamination in CFRTP is clearly suppressed and matrix resin is filled in the screw thread compared to the case with CFRP using thermosetting resin. In the joint strength test with shear loading and the cross-shaped tensile tests where the screw is pulled out in its axial direction, only the fibre micro-buckling is observed until fracture. These experimental results recommend that CFRTP laminates should be applied as composite side since this technique utilizes frictional heat by the screw that can contribute to plastic flow or deformation of the thermoplastic resin with high fracture toughness. It is also clarified that damage growth is further suppressed by using CFRTP/Al hybrid laminates where aluminum alloy sheets are inserted between CFRTP plies, which leads to improve the joint strength.

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  • Yasuhiro TASAKA, Ryosuke MATSUZAKI
    Article ID: 23-00049
    Published: 2023
    Advance online publication: April 05, 2023
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION

    The bed part of a fused-filament-fabrication-based composite 3D printer was simulated, and the use of a hot plate to control the trans-crystallization (TC) thickness in the bed part was evaluated based on the molding conditions under which TC is known to occur. An experiment using plastic, which is commonly used in 3D printers, showed that TC was generated vertically from the surface of carbon fiber. Some resins exhibited an increasing degree of isothermal crystallization as the temperature of the bed was increased, but the effect of the cooling rate on crystallization was significant; TCs with an average thickness of 38.5, 19.3, and 5.2 μm were generated in carbon-filled (CF)/PP, CF/PPS, and CF/PET, respectively. A simulated experiment that investigated the effect of the cooling rate from the melted state showed a clear reduction in TC during rapid cooling, indicating that controlling the cooling rate from the melted state can alter the thickness of the TC at the interface.

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  • Kazutoshi TACHIBANA, Kazuhiko KITAMURA
    Article ID: 23-00062
    Published: 2023
    Advance online publication: April 05, 2023
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION

    Effect of pretreatment by shotblasting to workpieces before lubricating of a non-chemical conversion lubricant in cold forging was examined by making several surfaces with different topographies, using wet shotblasting. Backward-cup extrusion test estimated the performance of the pretreatment. This test provides extremely large surface expansion to bring severe tribological conditions. After the tests, the insides of the cup-like workpieces were observed with scanning electron microscope and surface-analyzed energy dispersive X-ray spectroscopy to measure the distributive amount of the lubricant on the workpiece. The pretreated surface resulting large aspect ratio (Ra / RSm) raised the potential of lubrication performance. Especially, the surface treated with angular shaped media indicated higher potential to improve anti-galling performance.

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  • Masaaki ITABASHI
    Article ID: 23-00067
    Published: 2023
    Advance online publication: April 05, 2023
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION

    The free-cutting steel is one of the essential structural steels in electrical appliance industry and automotive industry. Most of the steel contains Pb, as solid lubricant, chip breaker, tool edge stabilizer and tool life extender. MnS grains also play the same role of Pb. However, Pb is toxic so that it will be prohibited to add to the steel in near future. Steel industry has tried to replace Pb with other element(s) and/or compound(s). The trials are still going on. This study proposes a candidate of the workability parameters for free-cutting steels with/without Pb. Investigated steels were loaded quasi-statically (strain rate: 1×10-3 s-1) and dynamically (1×103 s-1) up to fracture. Half of the specimens were pre-fatigued to form easier slip situation in steel matrix. After fracture, thin steel matrix penetrated into plenty of MnS grains. For the steel with Pb, the ratios of the number of such penetrations to those of total grains maintained almost the same value for all loading conditions. The ratios were varied with the loading conditions for the steel without Pb. These facts meant that Pb was a key element for easier slip of steel matrix. Therefore, this ratio had a feasibility to be one of the workability parameters for the free-cutting steel.

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  • Jinwen WEI
    Article ID: 22-00086
    Published: 2023
    Advance online publication: March 24, 2023
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION

    Cam contour fitting is greatly affected by data segmentation errors. Yet traditional segmentation methods are susceptible to data noise and not able to cope with contour of multiple curve type. Therefore, a new method is proposed based on Generalized Cross Product (GCP), and the segmentation of arc cam contour is taken as examples. Regarding the contour as a series of arc fragments, circular features of each fragment are transformed to a GCP norm by vector mapping. Based on the robustness of GCP, the disturbances of data noises on the GCP norms of a segmented arc are suppressed while those on its adjacent arc are amplified in the mapping. Then there is a sharp contrast in between the GCP norms, i.e. the differences of the features of 2 adjacent arcs are exhibited distinctly. Thus the dividing point between 2 segments can be easily identified. By this way, the cam contour is segmented accurately. Most importantly, the accuracy can be greatly improved through comparing the vector mappings of different mapping parameters. It is validated by experiments that the method can apply to cam contour of various curve type, including spline curves, and has strong robustness against data noise.

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  • Yosuke ICHIYANAGI, Yohei MICHITSUJI, Akira MATSUMOTO, Yasuhiro SATO, H ...
    Article ID: 22-00299
    Published: 2023
    Advance online publication: March 12, 2023
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION

    When railway vehicles run on sharp curves, the coefficient of friction (COF) between the outer rail and the leading-outside wheel flange of a bogie is an important value related to problems such as wheel/rail severe wear, squeak noise arising from wheel/rail contact, and running safety against flange-climb derailment. In general, it is difficult to grasp the actual state of COF, which changes from moment to moment during commercial operations. From the viewpoint of running safety and maintenance, it is desirable to detect curved tracks with relatively high COF from the entire service line. The monitoring bogie, which can measure wheel/rail contact forces during commercial operations, has realized a long-term observation of wheel/rail contact forces. For further applications of the monitoring bogie, the simulation-based estimation method of COF at the wheel flange have been proposed in the author’s previous paper. Furthermore, an investigation based on roller-rig tests have been conducted. However, the probability of the flange wear progress cannot be determined only by COF at the wheel flange, and other factors should be involved. The wear number is used to assess rolling contact fatigue and wheel/rail wear progress. In the present paper, on the basis of a multi-body dynamics simulation model of the roller-rig equipment, the difference of the wear number among four lubrication conditions on the bogie is clarified. The estimation method of COF is extended to estimate the wear number simultaneously. The extended method is applied to the roller-rig test and the wear number is estimated. The estimated wear number shows qualitative agreement with the amount of wear debris, which is observed in the roller-rig test conducted in previous research.

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  • Hironori ONO, Hitoshi TSUNASHIMA, Tetsuya TAKATA, Seigo OGATA
    Article ID: 22-00239
    Published: 2023
    Advance online publication: January 20, 2023
    JOURNAL OPEN ACCESS ADVANCE PUBLICATION

    Monitoring the condition of railway tracks effectively increases the safety of regional railways. A system that uses a compact on-board sensing device was previously developed for monitoring the track condition of regional railways. However, this system does not consider the running speed of the vehicle. In this study, we propose two new methods for diagnosing the condition of tracks considering the travelling speed of the vehicle: one based on the Mahalanobis distance and the other that uses Gaussian process regression. After conducting a test study to verify the effectiveness of the proposed methods, the results showed that both approaches can provide an accurate diagnosis when considering the influence of speed.

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