Mechanical Engineering Journal
Online ISSN : 2187-9745
ISSN-L : 2187-9745
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Recent Progress in Research on Mechanics of Materials by Young Researchers
  • Tetsuya MATSUDA, Motoki SAKAGUCHI, Go YAMAMOTO, Yuji ICHIKAWA, Kosuke ...
    2020 Volume 7 Issue 4 Pages 20preface2
    Published: 2020
    Released: August 15, 2020
    JOURNALS FREE ACCESS
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  • Yoshinao KISHIMOTO, Yukiyoshi KOBAYASHI, Toshihisa OHTSUKA, Shota ONO, ...
    2020 Volume 7 Issue 4 Pages 19-00545
    Published: 2020
    Released: August 15, 2020
    [Advance publication] Released: March 10, 2020
    JOURNALS FREE ACCESS

    Lithium-ion batteries (LIBs) are expected to be main power sources of automobiles. Nevertheless, LIBs easily lead to serious incidents because LIBs have high energy density. For application to automobiles, the reliability of LIBs should be guaranteed against various external loads. Especially, static loads and cyclic loads are constantly applied on LIBs because of vibration and thermal stress induced in automobiles, and fatigue damage occurs in electrodes of the LIBs. In this respect, it is important to evaluate mechanical strength and mechanical fatigue property of electrodes, such as tensile strength and S-N curves. This study has proposed a simple evaluation method of the mechanical strength and the fatigue property of electrodes for LIBs by using mechanical models of the electrodes. The actual alignment of particles of active material is random, and mechanical models based on the actual alignment are too complex to derive the main factor of mechanics of the electrodes. The proposed models approximate the alignment of the particles as the body-centered cubic (bcc) and the face-centered cubic (fcc) which are the well-known crystal lattices. In order to verify the proposed method, static tensile tests and bending fatigue tests of negative electrodes for LIBs have been conducted. From the test results, the tensile strength of the negative electrodes estimated by the proposed models agree with the experimental values, and the difference between the bcc model and the fcc model is smaller than the variation of the experimental values. The estimation value of the stress that initiates a crack on the negative electrodes by 1 cycle agrees with the tensile strength. The number of cycles linearly increases in the log scale with the decrease of the stress amplitude, and the stress amplitude at the 106–107 cycles agrees with the half of the tensile strength.

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  • Keiichi SHIRASU, Chiemi NAGAI, Kimiyoshi NAITO
    2020 Volume 7 Issue 4 Pages 19-00599
    Published: 2020
    Released: August 15, 2020
    [Advance publication] Released: March 13, 2020
    JOURNALS FREE ACCESS

    With the expansion of use of carbon fiber reinforced plastics (CFRPs), it becomes important to obtain precise knowledge of elastic properties carbon fibers in radial direction as well as axial direction. Although the elastic property in radial direction of polyacrylonitrile (PAN)-based carbon fibers have been investigated using ultrasound scatter measurements, compression tests of single fibers and nanoindentation, there is no experimental evaluation for the pitch-based carbon fibers which possess higher crystallinity and tensile modulus than PAN-based carbon fibers. Here, we investigate the mechanical anisotropy of PAN- and pitch-based carbon fibers by the nanoindentation technique. Nanoindentation tests are carried out on longitudinal (0°), 45° and transversal (90°) cross sections of carbon fibers by a Hysitron TriboScope (Minneapolis, MN) using a diamond conical indenter with a nominal tip radius of 10 μm. We demonstrate that the indentation modulus of both carbon fibers decreases with a decreasing orientation angle from axial to radial direction, but this tendency is more significant in the pitch-based carbon fibers. Supposing that the indentation modulus in the radial direction is same as the transverse elastic modulus, the anisotropy of elastic modulus (Ef/ET) of the pitch-based carbon fibers is calculated to be 165 which is approximately 15 times as high as that of PAN-based carbon fiber (Ef/ET = 11). This result suggests that the pitch-based carbon fiber possesses a large mechanical anisotropy. The higher mechanical anisotropy observed in the pitch-based carbon fiber is mainly due to the existence of the parallel arrangement carbon crystallite microtexture with high crystallinity in the axial direction.

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  • Yuichi KIMURA, Ryo UETA, Kazuyuki SHIZAWA
    2020 Volume 7 Issue 4 Pages 19-00612
    Published: 2020
    Released: August 15, 2020
    [Advance publication] Released: February 10, 2020
    JOURNALS FREE ACCESS

    The dislocation-based crystal plasticity model considering higher-order stress has been constructed and a finite element (FE) analysis is conducted for both a single crystal and polycrystal with a long-period stacking ordered (LPSO) phase on the basis of the obtained model. The mesh dependence of the kink band formation is discussed from the viewpoints of the strain gradient, size effect and higher-order boundary condition. Then, it is shown that the mesh dependence of kink deformation in the FE analysis can be removed even when the scale ratio is relatively small. The width of the kink band is determined by the intrinsic length scale. When the kink band occurs in the entire specimen, work hardening can be reproduced by appropriately defining the boundary conditions for slip. The effect of the micro-scale ratio on the kink deformation is small. The disclination quadrupole structure in the kink band can be expressed qualitatively by using the incompatibility of crystal slip. Moreover, it is shown the back stress behaves as the resistance to the slip deformation in a polycrystal consisting of LPSO phases in shape of rectangular strip.

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  • Manato KANESAKI, Kiyotaka OBUNAI, Tadao FUKUTA, Yoshihito KUROSHIMA, K ...
    2020 Volume 7 Issue 4 Pages 19-00621
    Published: 2020
    Released: August 15, 2020
    [Advance publication] Released: May 21, 2020
    JOURNALS FREE ACCESS

    This paper proposes a technique to determine the dimensions of a CNRB specimen to be used for plane fracture toughness tests. First, the brittle fracture behavior satisfying the small-scale yielding condition is investigated through an elasto-plastic analysis. The analysis parameters are the shape parameters such as the notch ratio of the specimen based on the parallel part diameter and notch bottom diameter; tip radius; and notch angle. Based on the analysis results obtained, a fracture toughness test is conducted on a JIS-S45C (quenched and tempered) specimen to evaluate the small-scale yielding condition. The experimental results confirm a linear relationship between the square of the value obtained by dividing the plane-strain fracture toughness by the yield stress and specimen diameter. Further, the diameter of the CNRB specimen satisfying the small-scale yielding condition varies with the shape parameters. With these results, a function that can determine the CNRB specimen diameter at which brittle failure occurs under uniaxial tensile loading is proposed and validated.

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  • Keita GOTO, Takuya TOMIOKA, Masahiro ARAI
    2020 Volume 7 Issue 4 Pages 19-00623
    Published: 2020
    Released: August 15, 2020
    [Advance publication] Released: February 11, 2020
    JOURNALS FREE ACCESS

    In this study, the damage-development behavior of carbon fiber-reinforced plastic (CFRP) laminates considering the nonlinear mechanical properties of a matrix resin was investigated through a numerical simulation based on a homogenization theory and continuum damage mechanics. A scalar damage variable was applied to elasto-viscoplastic constitutive equations, following which, the constitutive equations were introduced into the homogenization theory for elasto-viscoplastic materials. Uniaxial tensile tests including unloading and reloading phases under several strain rates were performed using a specimen made of an epoxy resin. The damage-development behavior of the unidirectional CFRP laminates was then analyzed using the homogenization theory. From the numerical results, viscoplastic behavior was observed in the stress–strain curves, and the stress decreased drastically as the damage of the epoxy resin developed. The microscopic distributions showed that the failure initiated at the epoxy resin around the fibers arranged along the loading direction and progressed by connecting the high damage variable regions of the epoxy resin. Uniaxial tensile tests of the unidirectional CFRP laminates were also performed to validate the numerical results. The experimental fracture stresses were distributed between the maximum and minimum stresses at the failure starting points obtained from the numerical results. Thus, it was confirmed that the proposed numerical method could analyze the damage-development behavior of CFRP laminates.

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  • Nao FUJIMURA, Koyo OOGA, Kosuke TAKAHASHI, Takashi NAKAMURA, Tatsuki W ...
    2020 Volume 7 Issue 4 Pages 20-00007
    Published: 2020
    Released: August 15, 2020
    [Advance publication] Released: May 21, 2020
    JOURNALS FREE ACCESS

    A machined material has a work-hardened layer at its surface. In this study, a surface modification technique, the scanning cyclic press (SCP), was applied to machined specimens of magnesium alloy, AZ31, to investigate whether SCP can improve its fatigue properties regardless of the surface finish. During the SCP process, a vibrating indenter reciprocally scanned the specimen’s surface, and it applied cyclical low-compressive loadings to the surface for 8 × 106 cycles. After applying SCP, the surfaces of the specimens were observed using a laser scanning microscope, and the surface roughness was measured. The surface observation and surface roughness measurement showed that the changes in the surface state after applying SCP were relatively small and the surface roughness after applying SCP was more homogenous than before applying SCP. Uniaxial push-pull fatigue tests were conducted for SCP-treated specimens and untreated specimens. The test results showed that the fatigue life of SCP-treated specimens was longer than that of untreated specimens. To clarify the reason for the improvement effect, the fracture surfaces were observed using a scanning electron microscope (SEM). The SEM observation showed that the fracture morphology was different between the SCP-treated specimen and the untreated specimen. In the SCP-treated specimen, fatigue fracture origins were sub-surface, while the untreated specimen fractured at the surface. These results suggest that SCP could improve the fatigue properties of AZ31 regardless of the surface finish of the specimen before SCP.

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Latest Research and Development in Power and Energy Systems
  • Hitoshi ASANO
    2020 Volume 7 Issue 4 Pages 20preface3
    Published: 2020
    Released: August 15, 2020
    JOURNALS FREE ACCESS
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  • Akihiro UEMURA, Hironori MIYAZAWA, Takashi FURUSAWA, Satoru YAMAMOTO, ...
    2020 Volume 7 Issue 4 Pages 20-00068
    Published: 2020
    Released: August 15, 2020
    [Advance publication] Released: July 15, 2020
    JOURNALS FREE ACCESS

    The purpose of this study is to simulate unsteady steam flows through three-stage stator and rotor blade passages in a middle-pressure steam turbine operated in a power plant while considering manufactured and secular-changed blade shapes. The shapes of the manufactured and secular-changed blades are measured during overhaul. The numerical method is based on an in-house code developed by Tohoku University. The time-dependent pressure and the Mach number are visualized, and the difference of the results obtained by assuming manufactured and secular-changed blades is explained. The simulated static temperatures assuming the blades shapes are then compared with each other and with the measured data. In addition, a simple method modifying the simulated static temperature considering real gas effect is introduced.

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  • Shuichi UMEZAWA, Katsuhiko SUGITA
    2020 Volume 7 Issue 4 Pages 20-00077
    Published: 2020
    Released: August 15, 2020
    [Advance publication] Released: May 14, 2020
    JOURNALS FREE ACCESS

    A clamp-on type flowmeter for steam and air, which does not require pipe-cutting for installation, is needed for diagnosing performance and saving energy in facilities such as factories and power plants. Therefore, in our previous study we devised a heater method for measuring steam and air flow, in which a circumferential heater was attached to the outside of a pipe and then the axial temperature distribution on the outside of the pipe was measured by thermocouples. Steam velocity was analyzed on the basis of the temperature distribution in the pipe axial direction, considering heat transfer inside the pipe and thermal conductivity in the steel pipe-wall. Thus, we determined a thermal boundary layer coefficient, which is the ratio of the thermal boundary layer flow rate to the flow rate in the whole pipe cross section, and two kinds of thermal transfer coefficient depending on position, which were that upstream of the heater and that at the middle of the heater. In the present study, we conducted further experiments under various steam pressures, calibrated the reference fluid flowmeter under supervision of the National Institute of Advanced Industrial Science and Technology, and reconsidered the fluid pressure values. Using the experimental data obtained, we could decide the parameters more precisely compared with in the previous study, and thus improved the accuracy of the heater method.

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  • Zhen-Qiang SONG, Heng-Tong CHENG, Kazuhiro OHYAMA, Shijie ZHU
    2020 Volume 7 Issue 4 Pages 20-00092
    Published: 2020
    Released: August 15, 2020
    [Advance publication] Released: May 14, 2020
    JOURNALS FREE ACCESS

    The energy conversion performance of the dielectric elastomer generator (VHB 4905 acrylic elastomer, 3M) was investigated with the diaphragm configuration. Under the “triangular” harvesting scheme, the average energy density and energy conversion efficiency within one electromechanical cycle are measured to be about 102±5 mJ/g and 9.5±2.6 %, respectively, which are 75% and 98 % higher than that of the “quadrangular” harvesting scheme with the identical loading configuration. Large proportion of mechanical energy is dissipated via viscosity of the acrylic elastomer material, which implies that the energy conversion performance of dielectric elastomer generator is able to be considerably improved by adopting dielectric elastomer material with low viscoelasticity. For the diaphragm configuration, the capacitance of the dielectric elastomer film is proportional to the square of stretching displacement.

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  • Kotaro NAKAMURA, Takehiko MURAMATSU, Takashi OGAWA, Takao NAKAGAKI
    2020 Volume 7 Issue 4 Pages 20-00103
    Published: 2020
    Released: August 15, 2020
    [Advance publication] Released: June 01, 2020
    JOURNALS FREE ACCESS

    Natural gas-fired combined cycle power plants (NGCC) have the advantages of high efficiency and low CO2 intensity compared to coal-fired power plants. When variable renewable energy sources are introduced to the grid in large quantities, the NGCC is expected to have rapid start-ups, rapid shutdowns, and increased partialload operations to stabilize the grid. Due to these temporary operations, the ratio of NO2/NOX in the NGCC exhaust gas changes significantly. In general, when the NO2/NOX ratio is high, the efficiency of the de-NOX systems decreases. Moreover, the performance of de-NOX systems has a transient response due to changes at the catalyst surface and the adsorption of NH3. Considering the trajectory of increased variable renewable energy, it is necessary to develop an efficient NOx removal system that is effective over a wide range of NO2/NOX ratios. In the modeling of de-NOX system performance, this study extends the general Eley-Rideal reaction between adsorbed NH3 and gas-phase NOX to include the existence of O2, H2O, CO2, and transient NO2 in the exhaust gas along with changes in redox sites (i.e., V5+=O and V4+-OH). A two-dimensional transient numerical simulation code was developed and adapted using experimental results obtained from treating simulated NGCC exhaust gas using a commercial honeycomb-shaped selective catalyst. Numerical simulations incorporating the empirically determined kinetic equations accurately predict the transient and equilibrium concentrations of NOX and NH3 exiting a honeycomb catalyst even under gas conditions including high NO2.

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  • Kazushi MIYATA, Yuki YAMASAKI, Kizuku KUROSE, Yoshinori HAMAMOTO, Hide ...
    2020 Volume 7 Issue 4 Pages 20-00107
    Published: 2020
    Released: August 15, 2020
    [Advance publication] Released: May 14, 2020
    JOURNALS FREE ACCESS

    In industrial fields, heat source over 130°C are widely needed, and for this development of industrial high-temperature heat pump systems has been promoted. For the heat release process in such the heat pump systems, it is considered to use of a plate heat exchanger (PHE) in which a high pressure working refrigerant flows. In this study, to examine the effect of chevron angle on heat transfer of refrigerants flowing in chevron PHEs at supercritical pressure and high subcritical pressure, experiments were conducted using a chevron PHE with a chevron angle 75°. The measured heat transfer coefficient was compared with the data of three chevron PHEs with respective chevron angles 30°, 47.5° and 65° obtained previously. The effect of chevron angle on heat transfer at 65° and more was smaller than that at less than 65°, and the heat transfer coefficient in 75° PHE was almost the same with that in 65° PHE, considering difference in hydraulic diameter between the PHEs. Furthermore, the value of heat transfer coefficient achieved in 65° or 75° PHE was estimated to be almost maximum between 0° to 90°. On the other hand, the friction factor of 75° PHE was markedly larger than that of 65° PHE.

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  • Tsuneaki ISHIMA, Asuka TAKATSUKI, Takahiro MIYAOKA, Katsuhiko SUGITA, ...
    2020 Volume 7 Issue 4 Pages 20-00115
    Published: 2020
    Released: August 15, 2020
    [Advance publication] Released: May 14, 2020
    JOURNALS FREE ACCESS

    Air cooling performance and water spray characteristics are experimentally evaluated to obtain the basic knowledge for the suction air cooling of power plant. Novel optical measurement technique is proposed for measuring spatial number density of water droplet and water quantity in the air flow. The technique is based on Lambert-Beer law. An attenuation rate of the power of a laser beam passing through the mist flow is measured and the number of droplets is evaluated. Characteristics of the water spray are also evaluated by a phase Doppler anemometer (PDA). The data are compared with cooling performance. All experiments are tested in a wind tunnel with 1m x 1m square shape and 2 m in length. Mean velocity of main flow is set at 2 m/s, temperature at inlet of wind tunnel is set at 33 degree Celsius. Humidity of the inlet air is varied from 60 % to 90 %. The results show that the cooling efficiency by the water spray is depended on the water droplet diameter and humidity. The PDA data and the cooling efficiency are well correlated. The proposed method can present the data related with the droplet number and quantity.

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  • Shohei MATSUNARI, Kazuhiro WATANABE, Emi OHNO, Makoto ECHIZENYA
    2020 Volume 7 Issue 4 Pages 20-00117
    Published: 2020
    Released: August 15, 2020
    [Advance publication] Released: July 14, 2020
    JOURNALS FREE ACCESS

    In Japan, a feed-in tariff was introduced to promote and expand the renewable energy ratio to 22-24% by FY 2030. Biomass is one of important renewable energy. Recently, several biomass projects for not only fluidized bed boilers, but also pulverized coal fired boilers, are being planned around the world to reduce CO2 emissions as the main reason. The required particle size of woody biomass for combustion in a pulverized coal fired boiler is around 1mm, while that of coal is several tens of m. Woody biomass particles grinded by a mill are sent to burners via a fuel pipe by air. It is important to measure the particle size distribution in order to understand combustibility and grindability. However, it was unknown whether the particle size distribution could be measured by the same sampling method for pulverized coal. We conducted sampling tests of woody biomass particles in a fuel pipe using the isokinetic sampling method. As a result, we observed that the flow of woody biomass particles in the pipe was significantly non-uniform to the influence of the upstream elbow. It is necessary for woody biomass to measure at a pitch of at least 45 in order to obtain the particle size distribution in a fuel pipe.

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  • Koichi YONEZAWA, Masahiro TAKAYASU, Kazuyasu SUGIYAMA, Katsuhiko SUGIT ...
    2020 Volume 7 Issue 4 Pages 20-00122
    Published: 2020
    Released: August 15, 2020
    [Advance publication] Released: July 28, 2020
    JOURNALS FREE ACCESS

    A numerical study of aerodynamics in a deteriorated gas turbine was carried out. In the present study, a hybrid method of CFD simulation and heat balance analysis were used to estimate entire performance of the gas turbine cycle and local flow characteristics in the turbine section. Using this analysis method, flows in a deteriorated gas turbine were simulated under an operating condition, which was designated using the same procedure with that used in a real power plant. In our previous study, the degradation of the gas turbine performance due to blades deterioration had been observed. In the present study, flow patterns were observed and mechanisms underlying the degradation of the gas turbine performance were discussed in detail. Influences of two kinds of deterioration on flow patterns were examined: the first was thinning of nozzle guide vanes in the first stage and the second was increase of rotor tip gap in the first stage. The results showed that the deterioration of nozzle guide vanes leaded to decrease of the Mach number through the nozzle, and this leaded to increase of the turbine isentropic efficiency due to decrease of the friction loss. The increase in the rotor tip gap affected a loss generation of the following stage. Changes of flow patterns and its effects were discussed varying operating points of a gas turbine.

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  • Hideki MURAKAWA, Shuhei ICHIMURA, Masaki SHIMADA, Katsumi SUGIMOTO, Hi ...
    2020 Volume 7 Issue 4 Pages 20-00131
    Published: 2020
    Released: August 15, 2020
    [Advance publication] Released: April 30, 2020
    JOURNALS FREE ACCESS

    Energy management in industrial plants requires measurements of the steam flow rates at each usage location. A clamp-on ultrasonic flowmeter can be used to effectively measure the steam flow rates in existing pipes. An ultrasonic flowmeter is used to calculate the transit time of ultrasonic signals between the downstream and upstream sensors, which is affected by the line-averaged velocity along the ultrasonic beam. The intensity of the transmitted ultrasonic signal is crucial for measuring the steam flow rate using the clamp-on ultrasonic flowmeter. The authors focused on the effects of the ultrasonic incident angle on the transmitted ultrasonic signal intensity in steam flow. Ultrasonic transmission experiments were carried out on three pipes (SGP 25A, SGP 50A and SGP 80A) filled with stationary nitrogen, and the transit time in steam flow was measured on SGP 80A pipe by changing the ultrasonic incident angle. The pipes are made of carbon steel and generally used for the steam flow. The results indicate that the appropriate incident angle that allowed the maximum transmitted signal intensity differed depending on the thickness of the pipe wall. Furthermore, a good agreement with the critical angles of the zero-order of symmetric mode in Lamb waves was noted. Thus, the propagated ultrasonic waves can be considered Lamb waves, which increase signal intensity. The transmitted signal intensity decreases because of the turbulent dissipation as the steam velocity increases. Appropriately setting the incident angle depending on the wall thickness, particularly for higher steam flow rates, is essential for evaluating the transit time difference between upstream and downstream transducers.

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  • Kenichiro TAKEISHI, Yutaka ODA, Shohei MORI, Robert KREWINKEL
    2020 Volume 7 Issue 4 Pages 20-00176
    Published: 2020
    Released: August 15, 2020
    [Advance publication] Released: July 28, 2020
    JOURNALS FREE ACCESS

    The reliability of turbine blades and vanes of modern high temperature gas turbines is assured by turbine blade cooling technologies. Among the various cooling methods, film cooling has been a key technology to ensure the long-term operation of turbine blades and vanes that are exposed to hot gas-path flows. Therefore, many papers have been published aiming at the improvement of film cooling effectiveness by optimization of film cooling hole geometries. Although the turbulence intensity of the mainstream generated in the gas turbine combustor is very high and may reduce the film cooling effect on the turbine vane and blade, there are few papers investigating quantitatively the effect of the mainstream turbulence on the film cooling. For this reason, the influence of mainstream turbulence intensity on film cooling effectiveness was investigated with an active turbulence generator equipped with electric-motor driven propellers for circular and fan-shaped film cooling holes. Spatial distributions of the turbulent mixing field between turbulent mainstream and film coolant jet were measured with quantitative measurement methods, such as PIV and LIF. As a result, it was revealed that when the mainstream turbulence is high the counter-rotating vortex pair is weakened, the film cooling air spreads in the span-wise direction and the lateral-averaged film cooling effectiveness decreases about 10%.

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Solid Mechanics and Materials Engineering
  • Tomomichi DOI, Masayuki ARAI, Kiyohiro ITO
    2020 Volume 7 Issue 4 Pages 20-00232
    Published: 2020
    Released: August 15, 2020
    [Advance publication] Released: July 14, 2020
    JOURNALS FREE ACCESS

    The creep exponent, n, and creep coefficient, k, in Norton’s law characterizes the creep deformation of a high-temperature material. For identifying the creep constants, the uniaxial creep test is generally conducted. However, it is required to prepare many round-type cylindrical specimens. As an alternative to the uniaxial creep test, we proposed the indentation creep test using a spherical ball. However, this creep test has to be interrupted to evaluate the progression of impression size with dwelling time. To prevent the need for such complicated procedure, a simple estimation method based on the indentation creep test using a cylindrical indenter was developed in this study. This method allows us to directly estimate the creep constants from the relationship between impression pressure and penetration rate, which can be continuously measured during testing. A fundamental formula was derived in this study based on a cavity model introduced by Johnson, and it was subsequently corrected using finite element analysis. To check verification of this method, the creep indentation test was conducted on pure aluminum A1050 plates using a cylindrical alumina indenter. It was confirmed that the creep constants estimated from the developed method perfectly coincide with those estimated by conventional methods such as the uniaxial creep and ball indentation tests. Furthermore, it was inferred that the testing procedure of the developed method is simpler than those of the other methods, which is an advantage of usage of this method.

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  • Jinqi LYU, Masakazu ICHIMIYA, Ryunosuke SASAKI, Naoto KASAHARA
    2020 Volume 7 Issue 4 Pages 20-00167
    Published: 2020
    Released: August 15, 2020
    [Advance publication] Released: July 16, 2020
    JOURNALS FREE ACCESS

    Ratcheting is one of the dominant failure modes under excessive earthquakes and may cause extreme failures of structures (e.g., collapse). We focused on clarifying the ratcheting mechanism of piping under sinusoidal excitations. Both finite element analyses and experiments were conducted on bent solid bars, which represented piping in this study. Seismic ratcheting occurred due to the combined effect of constant external compressive force and cyclic vibrations. The external compressive force acted as a load-controlled load. Vibrations were applied to provide the source of the dynamic load. Characteristics of vibrations between load-controlled and displacement-controlled properties were studied from the viewpoint of the frequency ratio of the forcing frequency to the natural frequency of the piping model. In addition, the influence of supports on the occurrence of ratcheting was also considered. The results showed that the resonance effect was evident in the piping model compared with the beam model due to the limited plastic area in the piping model. The vibration with a lower frequency had load-controlled characteristics. In contrast, the vibration with a higher frequency presented displacement-controlled properties. In terms of the occurrence of ratcheting, providing more supports sometimes increased the possibility of the occurrence of ratcheting under relatively higher forcing frequencies because more supports increased the natural frequency and decreased the frequency ratio.

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  • Takahiro OHTA, Ninshu MA
    2020 Volume 7 Issue 4 Pages 20-00152
    Published: 2020
    Released: August 15, 2020
    [Advance publication] Released: July 20, 2020
    JOURNALS FREE ACCESS

    Shot peening is applied to many manufactured parts to improve the fatigue strength of metals by introducing compressive residual stress near the surface. The distribution of compressive residual stress is mainly determined by shot diameter, shot velocity, angle of incidence, and peening time which affects coverage. In this study, the shot velocity was measured using particle image velocimetry (PIV) for shots fired at two different air pressures. The finite element method was used to analyze the residual stress distribution in a high strength aluminum alloy (A7075-T6) plate during shot peening. The shot was accelerated up to a standoff distance of approximately 200 mm from the nozzle outlet. The measured maximum shot velocity increased proportionally to the air pressure to the 0.59th power. The analyzed residual stress distributions using measured shot velocity with PIV through the thickness of the specimen agreed well with the measurements under two types of peening conditions with differing air pressure and angle of incidence. The shot velocity measurement technology and the numerical model for analysis of the shot peening residual stres were both validated in this study.

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Thermal, Engine and Power Engineering
  • Takuya YAMAGUCHI
    2020 Volume 7 Issue 4 Pages 19-00626
    Published: 2020
    Released: August 15, 2020
    [Advance publication] Released: June 29, 2020
    JOURNALS FREE ACCESS

    In heavy duty diesel engines, reductions of exhaust emissions and improvement in thermal efficiency have been strongly required from a view point of the prevention of air pollution and global warming. Premixed charge compression ignition (PCCI) can reduce NOx and Smoke simultaneously at partial load operating conditions in a diesel engine, and this type of combustion has been studied for a long time because it has the potential to reduce exhaust emissions compare to the conventional diesel combustion. Meanwhile, conventional diesel combustion (diffusion combustion) can also achieve low NOx and Smoke level by combining with high rate EGR and high fuel injection pressure in the past decade. In this paper, such conventional diesel combustion is referred to as the low temperature diesel combustion (LTDC). Although each combustion type has the characteristic regarding exhaust emissions and thermal efficiency in a diesel engine, there are few reports which investigated the effect of the difference between PCCI and LTDC on exhaust emissions and thermal efficiency in a modern heavy duty diesel engine. In this study, the experiments conducted to compare the exhaust emissions and thermal efficiency between PCCI and LTDC at brake mean effective pressure = 0.4 MPa in the heavy duty single cylinder diesel engine. For comparison of PCCI and LTDC, swirl ratio and fuel injection pressure that strongly effect on combustion was optimized in each combustion type. As the result of an experiment, it was found that the improvement of NOx by PCCI is large compared to LTDC, although PCCI has the problem to be solved such as the improvement of brake thermal efficiency.

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  • Jorge Enrique MUÑOZ GARCIA, Cécile PÉTESCH, Thierry LEBARBÉ, Dominique ...
    2020 Volume 7 Issue 4 Pages 20-00052
    Published: 2020
    Released: August 15, 2020
    [Advance publication] Released: July 14, 2020
    JOURNALS FREE ACCESS

    The very last edition of the RCC-MRx Code (Design and Construction Rules for Mechanical Components in high-temperature structures, experimental reactors and fusion reactors) was published end of 2018 by AFCEN, the French Association for the rules governing the Design, Construction and Operating Supervision of the Equipment Items for Nuclear installations. The RCC-MRx Code is a consistent set of technical rules to be applied on the design of research reactors (derived from the last edition ever of RCC-MX Code in 2008, code especially developed for the Jules Horowitz Reactor (JHR)), on high temperature structures (derived from the last edition ever of RCC-MR Code in 2007, code devoted to high temperature reactors, the ITER Vacuum Vessel and to the French Fast Breeder Reactors) and on Fusion reactors. The scope of the RCC-MRx Code is restricted to mechanical components of high temperature structures, Sodium Fast Reactors (SFR), Research Reactors and Fusion Reactors (ITER/DEMO), but the RCC-MRx Code can also be used for mechanical components of other types of nuclear installations, as the European Spallation Source Target (ESS) for example. This paper is presenting the content and organization of the last edition, the RCC-MRx Code 2018, and the recently incorporated feedback from users, such as ITER project, JHR (Jules Horowitz Reactor) in France, ASTRID (Advanced Sodium Technological Reactor for Industrial Demonstration) project in France, PFBR project (Prototype Fast Breeder Reactor) developed by IGCAR (Indira Gandhi Centre for Atomic Research) in India, and MYRRHA (Multi-purpose hYbrid Research Reactor for High-tech Applications) project in Belgium.

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  • Masaaki SUZUKI, Kazuyuki DEMACHI, Shigeru TAKAYA, Yoshitaka CHIKAZAWA
    2020 Volume 7 Issue 4 Pages 19-00570
    Published: 2020
    Released: August 15, 2020
    [Advance publication] Released: July 28, 2020
    JOURNALS FREE ACCESS

    To identify functions and facilities that are critical for ensuring safety in advanced reactors, for which only a limited usage history is available, it is necessary to consider the characteristics of each reactor type by utilizing more risk-related information. In this study, we compare the response capability during an accident for light water reactors and fast reactors to quantitatively evaluate the impact of the reactor type on resilience. A resilience evaluation procedure is developed for assessing the response margin and response reliability of a nuclear power plant during an accident; this procedure was then applied to a simple pressurized-water reactor and a sodium-cooled fast reactor plant model using an accident scenario involving an earthquake that generated a leakage of coolant from the primary heat-transport system. Our research indicated a relatively large difference between the response reliability with respect to time for the two reactor types.

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Dynamics & Control, Robotics & Mechatronics
  • Keisuke YAMADA, Hideo UTSUNO
    2020 Volume 7 Issue 4 Pages 20-00003
    Published: 2020
    Released: August 15, 2020
    [Advance publication] Released: June 15, 2020
    JOURNALS FREE ACCESS

    This paper describes the theoretical modal analysis of continuous systems that are subjected to displacement excitation. Because vibration modes of continuous systems whose boundaries actively move are unknown, we proposed an equivalent replacement method of displacement excitation with an excitation force and fixed boundary. We can easily derive the vibration modes of the continuous system because the excitation boundaries are fixed by this replacement method. Using the proposed replacement method and modal analysis, we can derive a certain vibration mode independently. In other words, the number of degrees of freedom can be decreased using the proposed method even when continuous systems are subjected to displacement excitation. The equivalent replacement methods for ‘one-dimensional and multi-dimensional continuous systems whose equation of motion is a wave equation’, and ‘one-dimensional and two-dimensional continuous systems whose equation of motion is a fourth-order partial differential equation’ were proposed in this research. As a representative, an acoustic tube and a cuboidal room were used as the analytical models for the one-dimensional and multi-dimensional continuous systems whose equation of motion is a wave equation. In contrast, an Euler-Bernoulli beam and a Kirchhoff-Love plate were used as the analytical models for the one-dimensional and two-dimensional continuous systems whose equation of motion is a fourth-order partial differential equation. The correctness of the proposed methods was mathematically proved. In addition, the effectiveness of the proposed method was verified through numerical simulations.

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  • Masahiko UTSUMI
    2020 Volume 7 Issue 4 Pages 19-00554
    Published: 2020
    Released: August 15, 2020
    [Advance publication] Released: June 15, 2020
    JOURNALS FREE ACCESS

    The vibration of a cylindrical rotor partially filled with liquid is analyzed by a semianalytical method allowing for all nonlinear terms and arbitrary liquid depth. The method is verified by comparing with earlier experimental results and the nonlinear mechanism is examined that causes transition from unstable response to stable vibration. The examination shows that the transition arises from the nonlinearity of the kinematic boundary condition on the liquid surface. A closed loop mechanism is introduced to explain why the vibration suppression effect of nonlinearity in one boundary condition results in stabilization of the whole system. The case with larger dimensionless liquid depth is also addressed. Studies for this case were relatively scarce because many earlier studies were based on shallow water approximation.

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  • Isao OKAWA, Yoshihide MIZUSHIMA, Kenichiro NONAKA
    2020 Volume 7 Issue 4 Pages 19-00632
    Published: 2020
    Released: August 15, 2020
    [Advance publication] Released: June 18, 2020
    JOURNALS FREE ACCESS

    This paper focuses on acceleration trajectory shaping using model predictive control for autonomous vehicles. The proposed method employs two types of constraints for the shaping: hard constraints, which must be satisfied and soft constraints, which can be relaxed if required. The soft constraints require that the acceleration trajectory be shaped into the desired piece-wise linear function of time, while collision avoidance is guaranteed by utilizing hard constraints. Since we can specify the desired level of acceleration and jerk directly, it becomes straightforward to design and adjust the shape of the trajectory. Further, fast and stable solvers are available, since the optimization problem is formulated in convex quadratic programming. We employ a desired trajectory with constant acceleration (deceleration) as a typical target, and validate the reshaping performance and verify the feasibility of the method through experiments with real vehicles. Two experimental scenarios are considered to ensure the compatibility of trajectory shaping and collision avoidance: sudden braking of a preceding vehicle and cutting-in by a slow-moving vehicle. The experimental results show that the proposed method successfully shaped the trajectory satisfying collision avoidance, while soft constraints for shaping were appropriately relaxed as demanded, which supports the effectiveness of the proposed method.

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  • Satoshi MIURA, Takayuki NAKAGAMI, Victor PARQUE, Tomoyuki MIYASHITA
    2020 Volume 7 Issue 4 Pages 20-00088
    Published: 2020
    Released: August 15, 2020
    [Advance publication] Released: June 18, 2020
    JOURNALS FREE ACCESS

    This paper presents a method to inspect the interior of a winding small gas pipe using a hollow guide wire. There is no conventional method to insert an endoscope into an 8-bend 25-mm-diameter gas pipe within 2 hours. In medical practice, a guide wire inserted in advance enables insertion of a catheter into a vessel. However, it is impossible to insert a normal guide wire into a gas pipe because the wire buckles in the pipe. Thus, we designed a hollow guide wire with a small front diameter and large rear diameter, making the front soft and the rear stiff. This guide wire can be inserted without buckling or meandering. First, we measured mechanical properties such as the torsional spring constant and damping coefficient of the wire and the frictional coefficient between the pipe and wire. Second, we conducted an experiment inserting guide wires with various tip pitches, front lengths, front outer diameters, and rear outer diameters. Third, we analyzed the insertion distance by simulating guide wire insertion using the Lagrange method, and optimized the guide wire shape via the response surface method. Finally, the optimized guide wires were tested experimentally to validate the analysis. As a result, an optimized guide wire and an endoscope can both be inserted into a gas pipe and removed within just 3 minutes.

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Computational Mechanics
  • U OH, Norihiko NONAKA
    2020 Volume 7 Issue 4 Pages 20-00084
    Published: 2020
    Released: August 15, 2020
    [Advance publication] Released: July 01, 2020
    JOURNALS FREE ACCESS

    Automotive fuel can be efficiently combusted by injecting it into the cylinders at high pressure to atomize it to pass gas and fuel economy regulations for exhaust. Automotive companies have developed direct injection engines, which inject gasoline directly into the cylinders. Demand for quieter high pressure pumps is also increasing because this contributes to automotive comfort. The valve motion need to be predicted with high accuracy under the operation condition because the noise of the fuel pumps is caused by solenoid valve impingement, which causes the noise level to rise. Measuring the valve motion is difficult because of the components around the valve region, and making a prototype is very time-consuming. An analysis method that can accurately predict valve motion is needed. The valve motion is defined by the total balance of spring, fluid, and magnetic forces acting on the valve. The mechanical, fluid, and magnetic effects must also be predicted simultaneously. To address these issues, we developed an integrated simulation method with coupling 1D system analysis, 3D fluid analysis, and 3D magnetic analysis. We tested this method, and the fluid, magnetic effect also can be predicted high accurately with this method. In addition, the simulation accuracy of the valve motion rose to 7% with this method.

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  • Toshio NAGASHIMA
    2020 Volume 7 Issue 4 Pages 20-00098
    Published: 2020
    Released: August 15, 2020
    [Advance publication] Released: July 20, 2020
    JOURNALS FREE ACCESS

    A three-dimensional crack analysis method based on XFEM using only the Heaviside step function was applied to heat transfer and subsequent thermal stress analyses of cracked structures. The proposed method employs tip elements to discretize the weak form governing equations using the approximation function with discontinuity. Two kinds of XFEM analysis software, which perform steady-state or transient heat transfer analysis and thermal stress analysis to evaluate J-integrals and stress intensity factors, were developed. As the XFEM model for the stress analysis is consistent with the heat transfer analysis model, nodal temperature data can be directly imported for stress analysis as thermal load data. The developed codes were verified by solving some benchmark crack problems, including both mechanical and thermal loading cases, and comparing the results with those of conventional methods and a reference. It was shown that the developed codes provide appropriate results for practical thermal stress analysis of cracked structures considering temperature-dependent material properties.

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Design, Machine Element & Tribology, Information & Intelligent Technology, Manufacturing, and Systems
  • Naoto KIMURA, Nobuyuki IWATSUKI, Ikuma IKEDA
    2020 Volume 7 Issue 4 Pages 20-00039
    Published: 2020
    Released: August 15, 2020
    [Advance publication] Released: June 16, 2020
    JOURNALS FREE ACCESS

    In order to synthesize a human-friendly flexible mechanism with a simple structure, a revolute pair with flexible kinematic constraint in multiple directions is proposed. It is called the multi-directionally flexibly constrained revolute pair (MFCRP). The structure of the MFCRP is composed of a link with two same spherical surfaces and a link with two same cam surfaces, and each set of the cam surface and the spherical surface is in contact at a point. The connection between the two links is kept by two linear springs arranged between the two links. The MFCRP can generate 1-axial relative rotation between the two links and relative motions in the other directions are flexibly constrained. In order for the MFCRP to have both flexibility for safety and rigidity for the force transmission, the specified non-linear stiffness can be implemented in the two relative translational directions between the two links. This flexible translational constraint is generated by the spring forces and the reaction forces between the two links. In this paper, two methods to design the cam surfaces to implement the specified non-linear stiffness are proposed. The validity of the proposed design methodology is confirmed by comparing measured stiffness characteristics between two links of some prototypes with the theoretical characteristics. As an application, a flexible closed-loop linkage with the MFCRP is fabricated and its flexibility and kinematic performance are investigated through some experiments.

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Bio, Medical, Sports and Human Engineering
  • Hayato NAKAHARA, Akihiro MATSUDA
    2020 Volume 7 Issue 4 Pages 20-00072
    Published: 2020
    Released: August 15, 2020
    [Advance publication] Released: July 17, 2020
    JOURNALS FREE ACCESS

    Materials such as natural leather and artificial leather are some of the most important materials in sports. Natural leathers have been widely used for sports equipment. Currently, artificial leathers are also often used in sports as an alternative to natural leathers. However, the structure of both artificial and natural leather materials is complex because both biochemical and artificial fibers are contained in the body. Due to the effect of internal fibers, anisotropic mechanical characteristics of leathers are observed. Also, the fiber orientations are dispersed, and fiber orientation dispersion and degree of anisotropy have correlations. Regarding the manufacturing process of sports equipment made with artificial and natural leather materials, it is important to consider the anisotropic mechanical characteristics and fiber orientation dispersion to improve design performance. In this study, uniaxial tensile loading tests were conducted on three types of leather materials to investigate their anisotropic characteristics, and an anisotropic hyperelastic model for leather materials was proposed. Also, numerical simulations using the finite element method (FEM) were performed. Tensile loading tests were performed on an artificial leather and two types of natural leather. The results revealed that all materials exhibited anisotropic behaviors and different anisotropic characteristics were observed in each material. The existence of one fiber family was revealed in the artificial leather and that of two fiber families was revealed in the natural leathers. Regarding the FE simulations, the mechanical properties of the three types of leathers were reproduced by the proposed model. The mechanical characteristics of leather materials which had one fiber family and two fiber families could be reproduced. The applicability of the proposed hyperelastic model to evaluate the mechanical properties of leather materials was demonstrated.

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Transportation and Logistics
  • Takafumi ASAO, Yuki MOTOMURA, Hiroki HASHIGUCHI, Kentaro KOTANI, Satos ...
    2020 Volume 7 Issue 4 Pages 20-00175
    Published: 2020
    Released: August 15, 2020
    [Advance publication] Released: July 02, 2020
    JOURNALS FREE ACCESS

    Driving simulators (DSs) have been widely used to develop advanced driver assistance systems to improve driving safety in vehicles. A major drawback of using DSs is the lack of speed perception while driving. Hence, improvements to speed perception have been recognized as a major priority for enhancing DSs. One approach for achieving better speed perception is to manipulate the human visual space using distorted images in DSs. A previous study revealed that the visual space was distorted subjecting to a visual distance towards an object in a virtual space. Thus, this study aims to obtain optimized image distortions and to evaluate their ability to allow drivers to perceive speed more accurately. A set of computer graphic images representing driving in a straight rural-like road was generated by applying distortions to the original image. The first experiment was conducted to determine the participants’ perceived speeds when viewing the images. Four levels of image distortion were used on seven images representing different speeds. The perceived speed increased with the image distortion, and an equation defining the perceived speed as a function of both image speed and distortion was derived. Another experiment was then conducted to verify whether the images generated using the derived equation could allow drivers to accurately perceive speed. As a result, the optimized image distortion allowed the DS users to accurately determine the image speeds, with an average difference between the perceived and the image speed of 2.7%.

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  • Joohyeong LEE, Saya KISHINO, Keisuke SUZUKI
    2020 Volume 7 Issue 4 Pages 20-00015
    Published: 2020
    Released: August 15, 2020
    [Advance publication] Released: July 07, 2020
    JOURNALS FREE ACCESS

    In recent years, many Advanced Driver Assistance Systems (ADAS) have been proposed and introduced under the development of sensing technology and the issue of driving safety. But many kinds of ADASs have a specific threshold to control the alarm or some support. This is decided based on the experimental or mathematical calculations in terms of the optimization of the human-machine interface of each system. But almost all of the systems (especially warning systems) have just a single threshold value to issue the warning, and the driving performance of drivers fluctuating in real time is not considered. In this study, we proposed a quantification method of riding performance and performed the logistic regression analysis for the collision prediction model based on riding performance to optimize the warning threshold of ADAS. For this study, 64 test subjects (Mean age = 22.14, S.D. = 3.71) participated in the experiments using simulator. Experiments were conducted for three risk events (left-angle collision when a rider was driving on priority road or driving on non-priority road, and right turning collision) and dummy events with the same road environment without risky situations. We proposed a quantification method of riding performance through the total sum of a product of the generalized value of riding behaviours. We also proposed the logit model, which can be constructed in terms of the collision probabilities and riding performance, which is quantified using our proposed method. In the logit model, collision occurrence was used as the dependent variable and riding performance was used as the independent variable for logistic regression analysis to clarify the condition where the probability of collision increases. Finally, we proposed a concept of the setting method of threshold value for the warning timing of ADAS according to the rider’s performance level based on collision probabilities during each riding performance.

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