Advanced Experimental Mechanics
Online ISSN : 2424-175X
Print ISSN : 2189-4752
ISSN-L : 2189-4752
Current issue
Displaying 1-16 of 16 articles from this issue
Special Submission
  • Wei - Cheng CHEN, Keh - Chin CHANG
    Article type: research-article
    2021 Volume 6 Pages 3-11
    Published: August 31, 2021
    Released on J-STAGE: December 09, 2021
    JOURNAL FREE ACCESS

    Particle image velocimetry (PIV) is a non-intrusive optical diagnostic in which the properties of fluid flow are made of the foreign or tracer particles (seedings), and it is, thus, an indirect measurement method. Twophase flow essentially consists of the continuous phase (carrier fluid) and dispersed phases (laden coarse particles or bubbles). The turbulent near-wake flow after a long circular cylinder laden with a binary-size group of particles is employed for demonstrating a two-phase complex flow case in the study. The fine particles (with the mean size of 2.7μm) serve as the seedings and their motion represents the flow behavior of carrier fluid, while the coarse particles (with the mean size of 55 μm) represent the dispersed phase. A double-discriminating process in terms of gray level and size of image pattern together with the median mask technique is employed for discriminating the image patterns of the carrier and dispersed phases in the flow field. However, confident measurements of turbulent flow properties using the PIV diagnostic, no matter what are of the continuous or dispersed phase, must meet the statistical conditions of sufficient numbers of particles falling within each interrogation window of the image. An approach in terms of gray-level ratio of the image is developed to judge attainment of statistically stationary status of the measured two-phase turbulent flow properties, particularly in the very upstream subregion of near wake. The thresholds of gray-level ratio set for the seedings and laden coarse particles are 0.58 and 0.63, respectively, in the study to assure statistically stationary results. It is shown that there indeed exists a core subregion in the very upstream near-wake where PIV diagnostic is incapable of providing confident measurements of turbulent two-phase flow properties.

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Fluid and Thermal Engineering
  • Ryosuke KOBAYASHI, Tetsuya YANO
    Article type: research-article
    2021 Volume 6 Pages 13-20
    Published: August 31, 2021
    Released on J-STAGE: December 09, 2021
    JOURNAL FREE ACCESS

    For plasma-assisting cell modification, it is important to understand the mechanism of a transport process of plasma induced chemical species into a liquid suspending target cells. In this study, a plasma jet was irradiated to a liquid surface. The pH change and flow in the liquid induced by plasma irradiation were investigated. All experiments were conducted varying gas flow rate under same input voltage conditions. Two kinds of pH indicators with different color transition pH range were used as the sample liquid to visualize the pH change due to plasma irradiation. It was confirmed that the pH drop due to plasma irradiation can be mitigated by increasing gas flow rate. Particle image velocimetry (PIV) measurement revealed the improvement in stirring effect with the increase of gas flow rate. These findings would contribute to improve the quality of plasma-assisting cell modification. Furthermore, a combination of visualizations of pH change and flow field would be a useful method to explore the optimal conditions.

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  • Tatsuro WAKIMOTO, Kokichi ABE, Kenji KATOH, Yoshiaki UEDA, Manabu IGUC ...
    Article type: research-article
    2021 Volume 6 Pages 21-26
    Published: August 31, 2021
    Released on J-STAGE: December 09, 2021
    JOURNAL FREE ACCESS

    The static and dynamic surface tensions of the molten eutectic solder were measured for various oxygen concentrations in the environment. When the oxygen concentration was more than 0.025%, an oxide film might be formed on the surface of the eutectic solder, and the surface tension tended to increase with the maximum droplet diameter. The dynamic surface tension was measured by the capillary jet method proposed by the authors in the previous reports. The measured results for oxygen concentrations under 0.025% showed that the surface tension changes during a relaxation time of several milliseconds. As the oxygen concentration increases, the rate of oxygen adsorption to the surface increases, while the time necessary to reach the equilibrium state increases as the increase of amount of saturated adsorption. As a result of these contradictory effects, it was shown that the relaxation time of eutectic solder is maximized at around 0.018% oxygen concentration.

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  • Yoshitaka ISODA, Yohsuke TANAKA, Takuma SADANAGA, Shigeru MURATA
    Article type: research-article
    2021 Volume 6 Pages 27-32
    Published: August 31, 2021
    Released on J-STAGE: December 09, 2021
    JOURNAL FREE ACCESS

    The purpose of this study is to investigate the influence of periodic flow on the laminar boundary layer of a pitching NACA 0012 airfoil at a low Reynolds number. The periodic flow is the freestream oscillating sinusoidally in the streamwise direction. The velocity field is measured by particle image velocimetry (PIV) under the conditions of a Reynolds number of 3700 and a reduced frequency of 2.01. In the processing, we introduce an overlapping technique and a rectangular interrogation window to evaluate the boundary layer profile with high spatial resolution. However, the velocity on the airfoil surface cannot be obtained because of the angle of view, so a numerical simulation is performed under the same conditions to obtain the velocity data on the surface. The flow reversal related to dynamic stall is evaluated with the wall shear stress calculated by numerical simulation, which is confirmed to agree with the boundary layer profile obtained by PIV. The periodic flow case is compared with the steady case to determine the effect of freestream oscillation on the flow reversal. It is found that the reversed flow vanishes during freestream acceleration, whereas the reversed flow region increases during freestream deceleration.

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Solid Mechanics and Materials Engineering
  • Naoya TOYAMA, Yuelin ZHANG, Satoru YONEYAMA, Satoshi KUWABARA, Hidetom ...
    Article type: research-article
    2021 Volume 6 Pages 33-38
    Published: August 31, 2021
    Released on J-STAGE: December 09, 2021
    JOURNAL FREE ACCESS

    This paper proposes a method to estimate stresses that cause the warpage of a silicon wafer from a deflection measurement. The deflection is measured by an optical method, a scan of a laser displacement sensor. A least-squares method with a finite element mesh is used for smoothing and differentiating the measurements. By applying this method, the surface strains of a silicon wafer are obtained as the 2nd derivatives of the deflection. The stresses that cause the warpage are estimated by assuming that the stresses are released and free in the warped wafer. The effectiveness of the method for obtaining surface strain from deflection is demonstrated by applying it to wafer simulation data and measured beam deflection. Results show that the surface strain can be properly obtained from the deflection measurement. Furthermore, the proposed method is applied to stress analysis of actual silicon wafers. This method is expected to be used to control quality of silicon wafers.

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  • Yuichi ONO, Sho OGAWA, Taichi TERAI, Shigekazu MORITO
    Article type: research-article
    2021 Volume 6 Pages 39-46
    Published: August 31, 2021
    Released on J-STAGE: December 09, 2021
    JOURNAL FREE ACCESS

    Round bars of SUS304 stainless steel were friction welded under five different conditions. The torsion tests were conducted on the friction-welded joints to obtain the torsional characteristics. The digital image correlation (DIC) was simultaneously applied to measure the full-field shear strain distributions in the inhomogeneous joint interface during torsional loading. Sufficient heat input per unit length in the upset stage was essential to obtain the joint with no defects and enough torsional strength. EBSD analysis also revealed that the recrystallized microstructure around the joint interface consists of very fine, equiaxed grains. For joints with no defects at the joint interface, local shear strains at the joint interface during torsional loading were smaller than those of a base material. This should be the result of increased interfacial hardness due to the reintroduction of dislocations into the recrystallized grains during the torsional load.

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  • Daisuke IMANISHI, Yoshiaki NISHINA
    Article type: research-article
    2021 Volume 6 Pages 47-52
    Published: August 31, 2021
    Released on J-STAGE: December 09, 2021
    JOURNAL FREE ACCESS

    Large numbers of conveyance rolls are installed in the rolling processes in steelworks. Although these rolls are inspected by magnetic particle testing (MT) after disassembling the roll components, inspection efficiency is extremely poor due to the disassembly and reassembly operations. Recently, a high-efficiency crack inspection technique for conveyance rolls using vibrothermography, which does not require disassembly, has been reported. Vibrothermography detects cracks as a local temperature rise when excited by ultrasonic vibration. In this method, it is important to propagate enough ultrasonic vibration. In this paper, a suitable horn shape for a structure which has a curved surface, such as a conveyance roll, is newly suggested. Laboratory tests and off-line tests of the suggested ultrasonic horn were conducted, and improvement of crack detectability was confirmed. A high-efficiency inspection system for actual production lines that consists of an infrared reflector, an ultrasonic vibrator, the new type of ultrasonic horn and an infrared thermography device is also proposed. Inspection efficiency can be improved significantly in the actual production line with this inspection system.

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  • Daisuke MORIOKA, HongSeok CHOI, Ichiro KITAYAMA, Masato KITANO
    Article type: research-article
    2021 Volume 6 Pages 53-58
    Published: August 31, 2021
    Released on J-STAGE: December 09, 2021
    JOURNAL FREE ACCESS

    We developed a displacement and torsion measurement system comprising a linear sensor system that directly measures PAFO deformation with very high accuracy. This system enables highly accurate and direct measurement and is free from measurement errors caused by infrared reflection. Using this system, we report the relation between deformation and angle in walking tests. Seven healthy men participated in experiments using this system with stride lengths set to 300 mm and cadence to 80 step/min. As a result of the walking analysis revealed that the toe or heel part of the PAFO was constrained between the floor and the foot immediately after the initiation of stance phase, and terminal stance phase, and adduction torsion occurred because the load was generated to cause plantar flexion. After that, consequently, it can be seen that due to the load shift and the flexibility act of the PAFO, the adduction torsion is decreased.

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Materials Science and Processing
  • Hiroshi SAWANO, Suguru WATANABE, Kentaro KOBAYASHI
    Article type: research-article
    2021 Volume 6 Pages 59-64
    Published: August 31, 2021
    Released on J-STAGE: December 09, 2021
    JOURNAL FREE ACCESS

    Recently, as the demand for high-strength parts has increased, there is a growing need for processing techniques for difficult-to-cut materials. Studies have been conducted to improve the workability of the workpiece by adding heat just before cutting and increasing the temperature at the cutting point. Lasers are often used for heating, which require secure safety measures and large-scale devices. Therefore, in this study, to improve the cutting efficiency by preheating with a simpler device, a discharge assisted cutting method was proposed. In the proposed cutting method, preheated cutting is performed by heating the cutting point by electrical discharge just before cutting. As a result of the discharge assisted cutting experiments, it was found that the machining point of the workpiece was softened by the heating of the discharge, and the surface roughness after machining could be improved by the proposed discharge assisted cutting. Therefore, we can conclude that the proposed discharge assisted cutting is useful for improving the machined surface properties.

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  • Chisa FUKUDA, Koya TAKAHASHI, Yoshiyuki NISHIMURA, Koichi OZAKI
    Article type: research-article
    2021 Volume 6 Pages 65-70
    Published: August 31, 2021
    Released on J-STAGE: December 09, 2021
    JOURNAL FREE ACCESS

    The effectiveness of porous nickel-plated films in the bonding dissimilar materials was investigated in this study. A microscopic rough surface was formed by porous nickel plating on a metal, and the plated surface was bonded with several plastics. Polyethylene, polypropylene, and polycarbonate were used as bonding plastics, and heat pressing was adopted as the bonding method. As the result of tensile test, the bonding strength was improved by depositing porous nickel-plated films on a metal. In particular, polypropylene could not bond with non-porous films but it could with porous films. The bonding strengths of polyethylene and polycarbonate were also improved with the deposition of porous nickel-plated films.

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  • Hiroki ITO, Kengo KATO, Hideki ONO
    Article type: research-article
    2021 Volume 6 Pages 71-76
    Published: August 31, 2021
    Released on J-STAGE: December 09, 2021
    JOURNAL FREE ACCESS

    Japan's steel stock has been increasing every year and the amount of steel scraps has been increasing as well.Therefore, it is necessary to utilize a lot of steel scraps as an iron source in the future. However, steel scraps generally contain tramp elements that are difficult to be removed when they are once dissolved in molten steel. Copper, which is one of the tramp elements, cannot be removed by oxidation because it is more noble than iron. Therefore, a new principle to remove copper from molten iron must be developed. Since silver is more noble than copper, it is possible to remove copper from molten iron by oxidation via silver. In this work, the mass transfer of copper through adjacent phases of Fe-C(l), γFe(s) and Ag(l) under a temperature gradient was investigated. The results show that copper in the Fe-C(l) phase is transferred through the γFe(s) phase into the Ag(l) phase, and the diffusion of copper in the γFe(s) phase was found to be the rate limiting step based on the variation of the mass transfer of copper with time. Limitation of copper removal was also discussed, and it is found that the copper content can be decreased down to 0.050 mass% by the oxidation via γFe(s) and Ag(l) phases under the temperature gradient.

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  • Tatsuya OHMI, Hideaki ICHIMURA
    Article type: research-article
    2021 Volume 6 Pages 77-82
    Published: August 31, 2021
    Released on J-STAGE: December 09, 2021
    JOURNAL FREE ACCESS

    The structures between closely located microchannels having Ni-Al intermetallic lining layers have been investigated. The microchannels were produced by a sacrificial-core method using nickel as the body metal which composes the device body and aluminum as the sacrificial-core metal which gives the shape of the microchannel. Three basic types of interaction of the microchannels were detected: isolation (no interference), coalescence of the lining layers, and coalescence of the microchannels. In a particular case when the two lining layers just touched each other, a coarse void defect formed near the tangent point. The formation mechanism of the void defect was successfully explained in terms of the unbalanced diffusion of aluminum and nickel in Ni-Al intermetallic compounds.

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Damping and Vibration
  • Allah RAKHIO, Yasushi IDO, Yuhiro IWAMOTO, Atsushi TOYOUCHI
    Article type: research-article
    2021 Volume 6 Pages 83-89
    Published: August 31, 2021
    Released on J-STAGE: December 09, 2021
    JOURNAL FREE ACCESS

    In this paper, the torque properties of a novel separated double-chamber rotary damper using elastomer particles instead of fluid have been introduced. The rotary elastomer particle damper was prototyped and experimentally tested. The effect of packing fraction, size of elastomer particles and rotational speed of the shaft on the damper torque of the rotary damper was investigated. It was noticed that increase in the damper torque of the rotary damper was observed with an increase in the packing fraction and size of elastomer particles. To understand the behavior of particles inside the damper, the qualitative and the quantitative analysis was conducted by numerical simulation using discrete element analysis method. The simulation results agree well with the experimental results, verifying the accuracy of the proposed simulation model. The numerical simulation also helped to analyze the working mechanism and high compressive regions inside the damper. The damper torque was found to increase as the packing ratio, rotational speed of the rotor and size of elastomer particles increased.

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  • Allah RAKHIO, Yasushi IDO, Yuhiro IWAMOTO, Atsushi TOYOUCHI
    Article type: research-article
    2021 Volume 6 Pages 90-97
    Published: August 31, 2021
    Released on J-STAGE: December 09, 2021
    JOURNAL FREE ACCESS

    Dampers are crucial for controlling the vibration of dynamic systems. A cost-effective and unconventional device of increasing damping is a particle damper. In this study, damper torque characteristics of a rotary elastomer particle damper using spherical and ellipsoidal elastomer particles are analyzed. A prototype of a rotary elastomer particle damper is produced and experimentally tested. Numerical simulation was performed to understand the behavior of spherical elastomer particles, while visualization experiment was conducted to observe the behavior of ellipsoidal elastomer particles. It was observed that the increase of packing fraction and rotor speed increases the damper torque. The spherical particles are capable of producing higher damper torque compared to ellipsoidal particles. Increase of aspect ratio of ellipsoidal particles decreases the damper torque.

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Geoenvironmental Engineering
  • Kohei UENO, Kazumi RYUO, Tomoaki SATOMI, Hiroshi TAKAHASHI
    Article type: research-article
    2021 Volume 6 Pages 99-103
    Published: August 31, 2021
    Released on J-STAGE: December 09, 2021
    JOURNAL FREE ACCESS

    Mortar flow tests were conducted using soil with several moisture conditions to investigate the liquidity suppression performance of a water absorbent polymer. It was confirmed that the liquidity of the soil after the mixture of the polymer can be predicted based on the liquidity index and the amount of the polymer. Furthermore, unconfined compression tests were conducted to examine the applicability of the Fiber-cement-stabilized soil method to soil containing polymer. The results showed that the method is applicable to modify the soil containing the polymer.

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  • Delima Canny Valentine SIMARMATA, Thomas Teguh WIJAYA, Tomoaki SATOMI, ...
    Article type: research-article
    2021 Volume 6 Pages 104-109
    Published: August 31, 2021
    Released on J-STAGE: December 09, 2021
    JOURNAL FREE ACCESS

    Landslides generally occur on sloping surfaces due to instability of soil mass movement. The calamity is aggravated by the high rainfall intensity which potentially generates the failed slope and a high-water content sludge. It is important to remove the sludge immediately and recover the damaged slope. However, the transportation to bring the soil material for slope recovery and remove the sludge are overpriced. Therefore, instead of disposing of the sludge, this work proposes recycling the sludge on-site by applying the recycling method, or so-called Fiber-Cement-Stabilized Soil (FCSS) method. The modified landslide sludge is then addressed to use as a filling material in the form of a cover layer. In addition, the stability of the modified sludge-covered slope is examined. Therefore, the direct shear test is conducted to obtain the shear strength parameters which are expressed by Mohr-Coulomb failure criterion. In this work, limit equilibrium technique is applied to obtain the Factor of Safety (FS) value as the safety level parameter. The geometrical properties and desired cover thickness are introduced to the FS analysis. The result shows that the FCSS method is effective to modify the sludge and usable for the failed slope cover.

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