Alkanethiol molecules chemically adsorbed on the gold (Au) surface are considered to investigate the characteristics of the Self-assembled monolayer (SAM) interface at room temperature. The analysis is based on the molecular dynamics (MD) method. We use two alkanethiols with different chain lengths, that is, ethanethiol (C_2H_5SH) and 1-propanethiol (C_3H_7SH) as the adsorbed molecule on the Au (111) surface. The probability distribution of the tilt angle of SAM molecules is obtained. It is shown that the peak position of tilt angle in the distribution has 30.0° for ethanethiol, and 28.3° for propanethiol, respectively. The calculated tilt angle agrees well with the previous MD result. The detailed structure of the adsorption position of thiol molecule also obtained. It is found that many thiol molecules for ethanethiol are seated on a fcc-hollow site of the surface although the thiol molecules for ethanethiol mainly have the adsorption position of a hcp-hollow site of the surface.

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In this paper, pressure is calculated by the virial theorem in molecular dynamics. This research aims establishing a method to calculate thermodynamic pressure and verifying molecular dynamics and experiment. A system of argon vapor-liquid equilibrium is the object of this paper. Pressure calculated with the virial equation state in vapor phase of argon vapor-liquid equilibrium system agrees vapor pressure of experimental values. Calculated pressure of vapor system, same number density to vapor phase of vapor-liquid equilibrium system, agrees vapor pressure. Calculated pressure of liquid system have large difference between those values, however, it is expected the difference is smaller by increasing sampling number.

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In our study, we investigated fluctuation structure of diatomic fluids around the critical point. We used molecular dynamics simulation to evaluate the principle of corresponding state of fluctuation structure of 2-center-Lennard-Jones fluid which has molecular elongation as a parameter. We evaluated the static fluctuation structure by calculating dispersion of number of molecules at divided cells and static structure factor. As results, the principle of corresponding state on the static fluctuation structure is satisfied because static fluctuation structure does not have dependence on molecular elongation. On the other hand, dynamic fluctuation structure of fluid which has longer molecular elongation disagrees with dynamic fluctuation structure of fluid which has shorter molecular elongation. Therefore, it was found that the principle of corresponding state of dynamic fluctuation structure might not be satisfied.

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In the present study, the effect of the Reynolds number on the incompressible turbulent channel flow is investigated by means of the direct numerical simulation. In the large Reynolds number case, the turbulence energy, Reynolds shear stress and bulk mean velocity increase and the anisotropy of the Reynolds normal stresses near the wall is weakened in comparison with the low Reynolds number one. The large-scale structures appear in the visualization result of the large Reynolds number flow and this behavior corresponds to the dependency of the length scales obtained from the two-point correlation on the Reynolds number.

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The dissimilarity between momentum and heat transfer was investigated numerically in a 2-D channel flow, in which turbulent mixing is exclusively dependent on the transverse vortex motion. Since the Reynolds stress can be suppressed by the effect of wall-normal velocity and pressure gradient fluctuation correlation, the dissimilarity is remarkably enhanced in 2-D channel flow. Here in this report, the time history of dissimilarity strength in Lagrangian path of fluid particle was considered from numerical results of 2-D flow. The results showed that the strength of dissimilarity is closely related to the above mentioned correlation through the vortex motion in the flow field.

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Turbulent boundary layer structures behind a functional riblet with multiple characteristic scales are investigated by means of a hot-wire technique. The functional riblet employs two characteristic scales of the turbulent boundary layer, where the riblet trapezoidal lower and straight higher combs carrying streamwise grooves reach the buffer and logarithmic layers of the boundary layer, respectively. The turbulent boundary layer profile behind the higher comb shows a friction reduction rate up to 41 %, because the velocity distribution near the wall has a linear profile normal to the wall. Whilst the boundary layer profile behind the lower comb indicates an ordinary friction reduction rate of about 5%. The turbulent boundary layer structures measured far downstream behind the functional riblet indicate how the modified boundary layer develops downstream.

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An Experimental study was conducted on heat transfer characteristics in the developing region of a flat channel with a combination of a dimpled surface and a protruded surface for relatively low Reynolds numbers of Re = 1000 - 5000. Detailed local heat transfer characteristics were measured by the naphthalene sublimation method. Attention was directed to the influence of the distance between the dimpled surface and the protruded surface opposing it on the local heat transfer characteristics. The depth/height of the dimple/protrusion δ was fixed at 2.2mm and the distance between two surfaces H was changed as 1.36δ, 2.27δ and 4.54δ. The influence of the protruded surface on the local heat transfer on the dimpled surface appeared in the transitional Reynolds number range of Re = 2500 - 3000 for H = 1.36δ and 2.27δ, but it was not observed for H = 4.54δ. The influence of the dimpled surface on the local heat transfer on the protruded surface was observed mainly on its flat area only in the channel of H= 1.36δ.

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We have investigated experimentally the turbulent diffusion processes of ethylene emitted from a point source in the upstream region of a two-dimensional hill model. By using the fast-response flame ionization detector (FFID), the mean and fluctuating concentration distributions are measured quantitatively. It is found that in the separated region, the mean concentration profiles are almost uniform in the vertical direction, and the locations of the maximum concentration appear along the dividing streamline formed in the downstream region of the hilltop. On the other hand, the r.m.s. values of concentration fluctuations become maximum at the outer edge of the concentration boundary layer, and become small in the separated region where the mean concentration keeps a high value.

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We have investigated experimentally the spatio-temporal characteristics of turbulent thermal boundary layers developing over a heated flat plate with various thermal boundary conditions. A ladder-structured temperature probe consisting of 10 cold-wires 3 μm in diameter has been used to measure temperature fluctuations simultaneously at the representative points - from the immediate vicinity of the wall to the outer region - in the thermal boundary layer. The present measurement technique enables us to investigate the effects of the wall thermal boundary condition on the spatio-temporal behaviors of the turbulence quantities of the thermal field. From the conditional sampling and averaging based on the VITA method with the temperature slope criterion, it is found that the spatio-temporal characteristics of temperature fields are strongly affected by the thermal boundary conditions.

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The onset of thermal convection has been investigated numerically in turbulent shear flows, i.e. plane Couette and plane Poiseuille turbulence, between two horizontal plates heated from below. For fixed Reynolds numbers (Re = 750 for Couette flow; Re = 3000,4000,5000 for Poiseuille flow), the bulk Richardson number Ri is gradually increased to inspect the effects of buoyancy on shear-driven and pressure-driven turbulent flows. In plane Couette turbulence, buoyancy-induced streamwise rolls are observed to appear around Ri = 0.003, and they are found to be deformed into streamwise-dependent wavy rolls around Ri = 0.0071. At the higher Richardson number Ri 0.05 the wavy rolls propagate in the streamwise direction. In plane Poiseuille turbulence, buoyancy-induced streamwise rolls also appear at a certain value of Ri which depends on Re. The thermal convection in Poiseuille turbulence exhibits distinct bistable states: one is represented by the narrower rolls (1.2 times channel height) in the spanwise direction, and the other is represented by the much wider rolls (2.3 times channel height).

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Reversal motions are often observed in the system with a parity symmetry. Reversals of large-scale circulation also exist in the case of thermally driven turbulence in a container. We investigate the onset of chaotic reversals of thermal convection cell in a two-dimensional square cavity using direct numerical simulation. In this system, the first observable reversal is related to the one-vortex state. The symmetric pair of the stable one-vortex periodic orbits approach each other as Rayleigh number increases. These orbits touch the steady saddle, which exists on the basin boundary between them, and become the homoclinic orbits to the saddle. This event is the homoclinic explosion which leads to the onset of chaotic reversals.

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Direct numerical simulation (DNS) of a thermally-stratified turbulent boundary layer subjected to a non-equilibrium adverse pressure gradient (APG) is carried out. DNS results clearly show characteristics of thermally-stratified turbulent boundary layer having a non-equilibrium APG. It is found that both the local skin friction coefficient and the local Stanton number decrease in case of stable stratification with APG, but increases of those APG affected are revealed. After the local skin friction coefficient in that case increases, that becomes similar to the local skin friction coefficient in case of stable stratification with ZPG, in which Reynolds shear stress and wall-normal turbulent heat flux are especially enhanced in the outer region.

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It is known that Taylor-Couette flow shows a transition in the Reynolds number dependency of the mean torque near Re 〜 10000. To investigate the turbulent vortical structures in the transition state, direct numerical simulations of Taylor-Couette flow with fixed outer cylinder have been conducted in the different Reynolds numbers from Re = 8000 to 25000. As the Reynolds number increases, the fine scale eddies are more populated in a large part of the domain and they tend to take more various angles. The joint probability functions of the tilting angles of eddies with respect to the tangential direction and their radial positions exhibit preferential distributions, which is due to the shear layer between the large scale Taylor vortex motions. The present results suggest that the distribution and the orientation of the fine scale eddies in this Reynolds number range are greatly affected by the Taylor vortex structure.

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In general, the drag-reducing effect in a pipe by a surfactant additive is attributed to rod-like micelles in the surfactant solution. This paper describes the results of experiments performed for determining the relationship between the micelle structure in the surfactant solution and the drag-reducing effect in a pipe flow. The experimental apparatus is circulation type by using pump and inner diameter of test pipe is 10.6mm. A fluorescence probe method was used to examine the micelle structure in the drag-reducing surfactant solution flow. Pyrene-1-carboxaldehyde was used as the fluorescence probe. The obtained experimental results were as follows. When the drag-reducing surfactant solution was irradiated with ultraviolet light, the fluorescence intensity at the wavelength of 487nm varied with the micelle structure. The fluorescence intensity decreased with the generation of the Shear Induced Structure (SIS) and increased with the disappearance of the SIS. The fluorescence intensity near the pipe wall increased simultaneously with the flow transitions to turbulence. In other words, the turbulent transition occurs along with the disappearance of the SIS near the wall.

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As a measure for giving adequate inlet boundary conditions in large-eddy simulations (LES) of spatially developing turbulent flows, attention was paid on 'linear forcing', a method for generating isotropic turbulence, and a specification method of turbulence length scale using the linear forcing was proposed in this research. The applicability of the linear forcing to LES and the validity of the specification method of turbulence length scale were evaluated using LES results of isotropic and anisotropic turbulent flows. As a result, it was found that (1) the basic characteristics of isotropic turbulence which should be generated by the linear forcing is reproduced under the grid conditions satisfying that the ratio of the subgrid-scale energy dissipation to the total dissipation is less than 0.9, (2) the time-averaging length introduced in this linear forcing could vary low-frequency power spectra of velocity to control turbulence length scale, and (3) the specification method of turbulence length scale is valid for both of isotropic and anisotropic turbulent flows. These findings indicate that this linear forcing method specifying turbulence length scale could be effective as an inflow boundary condition with turbulence in LES.

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In turbulent flow, the energy dissipation rate is an important physical quantity for evaluating the Kolmogorov scale which is the smallest scale in turbulent flow. In the present study, nearly isotropic turbulence at low Reynolds number was generated by a pair of oscillating grid so that the Kolmogorov length can be large. We observed the velocity field by using PIV(Particle Image Velocimetry) method, and the energy dissipation rate was obtained from the velocity two-point correlation, the combination of velocity gradient and the identification of the vortex. These evaluation methods were examined by comparison.

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It is necessary for the control of turbulent combustion to investigate the local flame structure and combustion properties. However, the detailed local flame structure has yet to be elucidated. Local flow velocity are necessary to evaluate flame stretch rate and strain rate in relation to the flame structure. The evaluation methods of these properties are different in numerical and experimental analyses: in the numerical analyses, direct numerical simulation (DNS) is used, while in the experimental analyses, visualization techniques are needed. Therefore, it is difficult to compare the results obtained from both techniques and to evaluate quantitative relationships. In this study, the differences between the experimental and numerical analyses on local flow velocity were investigated. The Particle Image Velocimetry (PIV) analysis was performed with the DNS data of hydrogen/air turbulent premixed flames. As a result, the vector map and probability density function (PDF) of the local flow velocity obtained from simulated PIV system is in good agreement with those from DNS.

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Thermocouple and infrared thermography have been widely used to measure a temperature. However thermocouple is only one point measurement, and infrared thermography cannot use through infrared impermeable material such as water or acrylic board. In order to solve these problems, we have developed a temperature measurement system by using temperature sensitive paint (TSP). TSP is a kind of luminescent paint and its luminescent intensity decreases with increasing temperature. Using temperature dependency of TSP, planar temperature distribution can be measured from an image of luminescent intensity taken by video camera. TSP is composed of luminescent molecule, binder, and solvent. In the present study, Ru(phen)_3^<2+> is adopted as luminescent molecule, and blue LED is used to excite the molecule. To evaluate the present measurement system, using the acrylic wind tunnel, the temperature of the flat plate was measured in backward-facing step flow in a uniform flow. In this study, we measured the temporal temperature field at the reattachment point for backward-facing step flow and tried the visualization with the animation of the temperature distribution.

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Experimental and numerical studies were made on the effect of a delta-wing row on the promotion of turbulent mixing of hot and cold airflows in a T-junction with rectangular cross sections. The wing row was attached on the upstream wall of the branch. The influence of the angle of attack of the wings on the distributions of mean temperatures and turbulence intensities was examined by experiments, and the experimental results were compared with numerical ones obtained by LES with a commercial code. The thermal mixing was promoted by strong turbulence produced by the delta wings with the backward tilting arrangement, and the degree of mixing could be changed with the angle of attack. The mean temperature distributions predicted by LES agreed qualitatively with those obtained by experiments, but the turbulence intensities were generally overestimated in downstream regions.

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In this study, in order to evaluate and improve a heat transfer turbulence model which is useful for a design of equipment in the engineering, Reynolds Averaged Numerical Simulation (RANS) of turbulent thermal mixing and heat transfer in T-junction channel flow is carried out using three linear two-equation models and a nonlinear two-equation model. As for the calculation of thermal field, two-equation heat transfer model and a zero-equation model are used. In predictions of wall friction coefficient, all models are difficult to quantitatively predict the behavior of wall friction coefficient, but AKN model gives proper prediction of downstream region behind reattachment point. In the prediction of thermal field, the mixedness is an important index for the temperature mixing and heat transfer. AKN model gives a good prediction of mixedness because of using the two-equation heat transfer model. However, zero-equation model for thermal field cannot adequately predict the mixedness, even as a nonlinear two equation model is employed for the velocity field. Thus, turbulence model should be improved for a turbulent thermal mixing and heat transfer in T-junction channel flow.

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In PEFC, flooding phenomena is one of the critical problems to be solved. Therefore, it is necessary to optimize water and reactant gas flow management in the cell. Our research group applied the lattice Boltzmann method (LBM) for the two phase flow with high density ratio, including the effect of wettability, and has carried out the analyses of gas and liquid water flow to propose the gas diffusion layer (GDL) with the high water draining capability. In this study, we simulated liquid water behavior inside of the GDL applying the equal density LBM in order to achieve shorter computational time comparing to the high density ratio LBM. In the equal density LBM code developed by the authors, we found two problems. One was a decrease in amount of water in the GDL, and the other was discriminating liquid water behavior compared with in the high density ratio LBM. This paper explains the applied improvements to solve these two problems by setting the wall boundary conditions appropriately.

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Capillary pressure boundary condition model was introduced into the numerical solver for polymer electrolyte fuel cell based on the OpenFOAM. The boundary condition module can predict water saturation jump so that the thermodynamic equation of state is satisfied on the interface between the catalyst layer and gas diffusion layer. In this paper, liquid water transport in the cathode electrode of PEM fuel cell was calculated by using the OpenFOAM solver. The result shows that the numerical model can describe typical behavior of water removal through porous materials.

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According to earlier studies, the porous flow fields of Polymer Electrode Fuel Cell (PEFC) are more tolerant against flooding phenomenon in comparison with conventional flow channels such as straight and serpentine type channels. However, the relationship between the porous structure and water management ability of porous media has not been clarified. This study investigated the influence of porosity and pore diameter of metal foam flow fields on the cell performance and water transport. Celmets, which are the porous media with foam structure and high porosity in comparison with sintered metal, is used as the porous flow fields. The results show that the influence of pore diameter on cell performance and water drainage is small under the condition of this study. And the usage of celmets with higher porosity, 96.8%, causes a decrease in cell performance. Such a performance decrease appears to be caused by the lower contact pressure and inferior gas diffusion.

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The effects of water cluster structures on the PT properties have been investigated using reactive molecular dynamics (MD) simulations. The two-state empirical valence bond (aTS-EVB) model was used to allow proton transport (PT) phenomena including the Grotthuss mechanism to be simulated within the simplicity of the theoretical framework in MD simulations. The systems were constructed to reproduce the experimentally proposed hydrophilic cluster structures (the cylinder model, the lamellar model, and the sphere-rod model) in the Nafion systems. The diffusion coefficients in each dimension were estimated to characterize PT properties. It was found that proton diffusion strongly correlates with the cluster size as well as the type of cluster models. The proton diffusion in the lamellar model is higher than that in the other two types of models when the water volumes are the same. In addition, the rod radius in the sphere-rod model, i.e., the bottleneck of the cluster domain, strongly affects the proton diffusion, suggesting that the rod radius, regardless of the sphere radius, is a dominant factor for the proton diffusion in the sphere-rod model.

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We have investigated proton transport property in polymer thin films in cathode catalyst layer (CL) of polymer electrolyte fuel cell using molecular dynamics simulations to characterize nanoscopic flow phenomena observed in CL. In the CL, polymer thin films cover supported carbon, and it is well known that the wettability of supported carbon depends on operating environments and materials. Therefore we have focused on the effect of the wettability of supported carbon on the structure of polymer thin films and proton transport. In this study, three different wettability surfaces, which are hydrophobic, intermediate, and hydrophilic, respectively, were used. It was found that the structure of polymer thin films strongly depends on the wettability of surface. Especially, the distribution of water molecules is different depending on the characteristic of each surface, leading to distinctive proton transport property because water clusters are served as a proton conductive path. A correlation between the structure of polymer thin films and the proton transport was also discussed.

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Using two different types of ionomers which are composed of perfluorosulfonic acid (PFSA) and hydrocarbon (HC), we constructed systems of the ionomers on Pt catalyst surface, and investigated water content dependence on oxygen permeability in the ionomers using molecular dynamics simulations. We have found that the oxygen permeability of the PFSA ionomer is better than that of the HC ionomer. Moreover, the oxygen permeability decreases as water content increases in the both ionomers. Next, we analyzed density distributions of the ionomer components and oxygen solubility in the ionomers. As a result, in the PFSA ionomer, the oxygen permeability decreases because the oxygen solubility decreases due to the increase in the solvent molecules. On the other hand, in the HC ionomer, the solvent molecules accumulate on the surface of high-density polymers and block the oxygen permeation.

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Enhancing performance and further reductions in size and cost are required to facilitate the commercial widespread adoption of fuel cell vehicles (FCVs). Toyota Motor Corporation met these challenges by developing the world's first FC stack without a humidifying system. This was achieved by the development of an innovative cell flow field structure and membrane electrode assembly, enabling a power density of 3.1kW/L and 2.0 kW/kg, more than twice that of the conventional stack, and allowing the stack to be installed under the floor in a sedan-type FCV. Major cost reductions were achieved by reducing the amount of platinum in the catalyst by two-thirds and adopting a carbon nano-coating for the separator surface treatment.

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Three-dimensional analysis of porous Ni-GDC (gadolinia-doped ceria) cermet for solid oxide fuel cell (SOFC) electrodes is demonstrated using focused ion beam tomography. The electrodes are fabricated through the infiltration technique, introducing nano nickel particles into the GDC ceramic framework structures. Microstructural analysis revealed that the infiltrated electrodes have one order of magnitude larger TPB density than conventional electrodes fabricated by powder mixing and sintering methods, and have a greater potential to satisfy a variety of requirement for SOFC electrodes, which is a significant advantage in developing design-optimized electrode microstructures.

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The current distribution is an evaluation index of PEFC because non-uniform current distribution leads to low utilization of reactants and catalysts. Additionally, current distribution is affected by the reactant flow arrangement and operation conditions. Therefore, it is important to measure and evaluate the current distribution of PEFCs. Many methods to measure current distribution exist, but most modify components of the PEFC. For instance, a method may segment the flow field and measure current distribution using the printed circuit board and resistors network. In order to measure the current distribution of PEFC systems, which are typically stacked, the methods must be non-destructive. In order to realize a non-destructive current distribution measurement approach for use in PEFC stacks, we use some magnetic sensor probes. Here, we described the measurement system and the method using these proves. And current distribution in PEFC was evaluated in its operating condition. The study showed that the current distribution changes by air flow rates and relates the performance of PEFC.

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Solid oxide fuel cells (SOFCs) consist of three layers; a cathode, an electrolyte and an anode. The anode consists of three phases; yittria-stabilized zirconia (YSZ), Ni and pore. In the anode, O^<2->, electrons, and gases pass through in YSZ, Ni, and pore, respectively. In a conventional anode, the three phases are uniformly distributed and the structure is not always appropriate in the view point of the transfer paths of O^<2->, electrons and, gases. In our previous research, the efficiency of power generation was improved by applying magnetic field in anode during the fabrication process. The magnetic field improved the connection of Ni and makes Ni array in anode. In this study, a difference in behavior of different-shaped Ni particles was observed by scanning electron microscopy. An orbicular Ni particle moved better than a rough Ni particle when a magnetic field is applied. The thickness of Ni array became thicker when a stronger magnetic field is applied.

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This paper describes performance characteristics of miniature cooling fans and blowers. In recent years, several types of miniature devices that can generate cooling airflow into electronic equipment have been developed. These devices are enough thin and small and these are available for use in narrow flow passages in high-density packaging electronic equipment. As a consequence of the downsizing and the improvement of the design, flow passages in these devices become narrow and significant pressure drop may be caused. In this study, we are evaluating an optimum selection of these devices in order to obtain higher cooling performance in high-density packaging electronic equipment by using these devices. In this report, we compared effectiveness of three types of the miniature fans and the piezoelectric micro blower mounted in the narrow flow passage from the viewpoint of operating flow rate and cooling performance by using 3-dimentional CFD analysis.

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This study describes a possibility of cooling performance enhancement by using a combination of micro fin heat sinks and miniature vortex generators. Water cooling system is a commonest method to dissipate large heat flux from the inverter of electric vehicles. Therefore, it is very significant to enhance water cooling performance in order to manage high heat dissipation density to handle more high power inverters. We are now trying to develop a high-performance water cooling device by using a combination of a micro fin heat sink and a miniature vortex generator. The combination of the miniature heat sink and the vortex generator may enhance heat transfer performance while inhibiting an increase of pressure drop by generating a swirling turbulent flow in a clearance between the heat sink fins. In this study, the water cooling performance in the narrow flow passage, which simulates the flow passage in the water cooling device, with the miniature heat sink and the miniature vortex generators was investigated by using 3-dimentional CFD analysis. The effects of the miniature vortex generator on the heat transfer performance in the flow passage was investigated while changing the geometry of the heat sink. From the analysis, we conclude that the combination of the miniature heat sink and the vortex generator was effective for the heat transfer enhancement in the narrow flow passage of the water cooling device while inhibiting the generation of the pressure drop when we can use the combination with the appropriate manner.

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This paper examines theoretically and experimentally the dynamic electromechanical response of multilayer piezoelectric actuators for fuel injectors at high temperatures. A phenomenological model of depolarization at high temperatures was used, and the temperature dependent piezoelectric coefficients were obtained. The high temperature electromechanical fields of the multilayer piezoelectric actuators under AC electric fields were then calculated by the finite element method. In addition, test data on the electric field induced strain at high temperatures, which verify the model, were presented.

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With the development of nanotechnology in recent years, many researchers have focused on the development of nanomaterials and nanostructures such as nanowires. To apply these nanomaterials and nanostructures into nanodevices, there are great needs of the quantitative measurement of electrical properties of materials in an infinitesimal area. Recently, it has been reported that the microwave gives an effect to an interatomic force in local area among materials. Therefore, it is thought that an identification of materials and an evaluation of electrical characteristics become possible by clarifying the relation between microwave and interatomic force. Therefore, we investigated interatomic force under the tip of probe by focusing on the force-distance curve measurement using microwave atomic force microscopy (M-AFM) as the first step. This paper describes the method and the results of the force-distance curve measurement on the sample of Au, Si, and glass. Results of this experiment indicate actually that the effect of microwave is large in material which has high electric conductivity.

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We describe the result of the electrical conductivity measurement of single crystalline aluminum nanowires. These nanowires are fabricated by simply heating the Al samples in air. The growth mechanism is stress-induced migration. Four electrodes were patterned on nanowires by the photolithographic technique and we obtained the resistivity of nanowires by four-terminal measurement. The relationship between electrical conductivity and diameter was examined experimentally.

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Dip soldering process with a simple model has been studied using CFD. The horizontal movement of PCB and the variation of temperature field are considered in this study. Open source CFD software OpenFOAM is utilized to simulate two phase thermal-flow of air and solder with moving mesh. Relatively large movement of PCB is reproduced by using two types of mesh and mapping numerical results between two meshes. Natural convection in liquid solder is observed. Moving PCB changes the height of solder surface. The un-equivalent level of solder surface causes flow under the PCB.

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In this paper, fatigue crack initiation lifetime of solder joints was evaluated using a lap joint shear specimen with high stiffness fixtures under the condition of high strain rate. That is, the influence of strain rates on the fatigue lifetime of solder joint was investigated. Consequently, an experimental relation between the inelastic strain range and the crack initiation lifetime at the high strain rate was obtained. The comparison of the results at high and low strain rate showed that the fatigue crack initiation lifetime increases in a higher strain rate.

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Whiskers initiation from plating metal in electronic equipment is a critical factor of reliability. Above all, plating of Sn is superior in several and used frequently in electronic equipment. But, it is easy to initiate whiskers on plating of Sn. Therefore it is necessary to take measures. On the other hand, whisker is expected as new electrode materials. It is confirmed that additional elements affect to whiskers initiation. In this study, we made samples of Sn-Cu, and Sn-Ru and observed the samples by AFM and SEM to elucidate the mechanism of atomic diffusion. By adding Cu, crystal grain becomes small and crystal that have different orientation crowd. The behavior of defects depends on local strain distribution measured by digital image correlation method. Whiskers initiation behavior when I added Ru is similar to added Lu very much. By adding Ru, a compound is oxidized, and stress is introduced by causing the volume expansion. As a result, whiskers initiation is accelerated.

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Solder joint is one of the main techniques connecting electronic circuit. The size of a solder joint became much smaller due to the downsizing of electronic devises. Micro solder joint has few crystal grains. It is not considered to be homogeneous material. In this study, we investigated the distribution of strain in a miniature specimen of Sn during tensile test. Crystal grains and their orientations were measured using the EBSD with a SEM. We took microphotographs of the specimens during tensile test, and obtained the distribution of strain using the digital image correlation method (DICM). We also performed anisotropic elastic plastic analysis of the specimens using the FEM. We compared experimentally measured and analyzed strain in the specimen.

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Power modules are widely used for hybrid and electronic vehicles to control current flow. They are flat shaped and composed of silicon, metals, ceramics and resin compounds. To predict the fatigue life, it is necessary to measure the internal strains as well as the morphology of the internal cracks and delamination. Synchrotron laminography has advantages over conventional computerized tomography to realize the nondestructive high-resolution measurement without cutting the flat-shaped modules. The trial measurements by synchrotron laminography were conducted at the beamline of BL47XU of SPring-8 to clarify the appropriate experimental conditions. Power modules subject to thermal fatigue under heat cycles were measured at BL33XU, TOYOTA beamline. Based on the reconstructed 3D images, full 3D internal strain field was analyzed by volumetric digital image correlation method. The result shows that strain localizations at the internal corner of resin molding compound can be visualized nondestructively, which cannot be realized by 2D analysis on the sectioned surface. The measurement of the actual internal strains during the fatigue process will help analyze and develop high-performance power modules of the next generation.

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A pressure tank is widely used in many equipment of the social infrastructure. We have been developing the protective cover for the metal pressure tank in order to enhance the safety of it. The cover is made of synthetic fiber and resin. The fracture analysis of the tank failure process has been carried out using the finite-element method under the different thickness of the cover and the surface condition. The physical properties of the cast metal and the cover are determined by measured data from the tensile tests with attention to their variation. The simulation result shows that the tank bursts in form of the brittle failure when an internal pressure reaches the withstanding pressure of it. Furthermore it shows that fragments fly outside the tank and that the protective cover catches the fragments. We confirmed that the cover with thickness in more than 2 [P.U.] has the effect of the prevention of scattering the fragments of the pressure tank.

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In this study, the effect of random fiber waviness on damage and fracture properties of a natural fiber sliver-reinforced composite laminate was discussed through three-dimensional finite element analysis (3D-FEA) and Tsai-Hill criterion. 3D-FEA was carried out by assigning a measured fiber-orientation-angle to each finite element and using the orthotropic theory. In order to predict risky areas causing damage in the composite laminate, Tsai-Hill criterion was first applied for the resultant stress distribution. Next, assuming that an applied stress is isolatedly given to each element, Tsai-Hill criterion was applied without using 3D-FEA. To differentiate such two kinds of evaluations, the subtraction of the latter value from the former was taken for each element. In the negative subtraction, risky Tsai-Hill distributions consisted of a cluster of inclined fibers in the composite laminate. In the positive subtraction, on the other hand, risky Tsai-Hill distributions appeared with dispersion and small-scale level. It was estimated from the comparison with the specimens' fracture paths that the laminate's fracture occurred from the cluster of inclined fibers. However, it was also considered that the fracture was not initiated from the cluster, but caused by fibers breakage on the counterpart in the laminate, because of tensile stress enhancement induced by the cluster.

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Under the prerequisite that the air flows, for obtaining a simplified sound absorbing structure which is absorbed much noise as possible, and develop a dedicated measurement apparatus for evaluating the transmission loss of the noise, and reports the examination results and the measurement results. While various soundproofing is carried out in order to prevent the noise and look at this time for them mute. Tone generator and for flowing exhaust gas and air different from the sound insulation and partitioning on the wall outside the factory and buildings release wind machines and outdoor unit, which silencer is mounted such as ventilators. By examining this characteristic because the mute amount of change coming by the structure and material to think that it might be of help to the noise troubleshooting. Than parallel-type structure, internal is observed complex maze type structure is high silencing performance, was able to confirm that there is a silencing effect against high frequency.

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Composite materials are well known to have superior specific stiffness and strength to conventional metal materials. Due to the excellent material properties, composites contribute to lighten the structures in various industrial fields. Moreover, it is known that engineers can intentionally change dynamic properties of composites by designing their lay-up configuration. Among the composites, shell structures are often found in the automotive and aerospace industries, but this type of structures has technical problem causing the buckling due to various external loads. Therefore, it is important to investigate buckling response of those structures on the safety design. In this study, the effect of generally shaped pressure on buckling eigenvalues of laminated composite shells is studied and those lay-up configurations are optimized to maximize non-dimensional buckling load or buckling parameters. First, stress distributions of shells under general external pressure are calculated by the Ritz method. Then, eigenvalues as critical buckling loads under in-plane stresses are derived by the Ritz method again where in-plane stress distributions determined in the first step are included as the potential energy. Finally, the layerwise optimization (LO) method is applied to optimize lay-ups and to maximize buckling load of laminated composites shells, and obtained optimum solutions are successfully result in higher buckling load compared with the typical lay-ups.

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This paper presents the stress evaluation at edges of an angle-ply laminated composite plate subjected to uniform tensile load. For this purpose, the basic equations are formulated by using the Ritz's procedure based on the Discrete-Layer Theory (DLT), and then stress distributions at edges are obtained numerically. Finally, the applicability of the present analytical models is discussed by comparing with the other numerical results.

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The present study proposes a multi-objective optimization method of productivity and dynamic strength for the fibrous composite plate with curvilinear fibers. The fibrous composites have some problems in the practical application to structures. The productivity decreases and fiber density becomes nonuniform with increase in the maximum curvature of curvilinear fibers. Therefore, the relationships between the productivity and curvature are formulated by the experimental results and a practical optimum curvilinear fiber shapes are searched. Curvilinear fiber shapes are defined by the coefficients of the cubic polynomial function. Because principal strains are important in design of aircraft main wings, principal strains of the plate are calculated by the finite element method with eight-node quadrilateral isoparametric element. An Optimized Multi-Objective Particle Swarm Optimization (OMOPSO) based on the non-dominated sorting and crowded distance metric sorting is employed as an optimizer with an inertia weight controlled by the auto-tuning method. The numerical results showed that the present optimization considering the relationships between the density and curvature resulted in the more practical solutions than the previous solutions.

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In this study, as one of the most flexible structural optimization methods, so-called topology optimization techniques were numerically applied to structural optimization problems for the intermediate core layers in sandwich composite simply-supported beams with upper and lower facing skin layers of thin aluminum plates under static flexural loads. General-purpose finite element analysis code, MSC Nastran, and its pre-post processor, Patran, were used in the present study, in which the density method (SIMP method), one of the numerical approach, was employed for seeking more light-weight and stiffer intermediate core structures by the optimization process of compliance minimization. From the results being obtained at the current moment, certain optimal inner structures or morphologies possibly could be found out for certain structural and material configurations and typical boundary conditions.

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Thermal buckling of laminated rectangular plates is considered under varying temperature effect, and the optimization of the buckling behavior is made to maximize the critical buckling load in terms of the fiber orientation angles. The literature survey was made to summarize the progress in analytical and optimization studies. In the report, the analytical procedure is described to clarify the formulation of the problem and some optimization methods are considered to obtain the optimum lay-up design.

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Fuel cell vehicles (FCVs) are being developed in order to reduce carbon dioxide and air pollution emissions, and CFRP pressure vessels have been used as the hydrogen storage systems. Since the FCVs are expected to increase driving distances of at least over 500 km, which is similar to those of conventional gasoline-fueled vehicles, the storage pressure of hydrogen must be raised from 35 MPa to 70 MPa. In order to promote the spread of the FCVs, the FCVs production cost must be reduced less than 10 million yen. Therefore, it is important to decrease the amount of carbon fibers in the CFRP pressure vessels. The authors developed CFRP pressure vessels reinforced with cylindrical shaped CFRP grids. The burst pressures of the CFRP pressure vessels with the cylindrical shaped CFRP grids were approximately 20 % higher than those of the CFRP pressure vessels without the cylindrical shaped CFRP grids. Moreover, the FEM results showed good agreement with experimental ones. In this study, an optimum structural design of the CFRP pressure vessels reinforced with cylindrical shaped CFRP grids was executed using FEM analysis, and the CFRP consumption for the 70MPa CFRP pressure vessels with and without the cylindrical shaped CFRP grids was compared.

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CFRP (Carbon Fiber Reinforced Plastics) has been widely used to manufacture precise structures, such as antenna reflectors, due to their superior stiffness-to-weight and high dimensional stability as compared to the metallic materials. When one uses CFRP laminates to antenna reflectors for spacecraft, their vibration property becomes important. This is because antenna reflectors are often placed under sever vibration and acoustic noise environment due to the launch of spacecraft. In addition to this, harsh thermal variation becomes also serious problem. Antennas flying on the low Earth orbit are subjected to significant temperature variations, and the thermal deformation of antenna is inevitable. It is possible to suppress this vibration minimally if the laminates are stacked symmetrically. It is known, however, that CFRP laminates show unpredictable deformation caused by the ply angle misalignments during fabrication process. Since the ply angle misalignments are unavoidable so far, it is important to choose the lay-ups mitigating the effect of misalignment. The present paper proposes a multi-objective Taguchi method (MO-TM) to optimize the lay-ups of laminated antenna shell structure to maximize the fundamental frequency and minimize the thermal deformation in robust sense. Both vibration and thermal properties are evaluated by a finite element analysis, ANSYS. The validity of the present optimization is successfully confirmed by the comparison between obtained results from the MO-TM and those from the typical lay-ups.

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