Gas circuit breaker is the very important safety device that instantaneously interrupts the circuit and protects the electric power equipment when an abnormal current in lightning strike for example flows to electric power transmission line of high voltage transmission system. Recently gas circuit breaker is required downsizing because cost and reduce use of SF_6 has greenhouse effect. In this study, we did three-dimensional analyses of high temperature gas behavior in gas circuit breaker using CRIMSON(Civa Refined Multiphase SimulasiON),and we compared experimental result with numerical result.

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Recently, the parallel processing of physical problems using GPU (Graphics Processing Unit) get scientists' and engineers' attention. Especially, CFD needs a lot of computing time, and such techniques to reduce computing time is one of the important issues. In this paper, we focused on the parallel processing of HSMAC algorithm for compressible multiphase flow on GPU. In this paper, we solved two kinds of benchmark problems, an underexpanded jet problem for compressible flow and a collapse of water column problem for multiphase flow. As the results, we achieved about 18 times speed-up computation on GPU of TESLA C1060 in comparison with that on CPU using INTEL Core2Duo 3 GHz.

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We study phase transitions of a triangulated surface model using the canonical Monte Carlo simulation technique. The model is defined by the Gaussian bond potential and the curvature energy, both of which depend on the metric degrees of freedom of the surface. We find that the model undergoes transitions of shape transformations and that a large fluctuation of the surface area is observed at the transition point. This fluctuation of surface area is considered as a phase transition, and this transition is a non-trivial result, which was not observed in the conventional surface model.

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This paper presents a new algorithm to generate principal stress trajectory grid. When a principal stress trajectory grid and an orthogonality trajectory grid are not the homeomorphic, the present system cannot picture the principal stress line. I call such the principal stress line pattern a inconsistent principal stress trajectory pattern. Therefore I suggest new algorithm to solve this problem.

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This paper proposes a new criterion for mobility calculation of closed loop mechanisms by using motor algebra. We represent a lower pair such as screw, rotational, or prismatic as a motor, and a higher pair, with n DOF, as a serial chain of n lower pairs between which n-1 links are interposed. In contrast to the well-known Jacobian matrix, the constraints imposed by a closed loop mechanism are expressed explicitly by pair loop matrix. By applying Gauss-Jordan elimination to the pair loop matrix of acceleration equation along with velocity equation, the rank of the matrix is obtained. The DOF of a mechanism can be determined from the number of lower pairs along the closed loop and the rank of the pair loop matrix. As far as we are currently aware, the new criterion covers much wider range of planar or spatial closed loop mechanisms and we have not found any exception yet.

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The Purpose of this study are to construct a concise algorithm by performing dynamics analysis of the closed loop mechanisms with collision and to produce dynamics analysis system based on that. The connection of links is represented by link-pair graph. Force and momentum on links, speed and the acceleration of pairs are described with motor algebra. The equation of a mechanism is defined as equilibrium equation of torque around each pair axis. Virtual spring high stiffness is put at the collision point, and the displacement of the spring and the speed change of the collision point a calculated in order to compute impulsive force.

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We are developing NC-programs to generate ball-end-mill whose cutting edges are located precisely on a spherical surface. The curve of cutting edges are the intersection of two surfaces, R-gash and R-2. First, numerical formulae of two surfaces are devised from existent NC-program. Secondly, the intersection curves with a sphere of each surface are computed. Lastly, plural line NC-program for R-gash is generated by setting several passing points in order to minimize the gap between two curves.

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We analyzed the adhesion energy of copper and silane cuppling agents interface by using density functional theory. We showed that electron-scale adhesion mechanism of interface is related to the character of adhesion. By using nano-scale simulation, in this way, we can predict the adhesion properties and suggest the best materials of micro electro devices.

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It is known that there exist various types of lattice defects in the reactor and/or aerospace materials due to long-term irradiation process. It is generally considered that these lattice defects cause the deterioration of materials. However, some atomistic simulations show that the nano-scale void acts as dislocation absorption and formation during deformation. The nano-scale void enhances dislocation activity and plastic deformation behavior becomes smooth, which means a crack growth may be deterred by the purposely introduced nano-scale voids in the vicinity of crack. However, experimental trial for the optimum nano-scale void arrangement is not realistic from a convenience and safety standpoint. We investigate this retardation effect by using a large scale parallel molecular dynamics (MD) method. MD simulation shows that a nano-scale void in the vicinity of a crack has a crack growth retardation effect due to a smoother plastic deformation mechanism.

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Due to the deformation or the damage, nano-scale voids can be created in metallic materials. These voids are regarded as the reason of the deterioration of the material's strength. However, there are several reports that the void in the material becomes the source of the absorption and the formation of the dislocation. So it can be supposed that these voids may enhance the ductility of the materials. In this study, based on molecular dynamics simulations, we perform several numerical experiments to investigate the relationship between crystals with voids at different locations and the property of material. The results show that (1) the closer the void is located to the surface, the more easily the dislocations are created, and the higher activity of the dislocations are observed, (2) the crystal with small amount of nano-scale voids is not weaker than the perfect crystal.

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Triangular or tetrahedral elements are broadly used because of compatibility to auto mesh or node-base calculation. It is also well known that a low order approximation in such elements results in poor accuracy. Therefore many elements with high precision have been proposed. Although the six-node isoparametric triangular element with second order trial function seems a standard nowadays, it requires adding mid-point nodes on its sides after tessellation. This becomes a large disadvantage in problems with frequent remeshing such as adaptive calculation. In order to solve this problem, high precision triangular elements with corner nodes have been proposed. In this paper, a high precision triangular element with Hermitian type interpolation functions only with corer nodes and its accuracy is estimated.

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The finite element method program becomes multifunctional as the computational mechanics technique develops, and it will be necessary to add more functions according to the progress of the research in the future. Naturally, it is not possible to correspond to the function addition of the kind of not assumed at first, though the possibility of the function addition is necessary to consider in any program. The use of the design pattern is advanced to correspond to more complex programming , though object-oriented approach is paid attention for more flexible programming. Here, the outline and directions of the Option pattern designed for the FEM program enhancing are demonstrated.

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There are numerous cases where a LTA (local thin area) has found near a piping branch in-service. Because the stress concentration at a piping branch intersection under internal pressure is always larger than that of a straight pipe, it is strongly necessity to establish a quantitative and reasonable plastic collapse assessment procedure. In this paper, a new assessment procedure for a piping branch with a LTA was proposed. The proposed assessment procedure was verified by the comparison of the FEA.

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It is important to establish the plastic collapse condition for a bend pipe with a local thin area under combined internal pressure and out-of-plane or in-plane bending. In this paper, a new procedure to evaluate a bend pipe with a local thin area was proposed based on the p-M diagram method using the reference stress. The procedure was verified by the results of the finite element analysis and data available in the literatures.

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It is generally believed that multiple fatigue crack growth prediction is difficult with the use of standard stress intensity factor (SIF) solution calculations because of the complicated nature of such issues as magnification and shielding effects. Therefore, almost all the existing FFS rules such as the ASME Boiler Pressure Vessel Code and JSME Code adopt the procedure of recharacterizing multiple cracks into one enveloping crack, after applying a certain alignment rule based on the initial crack configuration. In some cases, the results of the procedures in the existing FFS rules can be unrealistic and may lead to unreliable predictions of the service life of cracked components. This paper describes a new approach to predicting multiple nonaligned fatigue crack growth life under external bending by the use of standard SIF solutions. Several examples, as compared with experimental results in the literature for three-dimensional models, illustrate the accuracy and effectiveness of the procedure.

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Micro-pipe will be used to inject microbubbles into flowing mercury in high power pulsed spallation neutron source. The effect of mercury immersion on the fatigue strength of 316-type stainless steel had been recognized using micro-size specimens. The mercury immersion attach is enhanced on the surface layer contact with mercury. In fact, the hardness of the surface layer was increased by the mercury immersion. Because the micro-pipe will be suffered with the flow induced vibration under flowing mercury and the immersion effect might be enhanced in micro-size range, it is indispensable to evaluate the effects of mercury and size on the fatigue. In the paper, we will show the preliminary results on the tensile fatigue strength of the micro-pipe with mercury immersion and discuss the size effects on the fatigue strength.

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The mechanism of evironment-assisted crack growth of SiO_2 is analyzed by using an atomistic simulation model. Potential energy changes in various elementary processes of which a crack propagation process consits are calculated Based on the calculated results it is found that the rate contorolling process of the crack growth in region I of the ν-K curve is the water transport process.

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In this study, we developed a modeling technique that simplifies the C6L bolt-jointed A6N01S-T5 aluminum alloys by using shell elements and beam elements. We set the equivalent pressure area around the bolted joints, and the nodes in the area were connected to the beam element as rigid region by using constraint equations. We measured the stress of the bolted joints specimen from strain gauges under the quasi-static loading test, and calculated those by FE analysis. The analytical stress and shear load agreed well with the experimental results. By using this modeling method of bolted joints, we can evaluate the distribution of shear load of each bolt with a large quantities of bolted joints.

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We have developed the crack detection system based on the natural frequency changes. In the detecting system, we have employed the response surface method which uses a optimization solver tool installed in Excel. Monitoring the minimum errors between the natural frequencies obtained by the response surface and the natural frequencies obtained by the experiment, we have detected the crack position and the crack length. By using both the response surface method and Excel macro program, we were able to identify the crack in real time.

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This paper presents a elasto-plastic FEM program for two-dimensional problems based on the incremental theory. Today, current commercial FEM programs have been used as a versatile tool for simulating engineering problems. However, most of the programs have many commands and FEM beginners are sometimes puzzled as to how to use the commands. While the versatile FEM program is very powerful, the program requires not only computer resources but is also quite expensive. Therefore, we will propose a new compact elasto-plastic FEM program for FEM beginners. Our FEM program has GUI interface on pre-post processing and is so designed to have various user-friendly interfaces. To demonstrate the versatility of our FEM program, we applied to the interference fit of shaft and bearing where the plastic deformation arises.

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Advanced fiber-reinforced laminated composite materials have been used for structural members in various fields because of their high specific strength and stifmess. In general, composite laminated cylindrical shells behave differently from homogeneous orthotropic cylindrical shells due to their anisotropy and asymmetric lamination. In this paper, we describe the buckling strength of cross-ply laminated cylindrical shells with a circular cut-out under axial compression by the finite element method. Consequently, we analytically clarified the effects of various factors such as hole-radius, stress concentration, stacking sequence , and number of layers of cylinder on the buckling strength.

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This paper deals with the problem of dynamic stability of cross-ply laminated cylindrical shells subjected to impact combined loads. Firsy of all, the motion of cylindrical shells under simultaneous impact axial compressive load, external pressure and torsion is defined as axially symmetric motion and their effect on the behavor of the shell is investigated. The symmetric state of motion of the shell is called stable if the perturbations remained bounded. The solutions for the prebuckling motion and the perturbed motion are obtained using Galerkin's method. Stable regions are determined by utilizing Mathieu's equation. The inevitability of dynamically unstable behavor is proved analytically and the effects of various factors, such as combined load ratio, number of layers, dynamic unstable mode, are clarified.

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Advanced fiber-reinforced composite materials have been used for structural members in various fields because of their high specific strength and stiffness. In general, composite laminated cylindrical shells behave differently from homogeneous orthotropic cylindrical shells due to their anisotropy and asymmetric lamination. In this paper, we describe the buckling strength of carbon fiber/epoxy (CFRP) cross-ply laminated cylindrical shells with internal liquid pressure under axial compression by the finite element method. Consequently, we analytically clarified the effects of various factor such as stacking sequence, number of layers, liquid density, level of liquid, buckling mode and dimensions of cylinder on the buckling strength.

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This research examined deformation control for automobile hub. Experiment analysis used the stress freezing method in static load. And theoretical analysis used finite element method. From both parties, it calculated stress concentration factor. As a result, the deformation control of automobile hub in different contact condition was examined. Moreover, it calculated safety factor of fillet near the hub bearing press-fit part, and the improvement of the safety factor by contact was examined. At the result, contact with hub bearing rose safety factor of automobile hub at fillet.

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The compression ignition engines using dimethyl ether as an alternative fuel (DME C.I.engines) is necessary to promote the mixing fuel and air. Therefore, the effects of the combustion chamber configurations, injection methods and injection pressures on the engine performances and the exhaust emission are examined experimentally. As a result, two stage injection (Pre injection) is effective to reduce NOx at injection pressure with 40 to 80[MPa]. In the case of Pre injection ratio with 5[Mass%] with injection pressure at 80[MPa] using the Toroidal combustion chamber, the concentration of NOx emission is reduced about 26.1[%] as compared with that of single stage injection. And the brake thermal efficiency is maintained the same as in the single stage injection with the injection pressure at 40[MPa].

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Spray and evaporation characteristics of Dimethyl Ether (DME) in a constant-volume combustion vessel are examined under supercritical atmospheric conditions, as a basic research on the application of DME fuel to highly supercharged compression ignition engine. Results showed that there was no big difference in the shape and the development process of DME spray between supercritical and sub-critical atmosphere. With rise in the atmosphere temperature, evaporation was promoted and the liquid phase length shortened.

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The DME spray characteristics under turbocharged engine-like atmospheric condition (8.8MPa-920K) were investigated with numerical analysis using KIVA-3V code modified for DME. The air entrainment, equivalence ratio distribution in DME spray and the effect of injection pressure and injector nozzle diameter on these factors were analyzed comparing to diesel fuel spray. The calculation results showed that DME spray is overwhelmingly leaner compared to diesel fuel sprays even in lower injection pressure and larger nozzle diameter, and that NO emission could be reduced if injection pressure increased to 140MPa or higher.

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The low lubricity and viscosity of DME as a fuel affects the wear and leak problems at the injector system. A HFRR is the one of the method to estimates the lubricity. However there is no data regarding the nozzle tip. Then an newly developed test rig is used to evaluate the injector wear. As results, the polymer type additive around 200ppm shows the good wear resistance. In the engine examination, the wear depth has increased by about 80% compared with that of test rig. This wear depth doesn't influence the injection timing, therefore, there is no change the amount of the NOx emission. Furthermore, the polymer type additive decomposes at the temperature at 350C.

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φ-T map is useful for evaluating engine combustion and emission formations. The purpose of this work is to clarify the φ-T dependence of CO formation in DME combustion. CO φ-T map of DME was made from numerical calculation at constant temperature and pressure. CO formation of methane was also calculated to compare with DME, as a representative of the fuels which does not have low-temperature-oxidation mechanism. As the results, it was found that DME has two CO formation peaks, low temperature around 1000K and high temperature of over 2000K, while methane has a peak at high temperature of over 2000K. The chemical kinetic analysis showed that CO formation peninsula around 1000K in case of DME yields on low-temperature-oxidation.

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Recently, various problems occur because of increasing in demand for energy. We focus on DME as alternative fuel that can generate from various raw materials and reform at the low temperature. Moreover, the point of view of the thermal efficiency improvement, we propose DME hybrid combustion engine. This engine drive compression ignition in part load region by DME direct-injection and spark ignition excluding the part load region with DME reformed gas. In this report, we researched the DME reforming process and characteristic of Copper-Zinc, Aluminum, Nickel series Catalyst while changing reforming temperature and Gas Hourly Space Velocity.

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The ignition and combustion mechanisms of mixed fuels with different ignitability, toluene/DME, were investigated using elementary reaction models on the basis of both Emdee's toluene oxidation scheme and Curran's DME2000 scheme. Toluene is thermally stable with a high oxidation onset temperature, whereas DME has good ignitability with active low temperature oxidation reactions. When DME coexists, the toluene oxidation temperature decreased to a low temperature at which single toluene would not react. In this temperature range, toluene oxidation is totally controlled by OH supplied from DME low temperature mechanism. The subsequent excursive hot fame reaction is restrained because toluene oxidation proceeds in stages depending on a temperature rise. Therefore, it is suggested that the HCCI operation range could be extended to higher loads without knocking if DME quantity is adjusted so that the hot flame reaction shift to the piston expanding period.

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Combustion characteristics of ethanol-air mixture in homogeneous charge compression ignition (HCCI) were investigated experimentally using a single cylinder engine. The experiments were carried out at the constant engine speed with changing intake temperature and equivalence ratio. Numerical analysis based on Marinov's chemical kinetic model for ethanol oxidation was also conducted for ethanol-air HCCI process. The experimental results showed that autoignition temperature of ethanol-air mixture was 870K. Numerical analysis gave qualitative agreement on characteristics of HCCI process with experimental results. Additionally, numerical analysis showed that autoignition of ethanol-air mixture was depended on OH supply through H_2O_2 dissociation.

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This paper presents an investigation of the influence of the silicon addition to thermoelectric performance of DLC films on glass substrates using RF plasma CVD method. The DLC films were prepared using methan (CH_4) and hexamethyldisiloxan (HMDSO) concentration from 0% to 100% as the source gas. The respective thermoelectric performance of the DLC films were evaluated and compared. The Seebeck coefficients of the DLC films decreased with increasing the HMDSO concentration at the range from 0% to 50%. However the Seebeck coefficients was identical with 50% the HMDSO concentration increased to 100%. Resistivity of the DLC films was creased with increasing HMDSO concentration at temperatures from 50℃ to 200°C. However, vicinity the room temperature, the specific electrical resistance of the each DLC films were identical. The power factor of the DLC films was decreased with increasing the HMDSO concentration at temperatures from room temperature to 200℃.

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This paper is investigated the thermoelectric performance of DLC films deposited by RF plasma CVD method on glass substrates. The comparison of the thermoelectric performances of Si doped DLC film and non-Si doped DLC film are evaluated. DLC films showed Seebeck effect. And their semiconductor character was p type. In the temperature range from 80 to 200 degrees, the Seebeck coefficient of Si doped DLC and non-doped DLC were almost the same. The resistivity value of DLC films decreased exponentially as the temperature became high. From the above result, it is suggested that how to reduce a resistivity by the control of deposition condition, composition of doped elements and so on of DLC film must be examined in order to raise the thermoelectric performance of DLC film.

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Nitrogen doped diamond like amorphous carbon (DLC) thin films on grass substrate were prepared by radio frequency (rf) plasma chemical vapor deposition (CVD) using CH4 as the source of carbon and with different N_2 flow rates (N2 : CH4 gas ratios between 0 : 100 and 40 : 60), at 270〜300K. The resistivity of the film were measured by Van der pauw method. The nitrogen content in the films was about 3.8-6.0%, obtained from Glow discharge optical emission spectroscopy. The thermoelectric performance of nitrogen doped DLC was increased step by step with increasing nitrogen flow rate. The difference of thermoelectric performance was decreased with the increase temperature.

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The Japan Atomic Energy Agency (JAEA) has been conducting R&D on thermo-chemical Iodine-Sulfur (IS) process, which is one of most attractive water-splitting hydrogen production methods using nuclear heat of a high temperature gas-cooled reactor (HTGR). Direct contact heat exchanger (DCHX) is considered to apply for sulfuric acid concentration. DCHX is a contactor between low temperature fluid and high temperature fluid. It have several advantages over surface-type heat exchanger in terms of its simple structure and efficient heat exchange due to lager heat transfer surface area and no surface fouling to deteriorate the heat transfer. This paper discusses an experimental method for the measurement of mass transfer coefficient of H_2SO_4 and H_2O, which is an important factor for the optimum design of DCHX.

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Recently, exhaust gas from paint factories has become a serious problem as the air pollution in urban areas. In particular, air purification apparatus for small and medium-sized enterprises (SMEs) needs to be developed. Emissions from SMEs are large in volume and low concentration of volatile organic compounds (VOCs) and gelatinous particulate. Although granular activated carbon (PAC) is commonly used as adsorbent for VOCs, we developed the air purification apparatus using bag-filter coated with PAC. PAC could remove VOCs and gelatinous particulate. This study presents a new type of apparatus for paint factories.

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Experimental test of pretreatment for cellulosic ethanol production from rice straw with supercritical dimethyl ether (DME) was carried out. Finely-milled rice straw shreds were soaked in water-containing supercritical DME at 140℃, 40MPa for 45 minutes, to liberate the cellulose and hemicellulose from the lignin seal and to hydrolyze them. Componential analysis by HPLC was made to determine the saccharification. The result shows that monosaccharide such as glucose and fructose was produced although the saccharification was estimated to be only 1wt%, which suggests the possibility of cellulose liberation.

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The effect of ausforming on the kinetic and microstructure of a nano-bainite steel was studied. Observation of the ausformed nano-bainite was carried out by optical microscopy (OM), scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). Bainite transformation was accelerated by ausforming at 573K with 15% reduction, and the ausformed nano-bainite consists of refined lamellar ferrite and carbon enriched retained austenite. A strong variant selection occurred during bainite transformation due to ausforming.

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The effect of two stage deformation on ferrite transformation has been investigated by in situ neutron diffraction. Deformation induced ferrite transformation was found not only in the first stage compression but also in the secondary compression. The secondary compression was found to accelerate ferrite transformation even after the first compression effect disappeared. During the secondary compression, ferrite (110) diffraction intensity decreased by the evolution of compression texture of ferrite, while the integrated diffraction intensity of ferrite (110) was increased due to accelerated ferrite transformation. Hence, multi-stage or continuous deformation must be very effective to promote ferrite transformation.

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Nitrogen absorption processing was applied to a low carbon (LC) steel, to study the basic mechanism of recently developed nitriding-quenching treatment. IN a specimen treated at 973K in a N_2+NH_3 atmosphere followed by gas-cooling, layered microstructure was obtained. The nitriding layer is found to consist of multilayer I〜III; the surface layer I consists chiefly of Fe_4N and Fe_<2-3>N, the next layer II consists chiefly of austenite and martensite, while the layer HI consists chiefly of ferrite, Fe_4N is in ferrite grain. If a specimen is quenching rapidly, the nitriding layer become mostly martensite.

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Characteristic microstructure was formed in a low-alloy steel / Ni-base alloy welded interface region by solidification and thermal history. At welding, molten Ni-base alloy solidified epitaxially from low-alloy austenite grains in the beginning. However, the crystal growth often stopped at the place where concentrations of alloy elements changed rapidly. As a result, characteristic grain boundaries parallel to the interface were generated. During cooling after welding, a low-alloy steel region within one individual austenite grain transformed to martensite partially. Hence, the KS relationship was confirmed in such a grain, and the quenched martensite was tempered by the following heating.

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Severe plastic deformation is a kind of technology making ultra-fine microstructure. The copper of purity 99.99% subjected to equal channel angular pressing was examined by neutron diffraction and EBSD measurement. Dislocation density and grain size were determined by the Williamson-Hall and the integral breadth method. Dislocation density increased first, but decrease afterwards. Grain size becomes the smallest to around 500nm with processing. Because of the neutron diffraction the profile analysis could evaluate dislocation density relatively, but reliability was low in grain size.

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Nitrogen is not only a substitutive element for nickel but also an effective for mechanical properties. Therefore, High nitrogen bearing steel (HNS) is attractive as a green material and high strength alloy. In this study, the effect of nitrogen upon deformation behavior of HNS was examined paying particular attention to high work hardening behavior. It is noted that the magnitude of stress partitioning in grains was larger in HNS than low nitrogen steel. Namely, the larger stress partitioning seems to contribute high work hardening in HNS at a small strain.

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As the microstructure has great effect on the mechanical properties of nodular graphite cast iron, mechanical properties of two kinds of nodular graphite cast iron with different microstructures were studied by in situ neutron diffraction during tensile deformation with a time of flight method. It showed that in a cast iron consisting of pearlite and ferrite, the soft phase ferrite was a main factor influencing the yield point, and the hard phase pearlite was a reason of higher work hardening. There was also work hardening in a cast iron with high ferrite fraction, which came from the different stress distribution between hard grain (200) and soft grain (110). However, the work hardening from grain strain was smaller than that caused by phase strain.

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