Implant overdenture (IOD) is a treatment for edentulous patients. IOD is a method of fixing dentures made of acrylic resin with multiple implants. At present, there are some reports that evaluate the mechanical effect by stress analysis using the finite element method (FEM) of IOD. However, it is not clear how the number of support implants used in the maxillary IOD and the implantation position affect the gum. In this study, we created 3D CAD models of maxilla, gum, and denture used for stress analysis from CT images of unconnected and anonymized adult edentulous jaw patients. In addition, the support implant was made based on the actual product using CAD software. As the models used for the analysis, a model with four support implants (4IOD) and a model with two support implants (2IOD) were prepared, and a plurality of implant embedding patterns were prepared. The load conditions applied to each model were set so that the total load would be 100 N at the middle of the 3rd and 4th parts on both sides. The average compressive stress generated in the gingiva tended to decrease as the implant position was closer to the loading point. Comparing 4IOD and 2IOD, 4IOD showed a lower mean value of compressive stress in the gum in the embedding patterns of all supporting implants.

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Dental implants have various structures such as one-piece type and two-piece type. Two-piece types are mainly classified tapered-joint type or butt joint type. The selection of implants is important in order to prevent bone resorption in the jawbone in prognosis of the dental treatment. The purpose of this study is to evaluate the difference in the mechanical effects on the jawbone caused by the difference in the structure of dental implants. As analysis models, three CAD models of simple jawbone, using one-piece type and butt-joint type, tapered-joint type, were made by CAD software. The lateral load of 35 N was applied to the artificial tooth, and stress analysis was performed by FEM. The principal stress in the bone around the implant and in the implant were evaluated. In the result of analysis, the magnitudes of tensile stress and compressive stress caused by one-piece type in the cortical bone were almost the same. In the compressive stress, the magnitude of butt-joint type was 1.57 times that of one-piece type and that of the tapered-joint was 1.67 times that of the one-piece type.

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This study considers incorporating a mechanical analysis into the tool to examine the dentist’s rule of thumb from an engineering viewpoint. In order to perform mechanical analysis, it is necessary to create a bone model from CT. This study focused on the efficiency of this bone separation work. We attempted to shorten the work time for separating the bone by binarizing the CT image of the jaw bone. Using image processing software, we set CT-volume and compared the work time with exiting methods. Furthermore, the stress was compared with the model created by the existing method using analysis software. The work of separating bones was reduced by up to 43% by setting a threshold of 500. The 500-model created by binarization has 0.42 mm thinner bone than the conventional method. It was shown that there was little difference in the stress gradient in the implant position and that the maximum stress was affected by about 5%.

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We attempt to estimate the aerodynamic coefficients and time derivatives of a projectile by using geometrical quantities of its flight trajectory. The purpose of this study is to clarify the aerodynamic characteristics of a projectile in flight such as unsteady aerodynamic force acting on the projectile and its rotational axis. The present estimation method is based on time series position data along the flight trajectory. According to the theory of spatial curves, any curve is locally represented as general cubic curve. Therefore, flight trajectories can be interpolated by a cubic function by using the least-squares approximation, which means, in words of the dynamics, that the shape of trajectory is related to jerk (derivative of acceleration). The Frenet-Serret formula determines the local orthogonal basis on the trajectory and this gives the coordinate system of instantaneous aerodynamic force. The coefficients of drag, lift and sideway force are obtained from a measured three-dimensional trajectory of golf ball. The results of the present study show the smoothness of estimated quantities in the comparison to those of the previous method. In addition, the time derivatives of the aerodynamic coefficients are successfully estimated. In the case of trajectories of straight ball in the present study, the effect of the torsion to the time derivative of aerodynamic force seems to be small since the motion of ball keeps almost in two-dimensional plane.

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In order to analyze outputs of a baseball-type ball with built-in acceleration sensors, we formulate the acceleration of a rigid sphere in translational and rotational motion. This ball-type sensor consists of one three-axis sensor for low acceleration and three sensors for high acceleration. On the basis of the formulation, output simulator for the sensors is developed. In this simulator, the effect of temporal change of rotation axis is included. By using data of the flight experiment with this ball-type sensor, the sensor outputs are simulated under two conditions: one is the rotation axis varying in time and the other is constant. The result simulated in the former condition shows good agreement with the measured output and this means that the rotation axis of the ball in flight changes in time. Furthermore, the formula of translational acceleration along ball trajectories is derived by linearizing the motion equation of a particle, and this approach makes it possible to set drag and lift coefficients as input parameters of the simulator. Simulations of translational acceleration of sensor outputs are performed by using the data obtained from the flight experiments. The results are compared with the original measured data, and the oscillation period of the outputs is good agreement in both the results.

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Various things are replaced by simulation, but processing speed becomes the problem now. One of the technique to solve this is a parallel calculation. There is the thing which converts used GPU into image processing, and performs it that I prepare a CPU taking a normal step for a parallel calculation and perform it. Above all, the GPGPU parallel calculation using GPU has difficult making, but it is cheaper and can make an efficient parallel operation machine. I aimed at the speedup of the parallel calculation by GPGPU as a model by PFM analysis during the simulation in this article. It is the calculation of the matrix and the PFM analysis of the semiellipse surface crack model for the analysis that I performed in an article. I prepared for a program of the sequential processing to use only the CPU for and a parallel operation program to use including GPGPU and compared these. As a result, I was able to handle GPGPU program with the speed of about 12 times by about 65 times, PFM analysis by a matrix calculation. The parallel operation using GPGPU was found to function effectively from this result. I will inspect the versatility of the GPGPU parallel operation machine in future by speeding up general-purpose PFM analysis in a model.

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This paper is concerned with the isotropic elastic wave analysis in general isotropic solids using a parallelized Moving Particle Simulation (MPS). In recent years, the ultrasonic nondestructive testing methods with linear and nonlinear elastic waves have attracted attention. The MPS, which is one of the particle methods, has a potential to be an effective numerical simulation tool for the ultrasonic non-destructive testing methods. However, the MPS method needs much calculation cost. The parallelization of the MPS is essential to reduce the calculation cost, and in the field of numerical analysis, some researches on parallel algorithms using the Message Passing Interface (MPI) are promising progress to reduce the calculation cost. Therefore, in this research, 2-D isotropic elastic wave analysis in isotropic solids is implemented by using a parallelized MPS method with MPI to check the computational accuracy and performance of the parallelization of the MPS with MPI.

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This paper is concerned with 3-D inverse scattering analysis for a spherical cavity in a viscoelastic solid. In recent years, polymer and composite materials have been developed for various uses and applied to aerospace and civil engineering structures. Therefore, it is desirable to develop a defect detection method for polymer and composite materials by using ultrasonic non-destructive testing which is widely used in various engineering fields. Since the stress and strain of polymer and composite materials have time-dependency, the viscoelastic property must be considered. Therefore, it is required to develop a forward analysis technique to understand the ultrasonic wave propagation behaviors for defects and an inverse analysis technique to reconstruct the size and shape of defects in a viscoelastic solid. The forward analysis technique in time domain has already been developed by our group. On the other hand, the inverse scattering technique based on Born approximation for a defect in a viscoelastic solid has not been developed yet. Therefore, in this research, a 3-D inverse scattering technique is developed for the reconstruction of a spherical cavity in a viscoelastic solid. Some numerical results are demonstrated to verify the developed inverse scattering technique by reconstructing size and shape of a spherical cavity in a viscoelastic solid.

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This paper is concerned with the development of ultrasonic non-destructive testing (UT) method for a solid propellant. Solid propellants are fuels for motive force of a rocket motor. In general, the radiographic testing (RT) has been used to detect a defect in solid propellants. Since the use of RT needs much cost and time, it is strongly desirable to develop an alternative non-destructive testing method for solid propellants. Therefore, in this study, the use of UT, which is simple and widely used for various inspection for structures, is considered for detection of a defect in solid propellants. The voxel-based finite element method (FEM) is used to understand the ultrasonic wave propagation and scattering behavior in solid propellants. The fundamental elastodynamic theory and the FEM formulation used in this study are introduced. Some numerical results for UT simulation in which the complicated solid propellant geometry is considered are demonstrated to show the potential of the application of UT to on-site UT experiments.

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This paper presents a defect detection method based on the time-reversal method and topological sensitivity for the purpose of quantification of the ultrasonic non-destructive testing (UT). The time-reversal method is one of the effective inverse scattering technique to detect a defect in elastic solids. In general, it is difficult to quantitatively evaluate the convergence positions of the time-reversal waves. To overcome this problem, the use of the topological sensitivity has been considered for the 3-D scalar wave problems. However, these achievements for scalar wave problems cannot be applicable to elastodynamic problems directly. Therefore, in this research, we extend the task for 3-D scalar wave problems to 3-D elastodynamic problems, and try to determine the number and positions of defects in an elastic solid. The convolution quadrature time-domain boundary element method (CQBEM) for 3-D elastodynamics is used to obtain scattered and time-reversed wave fields. As numerical examples, some defect detection results obtained by using this approach are demonstrated to investigate the performance of the present method.

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Simulation of the formation of fine droplets, flight, and fragmentation and shape change due to collision with solid wall surfaces is a technology necessary for improving the printing accuracy of inkjet printers and saving ink. In recent years, flow and particle simulation has become an important design method to reduce product contamination caused by the generation of fine particles called mist. The purpose of this research is to investigate the effects of surface tension and contact angle on the deformation behavior of droplets. In this report, the accuracy of numerical simulation was verified by conducting collision analysis between a solid wall or liquid surface and a droplet. As a result of this study, the droplet vibration after a solid collision is rapidly attenuated in the simulation with a constant contact angle. It is necessary to use a dynamic contact angle model in order to capture the vibration phenomenon of a droplet after collision with a solid wall.

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Serious nuclear accident was occurred in Fukushima Daiichi Nuclear Power Plant in 2011, and as the results, the melted nuclear fuels were accumulated in bottom of the reactor building. For removing these debris, the laser melt-cutting technique is one of the most prospective approaches, but radioactive spatters and fumes will be scattered during melt cutting. We aim to predict the behaviors of spatters and fumes numerically and consider a new way to mitigate them. For the purpose, we have been developing a three-phase flow simulation code including the phase change effect. We apply the temperature recovering method for the phase change. For the validating the method, we analyzed some simple problems of water freezing , ice melting and water boiling problem. Through such benchmark analyses, we have confirmed that the three-phase flow simulation code is well organized and runs correctly. In future, we will develop the simulation code to the phenomena of laser melt-cutting of melted debris.

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Recently,renewable energy has been attractingattention as an alternative to thermal energyand nuclear energy. We are developing a wave power generation generator, considering that the use of ocean energy is effective among renewable energy in Japan. The wave power generator under development contains a plurality of power generation units consisting of coils and magnets. When the wave power generator receives waves, that rotates or vibrates. Utilizing those exercises, the coil and magnet in the power generation unit perform electromagnetic induction. In this way, this wave power generator generates electricity.In addition,this wave power generator can move on the water by changing the posture using the generator unit.To develop a generator,it is necessary to determine many parameters. To determine parameters, it is necessary to use analysisto determine the parameters. This time, we are analyzed the movement ofthe wave power generator on the water using the SPH method. However, it is difficult to model the internalstructure ofthe wave power generatorwith the SPHmethod.Therefore,the wave power generator is modeled with uniform particles, and the center of gravity of the wave power generator is forcibly moved. This makes it possible to simulate the change in the center of gravity by the movement of the magnet through analysis. And, we compared the experimental and analytical results.Itshowed roughly the same behavior, but itshowed that the timing of rotation was different.

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In this study, the deformation behavior of auxetic materials was evaluated by finite element analysis. The auxetic materials have periodic voids. Volume of auxetic materials decreases and the density increases under compression. This kind of behavior called self-contraction. This phenomenon occurs in the case of the model has specific rotational structure. The auxetic materials in impact protector devices enhanced energy absorption. In this paper, the 2-dimensional FE models ware applied to observe the structural rotation under compress deformation. The smaller the lateral strain for vertical compression, the higher the self-contractility. As the result of analysis, model with elliptical voids does not self-contract at low compression state because the structure rotation was small. Model with dumbbell-shaped voids showed good deformation behavior of almost constant self-contractility regardless of the compression state. However, the deformable range is narrowed due to contact of the inner wall. A more rotatable structure promotes better self-contracting behavior.

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Weakly nonlinear propagation of pressure waves in bubbly liquids is described by the Korteweg-de Vries-Burgers (KdVB) equation. The KdVB equation consists of the nonlinear, dissipation, and dispersion terms, and its solution may become a shock wave for the strong dissipation effect and a soliton for the strong dispersion effect as a long-time lapse. In this paper, we numerically obtain a spatiotemporal evolution of the nonlinear, dissipation, and dispersion terms (not coefficients) as the nonlinear, dissipation, and dispersion effects, respectively, and depict an evolution of the resultant waveform, during a long period. The following results are obtained: (i) Pulse waves are formed by a balance between the nonlinear and dispersion effects and may be the soliton features. (ii) Oscillatory shock waveforms (the so-called relaxation oscillations) previously observed in numerical and experimental studies are formed for a microbubble case. The relaxation oscillations are owing to a balance between the nonlinear and dispersion effects and the oscillatory shock waveform is a forming process of the soliton due to the large dissipation effect.

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In order to optimize the structure of the bellows installed in the engine exhaust system of a hydraulic excavator, the Taguchi method was applied to the design of the bellows structure. The relative displacement applied to the bellows in the actual mounting environment was set as input, and the stress generated on the bellows was set as output. In addition, the specifications of bellows structure were selected as control factors, the amount of displacement were selected as signal factor, and the displacement direction, the friction coefficient and the stress generation locations were selected as error factors. After assigning these factors to the L18 orthogonal table, calculations were performed according to the orthogonal table to derive the cause and effect diagram of the SN ratio and sensitivity. The result of deriving the proper structure of the bellows from the diagram was as follows; the material is SUS, the inner diameter is small, the height of the crowns is high, the pitch of the crowns is large, the number of layers is small, the thickness of the plates is thin, the angle of the crown is large (Ω-type), and the number of crowns is large.

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In order to study the deformation mechanism under the ideal strength level of high strength titanium alloy, Gum metal, titanium alloy samples with different manufacturing conditions were used. In order to study the related macroscopic mechanical properties, the influence of manufacturing conditions on the tensile properties was studied, and the clues to reveal the deformation mechanism of Gum metal under ideal strength level were studied.

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A gravitation vortex type water turbine is a water turbine which generates power by the gravitational vortex. Although this water turbine can be generated by a low head and a smallness flow, the flow field is a complicated thing which has a free surface. We researched effect of flow rate on performance and hydraulic loss of a gravitation vortex type water turbine using loss analysis. However, effect of number of blades on hydraulic loss has not been elucidated. In this study, we performed the free surface flow analysis of the gravitation vortex type water turbine and applied the loss analysis method proposed in the past to changes in the number of blades. Then, we also examined the causes and mechanisms of the losses. As the results, the following facts were clarified. Among the hydraulic losses, tank loss and tank outlet loss were dominant. The larger the number of blades, the smaller the tank outlet loss, and the difference in the tank outlet loss due to the difference in the number of blades greatly affected the difference in turbine output and turbine efficiency.

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In many small hydropower plants, obstruction by foreign body is likely to occur due to the use of a runner with multiple blades. Therefore, we tried to use a single-blade centrifugal pump which is used as a sewage pump as a reverse running turbine to solve this problem. However, an excessive radial thrust occurs due to biased pressure distribution in this runner. In this study, we tried to measure the radial thrust of a single-blade reverse running pump turbine and investigated the behavior of radial thrust with flow rate change by CFD. As a result, it was confirmed that the behavior of the radial thrust with flow rate change between the experimental value and the analysis value, its time-averaged value and the root mean square value of the fluctuation component are qualitatively consistent. Within the range of this study, the time-averaged value and the fluctuation component of the radial thrust had the minimum value even at a flow rate about 35% lower than the maximum efficiency point flow rate, and increased with the increase of the flow rate.

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In this study, we measured the wall shear stress by OFI (Oil Film Interferometry) on suction surface of twodimensional airfoil under the high lift condition with a Reynolds number of about 104 are performed. And I also tried to calculate the velocity vector of the Fizeau fringes using the PIV analysis method. As a result, the average of the local skin friction coefficient Cf was within 2.5% at the range of X/C=0.33 to 0.83. The error of Cf value at X/C=0.25 was 16.3% at 50CS and 7.2% at 300CS. Comparing the PIV analysis method and the analysis value of MATLAB, the maximum velocity difference of the Fizeau fringes at 300/CS was 0.0008 mm/s at the positions X/C=0.75 and 0.83.

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For safety enhancement of sodium-cooled fast reactor, decay heat removal system (DHRS) by using the natural circulation without depending on the pump as the mechanical equipment is recognized as one of the most effective method. The numerical estimation method which can predict thermal hydraulic phenomena in the reactor vessel under the natural circulation condition in the plant cooling process by the various DHRSs is necessarily required to estimate the coolability of the core. In this study, appropriate modeling to predict the inter wrapper flow which is caused in the gap between fuel subassemblies during operation of the heat exchanger dipped in the upper plenum as a DHRS is preliminary investigated. The validation of the numerical results is carried out in comparison with the measured temperature data in the scaled sodium test facility named PLANDTL-1. Through the simulation, potential applicability of the gap model using the correlation equations to simulate the thermal hydraulics behavior of the inter-wrapper flow in the core is indicated.

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In the industrial equipment which high temperature gas flows through packed bed of solid particles, the heat transfer rate affects productivity and operation efficiency. In order to research this heat transfer rate from gas to solid, several studies have been conducted. However, since there are many parameters such as types of solid and gas, particle size of solid, filling state, gas velocity, temperature of solid and gas, general-purpose model and formulation have not been reached. In this study, we conducted experiment and model analysis to investigate the basic heat transfer characteristics from gas to solid by flowing a hot gas into a packed bed of solid particles.

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It is known that carbon monoxide (CO) has perturbation in case of the B1Σ and b3Σ states. The radiation characteristics caused by the perturbation are not clear well. We will investigate it and discuss the radiation mechanism of carbon dioxide (CO2) plasma. Microwave discharge is useful to investigate the basic radiation characteristics of CO2 plasma because it can be easily generated and has hardly impurities from the electrodes. In this study, CO2 plasma was generated by microwave discharge under different power conditions and was spectroscopically measured. As the results, it was found that the radiation of CO Ångström bands and atomic oxygen (O) lines were dominant, and CO2 dissociated into CO and O, and that the electronic excitation temperature was estimated by the Boltzmann plot method for the O lines.

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Polyoxymethylene dimethyl ether (OME) with high cetane number and low emission of soot is promising for the fuel of compression ignition engines. However, the heating value of OME is much smaller than the diesel fuel, and it is necessary to optimize the injection system. In this study, using a multi-hole injector, characteristics for the spray and the combustion of OME were investigated under the condition corresponding to the engine operation. First, the OME and diesel sprays was observed under the non-combustion condition with O2 concentration 0%. The result showed that the penetration of the OME and diesel sprays was almost same. Next, the experiment under the combustion condition was carried out. The result showed that the luminous flame was not observed in the OME spray. This suggests that the soot was generated hardly. Compared with the diesel fuel, the ignition delay of OME was similar although the cetane number of OME is higher than that of diesel fuel.

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The analysis method to identify reaction intermediates of combustion is proposed in this study. In the method, accurate mass of molecular and fragment ions measured by a time-of-flight mass spectrometer (TOFMS) are used for the estimation of compounds. The method was verified by the discrimination of structural isomer of intermediates by low temperature oxidation of n-heptane. By using the method, it is expected to obtain unprecedented knowledge about the combustion and exhaust reaction mechanism of the engine.

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This study theoretically investigates one-dimensional weakly nonlinear interaction between short and long waves in a compressible liquid uniformly containing many spherical gas bubbles. Important assumptions are summarized as follows: (i) Two different wave modes coexist, one is the short wave and the other is the long wave; (ii) Amplitudes of the short and long waves are of the same order of magnitude; (iii) Bubble does not coalesce, break up, extinct, and appear; (iv) The effect of viscosity in the gas phase, heat conduction in the gas and liquid phases, and phase change across the bubble wall, are neglected for simplicity. By the use of a singular perturbation analysis based on the method of multiple scales, we can derive the coupled equations from the set of governing equations for bubbly flows, one is the nonlinear Schrödinger (NLS) type equation for the short wave with a nonlinear interaction term and the other is the Korteweg–de Vries (KdV) type equation for the long wave with a nonlinear term of the short wave.

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Weakly nonlinear propagation of ultrasound in an initially quiescent liquids uniformly containing many spherical microbubbles is theoretically investigated, especially focusing on the thermal conductivity and liquid viscosity toward medical application such as HIFU treatment. Although our group has derived a Khokhlov–abolotskaya–Kuznetsov (KZK) equation for the description of quasi-plane propagation of ultrasound with a long wavelength and a low frequency in bubbly liquids with a nonuniformity of the number density of bubbles, the effects of the thermal conductivity and liquid viscosity has been ignored. The present study re-derived a KZK equation incorporating the thermal conductivity and liquid viscosity. As a result, the nonlinear, dissipation, dispersion, and diffraction effects of ultrasound are expressed as a linear combination. Especially, the dissipation effect is divided into two terms, i.e., the second partial derivative and the term without differentiation with respect to a retarded time: the former is owing to the liquid viscosity and the liquid compressibility (i.e., acoustic radiation damping) and the latter is to the thermal conduction. Three types of dissipations (i.e., the liquid viscosity, liquid compressibility, and thermal conduction) are also expressed as the linear combination.

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Weakly nonlinear propagation of pressure waves of a short wavelength in an initially quiescent water uniformly containing many spherical microbubbles with an initial polydispersity of bubble radius is theoretically studied. Although many previous studies for nonlinear waves in bubbly liquids have assumed the monodispersity of bubble size, we formulate the polydispersity of bubble size and incorporate it into a nonlinear wave equation describing long-range propagation of pressure waves; the initial number density of bubbles is constant. The polydispersity is quite small and appears at a field far from the sound source. Bubble oscillations are spherically symmetric, and bubble does not coalesce, break up, appear, and disappear. The gas viscosity, the heat conduction, and the mass transport across the bubble-liquid interface are ignored. The basic set composed of the conservation laws of mass and momentum for gas phases and liquid phases, the Keller equation for bubble oscillations, and some constitutive equations is used. From a singular perturbation analysis up to the third-order of approximation, a nonlinear Schrödinger equation including an advection term with a variable coefficient is derived from the basic set. We conclude that the small polydispersity of bubble size affects the advection effect of pressure waves.

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To improve the performance of polymer electrolyte fuel cells (PEFCs), the improvement of the water transport in the cell is important. Therefore, it is required to establish the simulation method for the PEFC. In this study, a latticeBoltzmann method for the simulation in PEFCs was proposed. For the high-speed simulation of two-phase flow with a large density ratio in the PEFC, the spurious velocity was reduced by using the balanced force algorithm and the stability of the calculation at large time step was improved. In addition, to speed up the calculation, the odd-even SOR method was applied to solve the Poisson equation in the balanced force algorithm.

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From the viewpoint of measures against global warming and environmental protection, improvement of fuel economy of transportation vehicles is required, and weight reduction of a vehicle is cited as a solution means. Currently, the high-speed railway vehicle body is predominantly made of aluminum alloys, but by substituting magnesium alloys that are lightest among the commercially available metallic materials, it is possible to reduce the weight of the railway vehicle body. In order to realize this, flame-retardant magnesium alloys with calcium addition attract attention. MIG welding with high productivity is required for practical application of the flame-retardant magnesium alloys to high-speed railway vehicle structure, but hydrogen embrittlement resistance of flame-retardant magnesium alloy MIG weld is not clear. The SSRT tensile test and the HG-SCC test are performed on two types of MIG welds of AX92 and AX41 alloys that have been developed in the ISMA project, to evaluate the hydrogen embrittlement characteristics. For comparison, the same test was performed on MIG welds of an AZ31 alloy that is widely used as a wrought magnesium alloy.

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Spot welding is an important process in industry. High conductive materials such as copper and aluminum need huge current and high pressure in the welding, therefore tungsten and molybdenum materials are used for the electrode. In this study, hydrogen desorption of a unrecrystallized-tungsten, a recrystallized-tungsten, a copper-tungsten and a cerium-tungsten electrodes were measured by the thermal desorption spectroscopy. The welding operations were repeatedly carried out up to 3,000 cycles. As the result, an effect of residual hydrogen on the durability of tungsten electrode was not confirmed.

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In order to expand the spread of fuel cell vehicles, it is necessary to investigate the hydrogen embrittlement of aluminum alloys used for hydrogen-related structural applications. Crack initiation and crack propagation in the hydrogen embrittlement process have been evaluated without making much distinction between them. However, crack initiation and crack propagation should be assessed separately so that appropriate prevention measure can be taken for each. Therefore, firstly, in this study, constant load tests and slow strain rate tensile tests have been performed on Al-Zn-Mg and Al-Mg-Si alloys, mainly to evaluate the crack initiation.

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Carbon fiber reinforced carbon composite (C/C composite) and tungsten materials are expected as divertor materials that receive the highest heat flux load in large-scale fusion experimental device. Graphite materials for fusion reactors, such as C/C composite, have extremely high heat resistance (sublimation point of 3,650K) and high thermal shock resistance, and can withstand high heat flux loads such as plasma disruption. Ultra-low loaded hardness and micro Vickers hardness tests were carried out on isotropic graphite (IG-430U), C/C composite (CX-2002U) and pyrolytic graphite (PyG) for fusion reactors. The microstructures were also observed by SEM. As the results, IG-430U had isotropic property. CX2002U had data variation due to fibers and pores. PyG had anisotropic property due to extreme layered structure. It was necessary to be performed by ultra-micro load of 200 mN in the ultra-low loaded hardness test. And the micro Vickers hardness test was not suitable for the graphite materials.

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In recent years, renewable energy has been used to generate electricity. However, the problem is unstable output. Energy storage and transportation technology is required to compensate for fluctuations in output. Hydrogen is drawing attention as a storage medium. Compressed hydrogen, hydrogen storage alloys, liquefied hydrogen, methanol, and metal hydrides can be used as hydrogen storage methods. Among them, metal hydrides have excellent storage density and have the advantage that they can be stored at ambient temperature and pressure. Typical metal hydrides are LiH, MgH2, AlH3．Among them, AlH3 is practical, since the temperature at which the hydrogen-releasing reaction occurs is ranging from 80℃to 150℃. However, at present, high-temperature and high-pressure hydrogen atmosphere is required for aluminium hydride formation, and hence it has not been put to practical use. In this research, we tried to generate produce aluminium hydrides at room temperature and low pressure by causing nonequilibrium reactions by irradiation with hydrogen plasma. After irradiating a pure aluminium sheet with hydrogen plasma, the sample was observed by optical microscope, and SEM, and subjected to X-ray diffraction analysis, to confirm whether hydride was generated. The same process was applied to an Al-5mass%Ti alloy for comparison.

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In this study, we focused on the functional group for the friction reduction mechanism by graphene oxide dispersed water, and investigated the influence of dispersion amount, dispersion condition, and functional group substitution by heavy water as influencing factors on the friction coefficient. Friction tests were performed by Ring-on-Disk method and analyzed by DLS, XPS, SEM/EDX and TOF-SIMS. The results showed that the coefficient of friction was reduced to a maximum of 1/8th of that of pure water in the GO dispersed water. SEM/EDX analysis showed the adhesion of graphene oxide particles to the mating material and the formation of GO tribofilm on the sliding parts. GO particles were extracted from the GO-dispersed water by centrifugation and vacuum drying in a heavy water test. TOF-SIMS analysis with them confirmed the presence of COD in both the post-test specimens and extracted particles with heavy water. The results suggest that the functional group -OH on the graphene oxide surface was replaced by -OD after desorption.

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The authors focused on PPG and investigated the friction characteristics of DLC films in the middle and low temperature range. In the combination of ta-C and PPG, low friction was not obtained in the low temperature range, but once sliding in the high temperature range, it shows a significant friction reducing effect at 30°C. This phenomenon was unique to the ta-C film. It is expected that the formation of -O-H group on the DLC film also contributes to the reduction of the friction coefficient in the middle and low temperature range

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The age-hardenable Al-Mg-Si alloys are widely used for various products such as architectural materials and outer body panels of automobiles. Recently, severe plastic deformation (SPD) gets attention because its superior effect in improving strength to the conventional age-hardening. Examples of SPD are high-pressure torsion (HPT), accumulative roll bonding (ARB), etc. Also, previous studies have reported that the addition of Cu improves the strength of cold-rolled Al-Mg-Si alloys. However, the effects of alloying elements on mechanical properties have not been fully investigated. In this study, Al-0.6%Mg-1%Si alloys were solution treated at 540℃ for 1 h, water-quenched and cold-rolled by 90%. Tensile test was made in laboratory air to evaluate the effect of copper and iron on mechanical properties.

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This paper describes a commercial scale twin roll strip casting process for producing aluminum alloy strip of AC7A. Twin roll casting process is able to produce a strip from molten metal directly. Thus this process has a possibility to reduce total cost of strip making. However, strip casting process has some disadvantage. Casting speed depends on the material properties. It is difficult to decide the casting conditions. Many paper on the strip casting are reported. However, there are few reports on the commercial scale machine. In this study, the effect of roll speed on the strip casting was investigated. Continuous strip could not be produced at the roll speed 5 m/min. Continuous strip could be produced at the roll speed 10 m/min. However, the cracks were observed. Continuous strip was produced at the roll speed 20 m/min. However, cracks were observed too.

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Copper alloy C19210 have excellent corrosion resistance, heat resistance, and conductivity, and is used for precision electronic parts such as lead frame materials. Conventionally, copper alloy strips are manufactured by repeating heat treatment and cold rolling, and have a problem that it is multi-process and production cost is expensive. On the other hand, twin roll casting can improve the above problems because strips are made directly from molten metals. In this study, twin roll strip casting of copper alloy C19210 using commercial scale machine was operated. The aims of this study is to investigate the possibility of strip casting for copper alloy. The strip produced at roll speed of 7 m/min and 10 m/min had a lot of metallic luster. The lower the roll speed is, the greater the rolling load is. At a roll speed of 7 m / min, the rolling load became the maximum rolling load of the equipment. For producing strips with copper alloy C19210, higher rolling loads are preferred. The crystal grain of the manufactured strip was fine.

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The effect of the vibration fluidity of packing sand on the casting appearance in the expendable pattern casting (EPC) process were investigated experimentally. The aluminum alloy casting of the simple shape with the rib was cast by EPC process using the natural silica sand and two types of fused and sintered artificial sand, respectively. The effects of the filling sand material and flask vibration condition were examined using the appearance and dimensional accuracy of the castings. The vibration fluidity of the artificial sands were higher than that of the natural silica sand, and especially the fused artificial sand was considerably high. When the fused artificial sand was filled, even at lower vibration frequencies, the casting appearance and dimensional difference were insignificant. In this case, the increase in sand pressure between the ribs of EPS pattern due to the flask vibration was confirmed.

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Highstrength steel sheets for weight reduction and safety improvement of vehicles have been developed. Highstrength TRIP-aided steel with transformation induced plasticity of the retained austenite has high strength and ductility. Conventional TRIP-aided steels are subjected to austempering process after austenitizing. Generally, elongation and formability of TRIP-aided steel are improved by finely dispersing retained austenite in BCC phase matrix. The finely dispersing retained austenite and grain refinement of TRIP-aided steel can be achieved by rolling with heat treatment. TRIP-aided steel having higher strength and ductility by combining heat treatment and rolling can be expected to be obtained. In this study, thermomechanical treatment was performed by combining hot rolling and austempering process in the manufacturing process of TRIP-aided steel. The tensile properties of the hot rolled TRIP-aided steel were investigated, and the effects of thermomechanical treatment on the properties were discussed.

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The weight reduction of automobiles has been promoted to improve the fuel efficiency, and the research of highstrength automobile versions has been actively conducted. Low alloy TRIP steel utilizing transformation-induced plasticity of retained austenite has high strength and ductility and is therefore attracting attention as a high strength steel sheet for automobiles. By performing hot rolling before isothermal holding treatment of TRIP-aided steel, improvement of fine structure such as refinement of structure and increase of retained austenite amount can be expected. However, the conditions of hot rolling were not systematically investigated. Therefore, in this study, the effect of hot rolling conditions on the microstructure of TRIP-aided steel was investigated. In addition, the microstructure and retained austenite amount were discussed with hot rolling conditions.

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In recent years, global warming and depletion of energy resources have become problems, and energy saving in the field of transportation such as high-speed railways and automobiles is required as a countermeasure. To fulfil this demand, applying a promising lightweight structural material for next generation to transportation equipment such as railway vehicles is expected. Thus, flame-resistant magnesium alloys are paid attention to. When applying flameresistant magnesium alloys to vehicle structures, they are usually welded. In the previous studies, the characteristics of the weld zone were evaluated, but the characteristics of the heat affected zone were not evaluated. Changes in the characteristics of this zone may affect the safety of the structure. In the present study, newly developed flame-resistant magnesium alloys were heat-treated to simulate the temperature change in the heat-affected zone, and changes in solid solution/ precipitation and recovery/ recrystallization behavior as well as in mechanical properties were investigated.

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Steels can have a wide range of properties by changing the alloying elements, processing method, and heat treatment method. The cold-rolled Fe-Ni-Al-C alloys have been reported to have a good balance of strength and ductility, the strength is significantly increased by severe cold rolling while the decrease in ductility is suppressed. It has been also reported that deformation twinning, and deformation-induced martensite might contribute to plastic deformation with evolution of Luders bands, but the detailed mechanism has not been clarified. In this paper, the strain distribution of 70% cold-rolled Fe-Ni-Al-C alloy was evaluated by SSRT (Slow Strain Rate Technique) tensile test, and the inhomogeneous deformation behavior was microscopically analyzed with digital image correlation ,to investigate the relationship between the local deformation mechanism and ductility.

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Gum Metal is a β type titanium alloy that has both low Young’s modulus and high strength, and exhibits various other properties different from ordinary metallic materials. These specific functions have been considered to be related to its deformation mechanism. Therefore, the deformation mechanism in Gum Metal has been analyzed so far but has not been clarified yet. So we have investigated the local mechanical response near grain boundaries of Gum Metal for the purpose of examining the contribution of dislocation motion in the plastic deformation mechanism. Here we used Gum Metal and Ti20%Mo alloy for comparison. Mechanical characteristics in the nanometer range have been directly evaluated by nanoindentation and the effect of grain boundaries on the deformation behavior has been studied.

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We are pursuing the development of new grinding wheels and production technology grinding wheels using twin nozzles PELID. Using the PELID teghnology, I made of a mixture of phenol resin and ethyl cellulose. As a result of observing the fiber with SEM, that’s diameter was about 2 micrometers. And I made a liquid containing abrasive grains and used it to make fibers containing abrasive grains. I producted the fiber under a variety of manufacturing conditions and examined whether it affected the fiber diameter. As a result it was confirmed that the diameter of the fiber increases as the flow rate increases. By using these properties, fibers can be made in a state where two kinds of abrasive grains are held by using abrasive grains of WA#3000.

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At cutting, vibration causes deterioration of surface roughness, and increase of tool wear, so it is necessary to decrease of vibration. Currently, we are taking various measures to reduce vibration, but the anti-vibration tools are expensive. Therefore, damping alloys attract attention because to simply and to effectively reduced vibration. Damping alloys may be possible to reduce the vibration caused by turning by applying to the tool holder. The purpose of this research is to confirm the effect on vibration by sandwiching the tool holder with the damping alloy plate. In addition, it is necessary to study a method of applying the damping alloy in the order to enhance the damping effect. Therefore, it is also a research purpose to confirm the damping effect by surface friction by increasing the contact area between the damping alloy and the tool holder. As a result, it was confirmed that the tool holder to which the damping alloy applied reduced the vibration more than normal tool holder. Furthermore, it was confirmed that the groove tool holder having an increased contact area between the damping alloy and the tool holder reduced vibration as compared with the tool holder sandwiched between the flat plates.

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Many of the machine elements are made of wood in the Pre-modern Ages in Japan, which makes wood cutting work technologically important. Wood cutting work usually provided in a divisional system differs from metal cutting work mainly provided by smiths. The aim of this series of papers is to research how wood cutting work was provided in the Pre-modern Ages in Japan.

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The burring process is to form a branch pipe by raising the peripheral portion of the prepared hole formed in the mother pipe. There is a problem that the cutting of the edge is required in the post process. Therefore, a branch pipe batch forming method has been developed in which burring processing that does not require a cutting step in the subsequent step is combined with ironing processing using FEM analysis. The purpose of this research is to improve the accuracy of FEM analysis in the branch pipe batch forming method using burring process and ironing process by cutting the material into a cylindrical shape and performing a compression test to obtain the deformation resistance of the actual material.

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