Molecular dynamics simulations of tensile deformation of amorphous metals with dispersed nanocrystalline particles were performed in order to reveal the particle size effects on Young's modulus and the flow stress through all crystal volume fraction from 0% (amorphous) to 100% (nanocrystalline metal).The analysis model used in this research contains 32 nano-scaled crystal-particles with random orientation in a unit cell. It became clear that the Young's modulus of the nano-composite is increased as the average particle radius and the crystal volume fraction increase. On the other hand, the flow stress is not affected by the particle size when the crystal volume fraction is lower than 60%. The particle size effects appear gradually for higher crystal volume fraction models. This phenomenon is caused by an increase of the fraction of the grain boundary to the entire interface. We also demonstrate that the elastic constants can be estimated with a higher accuracy by employing a self-consistent compliance model based on the equivalent inclusion method. The Lennard-Jones potential, modified to enforce the continuity at the cut off distance, was used as an interatomic potential. The potential parametes were defined based on Inoue's three basic principles.

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The mechanism of enhancement for the nucleation and growth of oxide precipitates in heavily boron (B) doped Czochralski (CZ) Si crystals was analyzed by first principles calculation. At initial stage of oxygen precipitation including a few number n of interstitial oxygen (O) atoms with and without one substitutional B atom, i.e. B-O_n, complex and O_n, , complex, the reduction of the total energy of stable B-O_n complex formation was larger than that of stable O_n complex formation from isolated B and O atoms. The other calculations showed that O atom in B doped silicon diffused as O²⁺ charge state with the diffusion barrier of about 2.0 eV, which was lower than the barrier of about 2.5 eV for O⁰ charge stage in intrinsic silicon. This reduction of diffusion barrier should be the mechanism of enhanced oxygen diffusion and enhanced precipitate growth in heavily B doped CZ Si crystals.

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This paper describes an efficient monolithic method for shell-fluid interaction problems based on the fluid pressure Poisson equation (PPE). The PPE is derived so as to be consistent with the coupled equation system for the shell-fluid interaction. In the proposed method, the fluid pressure is derived implicitly so as to satisfy the incompressibility constraint and all the other unknown variables except those for the shell are derived explicitly. The coefficient matrix of the PPE is well-conditioned even if the structure is very stiff or heavy compared to the fluid, and even if the ill-conditioned submatrix is generated due to the shell elements. These characteristics are successfully utilized to combine the proposed method with the standard conjugate gradient method. To demonstrate fundamental perfermances of the proposed method, it is applied to evaluate the vibration characteristics of a thin elastic cantilever plate in a quiescent fluid.

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This paper presents the development of new structural optimization technique and its application to flat CRT. The hybrid genetic algorithm using 4 optimization parameters is proposed to apply to the lightweight design of flat CRT. In the design procedure, a unique penalty function method is introduced in order to improve the efficiency of optimization. The optimization was carried out by taking into consideration various limiting conditions associated with strength of materials, product functions and its manufacturing. It is found that the proposed hybrid GA is effective for improvements of efficiency and stability of solution. Moreover, the prototype of the flat CRT is manufactured on the basis of the optimum solution. Then it was proved that the measured stress of the prototype corresponds with the analysis and the achieved weight reduction of the prototype was 11% of the conventional CRT.

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The use of curved image sensor is effective for the miniaturization of camera modules fitted to digital camera, mobile phone, etc. This paper describes the strength data of curved image sensor and describes the structural optimization of the elements using this data. The main results are given below. (1) The bending strength and surface strength of Si elements and image sensors were clarified through experiments, and the effects of stress relief method, dicing method and thickness on the basic strength were made clear. In particular, a new surface strength test method is suggested. (2) A three-dimensional, larges deformation FEM analysis was carried out to obtain the stress generated when curving the image sensor. It was made clear, judging from the measured strength of image sensor, that there were several breakage modes caused by 1) bending stress fractures at the periphery of the element, 2) Surface stress fractures at the center of the element and 3) buckling due to compressive stress at the periphery of the element. (3) In order to reduce the fracture rate of curved image sensors, it is effective to use a genetic algorithms and an information integration method based on several conditions limiting its structural design. The fracture rate was found to conform to the experimental result.

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Bending deformation of a Flemion-based IPMC (a gold plated Flemion) upon applied low electric field across its thickness is dominated by non-uniform equilibrium hydration. Non-uniform equilibrium hydration that leads to a permanent deformation is expressed by the “equilibrium hydration state” of the membrane under ion concentration gradients. Consequently, there is strain distribution due to different hydration throughout the thickness. In the present study, finite element formulation is conducted for the basic field equations governing electrochemical-mechanical response of a gold plated Flemion actuator upon applied electric field. Some numerical studies are carried out in order to show the validity of the present formulation.

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A constitutive equation for elasto-plastic damageable solids is formulated by using Drucker-Prager's equivalent stress to analyze the damage failure behavior of concrete structural elements reinforced with carbon fiber sheets. The forumulated constitutive equation is implemented in the two-dimensional finite element program to simulate the experimental results. The constitutive equation is identified by using the uniaxial, compressive and tensile test results for concrete and carbon fiber sheets. The finite element analyses are carried out for real-scaled cantilever RC slabs with and without carbon fiber sheets. The calculated results are compared with the experimental results to illustrate the validity of the proposed method of analysis.

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The finite element models of the Kirchhoff (classical thin) plate theory and Mindlin plate theory are now standard. The Mindlin plate theory includes the effect of transverse shear deformation. This theory is called the first-order shear deformation theory. The first author developed a beam element based on a displacement formulation of Mindlin plate theory. The objective of this paper is to present a formulation for plate element based on the refined plate theory of Shimpi. The refined plate theory of Shimpi uses higher-order polynomials in the expansion of the displacement components through the thickness of plate. Furthermore, the transverse displacement ω is given by ω = ω_b + ω_s, where ω_b and ω_s are its components due to bending and shear, respectively. Several numerical experiments are performed and show that the present element gives excellent results for both thin and thick plates.

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Geothermal energy is one of the most enviroment-conscious resources among the natural resources. In developing an enhanced geothermal energy extraction system, a hydraulic fracturing is the key technology to emerge an efficient geothermal reservoir. The formation of the geothermal reservoir induced by the hydraulic fracturing has to be predicted to design the geothermal energy extraction system. In this study, crack propagation induced by the hydraulic fracturing of an inclined crack is numerically analyzed. In the numerical model, shear slip deformation is taken into account. When the fluid pressure acts on the inclined crak, shear slip deformation is takes place prior to crack opening due to the pressure that overcomes the normal stress acting on the crack plane. Furthermore, the numerical results suggest that the crack can be propagated by a critical fluid pressure less than the minimum tectonic stress under typical tectonic stress condition, since the stress state at the crack tip is intensified by shear slip deformation. Therefore, the critical fluid pressure for the inclined crack is characterized by the effective shear stress that indicates shear slip condition of the crack.

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A calculation method for three-dimensional elastic solid analysis is proposed using the Moving Particle Semi-implicit method (MPS). The angular velocities and the rotation angles of each particle are implicitly calculated from the velocities and coordinates of the neighbor particles respectively. Large deformation accompanied by rigid rotation can be analyzed with keeping the total energy by employing a symplectic scheme. By introducing a viscosity term, the total energy can be decreased without loss of angular momentum.

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The effects of crystal orientation (θ) on the structural strength of single crystal trubine vanes and blades calculated with the finite element method (FEM) are discussed in this paper. TMS-75, a 3^rd generation single-crystal Ni-base superalloy, is chosen as the model material for turbine vanes and blades. It became clear that, (1) the elastic constant matrix changes were equivalence for each of three coordinate due to the orientation variation (0°<θ<90°), and the strength of the turbine vane and blade were strongly related to θ, and also depended on the load and model shape. (2) The strength dependence of the turbine vane on the crystal orientation was depended on coordinate plane : there are lower Mises stress in XY plane and maximum Mises stress in near the θ=45°at both YZ and ZX Planes. (3) In the case of a blade, the influence is similar to the vane on blade tip, but the converse holds for the blade root. It is clear that the creep rupture time can be extended, when the <100> crystallographic axes is the Y or X axis of the blade under higher revolution speed.

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Fundamental equations for the simulation of phase transformation process by using the phase field model is derived. Compared to the conventional metallo-thermo-mechanical coupling equations, based on the volume fractions of every phases, the advantage of the phase field model is that this model can treat a dynamic evolution of the two-phase interface. Therefore, complicated stress distribution in the microstructure formed by heat treatment can be simulated. The derivation is achieved based on Gibbs free energy definition and the second law of the thermodynamics. The phase field equation includes the effect of stress-induced transformation as well as thermally driven transformation. In the stress-strain relationship, the elasto-plastic behavior is considered, which enables the evaluation of the residual stress distribution in the microstructure.

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This paper describes an evaluation method of primary stress in three dimensional (3-D) structures. In “Design by Analysis” for nuclear components, the stresses in structures are classified into the primary and the secondary stresses. The primary stress in axisymmetric structures can be evaluated by linealization of stress distribution in the specified section, but it is difficult to define the evaluation section in the 3-D structures, and to evaluate the primary stress with the conventional procedure. From this reason, the alternative evaluation method is needed. In this study, the evaluation method of primary stress in 3-D structures with elastic-plastic analysis is proposed utilizing the feature of primary stress that is independent from stress redistribution. The proposed method is verified through application to example problems.

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The structural optimization problems consist of phase optimization and size optimization steps. The size optimization is comparatively easily using a mathematical technique, but the more important phase optimization is difficult. Until now, researches using GA, NN, SA and CA as the phase optimization technique are done. In this paper, “the method by CA changing majority rule” is proposed. It is the method searching an optimal structure without increasing a design variable and keeping design space large. Moreover this method makes the operation from phase determination to size decision systematically. By using the method, the design problems of the optimum board thickness distribution are analyzed as an exercise about the validity

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CFRP pressure vessels are now widely used in compressed natural gas vehicles (CNGV) and have a possibility to be employed in fuel cell vehicles (FCV) for highly compressed Hydrogen. In order to increase a driving distance in CNGV and FCV, lighter vessels proofed against higher pressure are required. In the case of internal pressure, the tensile circumferential stress at the inner radius should be decreased in order to increase the burst pressure. This paper presents a method how to increase the burst pressure of CFRP vessels. For increasing the burst pressure of CFRP vessels, the shape memory alloy (SMA) wire memorized a compressive stress is wound around the outer surface of cylindrical part of the CFRP vessel. When the internal pressure acts on the CFRP vessel, its tensile circumferential stress can be reduced by being received the compressive stress of the SMA wire and the experimental results of increasing the burst pressure are shown. The experimental results are compared with numerical ones and they agree well each other. Furthermore, optimum design of CFRP pressure vessels by the change of winding method of SMA wire is numerically obtained.

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Bioactive ceramics β-tricalcium phosphate (β-TCP) particle dispersed bioabsorbable plastics poly-L-lactide (PLLA) composites have been expected to apply for the fracture fixations which have more biocompatibility than monolithic PLLA. In this study, β-TCP/PLLA composites containing three different β-TCP contents (4.8, 9.5, 14.3wt%) were prepared by injection molding. The results of bending tests show bending strength decrease with increasing β-TCP contents. On the other hand, bending modulus increases with β-TCP contents. After immersion tests in PBS at 37°C up to 8 weeks the mechanical properties were hardly degraded in all specimens. The results of fracture surface observation indicated that microscopic damage such as debonding between β-TCP and PLLA initiates at β-TCP agglomeration and grow with increasing loading. Analytical predictions of the relationship between stress and strain based on micromechanics considering the progress of β-TCP/ PLLA debonding were in good agreement with experimental results.

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The purpose of this study is to generate and characterize a microneedle that can be equipped in Bio-MEM which is applied to a developing HMS (Health Monitoring System) for the blood sugar level measurement. One of the most important subject to Bio-MEM is a microneedle with a inner diameter of 25μm and a outer one of 50μm, which mimics female mosquito's painless blood extraction mechanism. In this study, the microneedle generation was performed through (1) selection of a biocompatible material from titanium alloys by the cytotoxic assay, (2) RF magnetron sputter generating of the microtubes with a inner diameter of 25μm, a outer one of 50μm and a length of 2 mm, and (3) evaluation of the stiffness and strength by the bending tests. Consequently, the Ti-15 Mo-5 Zr-3 Al alloy microneedle generated by sputtering is not cytotoxic and possessed the practical stiffness and strength.

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The present study investigated experimentally the effects of temperature, pressure and time upon bulk density of packed bed of magnesium alloy particles. The test particles made of AM 50 A or AZ 91 D were poured into a cylindrical vessel and were applied a given superficial pressure for six hours under a constant temperature condition. The superficial pressure was changed between 2.5 MPa and 10 MPa, and the temperature was varied from 95.5°C to 437°C. The bulk density increased after the pressure was applied and then it reached to a terminal value in cases that the temperature was below 100°C. Continuous increase in the bulk density due to creep deformation was observed in cases that the temperature was over 150°C, and it became remarkable in cases that the temperature was over 250°C. The bulk density at a certain time was increased with an increase in the temperature and the superficial pressure. The increasing rate of the bulk density could be expressed as a function of temperature, superficial pressure and the bulk density.

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The adhesive protein of the mussel widely living in the ocean is expected as an ingredient of the adhesive. Adhesive strength of the protein to substratum has not been clarified because a method of measuring the strength does not exist. In this research, the plaque consisted of adhesive protein was peeled using the spatula-shaped jig inclined at the angle of 45 degrees to substratum. Adhesive strength was determined from the peeling load obtained by the jig with a strain gauge. To investigate the effect of the thickness of the plaque on the peeling load, based on linear fracture mechanics, peeling simulations of plaque from substratum were conducted using the finite element method. The simulation suggested that adhesive strength of the plaque to substratum is quantitatively evaluated by averaging the peeling load fluctuations.

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Interfacial debonding propagation is one of the most important problems for long-term creep in unidirectional composites because the strength of the unidirectional composites decreases with increase of the interfacial debonding length. In this study, time-dependent interfacial failure was investigated by using the Micro Raman Spectroscopy. The specimen was single fiber composite consisting of one carbon fiber embedded in the vinylester resin. It was subjected to a constant strain to assume the long-term creep in the unidirectional composites. To discuss the timedependent interfacial debonding propagation behavior, a time-dependency of a criterion for interfacial debonding propagation in the SFC must be determined. In this paper, the time-dependent boundary condition of the interfacial debonding was obtained from experimental results, and the interfacial debonding propagation was formulated. Here, the compression stress applied to the interface in the fiber radius direction was formulated as a function of time on the consideration of Poisson contraction and thermal residual stress. The interfacial debonding propagation and variation of the fiber axial strain distribution as a function of time were formulated by using the following three parameters : a relaxation of the frictional stress, an interfacial shear viscoelastic behavior and the time-dependent boundary condition at the interfacial debonding tip. These formulations showed a good agreement with the corresponding experimental results.

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In this study, an effect of physical surface treatment to mechanical properties for CFRP is focused. Three kinds of sand papers with different grain degrees are used for physical surface treatment to plain woven carbon cloth. DCB (Double Cantilever Beam) test, ENF (End Notched Flexure) test and static bending test for CFRP are conducted. Fracture surface of carbon fiber using SEM (Scanning Electron Microscope) is observed. Static bending testand bending creep test for honeycomb sandwich beam whose surface materials are treated CFRP are also conducted. As a result, fracture toughness and crack propagation resistance under Mode I and Mode II are improved by physical surface treatment. The surface treatment is effective to bending strength and stiffness. The treatment using coarse particle is effective for compressive side, and the fine grain is effective for tensile side. Physical surface treatment improves stiffness and bending creep properties for honeycomb sandwich beam.

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In the previous paper, it was reported that the forged and extruded P/M aluminum alloys with ultra-fine grain (200-500 nm) have relatively lower ductility and fracture toughness, and that fatigue crack growth resistance was lower than that of the conventional P/M Al alloys. In this study, the extruded material was upset forged at various forging ratios in order to improve the ductility. Fatigue crack growth tests were carried out using L-C and C-C orientation CT specimens of the extruded and upset forged materials, and the effect of pre-plastic working on fatigue crack growth behavior was investigated. Fracture toughness was improved by the upset forging, irrespective of specimen orientation. Fatigue crack growth resistance of the pre-plastic worked alloys became higher than that of the extruded one in the L-C orientation specimens. However, crack growth threshold value in the C-C orientation specimens, ΔK_th, became low for upset forging and remarkable anisotropy of fatigue crack growth resistance was observed.

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This study investigates the electromechanical fracture behavior of a normal crack in a semi-infinite piezoelectric material subjected to a uniform heat flow far away from the crack region. The crack faces are supposed to be insulated thermally and electrically. By using the Fourier transform, the thermal and electromechanical problems are reduced to singular integral equations, respectively, which are solved numerically. Both the cases of as internal crack and an edge crack are studied. Numerical calculations are carried out, and detailed results are presented to illustrate the influence of the crack location on the temperature distribution and the stress intensity factors

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In this paper, the mixed-mode crack problem for a functionally graded piezoelectric material (FGPM) strip is considered. It is assumed that the electroelastic properties of the strip vary continuously along the thickness of the strip, and that the strip is under in plane electric loading. The problem is formulated in terms of a system of singular integral equations. The stress and the electric displacement intensity factors, and the energy density factor are presented for various values of dimensionless parameters representing the crack size, the crack location, and the material nonhomogeneity.

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In this paper the stress intersity factors of an inclined elliptical crack near a bimaterial interface are descussed. The solution utilizes the body force method and requires Green's functions for perfectly bonded semi-infinite bodies. The formulation leads to a system of hypersingular integral equations whose unknowns are three modes of crack opening displacements. In the numerical calculation, unknown body force densities are approximated by using fundamental density functions and polynomials. The results show that the present method yields smooth variations of stress intensity factors along the crack front accurately. Distributions of stress intensity factors are indicated in tables and figures with varying the shape of crack, distance from the interface, and elastic constants. It is found that the inclined crack can be approtimated by models of vertical and parallel cracks with the error 24% even in the case of very close cracks neer an interface.

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On deformation condition for displacement zero in the width direction of upper and lower edges, a formulation of elastic stress was expressed for side plates in the case of the corrugated fiberboard box shape (CFBS) supported by upper and lower edges under compression loading as uniform displacement u_yh. Then from this formulation, the stress behavior for side plates was discussed.Normal stresses σ_x and σ_y in width (L=300mm) and height (h=400mm) directions x and y for the plate are symmetric to center lines of the width and the height, and shear stress τ_xy is antisymmetric, Maximum σ_xmax of|σ_x|is at centers of side plates and maximum|σ_ymin|of|σ_y|is about at corners. And maximum τ_xymax of |τ_xy|is at distance L/16 from corners in upper and lower edges. Ratios σ_xmax/|σ_ymin|and τ_xymax/|σ_ymin|are about 0.14 and 1.13.

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The influence of strain ratio on bending fatigue properties of TiNi shape-memory alloy thin wires and the process of fatigue crack growth were investigated. The results obtained are summarized as follows. (1) The martensitic transformation stress of a superelastic thin wire is higher than that of a shape memory wire, resulting in short fatigue life of the superelastic wire. The maximum bending strain of fatigue limit is the martensitic-transformation starting strain. (2) The plane-bending low-cycle fatigue life curve is expressed by a power function between maximum strain ε_max and the number of cycles to failure. The smaller the strain ratio, the shorter the fatigue life. (3) In plane bending, fatigue crack initiates on the surface of the wire. One fatigue crack grows preferentially and the fatigue-crack propagated region is fan-shaped. (4) If ε_max is larger than 1%, ε_max becomes a little smaller than that of the initial value during the rotating-bending fatigue test. (5) The fatigue crack length of the notched wire is expressed by a power function of the number of cycles.

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Oxygen-free copper was processed by equal channel angular pressing with different numbers of ECAP process cycles, NP. Tensile tests were performed to clarify the effect of NP on tensile strength and elongation. Tensile strength was increased with an increase in NP, but it tended to saturate after NP =4. Conversely, elongation was dramatically decreased by first pressing followed by salutation trend up to NP=3. However, it tended to increase after NP=4. In addition to this, specimens processed with NP=4 and 8 were fatigued at three constant stress amplitudes ; σ_a240, 120 and 80 MPa. The change in surface morphologies during fatigue process was monitored by OM and SEM. At the same time, change in surface hardness during fatigue was measured. Significant decrease in surface hardness due to cyclic stresses was measured. To discuss the physical basis of particular tensile properties and fatigue characteristics, TEM observation and measurement of heat-flow values by DSC have been carried out.

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Fretting wear and fatigue properties of an epoxy resin filled with crushed silica particles were examined under three levels of contact pressure. The three dimensional elastic-contact stress analysis was carried out for predicting the fretting fatigue limits. The fretting wear morphology was three-body abrasive wear accelerated by the mixed wear cluster of transferred metal particles with the silica particles isolated from the matrix surface. The friction coefficient between the specimen and the pad was 0.6-0.65. However it was reduced to 0.1 by interposing a PTFE film between the rubbing surfaces. At the contact pressure of 20 MPa, the fretting fatigue reduction factor at fatigue limit was 3.0, however by inserting the PTFE film the fretting fatigue strength was extremely improved up to the unfretted fatigue level. The fretting fatigue limits predicted by a surface stress criteria approach possessed relatively large errors especially at high contact pressures, but the prediction values by a simplified fracture mechanics approach successfully maintained reasonable and practical accuracy over the wide range of contact pressure.

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In order to investigate the effects of the substrate post quenching on the tribological properties of TiN film, a specimen which steel substrate (carbon tool steel, JIS SK3) was quenched after TiN coating was prepared, and the ball-on-disc type wear test was carried out using ZrO₂ ball. The delamination initiation life of TiN film was improved by the high adhesive strength of TiN film obtained by the substrate post quenching. The specific wear rate was also improved by the substrate post quenching, though the TiN hardness was lower than that of the conventional type specimen which was TiN coated after substrate quenching. The reason why the specific wear rate was improved could be explained as follows. In the substrate post quenching process, TiN was partly oxidized and titanium oxide which acted as a lubricant was formed on TiN surface. Attributed to the formation of titanium oxide, the friction coefficient lowered and the lower specific wear rate could be obtained.

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Blue brittleness is exhibited by some steels after being heated to an elevated temperature. Although at high temperature a given strain is associated with a lower stress level, at the temperature at which blue brittleness is observed there is a pronounced work-hardening effect. Furthermore, the temperature at which blue brittleness occurs is a function of the strain rate. Therefore, to improve the accuracy of numerical simulations of hot or warm working which utilizes the thermal softening of steels, a dynamic constitutive equation which can model the blue brittleness phenomenon is needed. In this paper we present such a constitutive equation, which has two parts : one models the ordinary constitutive relation and the other the phenomenon of blue brittleness. Unknown material constants in the equation are determined by a non-linear least-squares method from uniaxial impact and static compressive test results. The equation is then evaluated by comparing it to experiments over a wide temperature range.

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Slip deformation in Cu-9at.% Al symmetric type bicrystal models subjected to tensile loading is investigated by a finite element crystal plasticity analysis code. Accumulation of geometrically necessary dislocations (GNDs) and statistically stored dislocations (SSDs) are studied in detail. Results of the analysis show asymmetric non-uniform deformation and accumulation of GNDs on the primary and secondary slip systems with activity of secondary slip system near the grain boundary. Mechanism of asymmetric non-uniform deformation with GNDs accumulated near the grain boundary in the Cu-9at.% Al symmetric-type bicrystal models is discussed from the viewpoint effects of elastic anisotropy of Cu-9 at.% Al and heterogeneity of initial statically stored dislocations density.

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