The objective of this study is to design and fabricate novel lead-free piezoelectric materials through systematic investigation based on first-principles calculation. This study targeted perovskite compounds expressed with a chemical formula ABX_3, which show good piezoelectric response. At the first stage, biocompatible elements were employed for A and B, and oxygen was applied to X. The combination of biocompatible elements was then selected to satisfy geometric stable condition. The stable cubic structure was evaluated through density functional theory (DFT) calculations and the non-centrosymmetric crystal structures caused by soft modes were predicted from the phonon properties. Insulation properties were additionally estimated from band structure. The same approach was applied to composite perovskite (A,A')BO_3 and A(B,B')O_3 at the second stage, and (A,A')(B,B')O_3at the final stage. We compared computational results such as stable crystal structure and piezoelectric properties, and discussed major candidates for biocompatible piezoelectric materials.

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Body Force Method is a boundary type method for stress analysis .It expresses the solution of any problems by using Kelvin solution. This method enables us to introduce the phisical characteristics of given problem without difficulty. But the weak point is lack of versatility. Therefore , we hava expanded the extent of applicable problems by developing the special program suitable for the individual problems. Recently,the way for expressing the inelastic region is proposed. In this method, the pair of force so called body force doublet is used. As the inelastic problem,this paper treats the elastic plastic problem near a notch root. The Prandtl-Reuss equation was adopted for plastic constitutive equation. Our purpose is to investigate a relation between notch and the size of plastic zone or its shape.

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In this paper, the mechanical behavior of lattice sandwich panel is studied using FEM. This lattice panel are composed of slender beams (diameter d=200μm) connected to each other, and can be manufactured easily by selective laser melting technique. In this study, the effects of lattice's microarchitecture, number of unit cell in xyz directions and the thickness of facesheet on the mechanical response (initial stiffness under tension and bending rigidity) are investigated.

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We investigated the impact behavior of functionally giaded foam materials (FGFM) having density distribution in compressional direction by performing finite element analysis (FEA) in order to use effectively FGFM as impact absorbing matenal. In the analyses, compressive stress-strain relations depending on the density in the FGFM were linear approximation in three distinct deformation regions: elastic legion, plateau stiess region and densification region. The FEA results revealed that FGFM having high density in near the impacted end can absorb a large amount of impact energy without increasing the maximum fixed end load from that of the homogeneous foam.

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Bacterial Cellulose is the natural cellulose, characterized by a three-dimensional structure network of microfibril. BC possesses an array of unique properties, including high crystallinity, high tensile strength, therefore BC have been an interesting topic in the field of research and development. In this paper, the fabrication condition of Carbon/Carbon composites with BC and Phenolic resin, especially temperatures the effects of temperature condition on tribological properties were investigated. The testing specimens were prepared by burning at varous carbonizing temperature with different heating rate.

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Porous composites with several media are an attractive material system for multi-functional composite materials. Thermal conductive and thermoelastic properties are analyzed by mean of macro and microscopic treatments. For efficient numerical calculation, micromechanics model of the porous composite is proposed for predicting the behavior of a material. A periodical microstructure of the composite is assumed and a homogenization theory is applied with asymptotic expansion of temperature and displacement fields. Random distribution of voids and particle is generated in the periodical unit cell region and the effective conductive and thermoelastic properties are evaluated.

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The one-dimensional steady hygrothermal field in a porous infinite strip subjected to severe hygrothermal gap on its surfaces considering nonlinear coupling between heat and moisture is analyzed. Heat and moisture aie considered to diffuse macroscopically. Moreover, moisture is considered to take two phases, namely, dissolved and gaseous phases. Both types of moisture are considered to have different diffusivities. To consider the coupling between heat and moisture, the heat generation by transformation from gaseous moisture into dissolved one is considered as well as the transformation from dissolved moisture into gaseous one due to temperature change. The balance between dissolved and gaseous moisture is determined by an equilibrium condition. The effects of the coupling properties and the difference between the diffusivities of moisture on the distributions of heat and moisture are investigated.

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We study structural variations of flexible field-effect transistors due to bending. Under the plane strain condition, we estimate the relative change in capacitance under tensile and compressive strains. Each layer is assumed to be linear elastic and channel length is much larger than channel width. The predictions are compared to experimental data reported in literatures and shown to have good agreement in the small-strain range.

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In the present paper, three-dimensional Green's functions due to a point in a piezo anisotropic-isotropic elastic bimaterial are derived by using Stroh formalism and two-dimensional Fourier transforms. General expression of Green's function for piezo anisotropic-isotropic bimaterials is firstly derived, and a specified Green's function for piezo transversely isotropic -isotropic materials is secondly denved in a closed form Numerical example is given to demonstrate the validity of the present formulation of three-dimensional point-force Green's functions.

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Multiferroic composite materials, which consist of ferroelectric and ferromagnetic phases, enable us to control magnetic permeability by electric field and electric permeability by magnetic field. In order to estimate the performance and reliability of these materials, it is necessary to understand the correlation between microstructural crystal morphologies and macroscopic response. In this study we employed the asymptotic homogenization theory for scale bridging between macrostructure and microstructure. The objective of this study is to develop a multiscale finite element method to design crystal morphologies of microstructure for upgrading macroscopic homogenized material properties. As a computational example, the effect of volume fraction on homogenized material properties was investigated for a composite material of barium titanate and cobalt ferrite. The development method was verified by comparison with Mori-Tanaka theory.

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The fracture behavior of multi-cracked materials has become a key issue in fracture mechanics and recently has received large attention. In this research, an infinite solid containing penny-shaped ciack and spherical cavity under remote tension was investigated. The effect of spherical cavity on stress intensity factor (SIF) of penny-shaped crack in an infinite solid under tension was determined numerically. In older to calculate SIF, Body Force Method was used. The surface of the crack was expressed by the aggregation of planar triangles. The polar transformation scheme was introduced to integrate the fundamental solution of the body force doublet over the triangular area precisely.

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Method of elastic stress analysis for general Functionally Gradient Materials (FGMs) with 2D crack is studied based on the principle of superposition In the present study, the spacial variation of the elastic constants is expressed by an embedded force doublets in an elastic continuum. As a result, the stress field of an arbitrarily gradient materials is expressed by the superposition of Kelvin's solution for a homogeneous body. In the present study, a center cracked rectangulate plate whose Young's modulus varies with spacial coordinate was analyzed numerically.

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In this paper, the fracture problem of a piezoelectric material strip containing two coplanar cracks perpendicular to its boundaries is considered. The problem is solved for a strip that is suddenly heated from both the top and the bottom surfaces under static mechanical loading. By using the Fourier transform, the thermoelectromechanical fracture problem is reduced to a system of singular integral equations, which are solved numerically. The numerical results for the stress and thermal stress intensity factors are computed as a function of the normalized time and geometric parameters. The results for the crack contact problem are also included.

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In this paper, thermo-electric-elastic fracture behavior of two parallel cracks m arbitrary positions of a piezoelectric material strip under thermo-electric loadings is considered. It is assumed that uniform temperatures and a uniform electric displacement are maintained over the stress-free boundaries, and the crack faces remain thermally and electrically insulated. Fourier transform techniques are used to reduce the mixed boundary value problems to two systems of singular integral equations. Numerical calculations are carried out, and detailed results are presented to illustrate the influence of the geometric parameters on the stress and electric displacement intensity factors.

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The thermal strain and/or stress in CFRP plays an important rule in determining damage initiation and evolution around the interfaces such as the laminate interface and fiber/matrix interface, it arise from the difference between the longitudinal and the transverse CTE of carbon fibers. Experimental investigation has been made on the effect of anisotropic microstructure of carbon fiber on non-uniform thermal strain in CFRP during thermal loading. The measurement method on thermal deformation and strain distribution at different length scales was investigated by in-situ FE-SEM observation. A heating/cooling stage by Joule-Thomson effect was installed into the FE-SEM chamber. The composite material used was PAN-based (IM600) and pitch-based (K13D) carbon fiber reinforced epoxy matrix composites. The micro grid and random patterns were fabricated onto the CFRP surface. Electron moire method and digital image correlation method were applied to measure the multiscale deformation such as the fiber/matrix interface and the laminates interface acquired before and after loading. The nano scale thermal deformation inhomogeneity in CFRP was found at the interface due to the anisotropic microstructure of carbon fiber.

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Staple spun yarn is used as preform for natural fiber reinforced composites. In addition, innovative techniques to make spun yarn from carbon nanotubes have recently emerged; this enables us to make carbon nanotube reinforced composites more easily. However, spun yarn has very complex geometry of staple fibers such as twist, migration and discontinuity. The complexity gives rise to difficulty for analyzing staple spun yarn. In this study, an analytical method for the mechanical behavior of staple spun yarn reinforced composites is developed using the theory of anisotropic elasticity.

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Aluminium (Al) based composites containing vapor-growth carbon fibers (VGCF) and carbon nanotubes (CNT) are fabricated by spark plasma sintering (SPS) in this paper. The thermal conductivity of the composite is three times higher than that of Al material. The composite materials will be able to use as a radiation fin of a heat exchanger and a heatsink. To apply the composites to real used conditions, the strengths and thermal conductivities at several temperatures of the composites should be clarified experimentally. In this paper, therefore, pure tensile tests and laser flash methods are conducted to clarify strength and thermal conductivity of the composites at several temperatures. According to the experimental result, the composite has the different thermal effect on the strength from pure Al. And then the composite has better thermal conductivity than pure Al at high temperature.

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Effect of calcium carbonate fine particle dispersion on the ductility of polypropylene/montmonllonite(MMT) composites was investigated by tensile tests. The results showed that calcium carbonate fine particle dispersion improved the organized MMT dispersion, resulting the improvement of elongation at break by the reduction of local stress concentration during tensile loading.

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Notched fracture behavior of a thin-ply laminate made of spread tow plain-weave carbon fabrics has been studied with an emphasis on the effect of specimen size. For this purpose, static tension tests are performed on one-, two- and three-dimensional geometrically similar specimens with a center hole. The comparison of the results on 2D-geometrically similar specimens indicates that the tensile strength tends to slightly decrease as the width of specimen increases. Development and distribution of strain on the surface plies are monitored by means of digital image correlation to estimate the growth of damage indirectly. The DIC results suggest that the spread-tow thin-ply laminate has higher resistance to the growth of damage that is apt to develop from the edges of a hole. On the basis of these observations, a notch size effect law is also developed taking into account the scale effect in geometrically similar specimens.

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CFRP composites are used for the body of Boeing 787 jet plane about 50%. Many kind of damage, for example bird strike or lightning strike, may be introduced in the airplane during the long time use. The effect of electric shock similar to lightning strike on the flexural strength of CFRP with and without copper mesh sheet, were investigated. The flexural strength of CFRP without copper mesh sheet decrease strongly, depending on the through-thickness type electric shock damage. On the other hand, that of CFRP with copper mesh sheet decrease slightly under through-thickness type electric shock, and that of the CFRP with copper mesh sheet do not decrease under surface type electric shock. The effect of cure temperature on the strength of CFRP with and without copper mesh sheet, were slightly recognized. The flexural strength of CFRP with copper mesh sheet against electric shock was excellent compared to the result of CFRP without copper mesh sheet.

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This paper deals with fabrication and strength evaluation of PSZ-Ti composites fabricated by spark plasma sintering. In these composites, a volume ratio of PSZ and Ti is changed. Three-point bending tests and Vickers hardness tests are performed to determine the Young's modulus, bending strength, Vickers hardness and fracture toughness. These properties are characterized as a function of Ti volume fraction. The Young's modulus and Vickers hardness are higher than the prediction by the rule of mixture. The bending strength and fracture toughness decrease with increasing Ti content To discuss these results from a viewpoint of reaction products, the components of raw powders and sintered composites were investigated by X-ray diffraction analysis. It is concluded that titanium oxide and other reaction products were created after sintering and they affected the mechanical performances of the composites.

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This paper deals with the influence of compressive stress and load cycles on damage behavior in paper-based friction materials. Two kinds of paper-based friction materials used are composed of aramid fibers and phenolic resin, and cellulose fibers and phenolic resin. Out-of-plane compressive loading tests and compressive fatigue tests are carried out to investigate damage behavior in the aramid- and cellulose-based materials. During each test, a section of both materials is observed with a scanning electron microscope in order to identify damage evolution under compressive loading. The damage density is measured to clarify the damage evolution in both materials. From the out-of-plane compressive loading tests, the damage density in each material increases with increasing compressive stress. The dominant damage type is the damage in fibers for the aramid-based material, and the interfacial debonding for the cellulose-based material. From compressive fatigue test, the damage density increases with increasing load cycles in the cellulose-based material, while in the aramid-based material remains constant and low. The damage density in the cellulose-based material is higher than that of the aramid-based material.

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The statistical distributions of fatigue lives of a woven CFRP quasi-isotropic laminate at different stress ratios are examined, and a procedure for predicting the S-N relationships that consider the influence of the probability of failure P (i.e. P-S-N relationships) is proposed. Fatigue tests are performed at different stress ratios R = 0.1, 10 and R = x = σ_<UCS>/σ_<UTS>. To identify the statistical nature of fatigue life, a log-normal distribution and a Weibull distribution (two-parameter and three-parameter models) are applied to the fatigue data obtained. The anisomorphic constant fatigue life (CFL) diagrams for different probabilities of failure (10%, 50% and 90%) are constructed on the basis of the P-S-N curves for the critical stress ratio. It is shown that the P-S-N curves for different stress ratios can successfully be predicted using the methodology proposed in this study.

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In this study, we investigate the influence of geometrical imperfections on swelling-induced buckling patterns in gel films with holes in a square array. Finite element analysis is performed using the inhomogeneous field theory of polymeric gels in equilibrium proposed by Hong et al. (2009). Periodic units consisting of 2×2 unit cells are analyzed under a generalized plane strain assumption. Geometrical imperfections are introduced using randomly oriented elliptical holes. Results show that the resulting buckling patterns are sensitive to imperfections; three different buckling patterns are obtained, and the most dominant one is the diamond plate pattern observed in experiments, which cannot be described using the model without imperfections.

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This study aims at developing a practical microstructure design methodology for porous materials considering uncertainties at microscale using a stochastic homogenization method. After fabrication of the material based on the numerically predicted design, it is also required to update the prediction using the measured scattering. Therefore, the proposed design method consists of two steps; (1) prediction before fabrication, and (2) updating the prediction after fabrication and measurement. In the first step, the distribution of spherical pore radius, random pore arrangement and scattering of constituent's Young's modulus are considered. The update of this prediction in the second step is simply controlled by a scalar correction factor and the probability function of random arrangement without recalculating the stiffness equation. In this manuscript, the concept of new microstructure design, outline of the formulation and demonstrative example are briefly described.

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In this study, a two-scale analysis method based on a time-dependent homogenization theory is developed for the elastic-viscoplastic analysis of macroscopic structures made of microscopic heterogeneous materials such as composites and cellular solids. For this, boundary value problems for macroscopic and microscopic scales are derived to discuss the relation between the two problems. Using the relation, the two-scale analysis method and its computational procedure are established. This reveals that there is no necessity to rebuild stiffness matrices for both macro/micro structures, reducing computational costs significantly. The present method is then applied to the two-scale elastic-viscoplastic analysis of an aluminum honeycomb sandwich panel. It is shown that the present method is successful in simultaneously analyzing both the macroscopic elastic-viscoplastic behavior of the sandwich panel and the microscopic behavior of the honeycomb core in the sandwich panel.

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An algorithm is presented to design the microscopic morphology of structural materials from the macroscopic mechanical properties in consideration of the material and geometrical nonlinearities. A maximization and minimization problems of macroscopic external potential energy are defined with a constraint to the volume fraction of the microscopic material phases. Then the optimality criteria method is employed to solve the problems and the nonlinear homogemzation method is also used to obtain the macroscopic stresses caused by the macroscopic strain histories.

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We study the homogenized elastic-viscoplastic behavior of anisotropic open-porous bodies subjected to two pore pressures, p_1 and p_2. The open-porous bodies considered are assumed to be periodic and composed of metallic materials. Hill's macrohomogeneity equation is used to show three special cases in which one of p_1 p_2 or p_m (the mean of p_1 and p_2) entirely affects the homogenized viscoplastic behavior in the steady state. To verify the thiee special cases, we perform FE homogenization analysis of an ultrafine plate-fin structure subjected to p_1 and p_2, for which two base metals with different strain-rate sensitivities are considered. It is demonstrated that the three special cases typically occur under uniaxial tension and compression in the stacking direction, depending on the strain-rate sensitivity of the base metals. It is further shown that a macromatenal model reproduces well the homogenized stress-strain relations attained in the FE homogenized analysis if p_1, p_2 or p_m is entered for Terzagi's effective stress in the viscoplastic equation in the macromatenal model.

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Different microstructure features were obtained under various heat treatment conditions, which provided insight into the factors controlling the critical strength in a polycrystalline Ni-Co-base disk superalloy (TMW-4M3 alloy) with two-phase structure. The contribution of each microstructure feature, namely, the grain size, annealing twin boundary, and distribution of γ' precipitates, to the total strength was analyzed quantitatively by measuring the Vickers hardness over a range of nano- to micro-size. The grain boundary strengthening decreased with increasing solution heat treatment temperature, while the secondary and tertiary γ' precipitation hardening increased. Therefore, there is an optimum combination of microstructure features for achieving the highest tensile strength in such superalloys.

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The present study has investigated microstructural changes due to laser peening in modified 9Cr-1Mo steel subjected to creep. The EBSD or Electron Backscatter Diffraction studies have been made on round-bar type specimens creeping at applied stresses of230 and 240 MPa at 823 K and 105 MPa at 923K in air. Prior to the creep tests, laser peening was applied to some of the specimens at laser power of 8.4〜22GW/cm^2 per pulse in water. Microstructural changes in each specimen after its creep test was investigated by EBSD/SEM. The EBSD/SEM analyses revealed that the laser peening treatment makes creep rupture time longer and that the critical value of local misorientation value can be determined for creep rupture.

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In this paper, creep-fatigue properties of modified 9Cr and SUS316FR steels are studied under several conditions of creep-fatigue tests at high temperature considering the use in energy equipment. Durations of stress holding, i.e., durations of creep were different among the experiments. The experiments were stopped when the specimens reached to the same strain for observation of the microstructures. The differences among macroscopic creep-fatigue properties under several creep-fatigue conditions were discussed in terms of the effects of the durations of stress holding. The electron backscatter diffraction (EBSD) was used to observe the microstructures such as grain size and deformation inside grains. Even if the macroscopic strains were same, the microstructures were different from each other especially in modified 9Cr steel. The microstructures were related to the effects of the creep-fatigue conditions.

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Single crystal plasticity based on a representative characteristic length is proposed and introduced into a homogenization approach based on finite element analyses, which are applied to characterization of yielding behavior, yield-point elongation and grain size strengthening. Here we assume that the gram boundary inhibits the plastic deformation and that the resistance effect can be described with the internal characteristic length in the proposed constitutive model. In this context, the characteristic length is given explicitly as the distance from the grain boundary. The feature of the approach is that the scale can be introduced explicitly into a representative volume element model as the distance from the grain boundary with the hardening character based on the accumulation of the dislocations. Using finite element analysis for periodic microstructure, the nonlinear grain-size dependency on yield strength is characterized, in which both Hall-Petch relationship at coarse grain region and non-Hall-Petch relationship at fine grain region are consistently reproduced.

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A 0.4C-2Si-1Cr-1Mo steel with an ultrafine elongated grain (UFEG) structure and an ultrafine equiaxed grain (UFG) structure was fabricated by multipass caliber rolling at 773 K and subsequent annealing at 973 K. The impact and tensile properties were investigated. The microstructures in the rolled bars consisted of UFEG structure with a strong α-fiber texture. The rolled bar consisting of spheroidal cementite particles that distributed uniformly in the elongated ferrite matrix of transverse grain size of 0.26 μm exhibited excellent strength - toughness balance. On the other hand, the annealed sample which consisted of UFG structue of 0.5 μm with similar α-fiber texture decreased not only strength but also toughness. In conclusion, the strength-toughness balance is improved by refining crystal grains and controlling their shape and orientation.

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[in Japanese]

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The influence of specimen cutting direction on the susceptibility of stress corrosion cracking (SCC) in an extruded magnesium alloy AZ80 was investigated. The materials were extruded after the T4 or T6 heat treatment. The L- and R-specimens were prepared in the extrusion and radial directions respectively. SCC susceptibility was evaluated by a slow strain rate tensile test in 0.004wt% NaCl solution SCC susceptibility of L-specimen was higher than that of R-specimen. This is because of the difference in the SCC susceptibility. On the other hand, the SCC susceptibility of R-specimen increased by T6 heat treatment, resulting from the precipitation of p phase. These results suggest that SCC susceptibility of magnesium alloy is related with texture orientation.

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NTC thermistor is used as temperature sensor which would be hold in severe temperature environment. We must need to know not only electrical properties but also mechanical properties in the sever conditions. In this paper, we study mechanical properties and resistance to thermal shock of poly-crystal semiconductor. After doing tensile tests of 4 types of materials with different ratio of compounding, we clarified the difference of mechanical properties for these properties. Choosing one type of thermistor specimens, we have done thermal shock test and evaluate the Young's Modulus and flexural strength of NTC thermistor from the view point of composite.

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To take advantage of the toughness mechanism of double network hydrogel (DN gel) and explore its possibility for engineering application as the structural member, the information on the mechanical behaviour of DN gel under various loading conditions is indispensable. Therefore, in this study, we at first perform the cyclic compression test to clarify the dependence of the mechanical response of DN gel on the loading history and the loading speed. Continuously, we constitute a computational model to discuss the effect of triaxiality of the loading condition and the loading speed on the deformation behavior of DN gel with complicated shapes.

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In a design of fine structures, characteristic phenomena such as surface forces, which are usually negligible in a macroscopic scale, need to be taken into consideration. When a liquid exists between solid surfaces, a liquid column can form in accordance with the balance of their surface energies, called capillarity. In this study, deformation induced by capillarity is quantitatively evaluated. A pair of polymer plates fixed at one end and immersed in liquid, bends because of capillary forces from a liquid column formed between the plates. Although capillary-induced deformation is usually observed at the micro/nano scales, the dimensions of the prepared plate specimens are on the order of millimeters because the larger scale makes observation of the evolving deformation easier. Experimental results indicate that bending proceeds to either contact or collapse the plates if their gap spacing becomes smaller than 2/3 of the initial plate separation, regardless of plate dimensions. This phenomenon is theoretically validated by proposing a dimensionless number, which is derived from a balance of surface energy, potential energy of a liquid, and strain energy of a plate.

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In the tensile test of a flat plate with many holes, quantification of possible errors m the strain measurement by DIC was investigated. Large scattering was seen, but no significant difference in the scattering was seen between aligned and misaligned arrangement of holes. An influence of the texture for DIC measurement on strains was also found to be negligible.

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In this study, image-based non-linear elastic-plastic finite element analyses are carried out or dual-component materials in order to investigate the effect of microscopic morphology on its macroscopic mechanical properly of the material. Here the morphology of microstructure is extracted from digital image of microstructure. Based on the microscopic morphology, an unstructured finite element mesh is generated. A comparative study between finite element models of defere? morphologies is conducted to discuss the morphological effect.

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The deformation behavior of solder alloys shows remarkable strain rate dependency. Then, the fatigue life of solder alloys is possibly affected by the strain rate for the cyclic loading. In this work, the fatigue tests of Sn-3.0Ag-0.5Cu (SAC) solder were conducted using cyclic tension-compression loadings under several strain rate conditions. The fatigue life of solders alloys showed the strain rate dependency: the fatigue life under the slow-fast condition was shorter than that under the fast-slow condition even though the strain amplitude and the time period for the loading were equal. The appearance of the fatigue fracture surface also differed by the strain rate condition, such as the slow-fast condition or the fast-slow condition. To discuss the causes of these strain rate dependencies, the development behavior of the plastic and creep strains generated during each cyclic loading was investigated by employing stepped ramp wave loading. Using the investigated results, a method which can evaluate the fatigue life of the SAC solder suitably was also discussed.

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Indentation test has the usefulness to evaluate the non-linear behavior of the materials which have complicated mesoscopic and microscopic structure because they have the difficulties m the machining of test specimen. Then the trial results of indentation test for low-density porous material, which is one of typical material with mesoscopic structure, are shown in this report. The results indicate obvious difference from the results of normal elastic material, and show possibility of the indentation test to represent the non-linear behavior of the materials with the complicated structures.

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Since carbon nanotubes (CNTs) have unique electronic and mechanical properties, there have been many efforts to develop CNTs-based electronic devices and sensors. We have also validated the possibility of a highly sensitive strain sensor using popular resin in which multi-walled CNTs (MWNTs) were dispersed uniformly. It is, however, indispensable for clarifying how to change the electronic state of a deformed CNT for assuring the stable performance of the sensor because the reported sensitivity has ranged widely. In this study, the relationship between the deformation characteristic of a CNT under strain and its electronic properties was analyzed. The analysis result obtained from density functional theory (DFT) calculation showed that the radial strain-induced orbital hybridization causes a drastic change in electronic properties of CNTs.

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Graphene has great potential for ultra-sensitive strain sensors applications. This is because that its electrical conductivity response on structural deformation is very high due to the high piezoresistive sensitivity. In the current study, the effect of uniaxial strain on the electronic properties of armchair graphene nanoribbons (AGNRs) is investigated using a π-orbital tight-binding (TB) based Green's function method. When a bias voltage is applied to the strained AGNRs, the evolution of current is partly correlated with the band gap variations. The authors also found that the strain-current (ε-l) characteristics are strongly dependent on the length of strained region, so the strain sensitivity of AGNRs can be controlled precisely. This result indicates that our results provide a new possibility for ultra-sensitive strain sensors.

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An evaluatuation for threshold stress intensity factor range under a stress controlled condition, using effective threshold stress intensity factor range, was proposed. Threshold stress intensity factor range was evaluated by analyses of plasticity-induced crack closure for two types of crack size:a small crack and a long crack. Plasticity-induced crack closure was analyzed for two dimensional crack in plane stress. Besides, theoretical examinations were performed in order to explain the mechanism that the fatigue limit of high hardness steel decrease with a rise of hardness. Relationship between threshold stress intensity factor range and pre-crack length which was evaluated by analysis of plasticity-induced crack agreed with experimental results qualitatively. Dependency of yield stress was different between a small crack and a long crack. The threshold stress intensity factor range of a long crack decrease with a rise of yield stress. This result could be helpful to reveal the mechanism that the fatigue limit decrease with a rise of hardness in high hardness.

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A new finite heterogeneous element consisting of sliced microstructures (FHES) is applied in a multi-scale technique. The FHES represents a heterogeneous material with microscopic constituents without homogenization or microscopic finite element analysis. A representative volume element extracted from a heterogeneous structure is thinly sliced. Each slice is modeled as a combined spring to calculate properties of the FHES. Each FHES has the same number of nodes as an ordinary finite element, and the macroscopic analysis cost is the same as that for ordinary finite element analysis. However, the FHES retains information about the microscopic material layout (i.e., the distribution of a material's property) in itself that is lost during homogenization. In the proposed approach, materials are not homogenized. The FHES does not have a constant (homogenized) material property and can "change stiffness" depending on its deformation behavior. This reduces error due to coarse-graming, and allows us to calculate the macroscopic deformation behavior with sufficient accuracy even if a large gradient of strain is generated in the macroscopic field. The novelty of the research is the development of rational heterogeneous finite elements. The paper presents the theory behind the FHES and its practical application to a linear elastic problem.

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Water hammer occurs in a pipe when water flow is suddenly stopped. There are pipes having the square or rectangular cross sectional shape rather than the circular shape: micro channel, gutter, and so on. Moreover, a part of the walls is often composed by different material or different wall thickness. To reveal pressure wave propagation in such a channel, we examined water hammer phenomenon and measured wave speeds in rectangular tubes with different wall materials and thicknesses. We newly proposed theoretical wave speeds based on the classical theory and the junction conditions of two walls: fixed, simply supported, and mixed. We confirmed that theoretical predictions agreed with experimental wave speeds.

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This paper presents a numerical analysis method for the shape identification problem of thermoelastic fields to prescribe Mises stress distributions on sub-domains from the point of view of a strength design. The square error integrals between the actual Mises stress distributions and the prescribed distributions on sub-domains are used as objective functional. The shape gradient of the shape identification problem is derived theoretically using the adjoint variable method, the Lagrange multiplier method and the formulate of the material derivative. Reshaping is accomplished using a traction method that was proposed as a solution to shape identification problems. The validity of the proposed method is confirmed based on the results of 2D numerical analysis.

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Molecular dynamics (MD) analysis was applied to investigate effects of alloying elements (dopant elements) on strain-induced anisotropic diffusion of Al atoms around the interface between the γ phase and the γ' phase of Ni-base superalloy. In this study, a simple interface structure model corresponding to the γ/γ' interface, which consisted of Ni as γ and Ni_3Al as γ' structure, was used for the analysis. The diffusion constant of Al atoms was changed drastically by the dopant element and its atomic concentration. Both the atomic radius and the binding energy of the dopant element with Al are the dominant factors that change the diffusion of Al atoms m the Ni-base super-alloy. In addition, the magnitude of the binding energy between dopant elements is also dominant factor controlling the strain-induced anisotropic diffusion of Al atoms when two kinds of dopant elements were simultaneously added in the Ni/Ni_3Al interface.

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