The purpose of this preliminary study is to explore the prediction technique for the prediction of the internal constructions in the biomaterials. The tactile sensing device was used to obtain the reaction forces and the indention angles on the surface of the soft specimens which was contained the foreign materials. The prediction results which were combined with the fmite element analysis and the genetic algorithm, it showed the good agreements to the shape and the locations of the internal objects.

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Atherosclerosis is a disease which may cause a death with a rupture of plaque. Identification of mechanical properties of atherosclerotic vessels is essential for their prevention and treatment. We compared the experimental force-displacement data of strip-like specimen of a carotid artery with a lipid core and displacement data from digital image correlation (DIC) method with results from finite element analysis (FEA), and determined the material constants of incompressible isotropic hyperelastic models for the regions of vascular wall and lipid core. We used neo-Hookean for lipid core and reduced polynomial for vascular wall. The deformation of the specimen was reproduced qualitatively under stretching the upper gripper, but the displacement of a region analyzed by DIC was overestimated by the FEA. The deformation of the specimen was insensitive to the Young's moduli of 3, 30 and 66 kPa for the lipid core.

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Aortic aneurysm is a pathology that involves the enlargement of the aortic diameter and has risk factors including aortic dissection. Aneurysm wrapping and stent placement has been used in the treatment of aneurysms. This study aimed to investigate the biomechanical effects of wrapping and stenting on aneurysm. The three-layered aortic aneurysm were created and fluid structure interaction were simulated in wrapped model and stented model. The blood flow and wall mechanics were studied numerically in an axisymmetric model. We calculated Von Mises wall stress, streamlines and fluid pressure contours. The results provide quantitative predictions of flow patterns and wall mechanics as well as the effects of wrapping and stenting. This study shows that peak wall stress are highest in the media layer in the inflection position. Stent deployment reduced vortex inside the aneurysm and its impact on the aneurysm sac. The wrapped aortic wall showed reduced wall stress. The present simulation study indicated that wrapping and stent placement seem to offer a feasible technique in the effective treatment of aortic aneurysm.

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Vascular endothelial cells are affected by the mechanical environment in cyclically inflated arteries and respond adaptively to various forms of mechanical stimuli. Therefore, it is important to understand how the endothelial cells perceive the mechanical forces from the substrate and to quantitatively correlate this with cellular responses. In this study, we analyzed the displacement field for cultured endothelial cell bottom on a silicon substrate using sliced images of cells obtained by confocal laser scanning microscopy (CLSM). We measured the coordinates of the feature points on CLSM images of the endothelial cell bottom before and after stretching of the silicon substrate and calculated the relative displacement of the feature points. Experiments involving six cells when the substrate was stretched by 15 % showed that the cell bottom was almost uniformly deformed similar to the substrate. But, the displacements near the periphery of the cells were not uniform due to the blur of the acquired images.

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Tendon is subjected to continuous mechanical loading, which imposes cyclic tensile strain and interstitial fluid shear stress to tenocytes. Although a number of studies have characterized mechanical responses of tenocytes to cyclic tensile strain, only few studies have been performed to examine tenocyte responses to fluid shear stress. The present study proposes a newly fabricated cell culture device using MEMS technologies, which enables to apply cyclic tensile strain or fluid shear stress, or both simultaneously, to tenocytes seeded onto microgrooves. It was confirmed that tenocytes exhibited a similar morphology as observed in vivo. Numerical analysis of flow patterns within the device demonstrated that a wide range of fluid shear stress, including a previously predicted physiological value, could be applied to cells. In summary, the present study developed a novel experimental model, which will reveal further details of tenocyte mechanotransduction events.

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Bone has a hierarchical structure from macroscopic to microscopic levels and is often regarded as a composite material consisting of apatite crystals and organic matrix in microscopic scale. Microscopic bone quality changes with age. Recent studies suggest that osteoporosis is not just a simple loss of bone mass, but involves significant changes in the biochemical and physical properties of the collagen matrix. Irradiating high intensity X-ray into bone, both of small angle scattering by collagen matrix and wide angle diffraction by HAp crystals occur simultaneously. In this experiment, both structural changes between collagen matrix and HAp crystals in bone are observed by synchrotron X-ray diffraction in combination with micro-compressive device for dynamic image guided failure assessment. Then the difference of behaviors by aging, the aging effects on structural and mechanical properties of bone will be cleared.

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In general, reusable heat energy is wasted in most power plans. We have been developing a heat engine that utilizes shape memory alloy (SMA) wires that are supplied with hot and cold water. So, it is important to investigate the fatigue strength of SMA wires under different conditions. The purpose of this research is to test the fatigue strength of the SMA wires under thermal pressure during phase transformations. As a result, the fatigue tests and the FEM analysis show that the fatigue life increases with lowering the heating temperature and wire diameter.

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In this research, the influences of repeated heat-treatment for extend on flexibility and scalability (critical stress for inducing martensite and recovery strain) of Ti-Ni shape memory alloy (SMA) for stent was investigated by loading-unloading tests with constant strain condition. The chemical composition of the alloy is Ti-50.4at%Ni. The specimen shape is a wire with 1 mm diameter and 20 mm gage length. The condition of repeated heat-treatment for extend was in the following; heat-treatment condition is 773K for 18ks, applied strain in each heat-treatment is varied from 4 to 8%, and total applied strain is 40%. Critical stress for inducing martensite increases and recovery strain decreases with increasing applied strain. Therefore, the flexibility and scalability decreases with increasing of applied strain. Meanwhile, decrements of flexibility and scalability during repeated loading-unloading tests decrease with increasing applied strain. From these results, the initial performance decreases with increasing applied strain. However, the degradation of performance is improved with increasing applied strain.

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In the present work, tensile loading-unloading tests have been carried out using Ti-50.3at%Ni alloys heat-treated at 673K, 723K and 773K for 3.6ks, 36ks and 360ks under constant temperatures above reverse transformation finish temperature, in order to clarify effects of heat treatment temperature and time on superelastic behavior of the Ti-50.3at%Ni alloy. An increase in the heat treatment temperature decreases the critical stress for slip. The critical stresses for slip of 673K and 723K decrease with increasing heat treatment time. The critical stress for slip of 773K decreases with increasing heat treatment time until 36ks, and it increases at 360ks. The critical stresses for inducing the transformation decrease with increasing heat treatment temperature and time.

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Zr-Cu-Al bulk metallic glass matrix composite with crystalline B2 ZrCu was fabricated. Compressive test was carried out using the composite specimens with high volume fraction of B2 ZrCu in order to investigate the mechanical properties and deformation behavior of B2 ZrCu. As the results, it was found that the mechanical properties of the composite depend on the volume fraction of B2 ZrCu. Compressive strength, yield stress and Yong's modulus of the composite decrease with increase of volume fraction. On the other hand, plastic strain increases with increase of volume fraction. In addition, it was confirmed that a stress-induced martensitic transformation in B2 ZrCu occurs during compressive test. Furthermore, it was confirmed that the composite with high volume fraction of B2 ZrCu exhibits shape memory effect.

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An actuator with compact, lightweight and flexible properties as artificial muscle for use in rehabilitation has been fabricated by forming shape memory alloy (SMA) wire and band in the shape of wave, and its mechanical performance is experimentally investigated. As a result, it was found that the wave shaped SMA wire was expanded until strain of 20%〜30% and returned to original shape fully when heated above austenite finish temperature A_f. This suggests that the wave shaped SMA wire is applicable to an artificial muscle.

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It is meaningful to recycle waste heat of power plant. So we have developed a heat engine using shape memory alloy (SMA) wires which work under heating/cooling cycling. The purpose is to increase a lifelong output energy of the engine and to know how to increase the work of SMA. As a result, the output energy is depending on temperature of hot water and heat cyclic rate and there are optimum values for each parameter. The work of SMA can be controlled by changing the transformation temperature of SMA.

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The fatigue life of conventional heat-engines using shape memory alloy (SMA) wire is too short (lower than 10^5 cycles). Therefore, heat engines using SMA does not come into practical use. Our research team proposed the new heat engine with spiral spring actuator using SMA ribbon. This heat engine is expected to improve the fatigue life. In this work, the fabrication of spiral spring SMA actuator and investigation of the operating characteristics of this actuator was carried out. The chemical composition of alloys used in this study is Ti-49.9at%Ni. The dimension of SMA ribbon is 2m length, 6.8mm breadth and 0.125mm thickness. The SMA spiral spring is fabricated from SMA ribbon by heat-treatment. The actuator using the SMA spiral spring is operated by the heating with thermal water (373K). It is confirmed that this actuator is able to generate electricity by the thermal water. Besides, the output power of this actuator is 0.034W/g/%.

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The purpose of this study is to development weight transfer type heat engine using shape memory alloy. The shape memory springs were made from Ti-Ni-Cu wires of 0.7mm in diameter. Specimens were made by Furukawa Techno Material Co., Ltd. The outside diameter of coil is 6mm and the total coils are 20. The heat treatment condition is 500℃ -1h. The transformation temperature is 50℃. The results are summarized as follows. (1) The engine was rotate stably in the hot water above 90℃. (2) The rotation speed is 5 rpm at 90℃.

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Using a conductive soft Si probe for atomic force microscopy as an electrode of nanomanipulater installed in a transmission electron microscope, we successfully measured forces generated by one-way shape memory effect of a carbon nanotube (CNT). We revealed from the measured forces that the recovery moment is about several tens aNm for a CNT consisting of 4 walls. This value is consistent with a computer simulation result and around thousand times stronger than the output of nano-sized bio-molecular actuator. Our finding indicates that CNT has an advantage as a high-power actuator.

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The SMC (shape memory composite) belt composed of two kinds of SMAs with different phase transformation temperatures and SMP was fabricated and the three-way (reciprocating) movement and recovery force in bend actuation were investigated. The results obtained can be summarized as follows. (1) The three-way bend movement was achived during heating and cooling based on the characteristics of the SMA tapes and the SMP tape. (2) The recovery force decreased at first and increased thereafter during heating and decreased during cooling. (3) The SMC belt for electric control was fabricated. This tape of SMC is necessary to be improved for practical application. (4) The development and application of multi-functional SMCs with simple structure are highly expected.

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In order to develop a brain spatula or a brain refractor made of a shape memory alloy (SMA), the bending deformation characteristics of the brain spatula of TiNi SMA made by the precision casting were discussed. The results obtained can be summarized as follows. (1) The relationship between force and deflection obtained from the cyclic three-point bending test changes slightly except for a first cycle. (2) The fatigue life in pulsating-plane bending is longer than that in alternating-plane bending. (3) The relationship between dissipated work W_d and the number of cycles to failure N_f can be expressed by a unified power function for alternating- and pulsating-plane bendings.

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The subloop behavior for the superelastic deformation of TiNi shape memory alloy was investigated based on the local temperature variation and the surface observation in the tension test. The results obtained are summarized as bellows. (1) The upper and lower stress plateaus during loading and unloading appear accompanying the progress and reduction of the martensitic transformation (MT) band, respectively. In the case of unloading from the upper stress plateau under low stress rate, strain increases in the initial stage of unloading. (2) If stress is held constant in the upper stress plateau, creep deformation appears. The creep deformation appears based on the progress of the MT band. The volume fraction of the martensitic phase increases in proportion to an increase in strain.

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This study discusses multiaxial low cycle fatigue life of notched specimen under non-proportional loadings at room temperature. Strain controlled multiaxial low cycle fatigue tests were carried out using smooth and circumferentially notched round-bar specimens of type 316L stainless steel. Four kinds of notched specimens were employed with elastic stress concentration factors, K_t, are 1.5, 2.5, 4.2 and 6.0. The strain paths include proportional and non-proportional loadings. The former employed was a push-pull straining and a reversed torsion straining. The latter was achieved by strain path where axial and shear strains has 90° phase difference but their amplitudes are the same based on von Mises' criterion. The notch dependency of multiaxial low cycle fatigue life and the life estimation are discussed with employing inelastic finite element analysis. The lives depended on both K_t and strain path. The strain parameter for the life estimation is discussed with the non-proportional strain parameter proposed by an author with introducing K_t. The proposed parameter gave a satisfactory evaluation of multiaxial low cycle fatigue life for notched specimen of type 316L stainless steel under proportional and non-proportional loadings.

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This paper presents the low cycle fatigue life evaluation for circumferential notched specimens. Elastic-plastic finite element method (FEM) analysis was performed to obtain stress and strain around the notch root. Inelastic strain concentration factor in FEM analysis was smaller than that obtained by the Neuber's rule. The local strain at the notch root obtained by the Neuber's rule underestimated the crack initiation lives under push-pull low cycle fatigue but mean axial strain based on the crack depth obtained by FEM analysis satisfactorily estimated the crack initiation lives.

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Experiments have been performed for the growth of fatigue cracks in circumferentially notched specimens subjected to cyclic torsion and tension. In the experiments, sequential and overlapping mode I and mode III cycles were applied to the crack in the specimen made of rail steel. According to the load conditions, co-planar cracks occurred or branch cracks propagated making factory roof morphology. For the investigation of incipient crack path direction, the elasto-plastic finite element analyses were performed with the combination of the maximum tangential stress (MTS) criterion. It is shown that MTS criterion including plasticity and sophisticated work hardening law are well suited to predict incipient crack growth directions.

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In this paper, some discussions on the development of crack propagation software are given. The crack(s) are considered as an additional feature to the structure which is represented by a CAD data (solid model). The main issue is how to insert such an additional feature to the structure. There are several methodologies such as x-FEM, s-FEM, EFGM, etc. and they are briefly introduced in this paper. Finally, some thoughts of the author are presented.

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The extended finite element method (XFEM) has an advantage that an arbitrary shaped crack and its extension can be treated easily. But it is also pointed out that the results of the fracture parameter have significant errors that come from the existence of 'blending elements'. In the standard formulation of XFEM, the nodes in the element including the crack tip have enriched additional degrees of freedom. The nodes in the outer region have usual degrees of freedom, i.e. 2 in the two dimensional problem. The elements in the region surrounding the crack site have nodes with enriched freedom at the crack side and normal freedom at the outer region side. These elements are called 'blending elements'. In this paper, a new Hermite element with three nodes has been formulated and applied to a crack problem with XFEM. Errors of fracture parameters calculated by the M-integral method were discussed from the point of view of the effect of the blending elements. Stress intensity factor of CCT specimen has a 10% of error with a simple formulation. It decreases down to 0.5% by considering the improvement of XFEM proposed by Shibanuma et. al.

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Fatigue tests were carried out using extruded Mg alloy AZ31 to study effect of negative load ratio on crack propagation behavior. In the tests, R ratio was changed into the negative value. When the minimum stress exceeds over the value of the compressive yield strength of the material, the rate of crack propagation accelerated suddenly due to occurrence of the twinning.

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It is recognized that crack closure behavior is the important parameter that influence the crack propagation behavior. Fatigue crack was closed under the tensile load before the tensile load was completely removed. Until now, three crack-closure modes, i.e., plasticity-induced crack closure, roughness-induced crack closure and oxide-induced were proposed. In the present study, fatigue crack propagation behavior and crack closure phenomenon were studied to investigate effect of specimen thickness on the crack closure level using the aluminum alloy A6061-T6 which exhibits plasticity-induced crack closure behavior.

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In this study, influence of the die-design parameter on the forging-die life was studied using the crack propagation prediction method proposed in the present study. First we carried out the real forging experiment to study the load-stroke curve as well as the forging-die lives. For the evaluation of the forging die lives, the crack propagation prediction method was proposed. To do this, the stress distribution of the forging-die during forging process was evaluated using FEM-code. The evaluated results were combined with the fatigue crack growth experiment in laboratory air to estimate the forging-die lives.

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In this study, fatigue tests were carried out using a diecast Mg alloy AZ91 and an extruded Mg alloy AZ61 to study the distribution of fatigue lives under constant stress amplitudes. During the fatigue process of the diecast Mg alloy, cracks initiated from the casting defect existing inside of the specimen. In the case of extruded Mg alloy, cracks were initiated from the inclusions existing on the specimen surface. The extreme-value distribution of the defect sizes, and of the spatial positions of the defects were investigated experimentally in detail. The distributions of the fatigue lives of two kinds of Mg alloys under the constant stress amplitudes were evaluated using the Monte-Carlo simulation. An increase of scatter in the distribution of the fatigue life with lowering of the stress amplitude could also be predicted using the simulation.

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In this study, the enriched fmite element method is applied to compute the intensity of singularity for two-dimensional dissimilar material joints. Different mesh types, different size of the enriched region and mesh refinement technique are used to study their influence on accuracy of results. It is shown that changing mesh types from linear to quadratic elements can reduce numerical error and enriched element size should be smaller than singular area.

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This paper discusses effects of adhesive thickness, overlap length and material combinations on the single-lap joints strength from the point of singular stress fields. A useful method calculating the ratio of intensity of singular stress is proposed using FEM for different adhesive thickness and overlap length. It is found that the intensity of singular stress increases with increasing adhesive thickness, and decreases with increasing overlap length. The increment and decrement are different depending on material combinations between adhesive and adherent.

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In this paper, we present of strain singular field at cross point of surface and cuboidal inclusion. The Element Free Galerkin method(EFGM) was used for discussion of strain singular field. Recently, lightening of machine structures are done as a purpose of energy conservation. Stress and strain singularity occurs at vertex on interface in bonded structure when external load is applied to the dissimilar material joints, and it might be induced delamination or crack. Therefore, it is necessary to clarify the characteristic of the singularity near interface. In this study, strain singular field at cross point of surface are computed with dissimilar material joints that consists of resin and Aluminum.

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Residual stress distribution in thermally grown oxide (TGO) layer of thermal barrier coatings (TBCs) was measured by using Raman spectroscope. The residual stress in TGO near bond coat was higher than that near top coat, but the difference decreased with an increase in number of thermal cycles. Although the thickness of TGO and Al element amount in TGO increased with an increase in number of thermal cycles, the average residual stress in TGO decreased.

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New test equipment for high temperature materials of gas turbine has been developed. The equipment can give mechanical loading on the test sample in combustion environment by combination of an advanced combustor system and a servo hydraulic material testing system. In this study, by using of the apparatus, thermal barrier coated specimen tested under the condition of the cyclic burner heating together with constant tensile loading. After the testing, cracks of the coating were observed. Those cracks grew and increased with the number of the testing cycle. Degree of the coating damages indicated the dependence on the temperature distribution of specimens in the high temperature gas flow filed. The testing system has possibility of success to evaluate the damage of the thermal barrier coating system at closer condition with actual engine operation.

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This paper presents the finite element formulation based on the nonlinear constitutive equation of ceramic thermal barrier coatings. The finite element code that was developed herein was employed to analyze the problem of the surface cracked coating subjected to a tensile loading. The numerical result predicted that the surface crack could propagate along the plane normal to the crack plane, which was related to the damage evolution field.

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The present study reports the bending strength and elastic modulus from room temperature to 1000℃ of 9mol% scandia stabilized zirconia(9ScSZ), which can be used as electroyte for solid oxide fuel cells. The bending strength and elastic modulus of 9ScSZ greatly decreased to 500℃ while they increased slightly above 500℃. Moreover, the observation of the fracture surface tested at different tempreatures demonstrated that the fracture mode has generally changed from the intergranular fracture to the transgranular fracture with the temperature increase.

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Sputtered molybdenum disulfide films having various internal stresses, composition (S/Mo ratio, impurity), interplanar spacing and crystalline orientation were prepared with various positive bias voltages on stainless substrate during rf sputtering for 3 Pa argon pressure. The films were investigated by FE-SEM, EPMA and XRD. Internal stress of films was obtained from curvature of substrate with film. The main results obtained are summarized as follows: Internal stresses of all films were compressive. An increase of bias voltage brings decrease of internal stress, argon contents in film, and (00・2) interplanar spacing. However, an increase of bias voltage brings increase of S/Mo ratio, deposition rate, true density, and oxygen contents in films. Iron as impurity was included for films prepared over bias voltage 45 V. Increase of bias voltage brings increase of iron contents in film.

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The purpose of this study was to understand the effect of spraying method on residual stress in thermally grown oxide (TGO) on NiCrAlY coating. NiCrAlY alloy coat was sprayed by Air plasma spraying (APS) and high velocity oxygen-fuel spraying (HVOF), respectively, on a nickel based superalloy. The surface roughness and residual stress in TGO increased with an increase in thermal exposure time. The residual stress of APS coating was higher than that of HVOF coating.

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Protective coatings have been used in gas turbine blades and combustors. The resonance ultrasound spectroscopy method by the needle-transducer tripod was used in order to clarity all the elastic moduli of the protective coating. Following results were obtained from the measurement of atmospheric-plasma-sprayed CoNiCrAlY coatings: The anisotropies of both Young's moduli and Poisson's ratios were strong if the anisotropy of microstructure was strong. All the Poisson's ratios were approximately 0.3 only if the microstructure was almost isotropy. All the shear moduli were not depend on the anisotropy of the microstructure.

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In our previous study, it was successful to make thick Ni base superalloy coatings by cold spray (CS) technique. However, the mechanical property and microstructure of an as-sprayed CS coating have been unsatisfactory compared with a bulk material. Therefore, in order to improve the material prpperties, heat treatments were conducted to the CS coatings. As for an as-sprayed IN738LC coating, heat treatment (1121℃/2h + 843℃/24h) was applied. Prior to heat treatment, the as-sprayed coating had nano-order crystalline in the vicinity of the interface between coating and substrate. However, after heat treatment, the nano-order grains changed for micron-order grains. This grain growth can induce the enhancement of the material properties such as ductibility and adhesion strength etc., and release of residual stress. In order to improve mechanical properties of the CS coatings, high temperature solution heat treatment, namely 1171 ℃/2h, was applied to as-sprayed CS coatings. As a result, the coating strength by small punch tests and adhesion strength by 4-point bending were prominently improved.

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The influence of heat treatment on mechanical properties of a free-standing cold sprayed SUS316 and anisotropy of it were investigated. The microstructure observation of the free-standing cold sprayed SUS316 was also performed. The relationship between the mechanical properties and the microstructure was discussed based on the experimental results.

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We propose a method for realizing freestanding films having a wrinkled structure. In an experiment, we discovered that a wrinkle pattern can be made on the surface of a sacrificial resin layer by applying compressive strain under the appropriate conditions. Using this phenomenon, we made a freestanding wrinkled film by depositing a copper film on the wrinkled resin surface and then removing the resin layer with an organic solvent. Uniaxial tensile tests for 300 nm-thick freestanding copper wrinkled films revealed that the films have superior deformability: the fracture elongation is more than twenty times larger than that of its straight film counterpart.

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TiN films were deposited on out-of-plane rotating Si(100) substrate by an ion beam assisted deposition technique. The influence of out-of-plane rotation on the film morphology, orientation and mechanical properties was investigated by SEM observation, X-ray diffraction analysis and nano-indentation tests respectively. TN film on rotated substrate showed granular morphology, which is different from that on the fixed substrate showing the columnar morphology. XRD spectra revealed that the out-of-plane rotation promoted the growth of TiN film with (200) preferred orientation. The hardness and elastic modulus of TiN film on rotated substrate was higher than that of TiN film on fixed substrate because of the change of orientation.

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We developed a method for evaluating the fatigue crack propagation behavior of freestanding Cu nano-films to clarify the thickness effect in the nanoscale. We fabricated freestanding specimens with the nanometer or submicron-meter thickness and the width and length on the millimeter order to address the crack propagation over a long distance. Fatigue crack propagation tests were carried out for about 500 nm-thick single-edge-notch tension specimen, whose notch was introduced by focused ion beam, under constant gross stress of 150 MPa. Results revealed that the fatigue crack began to propagate from the notch tip and stably propagated. The crack then gradually accelerated and finally unstably fractured. The fatigue crack propagation rate da/dN of the nano-films was much higher than that of bulk counterpart in entire ΔK region. The fracture morphology depended on the crack propagation rate, i.e. the larger plastic deformation occurred near the crack tip in the faster region.

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High strength steels are used for various important components such as rolling bearings to ensure safety. Strength designs for these components require material properties at the local area. The objective of the present study is to evaluate the local mechanical properties of high strength steels by the dual indenter method. Non-dimensional Π function is developed for 118 degree trigonal pyramid indenter using finite-element method. Dual indenter method is conducted by indenters with 115 and 118 degrees for SUJ2 and SUJ3. The results reveal that good agreements are achieved between stress-strain curves of tensile test and those of the dual indenter method. The local mechanical properties are evaluated by the dual indenter method for induction-hardened and carburized components. There are some differences in stress-strain curves at the locations of the components by the influence of the heat treatments.

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LiNbO_3 is one of the typical piezo-electric materials that has been widely used in various transducers, sensors and actuators. In this material, internal strain can bring about a surface electric charge and an inside electric field. Although an internal strain and electric phenomena in piezo-electric materials are key issues, in-situ observation of stressed piezo-electric materials has been rarely performed. In the present work, the effect of internal strain on electric phenomena in piezo-electric ceramics was investigated in-situ using field emission scanning electron microscopy (FE-SEM). Single crystal plates of LiNbO_3 grown by the Czochralski method have been used for the present experimental. Vickers hardness tests and FE-SEM observation after the tests have been conducted for the samples with and without a bending stress. It is found that the electron beam related to the formation of SEM image was influenced by the bending stress of the samples. It was considered that a localized internal strain in a piezo-electric material could generate intense electric field and therefore strongly interact with the electron beam related to the formation of SEM image. This phenomenon may cause problems when a small and nano-scale structure based on piezo-electric materials is stressed in an electric system.

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To understand the nature of magnetic instabilities of atomic components, e.g., magnetization reversal or domain switching, as an origin of failure of magnetic devices, it is essential to evaluate a critical condition where the magic ordering collapses. In this study, we developed an analytical method to describe the magnetic instability criterion for arbitrary atomic structures based on the spin-lattice dynamics concept. According to the proposed method, the magnetic instability occurs when the minimum eigenvalue of the Hessian matrix of the potential energy reaches zero. The corresponding eigenvector indicates the displacement of magnetic structure at the instability. We applied the method to iron bulk that initially magnetized in the [001] direction under external magnetic fields, and it can successfully describe the onset of instability as well as their change in magnetic moment vectors. These clearly indicate the validity of the proposed method.

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The purpose of this work is to examine the effect of microscopic structure on the mechanical property in nano-component. Special shape of a designed thin specimen enables us to conduct an in-situ transmission electron microscope (TEM) observation on the plasticity and interfacial cracking. TEM images exhibit initial plastic deformation with high critical resolved shear stress (400-420 MPa) in the Cu film, and preferential development of plastic deformation only in one grain. Interfacial cracking occurs at the intersection between the grain boundary and the Cu/Si interface. Stress analysis proves that the characteristic behavior in the nano-component is governed by the microscopic stress field taking into account the crystallographic structure.

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To investigate the effect of multi-directional wear on subsurface microstructure, sliding wear tests on copper single crystals having (110) surface were conducted. In addition to a conventional sliding wear test, the single crystal was subjected to sliding wear along two directions which intersect at 90° with each other. The microstructures formed below the worn surface were composed basically of two regions in both cases: equiaxed fine grains were seen just below the worn surface, and below them long grain boundaries parallel to the worn surface were generated. From electron backscatter diffraction (EBSD) analysis on the single crystal subjected to the single-directional wear, most of generated high-angle boundaries which were parallel to the worn surface were classified into tilt boundaries where rotation axis is parallel to worn surface. This kind of the tilt grain boundary formation could be understood in terms of edge dislocation emission from the worn surface. On the other hand, through the two-directional wear, formation of twist boundaries was recognized in addition to the tilt boundaries. It is expected that activities of screw dislocations were involved during the two-directional wear to form the twist boundaries.

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Dislocation structures formed around a fatigue crack in copper were observed with electron channelling contrast imaging (ECCI) technique. The ECCI technique enables us to observe dislocations lying near surface using a scanning electron microscope (SEM). For a cyclically-deformed copper, self-organized dislocation structures such as vein structure were successfully observed with the ECCI technique. To investigate relationship between dislocation structure around a fatigue crack and stress concentration, a fatigue crack growth test was conducted on a center-cracked tensile (CCT) copper specimen. The ECCI observation along the fracture surface revealed that cell structures were generated at the close vicinity of the fracture surface and the vein structure existed around outer edge of the cell structure. The formation of the cell structure was affected by the degree of stress concentration: measured size of the cell-structured area l_c was a power function of stress intensity factor range ΔK_I. To estimate distribution of ΔK_I value along a fracture surface, a lot of ECCI observations of the subsurface microstructure were performed on a smooth-shape copper specimen which was fractured under push-pull fatigue. The distribution of ΔK_I value, which was calculated from the above l_c-ΔK_I relation, was consistent with crack growth direction that was predicted from striation.

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In order to assure the reliability of advanced gas turbine systems, it is very important to evaluate the damage of high temperature materials such as Ni-base superalloys under creep and fatigue conditions quantitatively. The mechanism of the directional coarsening of phases (rafting) of Ni-base superalloy under uni-axial strain at high temperatures was analyzed by molecular dynamics (MD) analysis. The stress-induced anisotropic diffusion of Al atoms perpendicular to the interface was observed clearly in a Ni(001)/Ni_3Al(001) interface structure. The stress-induced anisotropic diffusion was validated by experiment using the stacked thin film structure with the (001) face-centered cubic interface. The reduction of the diffusion of Al atoms perpendicular to the interface is thus, effective for improving the creep and fatigue resistance of the alloy. It was also found by MD analysis that the dopant elements in the superalloy also affected the strain-induced diffusion of Al atoms. Palladium was one of the most effective elements which restrain Al atoms from moving around the interface under the applied stress.

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Both mechanical and electronic properties of electroplated copper films used for interconnections were investigated experimentally considering the change of their micro texture caused by heat treatment. Both the mechanical and electrical properties of electroplated copper thin films were found to vary drastically depending on their micro texture. The quality of the grain boundaries can be evaluated by applying an EBSD (Electron Back Scatter Diffraction) analysis. New two experimentally determined parameters are proposed for evaluating the quality of grain boundaries quantitatively. It was confirmed that the crystallographic quality of grain boundaries can be evaluated quantitatively by using the two parameters, and it is possible to estimate both the strength and reliability of the interconnections.

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