This paper deals with investigation on microscopic damage in paper-based friction materials subjected to compressive loading at elevated temperature to clarify influence of temperature on damage. Two kinds of paper-based friction materials which were composed with aramid fiber, cellulose fiber and phenolic resin were used. The compressive tests were conducted at room temperature (R.T.) and 120℃ in air. After the tests, damage initiated during the fatigue tests was observed. Damage density in both materials increased with increasing load cycles for all conditions, and damage density also increased with elevating temperature. The paper-based friction materials were susceptible to damage at elevated temperature. From a viewpoint of the constituents, damage density in the cellulose-based material was much higher than in the aramid-based material.

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The effects of specimen size as well as notch size on the onset of longitudinal splitting in a unidirectional carbon/epoxy laminate have systematically been examined. For this purpose, static tension tests were performed on one-, two- and three-dimensional geometrically similar specimens containing a central circular hole of different diameters, respectively, at a constant nominal strain rate. The experimental results showed that no significant effect of 1D scaling on splitting strength was observed, regardless of the notch size. A tendency for splitting strength to slightly increase by about 5% with 1D scaling up in the thickness dimension was observed, while it was not appreciable overall. On the other hand, the splitting strength had a tendency to decrease by about 20% with increasing in-plane dimensions as well as in all the dimensions, regardless of the notch size. The 3D scaling effect in the splitting strength was governed more by the 2D scaling effect involved since the 1D scaling effect was much smaller, and accordingly the 3D scaling effect exhibited a tendency to decrease in the splitting strength as in the 2D scaling effect. Development of a phenomenological model that can describe the multi-dimensional scaling effects is also attempted.

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In the present paper, damage development within carbon fiber reinforced plastic (CFRP) laminates and CFRP/Al honeycomb core sandwich panels by impact loading was evaluated, and change in material properties due to the damage development was investigated. Falling weight impact tests, cross section observation and 3-point bending tests were carried out. As results, it is obtained that reduction rate of bending elastic modulus in a laminate is lower than that in an upper face-sheet of the sandwich panel, and difference in the reduction rate between them becomes maximum at 5.1J. As a result of investigating the relationship between reduction in bending elastic modulus and internal damage development, the reduction is caused by delamination mainly. Since total length of cracks in CFRP/Al core sandwich panels is smaller than that in laminates, the sandwich panels have high impact tolerance.

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Semi-crystalline polymers have complex hierarchical structures. The effects of these structures on the mechanical properties are not sufficiently understood, because of the difficulty in experimental measurement of deformation behavior of microstructures. In this study, molecular dynamics simulations were performed to study the plastic deformation behavior of crystalline phase of isotactic polypropylene (α-phase). We investigated the molecular chain behavior and stress-strain responses under four different directional shear deformations. As a result of simulations, we find that crystalline phase plastically deforms via molecular chain slip and those deformation occurs in four different slip systems ({110}<001>, {010}<001>, {110}<11^^-0> and {010}<100>). Furthermore, each slip system exhibits variation in critical resolved shear stress and yield strain.

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When grain size decreases to the nanometer scale, dislocation structures hardly form in the grain; hence, it cannot be expected to obtain a large work hardening rate for nanostructured materials within the conventional framework of the theory based on the dislocation-dislocation interaction. However, the strength controlling mechanism of nanostructured materials could be different from that of coarse-grained materials; dislocation emission from grain boundaries must control the strength of nanostructured materials because of a shortage of intragranular dislocation sources. Therefore, if the resistance to following dislocation emissions from a site of grain boundaries can increase after the first dislocation emission from the site, we can expect that nanostructured materials can show large ductility due to the grain-boundary dislocation source hardening mechanism. In this paper, we first show the possibility of the grain-boundary dislocation source hardening mechanism to various Al <112> tilt grain boundaries and then consider the effect of the grain-boundary dislocation source hardening mechanism on ductility of nanostructured materials by performing tensile loading tests of nano-sized round-bar specimens.

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Porous Polymeric Membranes are used for ion exchange membranes, membrane filter and separators of batteries due to its micro-porous structure. Extension method is one of the inexpensive processes. However, any suitable stability condition of the process has not yet been proposed. In this paper, SEM observations of production process are carried out and the simulation technology for production is developed for improvement in productivity. In the simulation model, the evolution equation of microscopic damage, constitutive equation depending on microscopic damage and the homogenization method are used for representation of evolution of micro-porous structure of crystalline polymer. It is indicated that numerical results obtained here agree with the SEM observations well.

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A multi scale computational method using stochastic homogenization method is applied to the prediction of homogenized material property of porous materials. The purpose of this work is to simulate uncertainty existing in microscopic field of spherical porous material so that the homogenized property of interest can be predicted with high reliability. Moreover the final goal is to build a bridge of feedback between microstructure design and fabrication to update probabilistic prediction by fabrication and measurement data. The uncertainty are identified as parametric variables in constituent material property and nonparametric variables in morphological fluctuation such as disordering and clustering in microstructure. First-order perturbation based stochastic homogenization method together with mixture distribution technique are employed for a stochastic prediction. The main conclusion coming from the new method derived by gap between measured data and prediction showed that, when the update is used for morphology prediction of microstructure, it is almost perfect agreement with parameters' setup of virtual experiment. After it is applied for update of probabilistic homogenized property, it could make the updated homogenized property closer to measurement data so that it becomes more realistic.

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Theory of free-vibration acoustic resonance for a two-dimensional grid-framework structure has been developed within the framework of micropolar elasticity and calculus of variations. Numerical analysis based on the Ritz method revealed the excitation of micro-rotational standing wave in a resonant state. It is also revealed that resonance frequency of the structure show a weak but finite size dependence, which is due to the breakdown of scale-invariant symmetry of the action integral.

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Metal thin films don't necessarily appear general fatigue behavior like a bulk material. By a balk and film material, there is difference of restricted state because of differing in the number of grains to the direction of film thickness. In previous report the diagram of ratio of slipped grains and number of cycle was sorted by film thickness/grain size ratio in carbon steel thin film. Then slip ratio dramatically changed film thickness/grain size ratio 0.81 to 1.00. The influence of grain's existence frequency to direction of film thickness was considered to slip band formation. In this research cross section of carbon steel thin film was observed. As a result, slip deformation occurred over two grains to film thickness. Slip band were faced out of plane when slip system was specified by EBSD.

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In this paper, effect of basement on the compressive response of the egg-box panels, which is consisted by a conical frusta and the base is studied by a using finite element method (FEM). It is found that there are various deformation modes by changing the length of the base and the cone angle. In addition, changing the strain-hardening coefficient and the thickness of the egg-box have a large effect on the axial crushing characteristic. Based on these facts, it is possible to propose an egg-box panel in which the peak load and load fluctuation are controlled.

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This paper deals with spark plasma sintering (SPS) process of partially stabilized zirconia (PSZ), pure titanium (Ti) and PSZ-Ti composites. To examine the densification process during SPS, the sintering schedule which was the condition of 5 min hold at 1200℃ was terminated at given temperature and sintering time to obtain semi-sintered materials, and their microstructure and relative density were examined. Up to 800℃ in sintering process, the densification progressed more quickly in the materials with higher Ti-content. Over 800℃, however, the densification in the 80% Ti composite was delayed as compared with the other materials. According to the X-ray diffraction (XRD) analysis Ti_2O and Ti_2ZrO were detected and pure Ti was not detected at higher temperature than 800℃. It was found that the creation of Ti_2O and Ti_2ZrO affects the densification in PSZ-Ti composites, especially in the Ti-rich composites.

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In order to improve thermal efficiency of land-based gas turbine, increase of turbine inlet temperature is known to be very effective. Thus, thermal barrier coatings (TBCs) are key technology to protect the blade metal. It is important to develop damage assessment technology for TBC maintenance, in addition to development of advanced material for TBC. In this study, finite element analysis installing the damage-inelastic coupled constitutive equation for Thermal Barrier Coatings (TBC) was developed. In order to simulate stress and damage field in microstructure of TBC under a tensile loading, the FE analysis was conducted utilizing SEM image-based model. It was found that damage field concentrated at the surface and TC/BC interface was relaxed by existence of a through-crack normal to the interface in testing condition of room temperature. When testing temperature was increased, associated damage field was relaxed over the microstructure, which was originated from brittle-ductile transition temperature of bond coating.

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We investigate the emergence of local ferroelectricity near SrTiO_3 surface steps under external tensile load using first-principles calculations. Nanoscale strain concentration at the surface step induces the local ferroelectricity in the nanoscale area. We found that the emerged polarization forms a closed-flux vortex pattern, which is characteristic of ferroelectric nano structure. In addition, the size and the strength of polarization vortices enlarge with increasing external load. These results suggeste that we can mechanically realize nanoscale ferroelectrics with the strain concentration fields.

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Lithium Niobate (LiNbO_3) is widely known as ferroelectrics. In this study, we produced artificial domain-walls using a bicrystal experiment, in order to understand the electrical conduction mechanism at domain-walls and construct a technique to control electrical conduction along the domain-walls. Electrical conduction measurements showed that the T-T and H-H domain-walls exhibited higher electrical conductivity than in bulk.

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Multiferroic properties of BiFeO_3 single-wall nanotube are calculated using the density functional theory. We find that it characteristically exhibits the double-helix distributions of polarization and magnetic moment, while those in BiFeO_3 bulk are uniform. This allows BiFeO_3 single-wall nanotube to have the chirality of double-helix multiferroic properties. Furthermore, torsion of BiFeO_3 single-wall nanotube switches the double-helix chirality.

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We investigated spatial distribution of spontaneous polarization in ferroelectric PbTiO_3 nanosprings with helicity using a real-space phase-field modeling based on Landau-Ginzburg theory. Without external loading, polarizations are aligned along the line of nanospring due to dominating depolarizing field. On the other hand, the tensile loading brings about the polarization vortices with a right-handed chirality on the cross-section of nanospring, leading the formation of polarization superhelix. We also showed that the compression inversely gives rise to the polarization superhelix with a left-handed chirality. These indicate that the loading conditions can tailor the chirality of polarization superhelix in ferroelectric nanosprings.

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Highly sensitive strain sensors have been developed by using multi-wall carbon nanotubes. It was confirmed that a fine bundle of multi-wall carbon nanotubes showed elastic deformation even under the compressive strain of 60%. The high strain sensitivity was attributed to the buckling (local heavy) deformation of the compressed multi-wall nanotubes, and the drastic change of the electronic band structure of the heavily deformed carbon nanotubes. The electronic conductivity of multi-wall carbon nanotubes can vary drastically from metallic to semiconductive depending on the amplitude of the local deformation and the chirality of each single wall nanotube. The large reversible deformation of multi-wall carbon nanotubes was also analyzed by using molecular dynamics simulation.

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Nanocrystalline nickel dispersed with nano-size WO_3 particles has been successfully synthesized using electrodeposition. In this synthesis, ionized WO_4^<2-> molecules in an electrolyte are hydrolyzed WO_3 particles and embedded into a nanocrystalline nickel matrix during electrodeposition by controlling the pH and potential of the electrode. The effect of the nano-size WO_3 dispersions on the mechanical property and thermal stability of the nanocrystalline nickel is investigated in detail. The nanocrystalline nickel electrodeposited with nano WO_3 particles have the same size as the nickel matrix of approximately 25 nm and the dispersed WO_3 particles which is approximately 15 nm. The nickel electrodeposited with the WO_3 particles has a higher hardness than that without the WO_3 particles in the range of the nickel matrix grain size which is less than about 130 nm. The increase in the hardness is attributed to dispersion strengthening of nano WO_3 particles. The nickel electrodeposits with the WO_3 particles possess an increased thermal stability compared to the material without the WO_3 particles. The nickel matrix grain size of electrodeposits associated with the WO_3 particles hardly changed even after annealing for 18 ks at 573 K. The thermal stability of the nickel electrodeposits with the WO_3 particles is attributed to the Zener drag effect of nano the WO_3 particle.

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A Co-Cu alloy film having high composition gradient was fabricated by electrodeposition method. The electrodeposition was conducted in the single electrolyte consisting of cobalt sulfate and copper sulfate, in which composition of electrodeposited alloy depends on applied electrochemical potential. The potential was controlled such that the electrodeposited film has a constant composition gradient of 8.0×10^<-4>nm^<-1>. By stacking the films having positive and negative gradients alternately, we could fabricate the high composition-gradient film of pm total thickness. This gradient structure was consistent with the x-ray diffraction analysis that a single broad (111) peak appeared in between the diffraction angles of fcc-Co and Cu crystals. Vickers hardness of the composition gradient film was Hv298, which was certainly higher than that of the Co/Cu multilayered film having 500nm layer thickness. The high strength of the gradient film can be contribute to the misfit dislocations distributing over the film and/or the internal stress arising from lattice constant mismatch.

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Combining composites with nanoscale materials such as Carbon Nanotubes (CNTs) has attracted much attention, because various synergic effects can be realized easily. Especially, grafting CNTs onto carbon fibers and reinforcing the interface between resin and the fibers are promising approaches in enhancing the mechanical properties. In this study, the effects of CNTs grafted onto carbon fibers on the mechanical properties of multiscale CFRP were investigated. CNTs were grafted on carbon fibers by chemical vapor deposition (CVD) using a Fe-Cu catalyst system at temperature <600 ℃. As a result, degradation of the properties of the carbon fibers was suppressed. Interfacial shear strength (IFSS) was increased by 45.8%. After that, static tensile test of unidirectional CFRP (0° and 10°) was performed. The elastic modulus was increased by CNTs around the carbon fibers. In case of the 10° specimens, the shear yield stress increased by 41.9%. It was the result from improvement of the yield strength of matrix resin around the carbon fibers by grafting CNTs.

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Argon ion sputter-etching of SUS420J2 martensitic stainless steel and SUS316 austenitic stainless steel were carried out to form fine protrusions on the specimen surface by using a radio-frequency magnetron sputter-apparatus. Plasma-nitriding was applied to the protrusions by using nitrogen gas of 0.53 Pa mixed with argon gas of 0.67 Pa at a power of 50W for 1.8ks. Micro-Vickers hardness tests on the top of cone-shaped protrusions with diameter of about 20 μm of SUS420J2 steel showed that the plasma-nitriding produces more than three times larger compressive strength than that of the as-sputter-etched protrusions. Nano indentation tests on ridge-shaped protrusions with sizes smaller than 500 nm of SUS316 steel also showed that the compressive strength of the plasma-nitrided protrusion is about twice as large as that of the as-sputter-etched one.

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In order to clarify the effects of vacuum on the strength and the time-dependent deformation of Ti nanocolumns, we conducted monotonically-increasing-loading and creep experiments using micro-specimens in laboratory air and vacuum environments. In the monotonically-increasing-loading experiments, critical apparent shear stress, defined as the critical force divided by specimen area, in vacuum environment was larger than that in air environment. The result indicated that an environment significantly influenced the strength. In the creep experiments, the Ti nanocolumns showed time-dependent deformation in both air and vacuum environments. The steady-state creep rate in air environment was much higher than that in vacuum environment. The results suggested that the time-dependent deformation in the nanocolumns was significantly accelerated by air or moisture environment.

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To estimate the strain energy caused by the macroscopic strain gradient, the relationship between strain gradient and its work conjugate higher order stress is formulated. Strain energy required for the macroscopic strain gradient of two-phase composite material was estimated by the Taylor, homogenization, extended Taylor and extended homogenization models. Extended models estimate the strain energy depend on the size of periodical microstructure.

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The connectivity of high energy random boundaries in SUS316L stainless steel and Inconel 600 nickel based alloy was investigated using fractal analyses, to prove the usefulness of a refined approach to grain boundary engineering (GBE) for more precise prediction and control of intergranular degradation phenomena resulting in intergranular brittle fracture in polycrystals. It was found that the maximum connectivity for random boundary network, termed the maximum random boundary connectivity (MRBC) had a fractal nature in the studied specimens of SUS316L stainless steel and Inconel 600 alloy specimens. The fractal dimension of MRBC tended to decrease with decreasing fraction of random boundaries. The lower fractal dimension of MRBC induced the higher intergranular corrosion resistance in SUS316L and Inconel 600 specimens. The optimum grain boundary microstructure for control of intergranular degradation phenomena was discussed based on the results of the relationship between fractal analyses of MRBC and intergranular corrosion resistance.

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Effect of grain boundary- and triple junction-character on the nucleation of intergranular fatigue cracks in SUS430 ferritic stainless steels during high-cycle fatigue was investigated based on the observation results of grain boundary microstructure by scanning electron microcopy (SEM)/electron backscattered diffraction (EBSD) analyses. Fatigue cracks preferentially nucleated along high-energy random boundaries, while the low-angle and low-E coincidence site lattice (CSL) boundaries showed the higher resistant to fatigue cracking. It was little dependent on the geometrical arrangements between the grain boundary plane and the stress axis. Moreover, the fatigue cracks were observed at triple junctions as well as grain boundaries. Their nucleation considerably occurred at triple junctions where random boundaries were interconnected. The optimal grain boundary microstructure for control of intergranular fatigue cracking for SUS430 stainless steel was discussed on the basis of these observed results.

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In situ TEM nanoindentation testing of α-alumina was performed using a double-tilt indentation sample holder to investigate {1-102}<-1101> rhombohedral twinning. It was clearly observed that a rhombohedral twin propagated with insertion of an indenter tip and the twin shrunk and disappeared upon unloading. This indicates that rhombohedral twinning in a-alumina is a reversible phenomenon.

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In order to investigate the criterion of unstable crack propagation induced by singular stress field less than 10 nm, the fracture toughness is examined using micro-scale silicon (Si) single crystal specimens with a precrack. Critical value of stress intensity factor at fracture, K_<IC>, is evaluated to be 0.93〜1.09 MPa・m^<1/2> where the minimum size of singular stress field is 6.3 nm. This clearly means that the fracture mechanics concept based on the continuum mechanics keeps the validity even in the single digit nanometer scale.

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Strain field around a dislocation-pair in a silicon single crystal was visualized from images taken with a high-resolution electron microscope (HRTEM). It was quantitatively confirmed that the strain field around the dislocation pair is measured comparing with the strain field calculated from isotropic elastic theory. In order to clarify the existence of shielding effect at a crack tip due to dislocations, a strain field around a {011} crack tip with dislocations was measured using HRTEM. The crack tip area was thinned using an iron-milling machine. It was found that the strain field around the crack tip is compressive, exhibiting the existence of the shielding effect due to dislocations in atomistic scale.

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Due to the planar defects (surface and grain boundary) energy, internal compressive stress occurs in the nano pillar or nanostructured materials. Therefore, we perform molecular dynamics analyses to examine the influence of surface-grain boundary energy on the yielding phenomena of the nanostructured materials with different structure sizes. The internal stress caused by the planar defects increases with decreasing the structure size; hence, the size dependence of the yield stress in tensile loading shows opposite tendency for compressive loading.

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Dynamic stress of micro-scale resonators of single crystal silicon using time-resolved micro Raman spectroscopy is reported. The incident laser light (488 nm) was modulated to synchronize the sample illumination with the motion of the resonator sample. The modulation was done using an electrostatically actuated MEMS optical chopper fabricated on a silicon-on-glass substrate. The response time of the chopper was 〜50 μs and extinction ratio was 31, which is enough for dynamic stress measurement for a resonating device oscillated up to a few kHz. The sinusoidal stress oscillation of the silicon resonator vibrating at 1 kHz was successfully measured and the stress amplitude was measured as 303 MPa.

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Focused ion beam (FIB) is one of strong nanofabrication tools for Si and its related devices. In this study, To produce ultra-fine Si nanowires less than 50nm, we propose a new nanostructure fabrication technique using FIB and anisotropic etching. Si nanowires of several tens of nm could be formed, and it was found that the nanowires consisted of Ga ion doped amorphous Si. Uniaxial tensile test of the nanowires was performed to directly measure the Young's modulus and fracture strength.

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This paper reports on two types of fabrication methods for Si nanowires (NWs) using focused ion beam (FIB), photolithography, TMAH anisotropic wet-etching, and sacrificial oxidation. Type A specimens made from silicon-on-nothing (SON) membranes are produced by FIB system's probe manipulation and film deposition functions. The mean Young's modulus of FIB-fabricated NWs evaluated by tensile testing in SEM using electrostatic actuated MEMS device is 129 GPa. After vacuum annealing, the Young's modulus is increased to 168 GPa. Type B specimens are produced by wire-thinning technique using sacrificial oxidation and oxide film removal. We succeeded in making freestanding bridge Si NW with the width of 76 nm.

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In order to examine the deformation behavior of a silicon nano-helix grown by the glancing angle deposition technique, tensile experiment was conducted with in-situ scanning electron microscope observation. An isolated nano-helix was prepared by removing neighboring nano-helices using a removable probe, and the top end was connected to a loading tip with an electron beam curing adhesive. The nano-helix was monotonically deformed up to fracture with a large elastic elongation due to the helical shape. It was found that the deformation stiffness of the nano-helix is governed by the geometry. Moreover, the yield stress was evaluated to be τ_γ = 550〜563 MPa.

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It is well known that ceramic materials generally exhibit brittle nature at low temperatures. This is because the translation vector of crystal structure is large and accordingly the Peierls stress of possible dislocations is large. It is noted that perovskite crystals such as strontium titanate often exhibit ductile nature at room temperature. However, the origin of ductility have not been understood enough. In this study, single crystals with perovskite crystal structure were deformed in compression in order to investigate the deformation behavior at room temperature. It is suggested that the formation of point defects can play an important role on the plasticity of perovskite crystal structure.

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Lithium niobate (LiNbO_3) is widely known as ferroelectrics. In this study, we fabricated LiNbO_3 bicrystals with a (0001)/<112^^-0> low-angle tilt grain boundary, and investigated atomic structure of boundary dislocations by using scanning transmission electron microscopy (STEM). It was found from the observation that (0001)/<112^^-0> low-angle tilt grain boundary consists of three types of dislocations with the Burgers vector of b = 1/3[1011], 1/3[1101] and 1/3[0111]. This indicates that the combination of these three dislocations compensates the tilt angle because the discontinuity of the [0001] perfect dislocation is too large to form.

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To investigate the restructuring of dislocation structure formed during fatigue, an imposed plastic strain amplitude was suddenly changed at a low-cycle fatigue test. Changes in stress-strain response and microstructures in cyclically deformed Cu single crystals with [123] stress axis was examined. The ECCI observation revealed that the PSBs and vein dislocation structures were developed at the condition of γ_<pl>=2×10^<-4> after the preliminary test of γ_<pl>=2×10^<-3> (γ_<pl>=2×10^<-3>+2×10^<-4>). This microstructure is identical to that at the constant amplitude of γ_<pl>=2×10^<-3>. The stress amplitude at the γ_<pl>=2×10^<-3>+2×10^<-4> condition was also the same as that of γ_<pl>=2×10^<-3>. Thus, the strain amplitude change within the plateau region had no influence on the fatigue property. However, the stress amplitude of the γ_<pl>=2×10^<-3>+2×10^<-2> condition, which was 10 times higher than the above condition, was certainly lower than that at the constant strain amplitude of γ_<pl>=2×10^<-3>. Microstructure of theγ_<pl>=2×10^<-2>+2×10^<-3> condition was developed cell structure. In contrast to the strain amplitude change test within the plateau region, the cell size was larger than that formed at the constant amplitude of γ_<pl>=2×10^<-2>: the restructuring of the dislocation arrangement occurred. The measured decrease in stress amplitude should be associated with the coarsening of the cell structure, which can be caused by the

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The results of the present study showed that hydrogen in silicon crystal had an effect on the mechanical properties. p type single crystal wafer was pretreated with reactive ion etching to introduce crystal damage on the surface. Then the wafer is exposed to hydrogen plasma to introduce hydrogen atoms underneath the surface. Finally, nanoindentation was performed to survey deformation capability. As a result, test pieces processed with hydrogen plasma were pushed into a deeper level than unprocessed ones at the same load level. Therefore, it was expected that hydrogen in silicon crystal works to degrade the strength.

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Surface of a fatigued copper was analyzed by the EBSD technique, to consider a possibility that self-organized dislocation structure is visualized through Kikuchi pattern analysis. In this study, the single-slip oriented copper single crystal was cyclically deformed under a constant plastic shear strain amplitude of 10^<-3> for 10^4 cycles. After the fatigue test, the specimen surface was observed with the ECCI and the EBSD method, equipped with an FE-SEM. The ECCI observation revealed that the vein and ladder-like PSB structure were generated. Because these dislocations cause local lattice distortion, a Kikuchi pattern measured by the EBSD can be modified slightly. In this study, morphology of a Kikuchi band was evaluated by analyzing Hough-transformed image of the Kikuchi pattern. The quantified positions of a target intensity peak corresponding to a Kikuchi band were plotted in a plane for all the Hough images measured. It is found that the plotted picture was similar to the dislocation structure of the ECC image.

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To investigate the microstructures developed below a fracture surface of fatigued copper, the ECCI observation and the EBSD analysis were conducted on small planes which were generated by FIB milling on the facture surface. First, a fatigue crack growth test was carried out on a CCT specimen of polycrystalline copper. After fatigue fracture, small flat planes at various crack lengths were generated along a single fracture surface by the FIB. The ECCI observation of the milled surfaces at high ΔK_I values revealed that the dislocation cell structures were developed below the fracture surface. In IPF maps obtained by the EBSD analysis, gradual changes in lattice orientation were clearly recognized even with the same grain: the crystal lattices near the fracture surface were rotated as a result of crack propagation. It was confirmed that the lattice was rotated anti-clockwise at the high ΔK_I value region. This lattice rotation can be understood in terms of accumulated edge dislocations which were emitted from the crack tip during fatigue.

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To clearify the creep crack propagation properties of gold (Au) submicron-films deposited by magnetron sputtering, creep experiments and creep crack propagation experiments for 260 nm〜400 nm-thick film specimens were conducted. In all specimens, crack growth rate decelerated at first, and then the creep crack stably propagated, leading to unstable fracture. The creep crack propagation rate da/dt of 260 nm-thick film was about one order of magnitude as large as 359 nm-thick film with similar experimental conditions. In the da/dt-net stress σ_<net> relationships, da/dt of 〜400 nm specimens was larger than that of the 260 nm specimen in entire σ_<net> region. The result indicated that the creep crack propagation acceletated as the thickness decreased from 〜400 nm to 260 nm.

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In this study, the change of crystallinity of the Ni-base superalloys (CM247LC) under creep loading was analyzed by applying Electron Back-Scattered Diffraction (EBSD) method. The image quality (IQ) value obtained from the EBSD analysis was used for the quantitative evaluation of the crystallinity. The quality of the atomic alignment of both γ' and γ phases was found to degrade with increasing creep damage. The degradation of crystallinity suggests that the ordered L1_2 structure of Ni_3Al became disordered and the density of dislocations and vacancies increased. Therefore, the dominant factor of the creep damage of this alloy is the strain-induced diffusion of elements under loading, and the decrease of the crystallinity.

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Effects of vacuum environment on fatigue crack propagation properties in freestanding copper nano-films have been investigated. Fatigue crack propagation experiments were conducted in both air and vacuum environments. In situ field emission scanning electron microscope (FESEM) observations of fatigue crack propagation in vacuum confirmed that the mechanisms of fatigue crack propagation in vacuum were the same as those in air: Intrusions/extrusions were formed ahead of the crack tip and the fatigue crack then propagated preferentially through these intrusions/extrusions in low-K_<max> region (K_<max>: maximum stress intensity factor), and the fatigue crack propagated by static fracture mode accompanied by a necking deformation in the thickness direction in high-K_<max> region. Fatigue crack propagation rate (da/dN) in vacuum against stress intensity factor range (ΔK) was smaller than that in air in entire ΔK region, especially in the low-K_<max> region. The clear difference in the morphology of the fracture surface between air and vacuum was not recognized as far as a relatively low magnification used in FESEM observations.

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Fatigue crack propagation experiments of an approximately 600-nm-thick freestanding single crystalline copper (Cu) film was conducted to clarify the intrinsic mechanisms of fatigue crack propagation excluding the effect of microstructure such as twin boundaries. The film specimen had (001) surface and [11^^-0] loading direction. A fatigue crack started to propagate from a single-side-edge notch, and stably propagated in the direction perpendicular to the loading axis: [110] direction. Field emission scanning electron microscope (FESEM) observations showed that crack propagated accompanied by intrusions/extrusions. In addition, in-situ FESEM observation of fatigue crack propagation experiment confirmed that the fatigue crack arrested by changing the environment from air to vacuum, and instead intrusions/extrusions were formed around the crack tip except just ahead of the crack tip. The fatigue crack then restarted to propagate stably from the crack tip by changing the environment from vacuum to air, suggesting that fatigue crack propagation behavior was influenced by the vacuum environment.

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Polyhydroxyalkanoate (PHA) is a microbially-derived plastic. In this study, a polycaprolactone (PCL) pellet was blended with a PHA-based pellet to improve ductility and tensile strength because PCL is a bioabsorbable and biodegradable polymer having high ductility. When the mixing ratio of PCL was 50%, the elongation at break of polymer blend was large and the gauge area of tensile test specimens whitened. A rheo-optical characterization technique based on near-infrared spectroscopy was applied to the PHA/PCL blend to clarify deformation mechanisms.

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Instrumented indentation is widely used to investigate the elastic and plastic properties of mechanical materials. In the previous study, the method for determining the constants for Cowper-Symonds constitutive equation (dynamic constants) using the response surface was established. But errors of dynamic constants remain as problem. The purpose of this study is to improve this method. First, the number of data for making response surface was increased. Then logarithmic scale was changed to linear scale. Finally, the degree of a polynomial for response surface was changed. Moreover, an approach of assessing error was discussed. This study provides more accurate dynamic constants.

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In this study, an effect of indium segregation on aluminum grain boundary cohesion were estimated theoretically. Σ5(310)/[001] tilt grain boundary models of aluminum containing sodium and indium substitution were employed to conduct first-principals tensile testing. As a result, an indium substitution decreased the ideal strength of Σ5(310)/[001] tilt grain boundary of aluminum to a similar extent as sodium substitution.

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In this study the aim is to clear the effect of molecular weight distribution on the microstructure and the mechanical properties of the epoxy resins with same average molecular weight. Four types of epoxy blends with the different molecular weight distribution were formulated using commercial Bisphenol-A diglycidyl ethers. The microstructure and the mechanical properties of the blends were investigated. Dynamic mechanical analysis and microscopic observation revealed that difference of the crosslink density in the resin and the size of the repeated heterogeneous structure became larger as the molecular weight distribution was broader. In particular, the epoxy blend with the widest distribution had a co-continuous phase structure in submicron-scale as a result of reaction-induced phase separation. Whereas the flexural modulus and the flexural strength was insensitive to the molecular weight distribution and the morphology of the cured resin, the fracture toughness enhanced as the molecular weight distribution broadened and the heterogeneity of the crosslink density increased. Fracture mechanisms were discussed using proposed microstructure models.

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Flexible sports protectors whose outer shells harden only under impact loading are proposed by virtue of the time dependency on elastic modulus due to the viscoelasticity. As an outer shell material, a bisphenol A-type epoxide resin with amine-based curing agent was selected because the mechanical properties can be controlled by changing the compound ratio of main and curing agents. The time dependency on elastic modulus was investigated by dynamic viscoelastic measurements. In addition, the performance as an outer shell was evaluated by drop weight impact test. The experimental results reveals that the soft epoxy resin is suitable as outer shell material for flexible protectors.

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We found an original PVDF film fabrication technique which enable us to turn crystalline structure to beta-phase structure only by solution drop and dry. This method can be applied to printing technology, and we will be able to fabricate printable sensor and actuator in near future. The aim of the present study is to investigate the PVDF crystalline structure change due to a kind of solvent in PVDF solution drop. First, three kinds of solvents (Acetone, DMF and HMPA) are prepared. Second, PVDF powder is mixed with a kind of solvent for 24 h using a magnetic stirrer. Third, the mixed solution is dropped on a glass plate using a micro syringe and is dried in a controllable desiccator. Then, we can obtain three kinds of PVDF films. Finally, the PVDF film crystalline structures are investigated by using X-ray diffraction and Raman spectroscopy.

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