In this study, negative through-the-thickness Poisson's ratios of angle-ply CFRP laminates are investigated macroscopically and microscopically using a homogenization theory for time-dependent composites. For this, first, an angle-ply CFRP laminates are modeled as heterogeneous materials composed of fibers and a matrix. Then, a multiscale elastic-viscoplastic analysis method for the laminates based on a homogenization theory for time-dependent composites with point-symmetric internal structures is proposed. Moreover, the substructure method is introduced into the method to enhance computational efficiency. Using this method, elastic-viscoplastic Poisson's ratios of angle-ply carbon fiber/epoxy laminates subjected to macroscopic uniaxial tension are analyzed. The analysis results obtained are used to demonstrate the negativity of through-the-thickness Poisson's ratios in the viscoplastic region and their variation with the degree of viscoplastic deformation.

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The fracture toughness, bending strength and bending elastic modulus of the nano-silica particulate-reinforced epoxy composites with different crosslinking densities were investigated experimentally to consider the interaction effects between the nano-particles and the network structure in matrix resin on the mechanical properties. The composite materials were prepared by adding silica particles of 240 nm in diameter to the bisphenol A type epoxy resins with the particle volume fraction of 0.2. The matrix resins in the composites having different crosslinking densities were manufacturing by non-stoichiometric curing. The fracture toughness and the bending strength of the near-stoichiometrically cured composites were found to be improved with by adding the particles. At lower crosslinking density, the particles worked against the mechanical properties as defects in the matrix resins.

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This paper deals with investigation of microscopic stresses and elastic moduli of three phase composites on the basis of double inclusion method (DIM) developed by Hori et al. The DIM, which is based on Eshelby's equivalent inclusion method, is useful to investigate the mechanical property of three phase composites. The applicability of the DIM to mechanical property of three phase composite is investigated by a finite element method (FEM). The stresses of each phase in the composites calculated by the DIM is a little different from those calculated by FEM. However, the average stresses of all phase in the composites calculated by the DIM agrees well with those calculated by FEM. Then, the elastic moduli and constituents of PSZ-Ti composites favricated by a hot pressing method are evaluated by the DIM.

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The effect of cyclic heating on the off-axis creep deformation of cross-ply CFRP laminate under a constant stress has been examined. Cyclic heating creep tests, in which a specimen is subjected to cyclic change in temperature between 40℃ and 70℃ under a constant stress, are performed for different fiber orientations (θ=0°, 15°, and 45°) at different constant values of applied stress (40%, 50% and 60%UTS at 70℃). The experimental results from the cyclic heating creep tests are compared with those from the constant temperature creep tests (40℃, 55℃, and 70℃) to observe the effect of cyclic change in temperature on constant stress creep behavior. For θ=15°, 45° the off-axis creep strain under a constant stress with cyclic heating becomes larger than that under a constant stress at constant temperature. It is suggested that the creep behavior is affected by the instantaneous plastic strain that develops during the initial temperature rise under a constant stress. The strain fluctuation with temperature is found to be comparable to that of thermal strain due to the change in temperature.

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Displacement distribution in an austenitic stainless steel plate specimen during tensile test was measured with Digital Image Correlation (DIC) method. Quantitative evaluation of anomalous deformation behavior accompanied with transformation induced plasticity (TRIP) was examined. The relation of strain and strain rate were investigated and it was found that the spatio-temporal progress of the TRIP equalizes strain distribution of the specimen.

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Two types of epoxy composites reinforced with an aligned multi-walled carbon nanotube (MWCNT) sheet and its thermal annealed analog were prepared and the effects of thermal annealing on the mechanical properties of the composites were investigated by conducting uniaxial tensile tests. The MWCNTs with lengths exceeding 1 mm were vertically grown on a Si substrate by chemical vapor deposition method, and were converted to horizontally aligned MWCNT sheets by pulling them out. The MWCNT sheets were then thermally-annealed at 2000℃ under Ar + 5% H_2 atmosphere. The composites containing annealed MWCNTs exhibited higher Young's modulus and tensile strength than those of the composites containing as-received MWCNTs. Uniaxial tensile experiments of individual MWCNTs revealed that thermal annealing led to an increase in Young's modulus, suggesting that the improvement in Young's modulus of the composites may be associated with the increase in the mechanical properties of individual MWCNTs. Young's modulus and tensile strength of the composites containing 22 vol.% annealed MWCNTs reached 94 ± 11 GPa and 474.2 ± 57.7 MPa, respectively.

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

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Natural fiber reinforced biomass plastics (NFRPs) have been development because NFRPs are made from renewable resources and waste disposal of NFRPs is easy. Natural fibers have high specific modulus and strength, and thus natural NFRPs have a high potential for load-bearing materials. However, the dynamic and static fatigue strengths of natural fibers have been little understood. In this study, the time-dependent fracture of jute monofilaments was experimentally investigated and the fracture mechanism was discussed based on Zhurkov's model.

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In this paper, statistical distribution of tensile strength of poly-p-phenylene benzobisoxazole (PBO) fiber with kinking damage was investigated in monofilament tests. Kinking damages was created on surface of virgin fiber by winding bundle fibers to steel rod. Diameter of steel rod was set to 5, 2.5, 1.25 and 0.65 mm. Kinking damage density was defined to evaluate occurrence of kinking damage. It was found that the tensile strength of fiber with kinking damage decreased with increasing kinking damage density. The tensile strength of fiber with kinking damage was well fitted the Weibull distribution function with 2 parameters. Tensile strength of PBO fiber with kinking damage was explained by concept of effective volume.

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Epoxy resins are utilized in various industrial areas as adhesives and matrix of composite materials. Epoxies are one of the network polymer and their crosslink density are mainly dominant of the mechanical behaviors. However the microstructures which is formed during curing process are not well known. In this study the effect of network structure of matrix resin on the fatigue crack propagation properties of rubber-toughened epoxy resin. Several DGEBA epoxy resins with different average molecular weight were used in this study. Core shell rubber (CSR) particles were well dispersed in the epoxy. Whereas the fracture toughness of CSR-modified epoxy monotonously enhanced with increasing molecular weight between crosslinks (Mc), the fatigue threshold had a peak against Mc. The size of the plastic deformation zone was well related to the fatigue resistance.

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Effects of variable fatigue loading with alternate R-ratios on fatigue life of a quasi-isotropic woven fabric CFRP laminate have been studied. Variable R-ratio fatigue tests are carried out in which the stress ratio of fatigue loading alternates between two values that are associated with the same number of cycles to failure. The fatigue life of the composite under variable R-ratio loading is examined not only for different pairs of stress ratios, but also for different constant values of fatigue life. By comparing the fatigue lives under constant and variable R-ratio fatigue loading conditions, the effect of alternation in R-ratio on fatigue life of the CFRP laminate is elucidated. Finally, prediction of fatigue life of the CFRP laminate subjected to the alternate R-ratio loading is attempted using a linear cumulative fatigue damage rule in conjunction with the anisomorphic constant life diagram by which the fatigue lives of component constant amplitude fatigue loadings are evaluated. It is demonstrated that the linear damage accumulation rule predict fatigue lives of the CFRP laminate for the alternate R-ratio fatigue loading with an accuracy of a factor of two.

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This paper deals with fatigue property of paper-based friction materials under cyclic tensile-compressive loading and damage behavior under cyclic compressive loading. The fatigue tests under out-of-plane compressive and slight tensile loading are conducted to evaluate fatigue strength of friction materials. The fatigue tests under compressive loading are also conducted to investigate of damage behavior under cyclic compressive loading. Two kinds of friction materials used are composed of aramid fiber and phenolic resin, and cellulose fiber and phenolic resin. The fatigue strength of both materials decreases with increasing load cycles. The damage in both materials initiates and accumulates under compressive loading.

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Notched off-axis fatigue behavior of CFRP laminate has been studied. Static and fatigue tests are performed at room temperature on unnotched (UN) and center-hole (CH) coupon specimens of a plain woven CFRP laminate for different fiber orientations as well as for different stress ratios. The static and fatigue strengths of notched specimens are lower than those of unnotched specimens, regardless of fiber orientation, but the degree of fatigue strength reduction is different depending on stress ratio as well as fiber orientation. Soft X-ray radiographs of notched specimens taken after fatigue loading show that a characteristic growth of fatigue damage. After tension-dominated fatigue loading, the damage due to fatigue develops in the form of matrix cracks from hole edges along fiber direction. The growth of damage at hole edges reduces stress concentration. Accordingly, the notch sensitivity decreases with cyclic loading to approach a notch insensitive fatigue behavior. Next, the notched off-axis fatigue life of the CFRP laminate is predicted using the notched fatigue life prediction method that was developed in an earlier study for on-axis fatigue life prediction. The off-axis fatigue lives predicted by means of the notched fatigue life prediction method are compared with the fatigue lives observed in this study. The predicted notched off-axis fatigue lives agree well with the experimental results, demonstrating the potential of the notched fatigue life prediction method.

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Effects of extrusion ratio (ER) and lubricant during extruding on mechanical properties and fracture behavior of poly(lactic acid) (PLA) screws were investigated in terms of shear strength and acoustic emission (AE). Self-reinforced PLA screws were manufactured from axially extruded PLA billets by forging. Shear strength for PLA screw increased by drawing. The result suggested that drawing is effective method to improve shear strength for PLA screws. This might be due to orientation of molecular chains during drawing. Shear strength did not increase linearly with ER, and shear strengths for screw extruded at low ER were slightly higher than that for screw extruded at high ER. This might be due to molecular orientations for screw extruded at high ER were lower than that for screw extruded at low ER. From AE measurement, AE event occurred in the specimens with extrusion was lower compared to that without extrusion, whereas AE energy was higher. This suggested that the number of micro-damages which occurred in extruded specimen was fewer and the size of micro-damages was larger.

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In order to increase compatibility of PLA/PBSL polymer blends, a chain extender was added. We examined the effect of the additive amount of a chain extender, 0% to 3%, on the mechanical properties, when the mixing ratio of PLA and PBSL was 70/30.The mechanical properties of PLA/PBSL specimens were measured at room temperature using a universal testing machine at low strain rates.

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Currently, fracture fixation surgery using the LCP (Locking Compression Plate) is increasing. However, poor fit of plate and screw of the LCP has been reported. In other words, the problem of screw not removed has been increasing in recent years. The purpose of this study is to reproduce the situation of the poor fit of the LCP's locking system. And I aim to establish the locking system that poor fit does not occur. In this experiment, the factor with fitting failure was examined focusing on materials, tightening conditions, and the behavior of everyday life. In order to simulate the behavior of everyday life, a cyclic load was given to the fitting part. In this study, the removal torque value of the fitting portion after cyclic loading was measured. If so result in poor fit, the removal torque value is increasing. The LCP surface is anodized. Thus, using the material obtained by anodization was reproduced state of the poor fit. As a result, under all the conditions, the values of the torque loosening decreased as compared with the values of the torque tightening. Therefore, the cyclic loading simulating the behavior of everyday life, was not a factor in causing the poor fit. The same applies to the influence of anodization.

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Hydroxyapatite (HA)/β-tricalcium phosphate (β-TCP) composites attracts attentions as bone implant materials. Mixing of HA and β-TCP powder is one of the fabrication methods of HA/β-TCP. This method enables the control the ratio of content of β-TCP easier. However, it is difficult to obtain dense composites. In this study, spark plasma sintering (SPS) was used for improving sinterability of HA/β-TCP composites. The sinterability is evaluated by relative density and grain size measurements and composition of sintering body. In comparison with pressure-less sintering, relative density of the composites was significantly increased without grain growth. Sintering additives inhibited phase transformation. It was suggested that sinterability of HA/β-TCP composites was improved by SPS.

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Artificial bone is used in the treatment of bone fractures and bone tumors. Hydroxyapatite is widely in the artificial bone. The apatite, has the ability to bind to the bone. Dense body is used to the area in need of strength. On the other hand, the porous material is used for the site reactions with body fluids such is required. However, both of the high reactivity and high strength is difficult. In this study, Fabrication of artificial bone composite of coral and HAp is the objective. The addition amount of coral is 10%. Composite artificial bone was sintered at 1300℃ 5 hours. It was possible to produce composite artificial bone. However, the sintered body was collapsed in about ten days. The reason for this is that it is fired at a high temperature. In other words, carbon dioxide elimination of coral is the cause. Furthermore, it is to the adsorbed moisture in the air. Crystal structure is changed to calcium oxide. As a structure, I expand. This is related to the collapse.

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Hydroxyapatite (HA) scaffolds have been utilized in bone tissue engineering. Although their bioactivity is suitable for formation of bone tissue, the brittleness of HA scaffolds sometimes results in sudden fracture of the scaffolds. In this study, continuous porous structures of HA were fabricated by the template method with polyurethane sponge as the template. These pure HA scaffolds were then coated with a natural bio-polymer, collagen. Also, secondary porous phase of collagen was introduced into the pores of HA by the freeze-drying method. Their microstructures were observed by FE-SEM to characterize the porous structures. Compressive tests were also conducted to evaluate the mechanical properties such as elastic modulus and strength. The results clearly indicated that the introduction of collagen coating or secondary phase effectively improved the mechanical properties of HA scaffolds.

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In this study, component analysis as mechanical evaluation was performed by Raman spectroscopy for cartilage consisted by macromolecule (such as collagen fiber and proteoglycan). Raman spectroscopy is a vibrational spectroscopy by Raman scattering, and allows simultaneous measurement of organic and inorganic components. The spectroscopy is suitable for measurement of biological samples because of little effect on water. The cartilage specimens were cut out from bovine knee joint and their Raman spectrum were analyzed under compressive loading. In addition, load response to cartilage by the spectroscopy. The results of Raman shift for hydroxyproline, proline, phenylalanine and Amide I show the mechanical response. Therefore, this study indicated the possibility of stress analysis for cartilage with Raman spectroscopy

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Bone is a kind of composite material with the smart microscopic structure mainly composed of collagen fibers and hydroxyapatite crystals. Recently, bioabsorbable composite materials, such as collagen/hydroxyapatite composite materials and hydroxyapatite/poly-L-lactic acid composite materials, had been investigated and developed as substitute and scaffold materials for the bone regeneration. Here, it is expected to complete the bone regeneration by transplanting artificially produced bone tissue itself into bone defects. In this study, we aim to develop the bottom-up-type designing method of optimized microscopic structures of collagen/hydroxyapatite for the artificial bone tissue materials. In this study, we developed an evaluation method of microscopic mechanical properties of collagen fibers, and evaluated the effect of concentration of bridging agent (1-ethyl-3-carbodiimide hydrochloride: EDC) on the tensile strength of prepared collagen fibers. As results, we successfully developed a micro-tensile-testing device using a micrometer head, a rack-and-pinion stage, a z-direction lifting stage, an acrylic plate and a stainless base. The tensile strength of collagen fibers with EDC concentration of 10 mmol/L was about 2 times higher than that without EDC. Within the range of EDC concentration of 10-50 mmol/L, the tensile strength of prepared collagen fibers decreased with increasing EDC concentration. It was suggested that the EDC concentration, where the fibrosis and bridging can proceed simultaneously, could optimize the mechanical properties of collagen fibers.

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A fibrous cap develops on the luminal side of the lipid core in an atherosclerotic plaque. A rupture of the fibrous cap may cause cardiac and cerebral infarctions. In the previous studies, we obtained human carotid arteries and thoracic aortas at autopsy and conducted uniaxial stretching tests for strip-like specimens. Then we obtained the stress-strain relationships for fibrous caps in white and yellow plaques and for normal regions on the intimal side of the arterial wall. Carrying out curve fitting with user-defined functions in the software Igor Pro (WaveMetrics, Inc.), we determined two or four material constants in Ogden model, which is an incompressible and isotropic hyperelastic model, for fibrous caps and normal regions. The results showed good agreements with experimental results. For fibrous caps, the material constants in Ogden model take larger values in a white plaque than in a yellow plaque for both carotid artery and thoracic aorta.

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Mechanical interactions between cells and extracellular matrix (ECM) direct many important cellular processes such as proliferation, migration and differentiation. It has been studied mostly about cell-ECM mechanical interaction in two dimensions, but enough knowledge was not obtained in three dimensions. It has been reported to be able to control the cell function by changing the elastic modulus of polyacrylamide gel. But many of its mechanism remain unknown. As a key to elucidate them, 3D mechanical interaction has been required. Therefore digital volume correlation (DVC), which is a method of measuring 3D displacement and strain fields within an object by using a pair of 3D volume images, is expected to be able to become a novel tool. In this paper, mechanical fields around hMSC cultured on collagen coated polyacrylamide gel is visualized by using DVC method based on confocal laser scanning microscopy. As a result, it is confirmed that hMSC on gel interacts dynamically with their surrounding 3D microenvironment. By studying the effects of mechanical fields on cell function by applying this analysis tool, we would be able to understand many physiological mechanisms clearly.

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Mechanical stretches on cells increase traction forces. This increase might involve in several cellular events including mechanosensing. Fluidization is a condition often observed in cells which have been stretched with excessive strain. In those cells, mechanical structures are destroyed and cells lose traction forces. In fluidized cells, it is obscure whether mechanosensing could be realized or not. To understand the mechanosesponsibility of fluidized cells, increase of traction forces in fluidized cells were observed with traction force microscopy.

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Since articular chondrocytes are in vivo exposed to complex mechanical environment, it is important to study whether chondrocyte responses to such mechanical environment are closely related to articular cartilage diseases such as osteoarthritis. In this study, chondrocytes are exposed to an impact loading with drop tower impact testing and the associated cell deformation is examined based on actin filament structures. Cell aspect ratio, an index of cell deformation, was significantly decreased after impact loading, exhibiting a circular shape for the control group and an ellipsoidal shape for the impact groups. This finding suggests that chondrocytes can be deformed by impact loading, possibly leading to an alternation in cell physiological functions.

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In the present study the effect of carbon nanofiber interlayers on the fatigue crack propagation of woven fabric CFRP laminates made by VaRTM is investigated. Double cantilever beam (DCB) tests are carried out to determine the mode I static fracture toughness and mode I fatigue crack propagation curve. The experimental results clearly show that the interlaminar fracture toughness and the fatigue crack growth resistance can be substantially improved by the addition of CNF interlayers to the CFRP laminates. In more details, as far as the mode I fatigue crack tests are concerned, thanks to the addition of MWNT-7 interlayers the number of cycles to failure becomes 1.5 or more times greater than that of base laminates. Furthermore, it is found that the fatigue fracture toughness Girna. (the upper limit of the energy release rate in a fatigue test) is increased by about 300%.

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Thin polyimide (PI) films have been widely used for spacecraft polymeric materials. However, small defects often initiate at the surface of PI films by the erosion of atomic oxygen present in space environment, especially in low earth orbit. Mechanical strengths of polyimide films are significantly reduced by these defects. To evaluate the material strength of PI films for space use, therefore, it is important to consider the crack propagation from the defect in the direction of film thickness. In this paper, tensile tests were carried out using PI films with a surface short crack and fracture processes from this short crack were observed by a color 3D laser scanning microscope. Based on the results, fracture toughnesses in the film thickness direction were estimated. The fracture toughness tests were carried out with two types of specimens having different pre-crack lengths, 20μm and 40μm. Fracture toughnesses of 20μm and 40μm pre-cracked specimens were about 12kJ/m^2 and 1.8kJ/m^2, respectively. These fracture toughnesses were compared with the data obtained by other researchers and the effectiveness of our data was discussed qualitatively.

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This paper studies the electromechanical response of multilayer piezoelectric actuators from room to high temperatures for fuel injector applications. A phenomenological model of depolarization at high temperatures was proposed, and the temperature dependent piezoelectric coefficients were obtained. The nonlinear electromechanical fields of the multilayer piezoelectric actuators due to the depolarization at high temperatures were then calculated by the finite element method. In addition, experimental results on the electric field induced strain at high temperatures were presented to validate the predictions.

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Development of internal damage under compression tests was evaluated in order to predict crack initiation and fracture. Moreover, three-point bending tests were carried out in order to clarify deformation and fracture under tensile stress state in comparison with those under compressive stress state. Columnar specimens for compression tests and square pole specimens for three-point bending tests were prepared by using clinical resin composites. In compression tests, loading-unloading-reloading was given to columnar specimens and Young's modulus was evaluated by the gradient of stress-strain curves at unloading. Internal damage was evaluated from the variation of Young's modulus. The variation of density and residual strain were also discussed in association with the development of internal damage. Accumulation of internal damage was found on the stress-strain curve under loading-unloading-reloading in comparison with the curve under monotonic loading. On the other hand, in three-point bending tests, dependence of stress-strain curves on strain rate was clarified. Compression tests have been carried out under similar experimental conditions by authors so far. Mechanical behaviors of resin composites under tensile stress state were discussed in comparison with those under compressive stress state. Brittleness under tensile stress state was indicated in comparison with compressive stress state.

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The effects of microstructural characteristics (secondary dendrite arm spacing, SDAS) and Si- and Fe-based eutectic structures on the mechanical properties and failure behavior of an Al-Si-Cu alloy are investigated. Cast Al alloy samples are produced by heated mold continuous casting (HMC) process. Dendrite cells appear to grow in the casting direction. SDAS decreased with increasing casting speed .There are linear correlations between casting speeds and tensile properties (ultimate tensile strength crurs and fracture strain ef). These linear correlations, however, break down, especially for ours versus casting speeds and ef versus casting speeds. These results cause a-Al phase and eutectic phase (Si- and Fe-based). These microstructural effects on tensile properties are explained using a proposed model.

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The harmonic generation characteristics in Rayleigh wave were studied experimentally in a quantitative manner. A tone-burst Rayleigh wave was generated in an aluminum alloy (A2024-T351) block by a wedge transducer. The use of a laser Doppler vibrometer allows measuring the out-of-plane velocity waveforms on the surface of the block quantitatively. Scanning the sensor head of the laser Doppler vibrometer along the beam axis of the Rayleigh wave, the dependence of fundamental wave amplitude and that of second harmonic amplitude on the propagation distance was evaluated.

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An ionic polymer-metal composite (IPMC) actuator, which consists of a thin perfluorinated ionomer membrane and electrodes plated on both surfaces, undergoes a large bending motion when a low electric field is applied across its thickness. IPMC actuators are lightweight and soft and can operate in solutions. They are thus promising for a wide range of applications including MEMS sensors, artificial muscles, biomimetic systems, and medical devices. IPMC actuator with palladium electrodes shows tremendous large bending deformation at the applied voltage of over 2.5 V. To investigate the mechanism of this large deformation, we fabricated the actuator which consists of a thin polyamide membrane and electrodes plated on both surfaces. Polyamide membrane is not an electrolyte membrane and, thus, the deformation mechanism should be different from that of IPMC actuator. The tip displacements of these actuators were evaluated by applying voltage between plated palladium electrodes in an electrolyte. Also, we conducted cyclic voltammetry (CV) to identify chemical reactions on platted palladium electrodes. As the result, the polyamide membrane with palladium electrodes also showed the bending deformation over 2.5 V. Cyclic voltammetry analyses showed that the electrolysis of water and hydrogen formation occurred at cathode and the oxidation of palladium occurred at anode. Palladium electrodes absorbed hydrogen and expanded its volume at cathode. Therefore, it is concluded that this volume expansion causes the bending moment of membrane and assists the bending deformation of IPMC actuator with palladium electrodes.

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Damping properties of foamed plastics is analyzed experimentally using an impulse technique. To investigate the influence of expansion ratio on vibration damping characteristics, vibration tests are implemented. The damping capacities of foamed plastics are identified by the experimental result. These results show that it is important to take the effect of the expans km ratio on the material damping into consideration.

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Mechanical characterization of microstructure is essential to estimate damages of FRP. In this study, an oblique unit model with 2 filaments arranged randomly has been proposed. Distance between filaments, loading direction, and volume fraction of fiber in the unit cell could be considered in the unit cell as random variables. Stress distributions around filaments and strength under transverse and shear loading were investigated. From these results, a failure envelope under tensile and in-plane shear stress can be estimated. Furthermore, in case of high volume fraction of fiber, strength of microstructure was estimated based on mesh superposition method.

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In this work, thermal residual stress in CFRP laminates is analyzed using two-scale analysis method based on a homogenization theory for thermoelastoviscoplasticity. For this purpose, the homogenization theory for thermoelastoviscoplasticity is constructed by introducing the effect of thermal expansion into the homogenization theory for time-dependent materials. Then, using this theory, two-scale analysis method is established. This method is applied to the analysis of thermal residual stress in CFRP laminates which have three types of laminate configurations, i.e. unidirectional, symmetrical cross-ply, unsymmetrical cross-ply. The effect of the laminate configurations on the thermal residual stress are investigated.

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The viscoplastic constitutive equation of epoxy resin reinforced with carbon nanofiber (CNF) is evaluated using a numerical approach based on the finite element method (FEM). Homogenization theory is employed to estimate the viscoplastic constitutive equation of the composite composed of matrix resin and carbon nanotube. Viscoplastic property of epoxy resin was evaluated by tensile tests under several strain rate. Viscoplastic constitutive equation of CFRP can be estimated numerically by homogenization theory with FEM. The effectiveness of the present study is verified by comparing the experimental and numerical results of stress-strain relation of the composite changing strain rates.

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Using a mesoscopic model is a common and effective approach to predict the physical properties of woven composites. However, the main drawback of the conventional meso-model, which has the continuous mesh, is the difficulty of meshing the matrix, especially near the interfaces with the reinforcement. The model superposing a reinforcement mesh and applying a constraint based coupling is considered to be an effective modeling technique to solve this issue. To assess the capability of the coupling model, we compare the predictive mechanical properties of UD and the plain woven model between the coupling model and conventional model. The results show a good agreement between the two models.

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SS400 in JIS G 3101 is supplied by many material manufactures, and the chemical properties other than those specified in JIS G 3101 may have different range in each material manufacturer. And so, the certified material testing reports (CMTRs) of SS400 procured in the past were reviewed, and the chemical properties and the tensile properties were organized. Based on the results, the applicability of SS400 to components of nuclear power generation facilities was evaluated.

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Rolled steels for building structure (SN steels) are expecting to be steels for support structures in nuclear power plants instead of rolled steels for general structure (SS steels). Comprehensive tensile properties for SN steels were compiled at room and high temperatures so that they can be incorporated into the JSME material code. The effect of temperature on the tensile properties was approximately similar in spite of the different origins, material type, or plate thickness.

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We study the load history effect on the plastic collapse load on the austenitic stainless steel piping subjected to combined axial force and torsion. Three loading patterns considers as follows: a) Torsion load followed by Axial force load, b) Axial force load followed by torsion load, c) Simultaneous load Axial force and torsion load. The present paper describes a method for evaluating the collapse load from the axial direction stress -displacement and shearing stress- rotation charts. The plastic collapse load evaluated by two-elastic-slope method of a notched austenitic stainless steel piping follows von Mises yield surface regardless of load history.

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In this study, relationship between metal loss shape and buckling moment was investigated for general tower in chemical plant by using finite element analysis (FEA). In addition, the results of buckling assessment using equations based on Donnell, API/ASME and NASA were validated by FE results. API/ASME and NASA assessment provides good results in the case of localized metal loss.

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Boilers and pressure vessels are heavily used in chemical industrial plant. The equipments are investigated the presence of damages periodically. The most damage types in the equipments are a wall thinning. Any damage must be repaired or replaced as necessary. On the other hand, optimization of the time required in order to replace damaged equipment by evaluating the load carrying capacity of pipes with wall-thinning is expected in chemical industrial field. In the present study, the estimated burst pressure of pipes with rectangular-wall-thinning is calculated by using FEA. And then, the estimated burst pressure is compared with experimentally obtained burst pressures. The estimated burst pressures agree well with the experimental results, because the difference between the estimated burst pressures and the experimental results is within ±10%.

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As the technical background by the domestic and overseas previous studies, only prevention of the fatigue damage was required as permission for the S class piping in the service condition Ds, and the primary stress limit for the purpose of the prevention of the plastic collapse was actually abolished in JEAC4601-2008. The plastic collapse of pipes is undeniable considering the variety of pipings. In this study, the needs was confirmed for stress limit for plastic collapse due to seismic load.

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In recent years, Japanese nuclear power plants experienced multiple large earthquakes. It is very important to assess the seismic safety of piping taken the occurrence of such a large earthquake into account, when a crack exists in pipe welding joint. One of the key issues is the effect of excessive loading in the seismic response wave on the fatigue crack growth behaviour. We performed fatigue crack growth tests under constant amplitude cyclic loading with a single excessive tensile/compressive load for Ni-based alloy weld metal. Acceleration and retardation was confirmed in crack growth due to the excessive loading. The stress distribution in front of crack tip and the shape of crack tip were investigated to clarify the cause of changes of crack growth rate. A crack growth evaluation method has been proposed considering the effects of the excessive loading based on the variation of the stress distribution in front of crack tip and the crack blunting. The predicted crack growth rate by the proposed method was in good agreement with the experimental ones.

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For the integrity assessment of reactor pressure vessel (RPV) under pressurized thermal shock (PTS) condition is the most important event. The integrity of RPV is assessed by comparing stress intensity factor on a crack tip and the fracture toughness obtained from surveillance tests. The miniature compact tension (CT) specimen machined from surveillance specimens is expected to directly evaluate the fracture toughness. However, it has been recognized that a constraint effect in CT specimens is greater than that of the postulated crack in RPV, and it causes a conservative evaluation. Therefore, clarification of the conservativeness is required for more reasonable evaluation. In order to examine the mechanical factors related to the constraint effect of the crack, T stress, Q factor, and Weibull stress are useful. In this study, 3D elastic plastic finite element analyses were performed for CT specimens with different size and RPV models, to evaluate the above mechanical factors. From the analysis results, a larger constraint effect for CT specimens is observed than that for the postulated crack for RPV. We discussed on the conservativeness of the current structural integrity assessment methodology.

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To assure the structural integrity of a reactor pressure vessel (RPV) is one of the most critical issues to maintain the safe long-term operation of a nuclear power plant. In Japan, the assessment methods for RPV integrity using deterministic fracture mechanics are provided in Japan Electric Association Code (JEAC). Meanwhile, a regulation on the fracture toughness requirements against PTS events based on a probabilistic fracture mechanics (PFM) analysis has been established in the U.S. In this paper, in order to apply probabilistic approach to domestic regulation, sensitivity analyses for flaw density or transient by reference to the data in the U.S. were performed using a PFM analysis code PASCAL3. We evaluated the effect of the flaw density or transient on through-wall cracking frequency (TWCF) and showed the specific example as a practical use of PFM.

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The overpack which is a disposal package for high-level radioactive waste has been required containment of radionuclides to prevent contact between groundwater and vitrified waste for a specified period. The method for ensuring long-term integrity of the over pack was considered on the condition that it corrodes as predicted. The structural integrity is ensured by strength design and flaw evaluation taking the effect of material deterioration into consideration. The material deterioration event that affects structural integrity is thought embrittlement due to exposure to radiation and absorption of hydrogen. The structural integrity of the overpack is ensured by confirmation that flaw size detected using non-destructive inspection is less than allowable flaw size calculated by fracture mechanics. The research and development issues are prediction method of embrittlement, and reduction of flaw size measurement error using ultrasonic testing in the future.

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In recent years, the demand has been increased for establishing nondestructive inspection technique for detection of pre-existing plastic strain to ensure integrity of the structure such as nuclear power plant. In this study, potentiostatic etching method is applied to detect and measure plastic strain imposed to austenitic stainless steel by tensile straining. After potentiostatic etching (1N HNO_3, -675 mV_<SCE>, 10min), twin lines and slip lines appear as etched lines on the surface of specimen because of the preferential dissolution of the both bands. The etched slip line density bears a proportionate relationship to true strain and straining temperature. On the relational equation between etched slip density and true strain, slope is a function of straining temperature. Besides, the etched twin density bears a exponent relationship to true strain and straining temperature.

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Potentiostatic etching method has been suggested as a technique for detection of pre-existing plastic strain of type 316 stainless steel which is strained at 250℃ that is a temperature assumed nuclear reactor water. After potentiostatic etching (1N HNO_3, -600mV_<SCE>, 20min, 35℃), slip lines appear as etched lines on the surface of specimen, and their density has one-to-one correlation with pre-existing strain. However, it is difficult to count the number of etched lines originated in slip lines because they are not clear. In this study, optimal electrochemical potential and exposure time which make counting easy have been investigated. As a result, electrochemical potential and exposure time are estimated -675mV_<SCE> and 10 minutes, respectively.

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Nondestructive evaluation of three-dimensional welding residual stresses is demanded to predict crack propagation for observed cracks in in-service inspection. However, it is difficult to use neutron diffraction as on-site measurement technique because neutron diffraction is available just in special irradiation facilities. In the bead flush method, welding residual stresses for whole structure can be calculated from eigen-strains which are estimated by an inverse analysis from released strains due to removal of reinforcement of weld. Here, the removal of the excess metal is nondestructive treatment essentially. Although estimation accuracy of the bead flush method becomes poorer due to processing strains in the removal process, the method has been developed for considering the influence of processing strains by the first author. This study aims to demonstrate the effectiveness of this method for an actual welded joint. In this method, three-dimensional welding residual stresses can be estimated from measured strains by X-ray diffraction. Estimated results show that it is effective to estimate welding eigen-strains with gradient in the welding direction based on the response surface methodology. However, estimation accuracy of residual stresses has to be improved as a future work.

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