In order to assess remaining life of aged thermal power plant, uniaxial creep test has been performed by utilizing a small sample extracted from those components. However, mechanical property is changed in HAZ of weldment and it is difficult to identify those localized properties by typical creep test. For this situation, we have developed a high-temperature indentation test based upon ball indentation. This technique has a benefit to be able to estimate directly a high-temperature mechanical property in a local area in HAZ. In this study, in order to extend our idea to commercial device, electric potential technique is developed to monitor the contact area during indentation test.

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Damping hardness is one of dynamic hardness, and is measured by the Herbert hardness tester. The Herbert hardness tester is a typical pendulum hardness tester. The tester swings on a specimen. The hardness is defined by the free damping oscillation of the tester. In order to clarify relationship between damping hardness and tensile properties for metals, the tensile test and Herbert hardness test are carried out for eight kinds of metals. Conclusions are follows: (1) Damping hardness is strongly and negatively correlated with 0.2% proof stress and ultimate tensile strength. (2) Damping hardness is negatively correlated with Young's modulus.

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Creep constitutive equation is needed to conduct damage evaluation for welded part in a high temperature component. However uniaxial creep test has been done to identify some parameter included in the constitutive equation, the typical testing method cannot be applied to the local region in the HAZ. The purpose of this study is to develop the indentation creep test method and to establish the method for estimating the creep constitutive equation. In this paper, the method for estimating the creep constitutive equation is improved. First of all, influence of temperature and size of specimen are discussed. As a result, this method is improved by introducing correction factor in considering relation between size of specimen and impression radius. Next, it is shown that applicable range of this method is identified by conducting inelastic-contact finite element analysis for the cylinder model of HAZ.

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The use of mesh based global digital image correlation is proposed for measuring displacement fields around a crack tip. Displacement components at all nodes of a finite element model are simultaneously obtainable from images before and after deformation by global digital image correlation. Therefore, discontinuous displacement fields can be obtained using a finite element mesh with a crack. The effectiveness is demonstrated by measuring the displacement fields around a desiccation crack. Results show that the near-tip displacement distributions are obtained using global digital image correlation with singular elements at the crack tip.

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It is well known that cyclic stretch regulates cellular function of cell, such as proliferation and differentiation etc. Human bone marrow mesenchymal stem cells (hBMSCs) are differentiated into tenocyte with the cyclic stretch. However, rigorous mechanical condition for tenogenic differentiation of hBMSCs, especially strain has not been fully elucidated. This study tried to clarify the relationship between tenogenic differentiation and strain stimulation.

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The present study examines the stress intensity factor for branch cracks of stationary bifurcated cracks. The displacement field around the branch crack tips of the bifurcated cracks is measured by digital image correlation, DIC. Then, the stress intensity factor is evaluated through the method approximating the measured displacement by theoretical displacement field. The results show that the stress intensity factor of each branch of bifurcated crack is smaller than that of a straight crack under the same external load. It is confirmed that the bifurcated crack requires larger external force for crack initiation compared to a straight crack. This result predicts that the energy release rate of the bifurcated cracks need twice larger than that of a straight crack if two branches of the bifurcated crack propagate as two-dimensional cracks.

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If TRIP steel with excellent mechanical properties dominated by strain induced martensitic transformation (SIMT) is applied to a shock absorber in automobiles, it is required that improve its reliability by a clarification of the mechanical properties. Thus, it is necessary to evaluate SIMT and then the correlation between SIMT and mechanical properties of TRIP steels must be examined. In the previous report, SIMT in cylindrical specimens made of SUS304 is evaluated by a measurement of relative magnetic permeability under quasi-static tensile tests. However, because of only restricted conditions, obtained relative magnetic permeability may change by factors except STMT. Therefore, it is necessary to measure its rate sensitivity on only different conditions of SIMT for further confirmation of the validity on this method. Here, martensitic volume fraction is evaluated by measuring the relative magnetic permeability in sheet specimens made of both SUS304 and SUS301 during quasi-static tensile test at various strain rates.

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This paper is concerned with an identification of moving direction of a load by utilizing deformation of a circular plate over which the load passes. A shock wave is formed in high-speed flow and the pressure behind the shock wave rapidly changes. A diaphragm type of transducer is often utilized to measure pressure changing rapidly. In this study, a circular plate with clamped edge is considered as a sensitive head of a pressure transducer and a strain gauge is glued on the center of the circular plate. The shock wave is assumed to be a load which moves on the circular plate. For different angles between the strain gauge and the moving direction of load, the deformation of the circular plate is analyzed by using FEM. And the moving direction of load is identified from the average value of strain in the strain gauge by using Rosette analysis.

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Measurement of frictional behavior of the dovetail joint was carried out and the influence on fretting fatigue life was examined. Relative displacement between dovetail contact surfaces was measured with high accuracy using image processing displacement measuring equipment. Tangential rigidity and the coefficient of friction were clarified by comparing the measurement results with FEM analysis results. It was found that strain at the contact edge was dominated by the shear traction range. It was further shown that the shear traction range was influenced by the pressure range, coefficient of friction and slip range.

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A failure mode of composite is so complicated that conventional failure criteria such as Hashin model are not sufficiently accurate especially under compressive loading. To bridge the gap between actual phenomena and failure simulation, authors investigated analysis method considering fiber-kink mode by combining Hashin model and "band broadening stress". In this method, compressive strength was assumed to be the strength of composite with kink band, and an area to apply the band broadening stress was assumed. In this paper, authors introduced the failure initiation criteria and consistent damage model (LaRC03) for considering the fiber-kink mode without any assumptions, and applied this method to OHC (Open Hole Compression). As a result, progressive failure mode and failure strength which were difficult to predict by conventional failure criteria are clearly described with good accuracy.

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Compression after impact (CAI) strength is a key design criteria for composite structure. In this study, impact damage and CAI strength were simulated by progressive damage analysis. The LaRC03 failure criteria which consider fiber kink failure mode was employed for each lamina, and cohesive zone modelling was applied for interlaminar resin layer. In these analyses, impact load and static compression load were applied successively. The simulated impact damage area and CAI strength were compared to tests results. Consequently, simulation well predicted test results for both of impact damage and CAI strength. In addition, it was suggested that CAI failure is caused by fiber kink in each lamina, not by propagation of delamination.

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As fiber-reinforced composites inevitably have initial imperfections such as fiber misalignment, voids, and fiber waviness, it is necessary to quantitatively assess the effect of embedded imperfections on the strength of composites. In this study, fiber waviness of unidirectional composites are focused on, and quantification of the fiber waviness and evaluation of the effect of the waviness on the strength of the composites are challenged. The distribution of fiber waviness inside unidirectional CFRP is investigated using the X-ray CT scanning, and the geometry of fiber waviness is quantified. From the CT images, it is confirmed that there is no internal waviness, and the observed fiber waviness on the external surface gradually disappear inside the specimens. 4-point bending test is conducted using the unidirectional CFRP specimens with and without fiber waviness, and their flexural properties are compared. It can be concluded that specimens with fiber waviness exhibit remarkably lower flexural strength than those without fiber waviness. From the video images taken with the high speed camera during the flexural test, it is clarified that waviness tend to induce initial crack formation.

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A peridynamics-based particle method has been employed to simulate the material deformation observed in a microbond test and the results were compared to the ones obtained by the finite element method. Imperfect modeling of a contact surface as a set of particles in Peridynamics causes a friction-like effect, which gives a similar result to the finite element method with the friction coefficient, μ = 1.0. In both analyses, the friction influences the stress distribution along interface. The results suggestes that the friction is a critical factor in simulating the damage process of the microbond test.

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Strength evaluations of L-shaped CFRP laminates were conducted by 4-point bending method based on ASTM D 6415/D 6415M-06a. Unidirectional CFRP laminates and quasi-isotropic CFRP laminates were used as the specimens. In the former specimens, just interlaminar delamination has been observed, however in the latter specimens, transverse cracking as well as delamination has occurred. Interlaminar tensile strength of unidirectional CFRP laminates was also obtained. However, the dispersion of the strength was not small. Further, the authors tried to investigate the effect of the bending deformation of the specimens on the accuracy of the interlaminar tensile strength.

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In this study, damage development of plain-woven laminates with laminate misalignment is analyzed using a homogenization theory. For this, a homogenization theory for plain-woven laminates with laminate misalignment is described. Hoffman's low is then introduced into the theory as a criterion for fracture of fiber bundles and a matrix material. The present method is applied to the damage development simulation of plain-woven GFRP laminates under on-axis tensile load in the weft direction. Fourteen cases of laminate misalignment including in-phase and out-of-phase are considered in the analysis. It is shown that the stress levels at initiation of damages and tensile strength quite vary depending on the laminate misalignment.

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The importance of TBC (Thermal Barrier Coating) is increasing with development of high performance gas turbine system that can operate at higher temperature. The TBC, which consists of ceramic top coating layer and metallic bond coating layer, deteriorate by the high temperature loading condition. The CMAS (CaO-MgO-Al_2O_3-SiO_2) infiltration into the topcoat is also one of degradation mechanism of TBCs. Delamination of the topcoat with CMAS infiltrated layer was observed in this study. Increasing in elastic modulus of a CMAS infiltrated TBC topcoat was also observed. Thermal stress analysis was conducted in this study. The results indicate that the compressive stress state that can promote a buckling-mode coating delamination developed in the CMAS infiltrated topcoat.

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The CoNiCrAlY coated Ni-base superalloy was exposed at 1000 and 1100℃ for up to 1000h. The morphology and residual stresses in the Thermally Grown Oxide (TGO) layer on the CoNiCrAlY coating were examined by microscopic observation and luminescence spectroscope. The low pressure plasma sprayed CoNiCrAlY coating (LPPS) shows the thinnest TGO layer and lowest residual stress, while the air plasma sprayed CoNiCrAlY coating (APS) shows thicker TGO layer and higher residual stress than the high velocity oxygen fuel sprayed CoNiCrAlY coating (HVOF).

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Residual stresses of a thermal barrier coating (TBC) system are important parameters because it will cause the damages of the system. The residual stresses of the TBC system was evaluated by the curvature method. The curvatures of the substrate with blast treatment, the specimen with blast and bond coat (BC), and the TBC specimen with blast, BC and top coat were measured. The residual stress of each layers in the TBC system was evaluated by the model based on the misfit strain between the coating and the substrate. The method can also provide the residual stresses of the BC in the TBC system. It was found that the method provides reasonable residual stresses as compared with literature values.

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In this study, fatigue crack propagation behavior of Thermal Barrier Coatings (TBC) and Porous-TBC (P-TBC) was examined. Fatigue test was conducted at a high-temperature by using TBC and P-TBC specimens with pre-crack which was induced by tensile loading. Fatigue crack propagation rate in top coating and at interface was focused on here. It was found that fatigue crack path depends strongly on brittle-ductile transition temperature of bond coating material. In both TBC and P-TBC, fatigue crack extension in TC was restrained by open pore, which brings about a large scattering to crack propagation rate curve against fatigue J integral. On the other hand, the propagation rate for the fatigue crack lying on the interface was accelerated by coalescing with secondary crack ahead of main crack.

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In the present study, the interface fracture toughness and adhesioln strength between a Ti coating film and Al-alloy substrate was evaluated using a laser spallation method. The fracture toughness and adhesion strength can be estimated using inverse analyses by the boundary element method using a transfer function computed from the history of the displacement of the specimen. In the present study, an alternative boundary element program is developed for unsteady state vibration of an axisymmetric solid body. The mode I interface fracture toughness between the Ti coating film and Al-alloy substrate is confirmed to be about 0.66 MPam^<1/2> from the present investigation.

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In advanced material such as composite material and coatings, interfacial crack initiation and propagation, which are caused by mechanical and thermal loadings, are serious problem. A lot of interfacial fracture testing methods have been proposed for those advanced materials. However, there are some difficulties when those testing methods are applied to arbitrary sample shape. Especially, the stress field at the interface in actual loading is known to be in mode-II condition, which gives us motivation to do this study. In this study, simple interfacial fracture testing method is proposed. In proposed method, the ridged indenter is just indented on the sample surface, which leads easily to mode-II stress state, and the interfacial fracture toughness can be estimated from both critical load and interfacial crack size.

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In carbon fiber reinforced thermoplastic matrix composites (CFRTPs), interface between carbon fiber and matrix resin play an important role on the performance of the composites. Because interfacial debonding easily takes place during processing or use due to bad adhesiveness of thermoplastics, detect and repair techniques of interfacial debonding are inevitable to utilize CFRTPs practically. In this study, direct heating of the fibers in a CF/PP composite by means of MHz high-frequency induction was applied to melt and re-weld debonding at the interface. Bending modulus increased with IH. and it was supported by SEM observation of fracture surface where gaps at fiber/matrix interface disappeared after IH. Temperature rise at specimen surface got faster in proportion to the bending modulus increase. It was considered to result from rewilding at the interface and so the temperature rise at the surface during IH can be adopted to detect interfacial debonding.

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The effects of shot peening (SP) on the wear performance of silicon nitride were investigated. Silicon nitride plate specimens with and without SP were prepared. Then, ball on plate tests were carried out using the silicon nitride plate specimens in air under dry conditions. The wear volume of the silicon nitride plate specimens with SP was lower than that without SP. The wear volume was lower because of the compressive residual stress that was introduced by SP. This result indicates that SP is an effective method to reduce the wear volume of silicon nitride, thus making it suitable for use as a slide member.

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We proposed a new test structure for the simultaneous electromigration (EM) evaluation of different micro-sized solder joints under high current density. Sn58Bi (SB, wt%) solder strips with different lengths of 50, 100 and 150 μm were fabricated. The solder strips were simultaneously current-stressed under a high current density being approximately 30 kA/cm^2 at 373K for 30 hrs. The results showed a length-dependent EM behavior of SB solder. Continuous Bi-rich layers were formed at the anode interfaces of 50 and 100 μm-long solder strips. However, hillocks instead of Bi-rich layer were formed in the 150 μm-long solder strip. The results were caused by a possible back flow that was dependent on the length of the solder strip.

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Micro-scale interface strength evaluation technique is essential for solid-state bonded materials. Focus ion beam (FIB) micro strength test that using a micro cantilever enable an evaluation of micro-scale interface adhesion strength. However, this technique cannot measure the strength of specimen directly. This work discussed the possibility of strain measurement by combined use of image analysis. Measurement accuracy is depending on the cantilever design and testing condition, this experiment allows evaluating to a precision of 0.1 μm in displacement and 0.03 in strain. Moreover this technique reveals that the local and small area adhesion strength of cold-sprayed copper material is much higher than conventional and macro-scopic evaluation results. Plastic deformation cannot occurred in it Extremely small strain, which is lower than the measurement accuracy, was only observed.

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A similar lap welding of Ti-6Al-4V and a dissimilar lap welding of Ti-6Al-4V/SUS304 were investigated by using of a low capacity laser. In this study, the welding deformation and the welding strength of the lap joints were evaluated. And the optimum welding condition was discussed based on the effect of the welding condition on the weld crack in a dissimilar lap welding of Ti-6Al-4V/SUS304 sheets.

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Aluminum and steel are difficult to bond with each other by surface activation bonding (SAB) technique, because it is easy for surface oxide to reform. On the other hand, copper is one of the easiest materials to bond by the SAB process. Using cold spray technique, it is possible to deposit Cu on Al and Steel substrates. This study considered whether cold sprayed Cu intermediate layer can improve the bondability of Al. Results of mechanical shear test indicated that cold sprayed Cu intermediate layer can be bonded by SAB and the bonding strength was higher than the strength of intermediate layer. Hence, the intermediate layer can improve the bondability of SAB fabricated joints.

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Strain-controlled cyclic behavior of angle-ply CFRP laminates [±θ] at high temperature has been studied. Strain-controlled symmetric tension-compression cyclic tests for different strain amplitudes were carried out on coupon specimens with different fiber orientations (θ = 30°, 35° and 45°), respectively. On the basis of the cyclic tests, the changes of stress amplitude, mean stress, non-elastic strain amplitude, maximum and minimum stress levels and loading and unloading tangent moduli with cyclic straining are examined. The experimental results showed that hysteretic stress-strain response to cyclic straining appears, regardless of the fiber orientation. The stress amplitude decreased with increasing number of cycles, and accordingly the non-elastic strain amplitude increased with cyclic straining. These observations reveal that the cyclic softening occurs in the angle-ply CFRP laminates tested in this study. The cyclic softening terminates rapidly in a small number of cycles, and a cyclic saturation stage is reached in all the strain-controlled cyclic tests, except some cases of large strain amplitude or small fiber orientation angle.

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CFRP has been used in aerospace field because of its high specific strength and stiffness. However, if defects like voids occur in manufacturing process, they will affect mechanical properties. Although previous studies indicate that strength of CFRP decreases as void volume fractions increase, there are few researches on the effect of void geometry and distribution. In this study, geometry and distribution of voids were observed by using X-ray CT and those of the specimens with several levels of void volume fractions were compared. In addition, void model for finite element analysis based on the observation was created, and stress distribution in the vicinity of voids was investigated.

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In the design of electronic packages, the FEM analysis for evaluating the strength reliability of the solder joint should be conducted with consideration for the presence of Cu/Sn intermetallic compounds (IMCs) generated at the interface between solder and copper wiring. To conduct such an analysis accurately, the deformation characteristics of Cu/Sn IMCs must be clarified by conducting tensile tests. In this study, we propose a method to evaluate tensile characteristics of Cu/Sn IMCs. The method employs a composite specimen whose first outer layer is Cu, second layer Cu/Sn IMCs, and core Sn-3.0Ag-0.5Cu lead-free solder. The specimen is made by a method in which a copper-plated solder specimen is heat treated at 453 K to generate Cu/Sn IMCs between the solder and the copper. Tensile tests were conducted using the composite specimen. After the tests, the fracture appearance of the specimens and the characteristics of the stress-strain relations of the specimens are investigated. Based on the results, a numerical method based on the rule of mixture (ROM) is proposed to estimate the stress-strain relation of Cu/Sn IMCs under the tensile loading.

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In this research, we aim to predict transverse shear stiffness of plain carbon textile by bending test which gives additional compression displacement by using our original bending machine. Using 3D image analysis, we evaluated the shape of specimen in a deformed configuration. We then presented approximate method to calculate the bending shape of carbon textile in elastic theory. By comparing the calculated shape with the actual one, we evaluated transverse shear stiffness of carbon textile.

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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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Macroscopic elastic constant of composite materials depends upon not only the elastic constant of reinforcements but also their shapes and degree of alignment. In this study, an analytical method based upon the micromechanics is proposed that can evaluate the macroscopic elastic constant of the composite materials with various types of distribution of reinforcements from unidirectional distribution to fully-three dimensional spacially random distribution, in addition to the two-dimensional random distribution. It implies the transversely isotropic material in three dimensional space and can be covered over all distributions mentioned above. By using the proposed method containing the two-dimensional distribution of reinforcements, the effect of distributions of reinforcements on the macroscopic elastic constant of composites will be examined and its magnitude will be evaluated numerically.

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Multiscale analysis is effective to predict the macro properties of FRP because the macroscopic material properties of FRP depend on the properties of constituent material and the microstructure. In this study, new stochastic multiscale mathematical model considering molding process was constructed for 4 layered textile GFRP modeled by hand layup. For the mathematical model, the parameters of the geometric information of the microstructure are determined and the statistical database is obtained. Based on the mathematical model, new FRP design method which can give feedback to molding process can be proposed when improvement of FRP's properties is needed.

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In this study, thermal residual stress and thermal deformation of CFRP laminates are analyzed from macro scale and micro scale simultaneously. For this purpose, a thermoelastoviscoplasitc homogenization theory is constructed by introducing the effect of thermal expansion into the time-depended homogenization theory. Then, using this theory, thermoelastoviscoplastic two-scale analysis method considered finite deformation of the macro model is established. Using this method, thermal residual stress and thermal deformation of CFRP laminates are investigated.

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Effect of the rafting of γ/γ' microstructure on the fatigue crack growth resistance was investigated, by specifying the artificially rafted directionally solidified Ni-base superalloy. The experimental results showed that the rafted structure improved the fatigue growth resistance at room temperature, when the fatigue crack propagated on the plane parallel to the rafted microstructure. By the observation of crack propagation path, it was strongly suggested that a confined cyclic plastic deformation and a development of crack face bridging by the γ' precipitates coalesenced might contribute to the above improvements.

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Titanium alloy (Ti-6Al-4V) with bimodal "harmonic structure", which consists of a coarse-grained structure surrounded by a network structure of fine-grains, was produced by sintering mechanically milled powder to achieve high strength and good plasticity. In this study, we examine the effect of a range of stress ratios (R = 0.1〜0.8) on the fatigue crack propagation and threshold behavior of Ti-6Al-4V alloy with harmonic structure. In the material with harmonic structure, the fatigue crack growth rate, da/dN, was high and the threshold stress intensity range, ΔK_<th>, was low compared to the material with coarse acicular structure. Furthermore, the critical stress ratio, R_c at which K_<min> = K_<cl>, of the material with harmonic structure was smaller than that of the material with coarse acicular structure. This result indicates that a fatigue crack opening significantly occurs in the material with harmonic structure, which results in decreasing the resistance of a fatigue crack propagation.

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A new ΔK-decreasing test method was developed by using metal film. The film was adhered to a through elliptical hole in a base plate and was fatigued in accordance with the displacement constraint along the hole circumference in the base plate subjected to a cyclic stress. Commonly, a stress intensity factor range was increased with a crack propagation under a constant stress amplitude but was decreased toward the hole edge because of the difference in thickness between the film and the base plate in this ΔK-decreasing test method. Using the ΔK-decreasing test method, the crack propagation test was conducted for pure titanium films with the thickness of 30μm and 80μm. As a result, the fatigue crack propagation rate was almost the same between the film of 30μm and 80μm thickness. On the other hand, the threshold stress intensity factor range is smaller for the film of 80μm thickness with grain size of 79μm than for the film of 30μm thickness with grain size of 37μm.

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Shot peening (SP) is one of the surface modification technologies to enhance fatigue strength. In this study, the mechanism of enhancement of bending fatigue property of shot peened pure titanium (JIS 2) was investigated. Surface roughness, vickers hardness of surface and subsurface, and bending fatigue strength was measured. Surface roughness and hardness of surface and subsurface were increased by SP. The bending fatigue strength was increased highly by SP because increasing of hardness effected more greatly than increasing of surface roughness. The maximum of amount of increase 2.7 times in 10^7 cycles. It was found that the bending fatigue strength was increased by increasing of hardness of surface and subsurface by SP. Therefore, it is obvious that fatigue strength of pure titanium is increased highly by SP.

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Torsion fatigue tests were conducted for circumferentially notched bars specimens of Ti-6Al-4V alloy to evaluate fatigue strength. The notch sensitivity was studied by using blunt (stress concentration factor Kt=2.0) and sharp (Kt=4.0) notched specimens. The number of cycles to failure was obtained and the crack initiation life was estimated from the applied torque to the specimens. The number of cycles to failure and fatigue strength decreased with increasing the value of stress concentration factor. When compared at the same fatigue life, the crack initiation life of Kt=4.0 specimen was much shorter than that of Kt=2.0. The crack propagation behaviors were analyzed by observing fractured surface. When stress amplitude is low, the tensile crack propagated toward a 45° direction of the longitudinal axis of the specimen, while under high stress amplitude, the shear crack propagated in the circumferential direction both in blunt and sharp notched specimens forming flat fracture surface. The fracture surface showed factory-roof pattern under middle stress amplitude. The angle of a fracture plane of the blunt notch under low stress amplitude was 45° to the axial direction. The formation of factory-roof may increase contact areas in the fractured surface, thus increase crack propagation life.

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In order to investigate the thermal stress due to grain anisotropy in tin and tin-copper alloy, thermal stress analysis was conducted using finite element code ANSYS. It was found that the free expansion could induce the plastic deformation in the polycrystalline of tin and tin-copper alloy. It was also found that the stress and strain in the grain whose grain orientation differs from neighboring grains is higher.

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In this paper, a model which represents the mechanical behavior is developed for the ferroelastic material, Lanthanum Strontium Cobalt Ferrite (LSCF), which is a ceramic material often used for a cathode of Solid Oxide Fuel Cell (SOFC). Nonelestic deformation analysis is performed to express the mechanical property of LSCF. At the same time phase transformation of ferroelasticity is analyzed by the use of phase-field model based on micro elastic theory. In the proposed ferroelasticity model, the information of deformation, which is calculated by the mechanical simulation, is introduced to the elastic energy term of phase-field equation. The mechanical properties change in accordance with the phase transformation. By coupling the deformation and phase transformation, the mechanical behavior of ferroelasticity is analyzed. On the basis of the developed model, a simple simulation is conducted.

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Displacement distribution in an austenitic stainless steel plate specimen during tensile test was measured with Digital Image Correlation method. Strain rate dependence of transformation induced plasticity (TRIP) in SUS304 stainless steel was examined. By using the measure of the maximum strain rate, the characterization of localized strain propagation in TRIP deformation was done.

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In this study, the creep properties of ultrafine plate-fin structures which possess uncertainty factors in material properties of a base metal and shapes are investigated using the Monte Carlo simulation. For this, a time-dependent homogenization theory is applied to the analysis of creep properties of ultrafine plate-fm structures. Moreover, Stepwise Limited Sampling (SLS) is introduced into the Monte Carlo simulation to reduce computational costs. Then, using the present analysis method, the effects of uncertainty factors on the creep properties of ultrafine plate-fin structures subjected to a macroscopic constant stress at high temperature are investigated. This enables us to obtain tail probability values of creep strain by one tenth of computational costs compared to the conventional Monte Carlo simulation.

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To evaluate the strength reliability of the electronics structure accurately, it is required to consider the creep deformation for the structure analysis. The indentation test is one of the effective test to estimate the creep deformation of microscopic specimen. However, the reliability of the indentation tests is dependent on the definition of the reference area to obtain stress. Therefore, the suitable reference area was determined by the authors based on the principal stress plane and the method to evaluate the steady-state creep deformation using the new reference area was proposed. In this paper, to apply the proposed method for the actual experimental test, a numerical indentation tests with constant depth were conducted to consider the inhomogeneous of the lead-free solder alloy. The numerical indentation tests were conducted in nine conditions varying the indent location and the deformation behavior of the eutectic phase. As a result, it is found that the proposed method can be applied to the inhomogeneous material. It is also found out that the effect of the nanostructure should be considered to determine the reference area with the principal stress from the result considering the nano structure of the intermetallic compound in the eutectic phase.

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In this study, the extended model with two scaling exponents is developed to reproduce the effects of swelling on the Young's modulus and the osmotic pressure of gels. Two scaling exponents, m and n, are introduced into strain energy functions separated into deviatoric and volumetric parts, respectively. The two different swelling effects are predicted well by independently adjusting two scaling exponents; m takes a wide range of values depending on elastomers, while n is almost independent of elastomers and takes a negative value. It is found that under uniaxial loading subsequent free swelling, the extended model is able to predict strain softening, which is thus related with strain localization followed by swelling-induced rupture. Experiments show that swelling-induced rupture occurs when small extension is applied with good solvents. This tendency is successfully predicted with an appropriate set of the material parameters including two scaling exponents.

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The objective of this study is to evaluate the contribution of fiber bridging on intralaminar and interlaminar fracture toughness under mode II loading in unidirectional CFRP laminates. We used X-ray CT apparatus to capture the 3 dimensional computer graphics (3DCG) of bridging fibers in specimens. By using 3DCG, the bridging process was revealed. Furthermore, we classified bridging fibers into four patterns and counted the number of these fibers from 3DCG. The number of bridging fibers of intralaminar fracture is more than that of interlaminar fracture. Moreover, the density of bridging fibers in the region 5mm behind damage region tip is same as that in the region 10mm behind. The number of bridging fibers under mode II loading is less than that under mode I loading by comparing with the results of our previous study. The characteristic behavior of fiber bridging agrees with the result of fracture toughness test.

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FRP can have various properties by compositing materials that have different mechanical property, but the fracture mechanism is very complicated. So far, it is known that strength property of Glass Fiber Reinforced Plastics (GFRP) is greatly changed by modifying the interface between resin and fiber. Consequently, coupling agents are applied to the interface for improving the interface strength. In our research, to improve the interface strength we used Epoxy resin that has similar structure with Polycarbonate (PC) used for matrix, and resin copolymerizing Polydimethylsiloxane (PDMS) that has siloxane bond (Si-O-Si) that is similar structure with glass. About these GFRTP, We did fatigue test and crack propagation test. After that, we considered influence of appearance of micro crack propagation on fatigue behavior of GFRTP

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The effects of temperature and fiber length on the fatigue life of discontinuous carbon fiber-reinforced polyamide composites have been examined. On the two kinds of polyamide composite specimens reinforced respectively by short carbon fibers of different lengths, tensile fatigue tests are carried out at room temperature (RT), 50℃, 70℃ and 90℃, respectively. Experimental results show that the difference in fiber length results in significant difference in static strengths between the two kinds of short fiber composites, regardless of temperature. The tensile strength of these composites exhibit the temperature dependence of the Arrhenius type. The S-N curves for these composites are similar in shape over the range of fatigue life. However, the comparison of the normalized S-N data with respect to tensile strength for the two kinds of thermoplastic composites suggests that the long fiber composite tends to deteriorate by fatigue a bit faster than the short fiber composite in the high cycle range.

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A waveform based methodology for prediction of variable loading fatigue life of composites is developed. The variable R-ratio fatigue tests in which the stress ratio of fatigue loading alternates between two specified values with different stress levels that correspond to the same number of cycles to failure are first reviewed. It is confirmed that the prediction of fatigue life using the Miner rule is excessively optimistic for alternating R-ratios loading, while it is satisfactory in the case of alternation of fatigue stresses of different magnitudes under a constant stress ratio. On the basis of these observations, it is assumed that a variable maximum stress loading at a constant stress ratio which is equivalent to a given alternating R-ratios loading can be identified. This assumption allows us to predict fatigue life for any given alternating R-ratios loading by applying the Miner rule to the constant stress ratio waveform identified. In order to test this idea, fatigue tests are performed for the variable maximum stress loading waveforms at a constant stress ratio that are equivalent to the alternating R-ratios loading waveforms examined in the previous study. A good correlation between the predicted and experimental fatigue lives suggests that the use of the concept of a single R-ratio waveform in conjunction with the anisomorphic constant fatigue life diagram approach provides a potentially useful tool for prediction of variable loading fatigue life of composites.

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