Recent years, porous composite scaffolds consisting of natural polymer and bioceramics have been considered to be used in bone tissue engineering. Collagen guarantees excellent biological conditions such as stimulation of generation and differentiation of cells. A typical bioactive ceramics, β-TCP, has good oseteoconductivity, cellular adhesion, accelerated differentiation and mechanical property. In this study, β-TCP/collagen composite scaffolds were developed by the freeze-drying technique and rat bone marrow mesenchymal stem cells were cultured in the scaffolds up to 28 days in order to assess the effect of cell growth on the mechanical behavior. The cell number and ALP activity were evaluated using a spectrophotometric plate reader. Compression tests were also conducted periodically by using a conventional testing machine to evaluate the elastic modulus. The increasing behavior of cell number and ALP activity with the composite scaffolds was much better than that in pure collagen scaffold. The compressive modulus also increased with increase of culture period. These results clearly indicate that β-TCP is very effective to enhance the cell growth behavior and the mechanical property.

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In this study, in order to improve interfacial strength between poly(L-lactic acid) (PLLA) and β-tricalcium phosphate (β-TCP), β-TCP surface was treated by 3, 4.5, 6, 7.5 and 12 phr L-lactic acid solution. β-TCP/PLLA compound was obtained by kneading and specimens were fabricated by hot-pressing. Mechanical properties of β-TCP/PLLA composites were investigated by tensile tests. Compared with non-treated β-TCP/PLLA composites, tensile strength of the composites with β-TCP treated using 6 phr L-lactic acid increased. No effects of interfacial treatment on elastic modulus were observed. DSC results indicated that crystallinities of interfacially-treated β-TCP/PLLA composites, both 15 wt% and 30 wt%, were comparable to that of non-treated β-TCP/PLLA.

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Hydrolysis degradation of bio-degradable HA/PLLA composites with different particle size distribution was investigated by immersing the specimens in phosphate buffer solution. Reduction behavior of bending strength and modulus was evaluated as degradability. It was found that such reduction behavior depends on the particle size distribution, suggesting that the hydrolysis degradation of the composites can be controlled by changing the particle size distribution.

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Bioactive ceramics/poly-L-lactic acid (PLLA) composites have been expected as a material for the bone fracture fixations which have more biocompatibility than monolithic PLLA. In this study, β-tricalcium phosphate (β-TCP)/PLLA composites containing three different β-TCP contents (5, 10, 15 wt%) were prepared by injection molding and tested to clarify the effect of immersion in simulated body environment and strain rates on the mechanical properties. These composites were immersed in phosphate buffered solution, and then compressive tests were performed at the strain rates ranging from 10^<-3> to 10^<-1>/s. In the results of these tests, β-TCP/PLLA composites showed that their Young's modulus have no dependence on the strain rate and their compressive strength increased with increasing strain rates. After 16 weeks immersion, compressive strength of 15 wt% composites were decreased slightly at strain rate of 10^<-1>/s. After 24 weeks immersion, compressive strength of 5, 10 and 15 wt% composites were decreased.

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Regeneration of articular tissues such as cartilage and bone has been one of the most important issues in orthopedic tissue engineering. Biodegradable and biocompatible scaffolds play an important role in the regeneration and implantation processes of tissues. An articular tissue usually has a layered structure consisting of a soft tissue of cartilage and a hard tissue of bone and therefore, scaffolds for articular tissue regeneration need to have multi-layer structures. In the present study, therefore, novel multi-layer scaffolds were developed from biodegrdable polymers such as PCL and PLLA and bioactive ceramics such as hydroxyapatite (HAp). The layered scaffolds consist of a soft layer of porous PCL, a hard layer of PLLA/HAp composite and an interlayer of PCL/PLLA/HAp located between the two layers. Compressive deformation behavior

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The biodegradable composite materials composed of stereocomplex poly-lactic acid short fibers (SAPLA) and poly-L-lactic acid matrix (PLLA) are one of the strong candidates of scaffold materials for a novel bone regeneration technology. In particular, the interfacial bonding condition between fillers and matrix is expected as excellent in these composite materials. In the present study, the static compressive properties and their change by immersion into pseudo-biological environment were evaluated for neat PLLA and SCPLA/PLLA composite molded by hydrostatic-pressure-extrusion. The anisotropy in compressive properties was scarcely caused by the hydrostatic-pressure-extrusion molding, and the compressive properties of composite were mainly governed by those of matrix resin. The compressive properties were gradually decreased by the increase of immersion time. The macroscopic fracture morphologies indicated that the main fracture process was tensile fracture caused by the Poisson's effect in both neat PLLA and SAPLA/PLLA composite. Finally, the fractographic observation was carried out, in order to discuss the fracture mechanism mesoscopically. It is suggested that the interface between SCPLAs and PLLA was well bonded, the fracture was initiated at matrix-rich portion, and the SCPLA fibers prevented the matrix-crack propagation.

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The effects of the annealing and Poly(e-caprolactone) (PCL) content ratio on the stress-strain curves of poly(L-lactic acid) (PLLA) was examined. Specimens were made using a melt-mixer and a hot press. After observation of cryo-fractured surfaces of specimens, the stress-strain curves were measured using universal testing machine. In the compressive tests, the yield stress of PLLA increased with annealing time. The peaks near the elastic limit of stress-strain curves of annealed PLLA were not observed. In order to calculate the crystallinity of annealed PLLA, differential scanning calorimetry curves (DSC curves) of specimens were measured. When PCL was added, the yield stress and Young's modulus of quasi-static compressive tests were deceased with increasing PCL content. In particular, the drastic change of yield stress between PLLA:PCL=50:50 and PLLA:PCL=30:70 was observed.

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Usage of the conventional bioabsorbable plastic bone fixation devices have been limited, because the mechanical characteristics of them are lower. In this study, poly-L-lactide(PLA) that is one of the bioabsorbable plastic was molded into the screw shape, and the mechanical characteristics of the PLA screw was investigated. A PLA bar was prepared by extruding a rectangular PLA block, and molding into the shape of the screw by forging. The molding conditions were varied to evaluate the formability of PLA. The mechanical properties, such as pulled out strength, shearing strength and the twist strength were measured. Decrease in shear strength and increase in twist strength for the screw extruded using lubricants were observed, which is due to lower extrusion ratio. Same tendency is observed for the screws molded at higher temperature. These results suggested the lubrication and higher molding temperature have similar effects. Decrease in shear strength at molding temperature of 120 ℃ was obtained, which was caused by crystallization.

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A new rotating slit system was designed for a 2D detector strain scanning method. The rotating slit system focuses the 2D detector on the center of the goniometer. The detectors had a spatial resolution enough for the strain measurement according to the applied stress test. However, the measured diffraction spots shifted for the 2D strain scanning. That is a coarse grain effect. To solve the coarse grain effect, we propose a diffraction spot trace method (DSTM). The bending stress distribution of the coarse grain aluminum alloy was measured by DSTM. As a result, the DSTM is very useful for the stress measurement of coarse grains.

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Internal distribution of residual strain in high-pressure composite vessel using high energy synchrotron radiation X-rays at BL22XU in SPrng-8 was carried out for evaluation of durability improvements. The specimen was high-pressure vessel made of aluminum with 170diameter mm × 500 length mm and the thickness 4mm. The strain scanning method was used to obtain each strain distribution of 3 directions. From the distributions by 311 diffraction of aluminum, it was found that the strains of axial and hoop direction were compression and that of radial direction was tensile. And it was clarified that these result almost agreed with residual strains which were expected to generate for high-pressure vessel rolled fiber.

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The crystallographic orientation changes during fatigue crack initiation process in ferrite steels with different grain sizes and chemical compositions were evaluated by the electron backscattered diffraction (EBSD). EBSD measurement and fatigue test were alternately carried out using small specimen. Misorientation parameter named Grain Reference Orientation Deviation (GROD), which is defined as orientation difference between each measuring point and datum orientation, was calculated. GROD_<ave>, which is average of GROD within observed area, increased until crack initiation, and then remained constant. However, the value of constant (the threshold of crack initiation) is different with grain sizes and chemical compositions. In order to consider the influence of grain size, a new parameter ΔGROD_<ave>/d_<ave>^2 (d_<ave>; the average of grain size) was proposed. The threshold of this parameter is approximately the same for the similar chemical component with the different grain size. Moreover, the threshold increased along with fatigue strength improvement for the different chemical compositions with the same grain size. This result suggests that the proposed parameter is effective for fatigue damage evaluation in crack initiation process.

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Crack propagation tests of lead-free solder were conducted using center-notched plates under cyclic tension-compression of three stress waveforms: pp waveform having fast loading and unloading, cch waveform with tension and compression holds, cph waveform having tension hold. Fatigue and creep components of the J integral were evaluated from the load displacements relations using simple estimates. For fatigue loading of pp waveform, the crack propagation rate was expressed as a power function of the fatigue J integral. The creep component due to the hold time greatly accelerated the crack propagation rate. The creep crack propagation rate was expressed as a power function of the creep J integral for each case of cph and cch waveforms. The crack propagation rate for cph waveform was higher than that for cch waveform. SEM observation after the removal of the surface layer showed many tiny cracks in the vicinity of the main crack for cph waveform, suggesting crack propagation acceleration. The grain fragmentation was observed near the crack by EBSD and its amount increased with increasing crack propagation rate.

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The lath grains in ferritic heat-resistant steel were coarsened with creep deformation. The coarsening behavior of lath grains was estimated by Electron Back-Scattered Diffraction (EBSD) method attached to a scanning electron microscope. Using this method, it could be estimated the coarsening behavior of the lath grains macroscopic and quantitatively.

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In this paper, the non-contacting stress measuring method by using the fluorescence lifetime is studied under tensile loadings. The test piece is made from acrylic resin that is contained a fluorescent material. The laser beam is applied to this test piece, and time dependence of fluorescence is observed by the streak camera. Various strains are added to the test piece by tensile machine, and time dependence of fluorescence is measured. The relationship between the strain and the fluorescence lifetime is confirmed. It is observed that the fluorescence lifetime is increasing with the increasing of the tensile stress.

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A defect with Focused Ion Beam (FIB) can be used as a crack for fatigue limit evaluation under some conditions. The condition which controls the applicability of an artificial defect as an ideal crack for fatigue limit evaluation is strongly dependent on the relation between (i) the length of a non-propagating fatigue crack and (ii) the crack length when the small fatigue crack growth behaviors from an artificial defect and an ideal pre-crack become almost the same. It is found that the length of (ii) can be obtained by the analyses using the number of cycles from a certain crack length to failure.

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Correlation between the strain range and fatigue crack growth rate was investigated using Type 316 stainless steel. Crack growth rates were obtained by pull-push axial fatigue tests using cylindrical specimens. The obtained crack growth rates correlated well with the strain intensity factor, in which γ^<-0.5> singularity was assumed at the crack tip. The integration of the regression curve of the obtained crack growth rates agreed well with fatigue lives obtained using conventional fatigue tests.

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In recent years, Japanese nuclear power plants experienced multiple large earthquakes, such as Niigata-ken Chuetsu-Oki Earthquake in 2007 and the Great East Japan Earthquake in 2011. Therefore, it is very important to assess the structural integrity of reactor piping under such a large earthquake when a crack exists in the piping. In this study, an effect of excessive compressive loading on the crack growth behavior of piping materials has been evaluated through cracked plate testing. It was observed that excessive compressive loading had an acceleration effect on crack growth rate. The evaluation method using J-integral has been proposed for the acceleration effect of excessive compressive loading on crack growth rate. It was indicated that the acceleration effect by excessive compressive loading for the condition beyond small-scale yielding could be conservatively evaluated using the proposed method.

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Fatigue crack propagation of Ni-base superalloys was investigated at room temperature, using a miniature CT specimen of which the specimen thickness was comparable to the grain size. At first, effect of crystallographic orientation on the crack propagation was studied, using a single crystal superalloy, CMSX-4, with different primary and secondary orientations. Based on the results of the single crystal specimens, the crack propagation in the poly-crystal superalloy, IN939, was discussed, focusing on the effect of the grains orientation and a constraint of the grain boundary on the crack propagation rate and the propagation path.

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Loading waveform dependence of near-threshold fatigue crack growth behavior of Ni-based superalloy at elevated temperatures was examined in the air and in a vacuum using constant Kn. and ΔK decreasing test method. It was found that the crack growth behavior at 850℃ and 900℃ on both environments was dependent on loading waveform. A difference was observed in appearance of fracture surfaces in correspondence to each C-P and P-C waveform at 850℃ in the air.

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It has been recognized that the threshold stress intensity factor range ΔK_<th> of a short crack is lower than that of a long crack. This behavior is unsafe in mechanical design if only ΔK_<th> of long crack is considered. Therefore many researchers have studied short crack behavior using plane fatigue test specimen. These studies provided quantitative understanding of the short crack behavior in relation to crack closure. However, for a short crack at notch root, the behavior has not been clarified yet. In this study, crack propagation tests using various kinds of notched specimens with a short pre-crack were done to consider the effect of notch root radius and stress ratios on the crack propagation behavior of the short crack at notch root. The crack closure was different depending on the stress ratio as well as notch root radius. This resulted difference in the ΔK_<th> of the short crack. When high stress ratio was applied, since there was no crack closure the ΔK_<th> was relatively low regardless of notch root radius. The effect of notch root radius on the ΔK_<th> of the short crack at notch root was significant when the stress ratio was low. The change in ΔK_<th> with the decrease in notch root radius could be understood by development of crack closure.

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Measurement of fatigue crack growth properties is difficult by relation of accuracy and device characteristic. Non-contact and the highly precise measurement are expected by the use of a magnetostriction effect to apply in this study. The small crack growth properties and crack length measurement by a magnetic field change with the magnetostriction effect that was one of a characteristic of magnetism of ferromagnetic substance was studied. Using a coil, a magnetic field change with magnetostriction effect was detected, and the waveform change of the output was inspected The experiment result was revealed that the small crack affects a magnetic field change by a magnetostriction effect and the crack length can measure by output of a coil.

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Many rolling contact fatigue failures, such as those that occur in railway rails, rolling bearings and gears, are due to the high repeated shear load. In order to prevent such fatigue a failure, the resistance of the material against such a load must be determined. The fatigue crack growth rate is dependent on the Mode II stress intensity factor range ΔK_<II>. However, the Mode II crack propagation characteristic varies according to different experiment methods. Therefore, in this study, we measured the effective Mode II stress intensity factor range ΔK_<IIeff>. As it is difficult to carry out the Mode II fatigue crack propagation in the laboratory, this test was carried out using a bending load in this study. This bending load was applied to the tips of a double cantilever specimen and the Mode II fatigue crack propagation could be carried out between the two cantilevers. Furthermore, in order to measure the ΔK_<IIeff>, several strain gauges were applied to the specimen around the crack tip. Using this technique, some ΔK_<IIeff> value during the Mode II fatigue crack propagation tests will be reported.

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In the present study, synchrotron radiation micro computed tomography (SR μCT) imaging of SPring-8 was applied to the observation of delamination defects in high-strength steels under rolling contact fatigue. The rolling contact fatigue crack initiation occurs under surface and these defects propagate to the surface. The conventional technique, such as optical microscope and scanning microscope, cannot give us the crack initiation and growth behavior under the surface. Therefore, the shape of rolling contact fatigue defects was observed by SR μCT imaging. The specimen with an artificial defect, which simulates an inclusion, was used to the contact rolling fatigue tests. The broken and non-broken specimens were observed respectively by SR μCT. The delamination defects and cracks can be detected from the artificial defetct. It is found from these results that the defect initiation and propagation behavior in the rolling contact fatigue process can be discussed from the measurements by SR μCT imaging. The number of crack, location and size of crack obtained by the CT imaging coincide with those by polishing and SEM measurements. It is found from these results that the defect initiation and propagation behavior in the rolling contact fatigue process can be discussed from the measurements by SR μCT imaging.

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Tensile stress is necessary for observing fatigue cracks by X-ray computed tomography (CT) because the fatigue crack tip is normally closing without fatigue loading. In this study, the influence of the tensile stress on the observing results of a fatigue crack by micro CT with synchrotron radiation was investigated. The area of the fatigue crack projected in the specimen axial direction has not changed with the increase in the tensile stress, though the opening displacement of the crack on the surface increased with the increase in the tensile stress.

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Fish eye failure that is unique fatigue fracture occurs in very long life region of high strength steel. However, mechanism of subsurface failure is unidentified. Measuring fish eye failure needs non-contact and the highly precise measurement. In this study, I examined using measurement by magnetostrictive effect and measuring magnetic property of high strength steel. As a result, high strength steel is magnetized in magnetic field. But fatigued high strength steel is not magnetized. This phenomenon is trapped magnetic wall movement by fatigue. Using measurement by magnetostrictive effect was difficult for high strength steel.

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Static strength tests and dynamic fatigue tests were conducted on single crystalline silicon (SCS) thin films under N_2 gas environment at 22℃ and 180℃. It was statistically confirmed that SCS suffers accumulation of fatigue damage under inert environment of N_2 gas, as well as polycrystalline silicon. By comparing the results of SCS and polycrystalline silicon, it is expected that grain boundary is sensitive to temperature leading to a significant increase in static strength with increasing temperature. In fatigue tests, the accumulation of fatigue damage of silicon was accelerated by increasing temperature both in SCS and polycrystalline silicon. It was therefore speculated that fatigue damage is accumulated in crystal, although strengthening is attributable to grain boundary.

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SUS304 steel is a kind of the austenitic stainless steel. It is used for various fields, example for the plant and the nuclear plant. The austenite phase is non-magnetism usually, but when SUS304 steel is received a big stress, a part of it is transformed into the martensitic phase that is ferromagnetism. In recently years, a lot of researches are done the nondestructive testing by measuring the magnetic characteri6stic using this character. It is hope that the method of detecting the damage before generation of the crack for to improve the safety of the machine and the structure. Then, we measured martensite fraction in the fatigue process of SUS304 steel, and we examined applicability from the change in martensite fraction to the fatigue damage evaluation in this study.

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The study considered the relation between fatigue strength property and damage mechanism in GFPC having modified resin/fiber interface by observing the fracture, and the fatigue testing. 1) Damage was initiated at the fiber end in the early stages of the fatigue process, and debonding propagated along the fiber interface. 2) In fatigue testing, the number of cycle difference in a high stress is based on the difference in a damage mechanism.

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Rolled magnesium (Mg) alloy AZ31 and cold-rolled steel SPCC sheets were welded by a friction stir welding (FSSW) using a scroll grooved tool without probe. Tensile shear fatigue tests using the welded joint were performed in order to investigate the fatigue behavior. The static tensile shear strength of Mg-SPCC dissimilar joint was 2.5kN, which was nearly the same as that of Mg-Mg similar joint. The fatigue strength of Mg-SPCC joint was also the same as that of Mg-Mg joint and the fatigue limit at 10^7 cycles was a little higher, which indicates that FSSW is effective for welding the dissimilar metals of magnesium alloy and steel. In the Mg-SPCC joint, the shear fracture occurred at the welded boundary while in the Mg-Mg joint, cracks propagated not along the boundary but through the base metal.

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Crack tunneling was observed in pure aluminum compact-tension test pieces. The influence of tunneling upon elastic-plastic fracture toughness measurement was studied. The crack tunnelings in the compact-tension pieces with and without side grooves were compared.

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A disclination is a line defect which violates rotational symmetry of elastic body. We propose a disclination-dislocation model for the elastic deformation of tricrystals in order to calculate the elastic incompatibility stress which arises around the grain boundaries junction in tricrystals when the crystal is deformed by external load. The calculated stress is compared with the result of FEM analysis of elastically anisotropic tricrystals.

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Comprehensive knowledge of the low-cycle fatigue properties of nuclear component materials, and nondestructive testing (NDT) techniques for fatigue damage detection are important when evaluating nuclear components affected by earthquakes. Acoustic emission (AE) testing can be used for the condition monitoring of the components. Therefore, we conducted low-cycle fatigue tests of austenitic stainless steel with AE monitoring. The results of fatigue tests showed that the estimation based on the usage factor (UF) could be useful for the life prediction. The results of AE monitoring also showed that the timing of AE generation changed by the remaining fatigue life, so the potential for characterization of fatigue damage was demonstrated by focusing timing of AE generation. Furthermore, the possibility of applying AE monitoring to NDT techniques was demonstrated through the results of these fatigue tests.

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Shot Peening is used as one of the most common surface treatment processes for mechanical and structural elements. In Shot Peening Process, the effect of surface treatments can roughly be divided into three factors, projection, particles, and specimens. These factors have complex effects on each other, so it is difficult to understand the specific factor to control the process. In this study, we carried out the numerical simulation of Shot Peening processes. Especially, we focused on the relation between moving shots and surface modification. The results show that the locations of particle collision on the specimen distributed broadly. This is due to the collision between shot particles flying from nozzle to specimen.

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The relaxation of clamping force in magnesium alloy AZ91D bolted joint was investigated under the initial clamping force of 5.6 kN at testing temperature of 20, 100 and 125℃. The fiber optic strain gauge was originally introduced to use in the clamping force relaxation test to monitor clamping force in real time. From the experimental results, it is clear that the increase in temperature resulted in the clamping force relaxation. The mismatch of thermal expansion between steel bolt and magnesium alloy joint is suggested to cause the reduction in clamping force induced by compressive creep deformation in magnesium alloy joint.

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The present paper investigates Electrical Resistance Change Method (ERCM) for thick CFRP laminates with a dent. The authors have proposed the damage identification method for CFRP using the ERCM and confirmed its applicability for beams and thin plate-type specimens in the previous studies. However, the dent is made for thick CFRP and the dent causes electrical resistance decreases. In the present study, we focus on the dent and the electrical resistance decrease is adopted for monitoring delamination location. FEM analyses are used to obtain electrical resistance decrease distributions. Response surfaces are adopted to estimate the delamination location here. The results show good agreements with the experimental data.

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CFRP laminated structures are applied to many aerospace structures. Although the CFRP laminates have high specific strength and specific stiffness, delamination cracks are easily created and the delamination cracks are usually difficult to be detected by visual inspections. Recently, high toughness CFRP laminates are adopted to primary structures. The tough CFRP yields small fiber breakages when delamination crack is made in many cases. This requires a detection system of fiber breakages at low cost for large laminated CFRP structures. In the present study, TDR method is adopted. TDR method uses an electrical pulse wave and observes the reflected wave. The method is applied to a 2m CFRP strip specimen and notches are detected from the reflected pulse wave. Besides, the propagation of the pulse wave is investigated by the electromagnetic simulation using FDTD method.

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The aim of present study is to investigate the nature meaning of the relationship between macroscopic spider-web structure its hierarchical spider-silk structures, and their deformation and fracture behavior. Firstly, we observe the macroscopic spider-web structure using digital camera and the spider-silk structures using optical microscope and scanning electron microscope. Secondarily, we attempt to develop the tensile machine for micro-fiber and investigate the mechanical properties and fracture behavior of spider-silk using developed tensile machine.

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In order to improve interfacial properties of bonded composites joints, in-mold surface preparation using nanoimprint lithography is proposed. In this method, CFRP is formed on the mold with microstructures and the shape of microstructures is transferred to the CFRP surface, which gives us adherent surface without any conventional surface treatment. In this paper, microstructures which improve mode I fracture toughness of adhesive joints were proposed and fabricated on CFRP laminates. It was confirmed experimentally that fracture toughness become stronger as the aspect ratio of microstructures increased.

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The purpose of this study is to investigate the physical properties of catheter, which made of soft nylon resin and is reinforced with thin stainless wires so called braid. In our previous study, the buckling tests under uni-axial loading have been carried out with various deformation speeds, and the relation between the phenomenon of stress relaxation and the buckling load has been revealed. In this paper, the buckling load obtained under initial torsion is estimated by changing the speeds of the axial displacement, and the relation between the buckling region and the stress relaxation is examined.

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During Resin transfer molding (RTM) of composites, entrapped air in resin during resin impregnation may remain as voids in the product and depresses the mechanical properties. In this paper, bundle scale void formation in anisotropic plane woven fabric is focused. The effect of anisotropy on void formation is described by simplified model of void formation. Experiments were carried for the validation and good agreement was obtained between the result and the expectation of the analysis model.

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The crack growth on adhesive interface was observed during shear indentation test. The acrylic materials and epoxy bonding adhesive were used for the specimen. The experimental results were compared with the numerical results of elastic crack propagation analyses. The results show that the crack propagation behavior is similar with each others. However, the maximum load and the interfacial toughness depend on the size of specimens.

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The effect of processing layer on fatigue property of extruded AZ61 magnesium alloy was investigated. Rotating bending fatigue strength test, micro structure observation, micro-hardness test, and observation of crack initiation and crack growth behavior during fatigue test were carried out. It is found that specimens which has processing layer by cutting (PL) exhibited significantly longer fatigue life compared with specimens without processing layer (PL-P). Fatigue life of PL was 10 to 50 times longer than that of PL-P. In case of PL, hardness increased in the region near by the surface region. According to the result of observation of crack initiation behavior by using replica method, crack initiation resistance of PL was higher than that of PL-P.

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There is quite a few literature with respect to earthquakes in geology field. To clarify the mechanism of deformation of faults and folds in stacking layers is also an important theme on solid mechanics. In this study, we deal with the kink fold which is idealized to have only straight and refracting cross sections. Relation between displacement and compression load is evaluated using the maximum strength theorem that is natural derivation of the principle of virtual power (Salencon, 1974). We also discuss the result using anisotropic cohesion model.

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A sound bullet is a high-energy area formed by elastic waves through non-linear acoustic lens (Spadoni and Daraio, 2010). In this study, simulations of wave propagation in an elastic body are carried out to obtain the characteristics of sound bullet for improvement of acoustic lens. Effect of boundary profile is investigated.

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If it is possible to inspect composite aircraft automatically and quickly after every flight, we can reduce the safety factor and allow for more flights. Although, an electrical resistance change method (ERCM) has been proposed as a self-monitoring method which can inspect rapidly even a large structure without expensive equipments, there are many problems with its practical application. In this study, a new diagnostic method, impact-damage visualization, was developed. Indentation damage increases fiber-fiber contact at the interlaminar interface and electrical conductivity. Consequently, electrical current applied to the material will concentrate around the damaged area, and lead to selective and intense resistive heating. This temperature increase can be observed by thermography or detected as a change in electrical resistance caused by the temperature difference. The lightning protection system of a composite aircraft was used to apply a uniform electrical current distribution and electric heat to a large structure. Subsequent coupled thermal-electrical analyses showed that even small indentations (depth <0.15 mm) could be relatively easily detected in structures >1 m in size.

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