In this study, we evaluated the dynamic motion of guidewire and catheter in blood vessels by numerical analysis. The model of the guidewire is constructed with viscoelastic springs and segments. The proximal part of the guidewire model is constrained by the catheter model, which is fixed and assumed to be a rigid tube. First, after displaced and released the guidewire, the damped free vibration was analyzed. Second, the motion of the guidewire in torus-shaped blood vessel model was calculated when the proximal part of the guidewire model was pushed and pulled. The vessel is an elastic circular cylinder, whose shape is defined by the centerline and the radii. Collisions between the guidewire and the vessel are calculated and the contact forces are determined according to the stiffness, damping and friction of the vessel wall. The viscous term for each joint of the guidewire model used in our previous studies was smaller than actual values. The viscous term affected the trajectory of the guidewire tip and the contact force.

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Stress fibers (SFs) play essential roles in various cellular events including cell movement and shape maintenance. They reorganize themselves in response to the mechanical environment as well. Recently, we found that SFs reappeared after temporal disruption with cytochalasin D had similar orientation to those before disruption in vascular smooth muscle cells (SMCs). This may indicate the cells have a memory of SF orientation. We previously found that focal adhesion arrangement served as this memory, while microtubules acted as its eraser. However, the role of intermediate filaments (IFs) to the memory remained unclear. Here we investigated the effects of IFs during the reorganization process of SFs. We preconditioned SMCs with cyclic stretch to make their SFs align in a uniform direction. We then disrupted SFs completely with cytochalasin D for 1 h, and let them reorganize in the drug-free medium for 3 h. IFs were disrupted with acrylamide during the disruption or reorganization process of SFs. The reorganized SFs appeared as they had been in the presence of IFs, while SFs showed random orientation in the absence of IFs. Interestingly, the orientation of SFs tended to coincide with that of IFs following the temporal disruption and the subsequent reorganization of both SFs and IFs, simultaneously. These results may indicate that IFs have a potential interaction with SFs and serve as a guide leading SFs to focal adhesions to facilitate their memory of orientation.

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Cytokinesis requires substrate in adhered cells. However, it is obscure whether cells require external forces under the cytokinesis. In this study, external forces applied on cells during cytokinesis were attempted to measure with traction force microscopy. It was investigated whether single MDCK cells divide on polyacrylamide gels and whether FBS, which is required for stimulating cellular division, and phenol red, which is required for indicating pH, crosstalk with GFP-tubulin and with fluorescence beads.

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Embryos develop to adults through a complicated process of cell division and migration, i.e., morphogenesis. Not only biochemical factors but also mechanical factors such as stress and stiffness should be involved in morphogenesis because cells move vigorously while pushing and pulling each other. Such pushing and pulling may cause complicated distribution of residual stress in the embryo. Residual stress of an elastic body can be estimated by measuring surface topography of a cross-section of the body because the area subjected to tensile stress dents and the area subjected to compressive stress bulges in the section. In this study, we estimated stress distribution in Xenopus laevis embryo during the gastrula stage (stages 10-13), where a hollow ball-like structure transforms into a complicated three-layered structure (endoderm, mesoderm and ectoderm) with a part of the outside wall of the embryo entering the embryo's interior, by measuring the surface topographies of the median section and a section perpendicular to the median plane and containing a dorsal marginal zone (DMZ). We found that 1) ectoderm was in tension whereas meso-endoderm in compression, 2) the magnitude of the stress decreased during stages 11 and 12, and 3) the stress was higher in the DMZ than in surrounding areas at stage 10.

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Fibrils were isolated from rat tail tendons and were stretched to failure in the air (dry condition) and physiological saline solution (wet condition). The tensile strength and tangent modulus of the fibrils in the dry condition were significantly larger than those in the wet condition. There were no significant differences in the strain at failure between the dry and wet conditions.

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In adaptive bone remodeling, it is believed that osteocytes embedded in calcified bone matrix have an important role as a mechanosensor. Osteocytes sense mechanical stimulus and transmit biochemical signals to the cells such as osteoblasts, osteoclasts and lining cells on bone surface. In this process, nitric oxide is one of essential biochemical signals to regulate bone resorption and formation. Besides, osteocytes have characteristic stellate shape with slender processes that is different from osteoblasts. Therefore, we postulated that the osteocytic characteristic shape is important in sensing mechanical stimulus. In this study, we observed nitric oxide production induced by mechanical stimulus in osteocytes isolated from calvaria of chick embryos. Nitric oxide production is known to be caused by two different pathways: one is dependent on calcium ion, and another is independent from that. In our experiment, first, we found a characteristic oscillation of nitric oxide production in calcium-independent pathway. Second, we applied mechanical stimulus to the cell process and cell body of osteocytes independently to compare their difference in nitric oxide production. As a result, we found that cell process is more sensitive to mechanical stimulus than cell body.

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This paper presents development of a technique to control cell adhesion using an array of magnetic microbeads. Using MEMS techniques, we fabricated an array of microholes (3 gm in diameter and 2 gm in depth) on the surface of a glass substrate, to trap magnetic microbeads (2.8 gm in diameter) in the microholes. The glass substrate was integrated with a PDMS-made device and a suspension of magnetic microbeads was then introduced into the device by a syringe pump. The magnetic microbeads were coated with cell adhesive ligands prior to the loading. A permanent magnet was placed under the substrate and was used to direct microbeads into the microholes, followed by an introduction of cell suspension to the device. After a 24 hours incubation, it was observed that cells attached only to the magnetic microbeads, but not to the other parts of the glass surface. The current method of controlling cell adhesion would be useful to develop advanced cell culture system.

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Proper positioning and maintenance of cells on the substrate by controlling cell migration non-invasively is critical for tissue engineering, cancer research and diagnosis. We fabricated silicon substrates consisting of a flat surface and a microgrooved surface, and investigated the response of three types of cells to the microgroove. Fish epidermal keratocytes turned at the boundary with the microgroove (1.5 pm width, 20 pm depth). In contrast, HT1080 fibrosarcoma cells and Swiss/3T3 fibroblasts crossed over the microgroove (1.5 pm width, 20 pm depth). We hypothesized that the cellular distribution of actin and the adhesion complexes would be an important determinant of cell motility characteristics in the microstructured surface. This study suggests the possibility to realize label-free control of cell migration by utilizing the microstructured surfaces.

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Several reports suggest that low-intensity pulsed ultrasound stimulation (LIPUS) facilitates chondrogenesis. Recently it has been suggested that LIPUS may be transmitted via Integrin. In this study, the Arg-Gly-Asp (RGD) amino acid sequence, which is a ligand of Integrin, was induced to the fibroin substrates by either gene transfer or physical mixing, and the variation of chondrocyte response to LIPUS was evaluated. Chondrocytes were seeded on three kinds of fibroin substrates: 1 wild-type, 2 transgenic and 3 mixed. LIPUS stimulation, with spatial and temporal average intensity of 30 mW/cm2, was applied to the chondrocytes at 12, 36, 60 hours and administered for 20 minutes each time. The results showed that GAG production, number of chondrocytes and mRNA levels of aggrecan, Sox 9 and Integrin ^ 1 was enhanced in the transgenic group by LIPUS administration, but these LIPUS-derived changes were not found in the wild-type and mixed groups. We previously reported that the adhesive force between chondrocytes and RGD transgenic fibroin surfaces was higher than that for mixed fibroin, suggesting that adhesive force is translated via RGD which bonds covalently to the fibroin proteins for the transgenic group. The present results suggest that the early biological adhesion via RGD on the transgenic fibroin is sensitive to LIPUS.

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Tendon is subjected to dynamic mechanical loading in vivo. Effects of cyclic tensile loading on tenocyte metabolism have been characterized well. However, the relationship between cell metabolism and internal tension within cytoskeleton has not been studied in detail. Elastic micropillars made from silicone elastomer (PDMS) have been proposed to measure cellular traction forces which reflect cytoskeletal tension. Micropillar substrates with three different elastic moduli were prepared by changing the height of the pillars. After tenocytes were seeded on each substrate for 24 hours, traction forces were determined. Real-time qPCR was also performed to examine the expressions of type I collagen (anabolic gene) and MMP-1 (catabolic gene) mRNA from tenocytes on these substrates. It was found that there were significant increases in cellular traction forces with the elastic modulus of micropillar substrates. Although there were no significant differences in the expression level of type I collagen among three substrates, increases were observed in the expression level of MMP-1 with decreases in the elastic modulus of substrate. This may indicate that intracellular cytoskeletal tension strongly influences tenocyte catabolism rather than anabolism.

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Cell migration is essential for a variety of biological and pathological processes such as wound healing, inflammation and tumor metastasis. However, a mechanical field within a group of multiple cells during a collective migration has not been characterized well. In this study, a polydimethylsiloxane-made multichannel device was fabricated using photolithography and soft lithography, and was used to monitor traction forces generated by cells during migration. The device consists of a reservoir for establishing a confluent cell monolayer, attached with 24 microchannels for cell migration. Four patterns of micropillars were designed on the bottom surface of the microchannels to measure cell traction forces during migration on four combinations of substrate stiffness and topography. Collective cell migration from the reservoir into the microchannels was initiated when the channels were backfilled with culture medium. Migration rate of 5.7 pm/h was measured in the microchannel equipped with micropillars whose dimensions were 6.5 pm in height, 2 pm in diameter and 7 pm in spacing. In detail, cells on the moving front of the migration, leading cells, generated the traction forces toward the backward and the maximum magnitude of 14 nN was measured at their front side. Traction forces generated by the cells behind the leading cells directed backward at both the front and the rear sides. However, traction forces generated by the cells behind the second row directed random directions with smaller magnitudes compared to those on the front and the second lines. It is assumed that cells on the front line generated a large magnitude of traction forces and migrated actively as single cells, pulling adjacent cells forward, whereas the movement of cells after third row was restricted by mechanical linkages between their neighboring cells, generating a small magnitude of traction forces.

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In this paper, we measure the elastic modulus of cell surface by indentation test with an atomic force microscope for each of tamoxifen sensitive and resistant breast cancer cell lines. From the comparison of measurements based on statistical test, we demonstrate that tamoxifen resistant cells might be 28% "softer" than sensitive cells, which evokes the necessity of biomechanistic point of view in cancer research.

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Mesenchymal stem cells (MSCs) have been extensively investigated for their applications in regenerative medicine. Successful use of MSCs in cell-based therapies will rely on the ability to effectively identify their properties and functions with a relatively non-destructive methodology. In this study we measured the surface stiffness and thickness of rat MSCs with atomic force microscopy and clarified their relation at a single-cell level. The role of the perinuclear actin cap in regulating the thickness, stiffness, and proliferative activity of these cells was also determined by using several actin cytoskeleton-modifying reagents. This study has helped elucidate a possible link between the physical properties and the physiological function of MSCs, and the corresponding regulatory role of the actin cytoskeleton.

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It has been reported that glycans play pivotal roles in biomechanical responses of cells. To reveal the roles of glycans in mechanical response of endothelial cells, we observed morphological changes of a murine vascular endothelial cell line F-2 treated with a drug DG, which modifies protein glycosylation. When a confluent cell monolayer was treated with DG in static culture, it formed mesh-like structure in 48 hours. To reveal the reason for the mesh-like structure formation, we measured adhesion strength between the cells and that between the cell and the substrate with laboratory-made testers and found that the mesh-like structure formation was accompanied by an increase in the intercellular adhesion strength and a decrease in the cell-substrate adhesion strength. These changes may facilitate local aggregation of cells in a cell monolayer and thus cause the mesh-like structure.

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Single cell analysis has been of a great interest in bioengineering as it can highlight heterogeneity of individual cells in medical screening tests compared to conventional bulk analysis. We have been developing a novel bioassay system designed for single cell analysis. The device mainly consists of a silicon/glass microwell slide and a PDMS microchannel, and enables to supply reagents to microwells in a well-controlled manner using micropumps. In this study, bovine aortic endothelial cells were cultured in the microwells for 48 h and then subjected to fluid shear stress at up to 2 Pa for 6 h. A result showed that realignment and elongation of endothelial cells to the flow direction were dependent on the level of shear stress. It was confirmed that the device could reduce consumption of expensive reagents and precious all samples. Moreover, unlike conventional bulk devices, multiple experimental conditions can be examined at the same time within a single device. It can be concluded that the device has a potential to be applied to multi-purpose single cell tests.

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3D-FEM models of two different types of PS type knee prosthesis were constructed using their CAD data. Model 1 has a non-symmetric design of the tibial insert surface, while Model 2 possesses a symmetric type surface. Deep flexional motion with and without internal rotation was adapted to assess the effects of such flexional motion on the stress states of the tibial inserts made from UHMWPE. Model 1 showed higher stress level than Model 2 under flexion without internal rotation, on the other hand, the stress level of Model 1 became smaller than that of Model 2 under flexion with internal rotation. It is thus concluded that the non-symmetric surface design is very effective for deep flexional motion with internal rotation that is the typical knee movement in vivo.

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Total hip arthroplasty (THA) is performed to replace the biological hip joint with an artificial joint for patients who suffer from rheumatoid arthritis or osteoarthritis of the hip joint. The hip joint simulator, which can generate the desired hip joint angle and the joint contact force, has been developed in order to evaluate the performance of the artificial hip joint. We generate the realistic behavior of artificial hip joint dislocation using the simulator considering the hip joint contact force which consists of the muscle force around the hip joint and the floor reaction force. In this paper, we discuss the effect of the hip contact force on artificial hip joint dislocation.

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Wear debris from ultra-high molecular weight polyethylene (UHMWPE) which is used in joint prostheses will affect biological reaction and joint loosening. Significant levels of biological reaction were produced in response to the wear particle size 1.0[1m or less. In a previous study, a newly-developed surface texturing was used to decrease the wear volume and increase wear particle size. Tetrahedral Amorphous Carbon (ta-C) coating on hard bearing materials made of Co-Cr-Mo alloy and Chromium nitride (CrN) coating on soft bearing materials made of UHMWPE were applied in order to alter the friction and wear characteristics. A pin-on-disc friction tester capable of multidirectional motion was used to investigate the friction and wear characteristics. CrN coating on UHMWPE and ta-C coating on Co-Cr-Mo alloys have the possibility to reduce the amount of wear of UHMWPE, however, friction was increased.

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In this research, the osteoarthritis of the hip was picked up. It compared examined the mechanical state of the hip joint of the normality person and the artificial hip joint by the total hip replacement. At the time of one foot standing position was supposed making use of photoelastic stress freezing method. The Charnrey type artificial hip joint has supplied satisfactory clinical record. And, 2-dimensional Photoelastic Method, 3-dimensional stress freezing method and the finite element method were used together, and shape was changed and was analyzed. Similarly, the stress state which form exerts on THR shape using hybrid method is reported. The mechanical indicator of the research and development of the total hip replacement is described.

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Treatment of proximal femoral fractures is done mainly with femoral nails. An important part of the femoral nail is the Lag-screw. The design of the Lag-screw is known to have significant influence on the rotation of the femoral head. However, the conventional Lag-screw is unable to sufficiently inhibit the rotation of the femoral head. Redesign of the Lag-screw is suggested to resolve this problem. In this study, we propose the design of the Rectangle Double Lag-screw system. In this paper, to examine the validity of our design, we performed torsion tests and an FEM analysis. Results of the comparison of the Rectangle Double Lag-screw system with the conventional Lag-screw system in torsion test and FEM analysis, indicated the validity of our design for inhibiting the rotation of the femoral head.

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In this study, proliferation behavior of osteoblast-like cells, MC3T3-E1, in collagen scaffolds were investigated. For comparison, cells were also cultured on well plates and collagen gels. Variations of cell number and ALP activity were evaluated and it was found that the culture condition using the scaffold exhibited the best increasing behavior. It is also noted that the compressive modulus of the scaffold tended to increase with cell proliferation. a-TCP particle filled collagen scaffolds were also fabricated and it was found that the compressive modulus was effectively improved by addition of a-TCP fillers.

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The bone has a property called the remodeling to become adaptational change of functional shape depending on load environment. In this study, We made simple model that mimics the cancellous bone with a trabecular structure and build the optimal shape model using growth-strain method. As a result, the top and bottom peripheries in the model were enlarged, and the center periphery was narrow, and the shape provided a result that look like shape of the real bone. In addition, the initial and final lattice bone models were molded by rapid prototyping (RP) device and were compressed. The stiffness on the shape after growth analysis became bigger in comparison with that of initial shape.

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In recently years arthroscopic surgery has been applied extensively to many diseases. It requires a skilled operator's performance because of the narrow view and decreased freedom of motion. The virtual reality simulator, DKASTM(Tol Tech, Inc.), conveys tactile sense from cartilage surfaces, behavior of menisci and tonus of cruciate ligaments but authors have found it lacked cutting sensation. This study attempts develop a system that conveys a cutting sensation to the simulation. In order to get the sensation of cutting, we made an apparatus using two load cells, one measuring cutting strength at the handle and the other measuring cutting resistance, and an actuator which provided the resistance. In the first part of the experiment, six subjects cut porcine meniscus with normal arthroscopic surgical scissors. In the second part of the study, the subjects used the new device to simulate the sensation of cutting porcine meniscus through the force feedback system. Compared to cutting porcine meniscus, the apparatus recorded higher cutting force values. However, all six subjects felt a cutting sensation. In future experiments, the practicality of this system will be improved by allowing a high degree of freedom for the apparatus.

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The foot joint has the great mechanisms. One of them is its arch structure. This makes bipedal locomotion possible. However, the mechanism is not elucidated, so engineering research is required. Experimental analysis by a photoelasticity method was done in this research. It targeted the normal foot and the flatfoot. The change in the height of an arch was investigated. And, it was investigated about the influence of a tendon. All loads were static loading. The 3-dimensional experiment was done with the result of two dimensions as reference. The 3-dimensional stress freezing method was used. All the bones of the foot joint were made separately. This is a method good in the model experiment of a living body. First, it experimented by the frame model. It is for knowing the fundamental stress condition of a foot joint. Next, the model in consideration of a muscle and a tendon was made. It is because the influence of a tendon can be investigated by comparing with a frame model. The stress distribution map showed some things. In a normal foot of the Skelton model, the stress of a Calcaneus ground plane decreases outside. A flatfoot of the Skelton model has much more stress concentration. Change in an arch influences the load distribution. And, the tendon had big influence. If a tendon works, stress distribution will move a healthy foot. As for a flatfoot, a function of a tendon will decrease a stress value.

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It is necessary to investigate the crack growth behavior of large deformation under the complex loading in order to maintain reliability of actual structures subjected to seismic forces. Therefore, a large deformation torsion fatigue testing machine is developed. Then, the crack growth behavior of notched plate specimens of stainless steel, SUS316L, used for piping is observed. The fatigue crack growth behavior of surface changed from the shear mode to the opening mode. As a result of fracture surface observation, it is found from crack front geometry that crack growth rate of surface is faster than that of inside. J-integral range of crack front for SUS316L is calculated by finite element method and crack growth characteristic is evaluated by J-integral range. These results corresponded to the mode I crack growth characteristics.

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In this study, low cycle fatigue tests were conducted for low ally steel, SFVQ1A, austenitic stainless steel, SUS316NG, and carbon steel, STS410, in order to investigate internal fatigue crack growth characteristics. The tests were conducted under repeated two-step variable amplitude strain condition to appear beach marks of cracks on the fracture surface. In addition to these tests, tests with surface removal were also conducted to suppress surface fatigue cracks by polishing the specimen surface during the fatigue tests. Cracks initiated from internal inclusion and those fatigue life were slightly larger under surface removal test for SFVQ1A and SUS316NG compared to those under no surface removal tests. STS410 specimen under surface removal test was not broken until its specimen diameter became too small. There was an internal crack observed on the section of the specimen cut longitudinally. Internal crack growth rate calculated from beach marks for SFVQ1A and SUS316NG was similar to that of surface cracks.

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In this study, a method to predict residual life of low-cycle fatigue in austenitic stainless steel (SUS316NG) was proposed based on indentation test. Low-cycle fatigue tests for SUS316NG were first conducted based on uniaxial tensile-compressive loading under the control of true strain range. Applied strain ranges were varied from about 3 to 12%. Their hysteresis loops of stress and strain were monitored during the fatigue tests. Plastic deformation range in hysteresis loop at each cycle could be roughly expressed by bi-linear hardening rule, whose plastic properties involve yield stress and work-hardening coefficient. The cyclic plastic properties were found to be dependent on the number of cycles and applied strain range, due to work-hardening. We experimentally investigated the empirical relationship between the plastic properties and number of cycles for each applied strain range. It is found that the relationship quantitatively predicts the applied strain range and number of cycles, when the plastic properties, or yield stress and work-hardening coefficient were known. Indentation tests were applied to the samples subjected to low cycle fatigue test, in order to quantitatively determine the plastic properties. The estimated properties were assigned to the proposed relationship, yielding the applied strain range and the cycle numbers. The proposed method was applied to the several stainless steel samples subjected to low cycle fatigue tests, suggesting that their residual lives could be reasonably predicted. Our method is thus useful for predicting the residual life of low-cycle fatigue in austenitic stainless steel.

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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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Sn-Ag-Cu solder materials have been used widely. However, the cost is increased by containing Ag. In this paper, tensile and low cycle fatigue properties of Sn-3.0Ag-0.5Cu and Sn-1.0Ag-0.7Cu were obtained at strain rate of 10-4/s order and room temperature. The difference between Sn-3.0Ag-0.5Cu and Sn-1.0Ag-0.7Cu couldn't be recognized for Young's modulus or low cycle fatigue strength. The yield stress and tensile strength of Sn-3.0Ag-0.5Cu were over those of Sn-1.0Ag-0.7Cu. On the other hand, the elongation of Sn-3.0Ag-0.5Cu was lower than that of Sn-1.0Ag-0.7Cu. Using obtained properties, inelastic finite element analysis for a power device was carried out under a thermal cyclic load conditions with large scale stress strain analysis code. The inelastic strain range was 0.45% at the edge of interface between the solder layer and alumina substrate and the fatigue life was estimated at 8,200 cycles.

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Procedure to calculate allowable depth of local corrosion in bottom plate of oil storage tank was proposed to prevent low cycle fatigue due to strong earthquake. The procedure was used to evaluate the possibility of low cycle fatigue failure for bottom plates in tanks in which deep corrosions were detected by continuous ultrasonic examination. In the case the depth of corrosion reaches to the half of original thickness of the plate, it was found that the possibility of low cycle fatigue failure should be considered depending on the configuration of local corrosion.

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Low cycle fatigue tests were conducted using sound elbows made of carbon steel (STPT410). The elbows were subjected to cyclic in-plane bending under displacement control with internal pressure of 9 MPa. Initially, fatigue tests were conducted under constant cyclic displacements. Then, two step fatigue tests were carried out to investigate the influence of cyclic pre-overload on low cycle behavior of elbow on the basis of the previous test results. The fatigue test results were evaluated by using the total usage factor UF_<total> (=UF_1+UF_2), where the UF_1 and UF_2 correspond to usage factor for δ_1 andδ_2, respectively. The residual fatigue life overloaded pipe in UF_1=0.6 was evaluated on non-conservative side by the cumulative fatigue damage rule. On the other hand, the residual fatigue lives in the range of UF_1≦0.4 can be estimated based on the cumulative fatigue damage rule generally. In addition, three-dimensional elastic-plastic analyses were carried out using the finite element method. The crack penetration area and the crack growth direction were successfully predicted by the analyses.

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Generally, the glossness of the lipstick is evaluated by human visual judgment. We irradiated the surface of the lipstick with the light of various wavelengths which was controlled by the band-pass-filter and measured the reflectance from the surface. As for the specimen of lipstick, it was turned to change an irradiation position, and, uneven coloring of the lipstick was evaluated by a change of the reflectance. The evaluation by the light reflectance from lipstick surface accorded with a judgment by the human visual well.Key Words :

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In the present study, the composite titanium (Ti) powder coated with un-bundled carbon black (CB) particles was prepared via a wet process using black ink solution collected from the used ink cartridges of inkjet printing. Un-bundled CB particles were independently and uniformly dispersed in the black ink, and coated on the pure Ti powder surface by dipping the powder into the ink. This coating process showed a uniform distribution of CB particles, and their agglomeration was never detected on the composite Ti powder surface. These composite powders were consolidated as powder metallurgy (P/M) titanium matrix composites (TMCs) reinforced with CB particles by spark plasma sintering (SPS) and subsequent hot extrusion. In-situ synthesized titanium carbide (TiC) dispersoids were uniformly distributed in the extruded composites. The TiC dispersion strengthening was effective for improving mechanical properties of the TMC. Consequently, the TMC showed an excellent balance of high tensile strength of 899 MPa and enough elongation of 18.7 % at room temperature.

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An underwater shock consolidation is effective to obtain denser ceramics and ceramic composites because of the very fast consolidation process within microsecond time scale and high shock pressure, which is generated by detonation of an explosive. The SEP high performance explosive with detonation velocity of 6970 m/s is usually used. In order to consolidate ceramic powders, a peak shock pressure used in shock consolidation is about 5 GPa-15 GPa. The peak shock pressure acting on the powders can be controlled by shape of a water container. The shock-consolidated ceramics and ceramic composites have unique characteristics such as no grain growth, no phase transition and surface bonding/interparticle melting between powder particles, and high electric resistance as well as broadened peaks due to lattice defects.

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Although ceramic particle additives in precursor metallic powder compacts may be effective to avoid the collapse of the foams during the heating process, the excessive addition seems to disturb the expansion itself. To establish a method of stabilizing foam structures without losing foamability of the precursor, the effects of granulating SiC particles before addition to the compacts were examined for A1Si7. By adding SiC powder in the form of granules, the limit of SiC contents due to the drop in expansion was extended. The graded foaming of precursor with three-layer structures was also performed with SiC granules. The stability as well as the foamability of the layered foams was increased, and the effectiveness of granulating SiC particles on the graded foaming was confirmed.

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This study aims to improve the magnetic properties of soft magnetic parts by high densification of green compact in molding of metal powder injection molding (M1M) process. The metal powder used is Permalloy (Fe-Ni alloy) which is used as soft magnetic material. The effects of molding conditions on filling behavior of micro dumbbell specimen were mainly investigated by measuring cavity pressure, the weight and dimension of green compact. The flow analysis was also carried out to simulate the filling behavior in tiny cavity of micro dumbbell specimen.

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This study aims to develop the manufacturing method of metallic stamper for imprinting with micro structures by metal powder injection molding (MIM). The mold used was prepared by imprinting plastic sheet. In the micro-sacrificial plastic mold insert MIM named as p-SPiMIM process, the feedstock composed of Ni (D50=0.74pm) powder and polyacetal-based binder was filled into polymethylmethacrylate mold with line and space patterns from 47gm wide, 150pm high to 6p.m wide, 19pm high, and it was debinded and sintered in H2 and Ar gas atmosphere. The filling state of feedstock into micro-channels and transcriptional property in sintered parts was evaluated by cross-sectional SEM observation. The experimental results revealed reasonable evidences using submicron Ni powder could sinter at low temperature and accomplished high transcription in narrow cavity mold. It can be concluded that the p-SPiMIM process has potential to mass-produce the stamper for imprinting made of versatile highly-durable metals.

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Ti-Nb-Cu shape memory alloys were fabricated by powder metallurgy (PM) process. The fabrication conditions of the alloys and their shape memory properties were investigated. The relative density of the as-sintered alloy was more than 96% at a sintering temperature of more than 1123 K. It was found that the solution treatment is needed to homogenize the microstructure of the as-sintered alloy. Ti-18at%Nb-3at%Cu alloy clearly showed a two-step deformation and a superelastic behavior.

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The fabrication conditions of titanium powder were investigated using a selective laser sintering machine which has a 50 W Yb-fiber laser, a galvanometer scanner and a powder delivery and build system. The optimum laser power, scan speed and scan pitch were investigated by experiments. It was found that the smooth single-scan track can be fabricated at a laser power between 30 and 40 W and at a scan speed between 5 and 10 mm/s, and the width of the smooth single-scan track is around 450 [tm. The smooth surface could be successfully fabricated at a laser power more than 30 W.

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SiC whisker reinforced Si_3N_4 composite was used for studying crack healing behavior. The semi-elliptical surface cracks with the length of 200μm, 600μm, 3mm were introduced on the specimens using Vickers hardness indenter. The cracked specimens were heat-treated at 1000℃, 1100℃, 1200℃ and 1300℃ for 1 hour in air. Bending strength was measured at room temperature in air by three point bending test system. Bending strength of cracked specimen reduced to about 50% of that of smooth specimen. However, bending strength of some pre-cracked and heat treated specimens recovered completely up to that of smooth specimen.

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Authors have previously proposed a process for recycling waste GFRP. In this process, porous glass fiber reinforced ceramics were produced by mixing clay and the crushed waste GFRP, and then firing the mixture (1). In this paper, the bending strength of tiles produced using the waste GFRP such as the sprue and runner produced in the injection molding was examined. From the results, it was clarified that the porous tiles reinforced by glass fibers had high strength. In addition, the relationship between the strength of tiles and the mixture ratio of clay and resin was clarified. On the basis of the experimental results, the equation which can estimate the bending strength of the porous tiles reinforced by glass fibers was proposed.

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Ceramics are expected as high performance bearings. So investigation of the rolling contact fatigue strength is crucially important. To evaluate the effects of the shot peening and crack-healing on the rolling contact fatigue strength, rolling contact fatigue tests carried out on Si_3N_4/SiC composite. The residual stress, the apparent fracture toughness and Vickers hardness were investigated. The rolling contact fatigue strength was improved by compressive residual stress introduced by shot peening. The rolling contact fatigue strength decreased by pre-cracks. However, it was improved by conducting crack-healing and shot peening.

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Effects of dissolution treatment on the Charpy impact value (a_uc) of transparent silicate glasses were studied under 0.18 MPa at 390 Kin the distilled water. The dissolution phenomenon was confirmed by the clearly mass decrease of transparent silicate glasses. Dissolution treatment at less than 0.3 h enhanced a_uc values at the low fracture probability (P_f) of 0.06 were about 5.5 and 4.4 times higher than those of untreated soda and borosilicate glasses, respectively. Additional dissolution treatment at time after more than 1.0 h clearly reduced the a_uc values of both glasses. Consequently, dissolution treatment at short time raised the impact fracture toughness of transparent silicate glasses.

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This paper discussed strength reliability of gadolinia-doped ceria ceramics. By using strength data and fracture origin identification in the previous paper, the authors estimated shape and scale parameters in Weibull distribution on an assumption that all defects except for pores were removed from the GDC ceramics by improving its processing. It was revealed that strength reliability of GDC ceramics was remarkably increased when impurities as fracture origins were eliminated from the GDC ceramics.

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This paper presents probabilistic approach for estimating the dynamic fatigue strength inceramics under variable stress rate. First, a probabilistic model was proposed on the basis of the slow crack growth concept in conjunction with two-parameter Weibull distribution. Second, the four-point bending test was carried out for alumina ceramics under two-step stress rate at room temperature. The experiment result was compared with the predictions to verify the validity of the model. The fracture surface of the specimen after the bending test was also observed. It is seen that mirror, mist and hackle in the vicinity of the surface acting maximum stress. Therefore, the dynamic fatigue fractures under variable stress rate caused by slow crack growth from an initial crack. We constructed fracture probability - bending strength diagrams (F-S diagrams) with the experimental results using the model. The F-S diagrams were in good agreement with Weibull plots of the bending strength.

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2.7eV and 1.9eV photon emissions (PEs) were measured during crack propagation in brittle fracture of silica glass, borosilicate glass and soda-lime glass. In silica glass, an intense 2.7eV-PE was observed at the beginning of the crack propagation, and 1.9eV-PE was detected during the crack propagation. On the other hand, only an intermittent 2.7eV-PE was observed in both of borosilicate glass and soda-lime glass. The difference on the PE characteristics could be related to that on microscopic processes in the crack propagation. This result implies that the PE is a tool to study crack propagation in brittle materials on a microscopic scale.

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In this study, tensile tests of indium tin oxide (ITO) deposited on polyethylene naphthalate (PEN) films (ITO + PEN films) used in dye-sensitized solar cells (DSCs) were carried out. ITO + PEN films are fabricated at 150℃. Therefore, to clarify the influence of heat treatment on mechanical properties of ITO + PEN, the specimens with heat treatment were prepared. In order to discriminate AE signals in ITO from PEN films, PEN film specimens (ITO was removed by 17.5% hydrochloric acid) were also prepared. It was found from tensile tests that many AE signals were detected in ITO + PEN films, while few AE signals were detected in PEN films. On the other hand, the electric resistance of ITO was also measured during tensile tests. These results suggested that the critical damage in ITO was detected by the AE measurement more sensitively than the electric resistance. To identify AE sources, in-situ observation of specimen during tensile test with AE measurement was carried out. It was emphasized that AE behavior shows good agreement with the cracking behavior in ITO. Damages in ITO under mechanical strain were successfully monitored by AE technique in the present study. Consequently, it was suggested that AE technique could be a powerful technique for evaluating the damage accumulation process in DSCs.

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For the purpose of enhancing tensile strength of carbon/carbon (C/C) composites, an attempt was made to reduce the interfacial strength. Previous studies suggested that increase of fiber spacing (reduction of volume fraction) is one of the possible ways to do so. In this study, therefore, carbon black (CB) particles were incorporated between the carbon fibers to increase fiber spacing. In this process, CB particles were preliminary mixed with phenolic resin, in which a fiber bundle was dipped for impregnation, followed by the conventional resin-char process. It was found by microstructural observation that the CB particles were well dispersed in C/C composites and the fiber spacing was obviously increased by the CB addition. It was also suggested that the CB addition is effective to enhance tensile strength as shown in the tensile test results with 20wt% CB added specimen. Although magnitude of increase was rather low, the tensile strength of C/C composites is expected further enhanced by optimizing processing conditions.

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The effect of nickel interface layer on the mechanical properties of SiC fiber / SiC matrix composites was examined. Pure nickel was plated on the surface of SiC fiber (Tyranno Lox-M fiber) using non-electrolytic plating method. Amorphous SiC (Si-C-0) matrix was formed using polymer impregnation and pyrolysis (PIP) process of poly-titano-carbosilane (PTCS). Flexural tests were carried out at room temperature to evaluated the mechanical properties. The resultant SiC/SiC composites exhibit nonlinear load-displacement behavior before the final failure. Pullout behavior of SiC fibers was clearly observed at the fracture surfaces. The experimental results suggest that the suitable interfacial properties were achieved applying a nickel interface layer between SiC fiber and Si-C-0 matrix.

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Carbon-fiber-reinforced SiC matrix (C/SiC) composite is one of the promising materials for the combustion chamber of satellite thrusters. The most common processing of C/SiC composite is polymer impregnation and pyrolysis (PIP) method. However, due to the low volume yield of pre-ceramic polymers after pyrolysis, repeated PIP is required to obtain high density C/SiC composite, yielding high processing cost. In this research, to reduce the processing cost, the space in a 2D carbon fiber preform is first filled with SiC powders by a vacuum assisted slurry infiltration method. The powder filled preform is further densified by PIP method. It was found that the infiltration behavior of SiC powders during a vacuum assisted slurry infiltration method successfully make it possible to densify the preforms when the slurry is infiltrated from both surfaces. It was also suggested that the slurry with higher concentration efficiently densifies the preform. Since 35 vol% of vacancy still remains at present, pressure assisted impregnation process has been also examined.

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