A finite element analysis was carried on microscopic fracture process of the matrix resin layer in FRP laminates for the mode II interlaminar fracture. The analysis revealed the following microscopic fracture process. (i) First, the microcrack initiated at the main crack tip owing to the principal stress followed by successive microcracks at even intervals with increasing the shear strain. (ii) Then, the delamination at the interface between fiber and the matrix initiated at the forthermost microcrack from the crack tip and propagated towards the crack tip owing to the shear stress. (iii) Finally, microcracks were connected by delamination. The effects of the matrix resin layer thickness and the fiber mechanical properties on the interval of microcracks were also investigated. The interval of microcracks was linearly correlated with the matrix resin layer thickness and was not affected by the fiber mechanical properties.

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In this study, a temperature independent damage evaluation parameter is proposed. Ultrasonic wave velocity was measured for different propagation direction in order to evaluate angular dependence of ultrasonic wave propagation. Every experiment was conducted at constant temperature to eliminate influence of temperature variation. Consequently, it was found that anisotropy of wave velocity does not change even if temperature changes, although wave velocity itself changes with temperature. It was also found that formation of cracks causes significant change in ultrasonic anisotropy. Therefore, it can be used as a temperature independent damage evaluation parameter for FRP laminates.

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The fatigue tests of interfacial debonding were carried out to investigate the influence of a wet environment on the propagation properties of interfacial debonding of Aramid/Epoxy composite. For this purpose a specially designed model composite was developed, where single fiber was embedded in epoxy matrix : the fiber/matrix interface could be observed clearly. In dry air, interfacial debonding propagated faster than in laboratory air, whereas it hardly propagated in wet air. The propagation rate of interfacial debonding slowed down and retarded although a constant fatigue load was applied to the sample. This behavior was considered to be owing to the friction stress on debonded wakes.

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Reversed plane bending fatigue tests were conducted for two kinds of fine-grained Aluminium alloys (Nano aluminium) different in micro structures. The effect of specimen collection orientation was also investigated using totaly four kinds of specimens. Initiation and initial growth behavior of small fatigue crack were observed by means of plastic replicas technics. It was found that either inclusions or weak boundary between powders were responsible for fatigue crack initiation depending on the materials. Hardly any difference was found in crack growth behavior among those materials.

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In order to investigate facture mechanism of super-high cycle fatigue and subsurface inner failure, high cycle fatigue test was conducted for rotating bending on SUJ2 steel and SCM435 steel, and for pure bending and pure torsion on SNCM439 steel. FRASTA analysis to simulate the process of fatigue crack propagation using 3D configuration of coupled areas of opposing fracture surface via computer was conducted.

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This paper describes the low cycle fatigue lives under nonproportional straining paths using type 304 notched specimens at room temperature. Nonpropotrtional low cycle fatigue tests under 6 strain paths using 3 kinds of notched specimens were carried out and the number of cycles to crack initiation was determined by DC potential method. Nonproportional crack initiation cycle was strongly dependent on strain history and stress concentration factor of the specimen.

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This paper describes the nonproportional fatigue life prediction for type 304 notched specimens under nonproportional loading. Finite element analyses were carried out for 6 types of proportional and nonproportional paths to calculate the strain state at notch root. The nonproportional strain proposed by Itoh et al. was applied to the experimental data in combination with the finite element results. The nonproportional strain at the notch root properly correlated the crack initiation lives under 6 types of strain paths.

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Distribution of biting pressure applied on each tooth is measured by using the "Dental Occluzer System" and each occlusal force is then numerically converted by the developed system. 3-D finite element analyses are performed for the obtained occlusal loading with a set of teeth model including the mandible and the principle muscular system modeled by the beam element. The occlusal mechanical balance with the reaction to the TM joint can give useful information for considering the fracture of dental implants and the malocclusion of natural teeth.

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Temporomandibular joint(TMJ) disorder relates to the mechanical irregularity of the structual joint components, and disc and behevior of retrodiscal tissue is considered as a key to understand the biomechanical condition in the TMJ. Permanent anterior disc displacement and derangement are typical finding in TMJ disorder. The mouth opening motion naturally induces the anterior disc displacement tentatively even in normal TMJ. Since the condyle motion has the direct influence on the soft tissue stress, this study examined the possibility of the rearrangement of stress in disc and retrodiscal tissue by adjusting the condyle trajectory in the context of finite element analysis with individual modeling.

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On a structure using the material which demonstrates its mechanical function to the limit under given conditions, the most effective design of the function can be expected because the design of material and structure matches pertinent. One of the actual structures is natural bone. Design concept is based on the assumption that bones have optimum structures to mechanical conditions. For a long evolution process, bones have tried remodelling many times and have demonstrated its mechanical function to the limit. Therefore, development of the new material that considers the modelling of the mechanical composite structure of the bone to the optimum design of the new material, that is biomimetic design, is very rational thought. Cortical bone is the objective material of biomimetic design for the load support. At the beginning of our biomimetic design, the relation between the orientation of collagen fibers and the load support characteristics of cortical bone is investigated. The orientation of collagen fibers was measured by using square pillar specimens obtained from bovine femurs. Static compression tests were carried out using pillar specimens and internal micro fractures were observed by SEM. The characterization of the stress-strain curves was discussed on the fiber orientation and the micro fractures.

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Collagen fascicles obtained from mouse tail tendon were cyclically loaded to 90,75,and 50 % of their tensile strength. The mean repetition number to failure was 4,7,and 129 in 90,75,and 50 % groups, respectively. Microscopically, the partial rupture of some fibers was observed before the complete failure of the fascicles.

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Effects of cyclic load on the mechanical properties of ligament-like tissue constructed in vitro were studied. Fibroblasts obtained from the rabbit anterior cruciate ligaments were seeded within collagen gel which was combined with biodegradable polymer mesh. The fibroblast-collagen gel-mesh complexes were cultured for 7,14,and 21 days under non-loaded or cyclic loaded conditions (non-loaded and loaded groups, respectively) and, then, tensile tests of thus reconstructed ligament-like tissues were performed. Cross-sectional area of the complexes decreased with culture period in both groups, and the maximum load of the tissues markedly decreased by 14 days, The maximum load at 21 days was almost the same as that at 14 days in the non-loaded group; however, that in the loaded group was larger at 21 days than at 14 days. These results indicate that cyclic load may improve the mechanical properties of the reconstructed ligament-like tissues.

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U1trasound diagnosis is imaging diagnosis for a clinical use. By using contrast agent, this ultrasound diagnosis obtain more clear image and possible to precise diagnose .In this study, we tried to prepare bubble contained alginic gel particles as new ultrasound contrast agent. Nitrogen bubble contained gel particles were made by atomizing a nitrogen solved alginic acid solution using a solid injection nozzle. An ultrasound scattering intensity of these particles was measured. As a result, we could prepare bubble contained gel particles having some strong ultrasound scattering characteristics. However, a diameter of these bubbles is too large for use of an ultrasound contrast agent in the moment.

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We have developed a confocal microscope for fluorescence lifetime imaging by asynchronous sampling. This system consists of a fast response photomultiplicr, a fast sampling module, and a low-pass filter and a colnfocal microscope. Since imaging by laser scanning and detection is asynchronous with laser excitation. It is possible to attach the detection system to the commercial confocal microscopy system. We also observed the relationship between the concentration of Ca^<2+> and the fluorescence lifetime of fluo-3,and confirmed that the fluorescence lifetime is sensitive to the concentration of Ca^<2+>.

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In this study, simulation experiments in vitro on a blood-pressure measurement when a radius artery was locally compressed at a protuberance of a radius by a small pneumatic cuff were performed. Temporal change in internal pressure in a tube, a cuff pressure and a flow rate were measured during a cuff pressure decreasing. A cuff pressure waveform was analyzed to estimate maximum, minimum and mean pressure in a tube by an oscillometric method and a frequency analysis of the waveform. As a result, the pressure shown the maximum amplitude of a power spectrum agreed with the mean value of the internal pressure. However, an internal pressure in a tube could not be estimated using oscillometric method.

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Tensile properties of contracted and relaxed vascular smooth muscle cells (VSMCs) were determined. VSMCs were isolated from the rabbit thoracic aorta with an enzymatic digestion method. Each cell floated in Hanks' balanced salt solution of 37 ℃ was attached to the fine tips of a pair of micropipettes with an urethane resin, and contracted and relaxed with norepinephrine and papaverine, respectively. Then the cell was stretched at the rate of 6μm/sec by moving one of the micropipettes with a linear actuator. Load applied to the cell was measured with a cantilever-type load cell : its elongation was determined from the distance between the micropipette tips using a video dimension analyzer. Activated (contracted) and passive (relaxed) VSMC_s were not broken even at the tensile force of 6.5μN and 1.7μN, respectively. Their stiffness was significantly higher under activated condition (0.89N/m) than under passive one (0.14N/m). The higher stiffness in contracted cells is attributable to the tension generated by contractile apparatus and reorganization of actin filaments.

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It has been known that erythrocytes can deform largely to go through capillaries. It has been considered that the deformability of erythrocytes affects microcirculations characteristics. Therefore it is important to clarify the deformability of erythrocyte at capillary vessels. In this study, microchannel array simulating human blood capillaries was fabricated on a silicon substrate and erythrocytes were observed flowing through the microchannel using a microscope. The fabricated chip whose microchannel was 5 μ m in square cross-section and 100 μ m in length, had 200 microchannels to observe the deformation of erythrocyte. As a result, the deformation of erythrocytes in the microchannel were observed

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In this study a model blood was produced in order to use in an in vitro experiment to simulate a circulation. Blood consists of red blood cells and blood plasma. Therefore we produced alginic acid gel particles as a model blood cell, and made a dispersion agent that consists of the model blood cells and a solution of calcium chloride as a model blood. A solution of alginic acid sodium was atomized by a nozzle, and was poured on a solution of calcium chloride to lead to a chemical reaction to form the alginic acid gel particles. In this study we tried t produce the fine particles of alginic acid gel having a similar diameter to that of red blood cells. A new alginic acid gelation system was designed to produce smaller gel particles. As a result, gel particles ranging from 1 to 5 μ m in diameter would be produced.

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The effects of sputtering gas pressure on the relationship between bias voltage and the mechanical properties, residual stress, hardness, toughness and adhesive strength of TiN films deposited on carbon steel S45C by D.C. magnetron sputtering was investigated. The residual stress once increased and then decreased with increasing bias voltage at relatively low gas pressure 0.5Pa and 0.8Pa, but increased monotonously at higher gas pressure 1.76Pa. The adhesive strength decreased with increasing bias voltage at gas pressure 0.5Pa, but increased with increasing bias voltage at 1.76Pa. The both changes of hardness and toughness could be related directly to residual stress, irrespective of the value of the bias voltage and the gas pressure, but the variation of adhesive strength could not explain only by the residual stress. In order to explain it, it should be necessary to take the increasing of the adhesive strength by the mixing between sputtered particles and the substrate surface promoted at lower gas pressure into consideration.

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Shear delamination strengths of plasma-sprayed CoNiCrAlY coatings were examined using an edge-indentation method. In order to examine the effects of spraying treatments on delamination strengths of sprayed coatings, APS CoNiCrAlY, LPPS CoNiCrAlY and LPPS CoNiCrAlY with diffusion thermal aging were fabricated. Load-displacement curves during the indentation were measured, and delamination energy per delamination area was estimated. The delamination load was large when the distance from an edge was large, however the energy was almost independent of the distance from an edge. The delamination energy of APS coating and LPPS coatings were found to be almost the same. The delamination energy of the LPPS coating with diffusion thermal aging was found to be larger than those of both APS and LPPS coatings. It was concluded that diffusion thermal aging was effective in improving the delamination strength.

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Evaluation of the mechanical properties of microelements is difficult because of the small size of the specimens. In this paper, a tensile testing machine for a microelement was developed using the glue grip and the double-field-of-view microscope. Using this system, the tensile strength and Young's modulus of polysilicon specimens have been measured. The tested part of the specimen is 250μm in length, 11μm in width and 3.8μm in thickness. The tensile strength measured was 2.2±0.2 GPa.

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The weight reduction in vehicles without decreasing their safety is an important subject in manufacturing automobiles to improve the fuel efficiency and eventually to reduce the environmental pollution. To use high-stiffness urethane foam is one of the possible solutions to improve the body stiffness and the energy absorption of the vehicle. Therefore it is important to clarify the consolidation condition of the urethane foam under multi-axial loading conditions. Compaction properties of the uretahne foams were examined through both uniaxial compression and three-dimentional compression tests. Experimentally obtained true stresses at several compaction densities are shown on the Rendulic plane where principal stresses σ_2 and σ_2 take the same value. From the results compaction behavior of urethane foam is found to be successfully described by the constitutive equation proposed by Oyane & Shima (1976) for porous materials.

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To investigate the effect of environment on fatigue strength, commercially pure aluminum wires of 1mm diameter was employed for the fatigue tests. By electrolytic polishing, the minimum diameter of 200μm or 600μm was obtained. It was found that the variations in fatigue life at the same stress amplitude were much larger than that for large specimens, and the variations in fatigue life were larger for smaller specimens. There were two types of fracture morphology in both air and 3%NaCl aqueous solution.

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Fatigue crack growth behaviors at elevated temperatures were investigated for SUS304 stainless steel. Fatigue crack growth tests were conducted in the near-threshold region using single-edge-cracked specimens at 350,550,and 650(℃). Crack growth behaviors of SUS304 in a vacuum were compared with those in air. It was found that the crack growth rate da/dN in a vacuum was as low as one-tenth of that in air. Threshold value, ΔK_<th>, was higher than that in air. The crack growth restarted when the maximum stress intensity factor, K_<max>, was increased for a crack exhibiting threshold behavior. An investigation of the fractal properties of fatigue fracture surfaces in SUS304 steel tested at 550℃ was performed. It was found that measured values of fractal dimension was scarcely dependent on stress intensity factor range ΔK.

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Understanding the surface crack growth is important to clarify the mechanisms of rolling contact fatigue (RCF) of SUJ2,because the surface defects are made by indentations and cause flaking failure. In the present work, the small holes were artificially made prior to the RCF tests and the initiations of the surface cracks from the holes were observed. Based on the features obtained by the experiments, the initiation and propagation of the cracks from the holes were evaluated by calculating stress intensity factors.

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Testing for bending fatigue crack propagation under mixed-mode condition was carried out using the fatigue and the annealed slant precracks with the different slant angles, β, in a rectangular plate. As a result, bent fatigue crack from the fatigue precrack with β=45deg. propagated under mixed-mode condition with the mode II stress intensity factor (K_<II>)_<est>, while that from the fatigue precrack with β=60deg. propagated under mode I crack behavior. This is because the compressive residual stress near the fatigue precrack was apt to contact between the upper and the lower crack surfaces in the precrack with smaller slant angle. The fatigue crack propagation rates during bending had almost the same relation for all the data, using the mixed-mode stress intensity factor (K_M)_<est>, which derived from the (K_I)_<est> and (K_<II>)_<est> evaluated from the discontinuous displacement measured along the crack.

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Fatigue crack growth tests under variable amplitude load sequences were carried out using compact tension specimens of Ti-6Al 4V alloy. Fatigue crack growth rate and macroscopic crack closure were measured by means of an unloading elastic compliance method. The effect of frequency and overload ratio on fatigue crack growth rates were discussed in terms of effective stress intensity factor range, ΔK_<eff>.

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The stress shielding effect in silicon nitride plays an important role on the improvement of crack growth resistance. In this study, the effect of compressive loading on stress shielding and cyclic fatigue crack growth behavior at elevated temperature was investigated. In order to clarify the crack growth mechanism at the vicinity of a crack tip, cyclic fatigue tests of silicon nitride at elevated temperature (1273K) under various stress ratios including negative stress part were conducted. As a result, crack growth rate at elevated temperature was found to be lower than that at room temperature. Especially under high compressive loading, crack growth rate was extremely lower than the crack growth rate under the positive stress ratio. It may be caused by the healing of process zone under the negative stress ratio at elevated temperature.

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Cyclic fatigue crack growth behavior in Si_3N_4 was investigated using a small bending specimen with a micro notch. The micro notch was introduced by a Focused Ion Beam device. The bending fatigue tests were carried out under constant amplitude load at stress ratio R=-1. Fatigue crack growth rate and macroscopic crack closure were measured by means of an unloading elastic compliance method. It was found that the crack growth rate of a small crack was faster than that of a long crack due to the immaturity of grain interlocking.

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In this paper, we deal with an isothermal plane elastic problem of an inhomogeneous medium. As an analytical model, we consider the plane elastic problem for a thick plate with a Griffith crack in arbitrary position subject to uniformly distributed internal pressure on the crack surfaces. Making use of the fundamental equations system, which is already established in our previous paper, the analytical solution for such singular stress field is successfully developed. The elastic behaviors are evaluated through the numerical calculations.

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Damage evolution of random particulate composites is formulated by combined micromechanics and damage mechanics. Damage mechanics is applied to filler particles to describe interfacial debonding, which in turn incorporated into Mori-Tanaka's mean field theory for stiffness prediction of damaged composites. The model uses an energy balance concept to account for nonlinear behavior due to particle debonding. With this model, the effect of partial debonding on anisotropic damage development of composites are analytically investigated.

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It was discovered that the stress fields caused by the spherical Hertzian contact fulfill the mechanical conditions of a plate subduction boundary, and also that crack growth under rolling contact fatigue simulates the behavior of plate subduction boundaries. Great similarities are found between the earthquake faults and subsurface cracks under rolling contact fatigue

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A buckling analysis is carried out for inhomogeneous rectangular plates under in-plane compression. It is assumed that inhomogeneous material property of Young's modulus of elasticity is changed in the thickness direction with the power law, while Poisson's ratio is assumed to be constant. Based on the Kirchhoff (or classical thin) plate theory, the fundamental equations system can be derived by introducing the technique of the newly defined position of the reference plane. The critical buckling loads of the simply supported rectangular plate are presented using the derived fundamental relations. Effects of the inhomogeneous Young's modulus of elasticity, material orthotopy, aspect ratio and thickness of the plate are discussed.

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This paper is concerned with theoretical treatment of a thermoelastic buckling problem for a rectangular plate which possesses orthotropic material properties in in-plane direction and inhomogeneous properties in thickness direction. We assume that rectangular plate is subjected to a non-uniform heat supply from both boundary surfaces and has symmetric material properties in thickness direction which is given by power product form of thickness coordinate z. Three dimensional temperature change in a steady state and associated thermoelastic buckling behavior are developed theoretically for an orthotropic inhomogeneous rectangular plate under mechanical boundary condition of simply supported edge. Effects of orthotropy and inhomogeneity in material properties on critical buckling temperature change and post-buckling behavior in a rectangular plate are examined through numerical calculation.

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An approximate analytical solution is presented for free vibration of a symmetrically laminated curved panel with simply supported (SS2), clamped (CC2), as well as mixed simply supported and clamped boundary conditions. The coupled partial differential equations with associated boundary conditions to first-order shear deformation theory are solved by using modified Galerkin method; vibration fequencies and mode shapes are determined. Effects of the boundary conditions, thickness ratio a/h, curvature, R/h, and lamination angle, θ, on the vibration frequency are discussed.

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This study is concerned with theoretical development for thermally induced vibration problem of an inhomogeneous beam. We suppose that thermal and mechanical material properties in beam are given as power function in term of transverse coordinate z. Firstly, we have developed one-dimensional transient heat conduction problem of an inhomogeneous beam due to cyclic heat supply. Then, we have developed thermally induced vibration problem of an inhomogeneous beam clamped at one edge and free at opposite edge. Next, we have carried out numerical calculations and have discussed about effects of both cyclic temperature fluctuation and inhomogeneity of material properties on thermal displacements, thermal stresses and resonance characteristics.

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In this study, the theoretical analysis of two-dimensional transient piezothermoelasticity is developed for a two-layered composite strip consisting of piezoelectric materials of crystal class mm2,subject to nonuniform heat supply in the width direction. Using the analytical procedure of a laminated of composite strip model, we obtain the exact solution for the two-dimensional temperature change in a transient state, and two-dimensional transient piezothermoelasticity of simply supported combined strip under the state of plane strain. Numerical calculation are carried out and the numerical results are shown in figures.

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A stochastic temperature solution is derived for the heat conduction problem in a nonhomogeneous plate with random thermal conductivity by the perturbation method and the Laplace transform. The nonhomogeneous plate has the exponential variations in the thermal conductivity and mechanical properties through the plate thickness and is heated by the prescribed deterministic temperature on the plate surface. A stochastic thermal stress problem in the nonhomogneous plate is analysed for the random thermal conductivity or the random coefficient of linear thermal expansion by the reported thermal stress expression by one of present authors. Numerical results of the variance of thermal stress are presented for the case that the randomness in the thermal conductivity and coefficient of linear thermal expansion is assumed to be a uniform distribution.

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