On the assumption that an impregnation of polyimide using the filament winding method, the impregnating ability of polyimide into a PAN based high strength carbon fiber bundle was discussed. Polyimide precursor solution (Skybond 703) for the prepreg manufacturing process was diluted to control viscosity in a range from 0.01 to 1.41 Pa·s by n-methyl-2-pirroridon (NMP). Impregnation into a carbon fiber bundle (T 1000 GB-12000) was under atmospheric pressure. The impregnated bundle was heat to 343°C for imidization. The bundle was held vertically and also horizontally on a substrate. Fiber volume content of the prepared bundle was measured from the cross-sectional morphology by optical microscopy. When the impregnated bundle is laid level on a substrate buring the heating process, the viscosity of the precorsor solution from 0.1 to 0.6 Pa·s must be adjusted to obtain the desired fiber volume content of 50-60 vol% for the carbon fiber reinforced polyimide.

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To improve unwanted pigments in the skin laser light is irradiated on the pigmented lesion. Melanin, locally existing in the skin, selectively absorbs the laser light. At the present time, the laser guns used in dermatology are manually operated and their laser spots are as large as 3 to 7 mm in diameter. It is thought that normal tissues, which do not contain melanin so much, are hardly damaged by the laser irradiation. However, in reality terrible burns appear after the laser irradiation even in the normal tissue. We have developed a new type of laser apparatus for removing only the pigmented lesions with laser scanning technology. A fθ lens unit assembled by a shrink fitter can focus the laser beam well over a wide scanning width. The effect of the laser pinpoint irradiation to only the pigmented lesions on the pigmentation therapy was experimentally examined with the developed apparatus. As a result, the pigmented lesions were able to be removed without affecting any damage to the surrounding tissue. Thus, the laser pinpoint irradiation was proved to be effective in the pigmentation therapy.

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In this paper, a new inverse analysis method were introduced for optical computed tomography (optical C.T.). In optical C.T., near-inferred light is exposed into human body and scattered light is measured to detect a oxygenated part. This inverse problem is reduced to estimate the absorption distribution from scattered light on a surface of human body. To relax the ill-posed of this inverse problem, we proposed this problem is reduced to 0-1 integer problem by considering absoption coefficient as two discrete values of tumor and normal tissue. And severe constraint on discrete value is relaxed by treating absorption coefficient as probability variable. Simple 3D example problem was solved to demostrate the usefulness of this method.

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In this study, to determine incremental, perturbed displacement fields in periodic inelastic solids, an incremental homogenization problem is fully implicitly formulated using a linearized constitutive relation, a micro/macro-kinematic relation, and a stress balance equation. It is shown that the homogenization problem can be iteratively solved with quadratic convergences by successively updating strain increments in unit cells, and that the present formulation allows versatility in the initial setting of strain increments in contrast to Terada-Kikuchi (2001) and Miehe (2002). This homogenization algorithm is then examined by analyzing a holed plate, with an elastic-plastic micro-structure, subjected to tensile loading. It is thus demonstrated that the convergence in iteratively solving the homogenization problem strongly depends on the initial setting of strain increments in unit cells, and that quick convergences can be attained if the initial setting of strain increments is appropriate.

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The feasibility of the GeoFEM as the platform of parallel finite element method on the earth simulator was investigated. Since the earth simulator consists of 640 SMP nodes and each node has 8 vector processors, there are three level hierarchical parallelization methods : One is inter-node, the others are intra-node and vectorization. The GeoFEM shows extremely high inter-node parallel efficiency, however, it is not yet examined in over one thousand processor environment. Furthermore, the hierarchical architecture of the Earth Simulator requires the optimization for intra-node paralleization and vectorization for better practical performance. Some ordering methods were used to accomplish the, intra-node parallelization and vectorization, and we achieved to 10 tera flops on 6.4 GDOF problem finally.

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In general, internal cells are required to solve elastic problems with centrifugal load in non-homogeneous materials using a conventional boundary element method (BEM). However, in this case, the merit of BEM, which is ease of data preparation, is lost. In this study, it is shown that two-dimensional elastic problems with centrifugal load in non-homogeneous materials with variable mass density can be solved without the use of internal cells, using the triple-reciprocity BEM. A body force distribution is interpolated using boundary integral equations. A new computer program was developed and applied to solving several problems.

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In this paper, elastoplastic nonlinear behaviors of circular tubes with grooved surface subjected to axial compression are studied by using finite element method. The effect of grooves is to control the deformation pattern and to decrease the fluctuation in the load-displacement curve for circular tubes. It is found from numerical results that the deformation mode corresponding to the corrugation can be classified into aisymmetric mode and non-symmetrical mode, and the axisymmetric mode is classified into progressive crush mode, in which compressive force vibrates with the wrinkles forming one after another, and simultaneous crush mode, in which compressive force increases uniformly. A mode classification chart is produced for various combination of wavelength 2λ and wave-altitude a.

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Bio-compatible piezoelectric materials are becoming important for actuators and sensors in medical devices, that is Bio-MEMS such as health monitoring systems and drag delivery systems. In this study, we focused on perovskite-type compounds ABX₃, and searched systematically new bio-compatible and lead-free piezoelectric materials by first principles calculation. Especially, halogen and chalcogen atoms were widely applied to X. And then, a crystal system distinction based on Pauling's rule was proposed to find the compounds with good piezoelectric response. The validity of crystal system distinction was proved by application to existing compounds and first principles evaluation. The obtained new compounds were distinguished among cubic, tetragonal and orthotropic structures, and their stable crystal structures were evaluated by first principles calculation.

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Asymmetric three-point bending of a layered beam containing an interior interface crack is analyzed on the basis of classical beam theory. The point of load application is assumed to lie on the delaminated part, so that a part of the crack faces is contacting one another, while the remaining part of the crack faces is open. Axial compressive and tensile forces are induced by bending in the parts of the beam above and below the delamination and they are determined by modeling the cracked part as two lapped beams hinged at both ends. When the magnitude of the applied load is small, the beam deflects retaining mutual contact of whole crack faces, but as the applied load reaches a critical value, local delamination buckling occurs. The relation between the magnitude of the applied load and the deflection at the point of load application is found to be nearly bilinear. The validity of this prediction is confirmed by experiments. It is also shown that once the delamination buckling occurs, energy release rate generally becomes larger as compared with the case of perfect contact of delaminated surfaces.

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This study investigates the electromechanical fracture behavior of a normal crack in a piezoelectric material strip subjected to a uniform heat flow far away from the crack region. The crack faces are supposed to be insulated thermally and electrically. By using the Fourier transform, the thermal and electromechanical problems are reduced to singular integral equations, respectively, which are solved numerically. Both the cases of an internal crack and an edge crack are studied. Numerical calculations are carried out, and detailed results are presented to illustrate the influence of the crack location and length on the temperature distribution and the stress intensity factors.

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In this paper, we consider a dynamic problem of a functionally graded piezoelectric material (FGPM) strip containing a crack parallel to the boundaries. It is assumed that the electroelastic properties of the strip vary continuously along the thickness direction of the strip, and that the strip is under the in-plane mechanical and electric impact in the nonhomogeneous direction. The problem in this case is always a mixed-mode problem. Integral transform techniques and dislocation density functions are employed to reduce the problem to the solutions of a system of singular integral equations. The system of singular integral equation is solved by using the Gauss-Jacobi integration formula. Numerical methods are then employed to obtain the time dependent solution by way of a Laplace inversion technique. The dynamic stress and electric displacement intensity factors versus time are presented for various values of dimensionless parameters representing the crack size, the crack location, the material nonhomogeneity and the loading combination.

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In this paper, the mixed-mode thermoelectromechanical fracture problem for a functionally graded piezoelectric material (FGPM) strip is considered. It is assumed that the thermoelectroelastic of the strip vary continuously along the thickness of the strip, and that the strip is under the thermal load. The crack faces are supposed to be insulated thermally and electrically. By using the Fourier transform, the thermal and electromechanical problems are reduced to a singular integral equation and a system of singular integral equations, respectively, which are solved numericaly. Numerical calculations are carried out, and detailed results are presented to illustrate the influence of the crack length, the crack location and the material nonhomogeneity on the stress and electric displacement intensity factors. The temperature-stress distributions are also presented. The normalized intensity factors are under the great influence of the geometric parameters. The effect of the material nonhomogeneity on the intensity factors depends on the geometric parameters.

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Porous ceramics possess the excellent penetration and adiabatic characteristics, etc., and are used as heatproof filter materials for environmental equipments, etc. Moreover, porous ceramics controlled with porosity and pore size in the wide range have been actively developed. However, how the strength characteristics of porous ceramics are influenced by porosity and pore size of the material are not understood still enough. In this research, the evaluation tests on fracture strength, fracture energy and fracture toughness of porous alumina ceramics specimens which porosity are almost equal, while pore sizes are different mutually were performed, and the relation between the pore size and the fracture strength was obtained. The tests results show that the dispersion of fracture strength data is few though fracture strength of porous ceramics is lower than that of high-density ceramics. Moreover, the relation based on linear fracture mechanics between the defect size and the fracture strength is valid when the one that a pore accompanies with the peculiar defect observed in fracture surface of the material was assumed to be a defect size. In addition, fracture energy increases with the increase of pore size, and this seems based on a crooked propagation path of a crack. Finally, the process zone fracture model by considering the effect of the pore and grain size of the material are presented. According to this model, for all pore size and crack length, it was shown that the fracture strengths of cracked specimens are evaluated.

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Local approach to fracture based on continuum damage mechanics and finite element method is a powerful method to estimate fatigue strength, which can reduce computing time and cost for the analysis of fatigue crack initiation and propagation. In the present study, this approach has been applied to the analysis of the behaviors of circular cracks in stainless steel pipes under thermal cyclic loading. The obtained solutions have been compared with the experimental results to discuss the accuracy of uncoupled, locally-coupled and fully-coupled approaches. A new technique to remove the mesh-dependence of the solutions has been proposed and its validity has been discussed through numerical studies on the low-cycle fatigue crack propagation.

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In order to clarify the effects of a hydrogen gas environment on the fatigue characteristics of stable austenitic stainless steels, bending fatigue tests were carried out on SUS316L in a H₂ gas, in a N₂ gas of 1.0 MPa and in air. The fatigue tests were also carried out on a metastable austenitic steel SUS304 as a material for the comparison. The main results obtained are as follows. Hydrogen gas accelerates the fatigue crack growth rates of both materials. The fracture surfaces of the both materials consist of two parts practically ; the faceted area seemed to be brittle and the remaining area seemed to be ductile. The faceted area does not significantly contribute to the acceleration of the fatigue crack growth rate, but the ductile fracture mode predominantly does. The slip-off mechanism seems to be valid not only in air and in N₂, but also in H₂. The fatigue crack growth acceleration by hydrogen occurs in this mechanism. The difference of the degree of the acceleration, which is smaller in SUS316L than in SUS304, seems to be caused by the difference in the stability of γ phase.

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Fatigue crack propagation tests were performed using specimens with multiple parallel edge notches at regular intervals. Fatigue pre-cracks of uniform length were successfully introduced by eccentric tension-compression loading at ten odd notches located in central part of the specimen. After pre-cracking, fatigue crack propagation tests were carried out under 4-points bending loading. Central eleven cracks of the specimen were located within the inner span of bending in which the bending stress was kept constant. These eleven cracks propagated at almost the same rate when the cracks were relatively short. After the cracks grew a few milli-meters, however, the propagation rate of some cracks was selectively accelerated while that of the other cracks decelerated. In addition, a series of finite element analyses, were performed for multiple edge cracks whose lengths were different alternately. Stress intensity factor solution for these cracks was developed and utilized to simulate experimental results. As a result, the developed solution could successfully simulate the complex propagation behavior of the multiple cracks.

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In order to investigate the growth mechanism of a fatigue crack of Ni-based super alloy at ultrasonic frequency, ultrasonic fatigue and rotting bending fatigue tests were carried out for Inconel 718 in ambient air and in N₂ gas using plain and notched specimens and the results in both tests were compared by focusing on the effects of strain rate and environment. In ambient air, fatigue strength was higher in ultrasonic fatigue than in rotating bending fatigue in plain specimen, while the results in notched specimen were the reverse. Many transgranular cracks and cleavage like cracks were observed on the fracture surface in ultrasonic fatigue in addition to striation and transgranular facets observed in rotating bending fatigue and there was no difference in the fracture mechanism between plain specimen and notched one. Moreover, these effects of frequency on the growth mechanism of a crack in ambient air were nearly the same in N₂ gas, though fatigue strength in N₂ gas was higher than that in air. The increase in fatigue strength in N₂ gas was mainly caused by the retardation of a crack initiation.

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This study was conducted to investigate the effect of diamond-like carbon (DLC) coating on the fatigue properties of stainless steel SUS 304. For the DLC coating, unbalanced magnetron sputtering (UBMS) method was used. The generated surface layer of about 2 μm thickness was composed with the DLC layer possessing a high hardness and an intermediate layer to improve the adhesion to the substrate. The DLC coating at a relatively low temperature had no influence to the microstructure so that the mechanical properties of the stainless steel were unchanged. The results of plane-bending fatigue test showed that the DLC coating improved the fatigue strength by 18%. From the detailed observation on the fracture surface, it was suggested that the improvement of the fatigue strength was made through the suppression of fatigue crack initiation from the surface due to the existence of the surface layer with a high adhesion and strength.

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Brittle fracture behavior of MBS resin under impact tensile loading was studied using single-edge-cracked specimens. The dynamic load and displacement were measured using a piezo sensor and a high-speed extensometer, respectively. The load and displacement diagram, i.e. the external work U_ex applied to the specimen was used to determine the elastic energy E_e and the fracture energy E_f for creating a new fracture surface A_s. Energy release rates were then estimated using G_t = U_ex/A_s and G_f=E_f/A_s. The values of G_t and G_f were correlated with the fracture loads and the mean crack. velocities determined from the load and time relationships.

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The present study investigates plasticity-induced martensitic transformation in two types of austenitic stainless steels SUS 304 and 316 L subjected to uniform tensile stresses at room and liquid nitrogen temperatures. The X-ray diffraction method was used in order to measure volume fractions of transformed α' and ε martensitic phases and to obtain the dependence of the volume fractions of these phases on the applied strain level ε. The difficulty in the measurement of the martensitic phases by the X-ray diffraction method caused by the preferred orientation which had been introduced during the rolling process and during the tensile tests was overcome by the help of Arnell's Method. Two types of target materials, i.e., Cu and Mo for the X-ray source were used to verify the accuracy and reproducibility of the present X-ray diffraction analyses. The results were also compared with those obtained by the saturation magnetization method using VSM, or vibrating-sample magnetometer reported elsewhere. It was revealed that α' was transformed in SUS 304 both at 297 and 77 K whereas in SUS 316L only at 77 K. Another type of martensitic phase, i. e., ε was transformed in the both steels only at 77 K. Almost the same values of the volume fractions of α' and ε phases were obtained by the two types of target materials. The plots of α' volume fraction obtained by the X-ray diffraction methods vs. that by VSM showed a good linear correlation.

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Slurry erosion with sand particles is a serious problem for pumps operating at the Yellow River pumping station. Therefore, a technique to predict erosion volume loss is required for selecting erosion resistant material and determining specification of the maintenance period. This paper reports a method to predict the volume loss of SCS6 specimen using slurry jet apparatus. An equation for prediction is derived from combining an analysis of sand particle behavior in the slurry jet apparatus with measurement of surface profile on specimens obtained by slurry jet test by silica sand of approx. 60μm in mean diameter. There is a critical value for kinetic energy of particle above which erosion occurs, being about 1.0×10^-6 N·m for SCS6. It was found that the loss was a maximum at an impingement angle of about 40 degrees. The equation can predict the amount of volume loss on the slurry jet test with the Yellow River sand of approx. 30μm in mean diameter.

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This paper simulates the macroscopic thermal conductivities of randomly-packed, sintered balloons for various degrees of sintering and for a wide range of the balloon diameter ratio. Although this problem was already studied by Ono et al., we found some errors in their paper, including a critical one. Thus, we re-examine the same theme and correct all errors. Furthermore, we extend its contents and discuss the results in more detail. For practical purposes, we present all the macroscopic conductivities in terms of a simple expression of two balloon's geometrical parameters. “Specific” macroscopic thermal conductivities (i.e., those per weight) are precisely estimated and found to have a peak when the balloons have the diameter ratio larger than approximately 0.8.

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The purpose of this paper is to present a method of material design of functionally graded material (FGM) plates with a function of electromagnetic noise suppression under an incidence of electromagnetic plane wave. The FGM plates are considered as multilayered plates while electromagnetic properties are homogeneous inside the same layer. The approximate analytical solutions of electromagnetic field in the multilayered plates are therefore derived for electromagnetic plane waves. The expressions for reflection and transmission coefficients are then obtained based on the above analytical solutions. In this paper epoxy resin/titanium oxide FGM plates for numerical calculations were used with a graded composition expressed in the form of power function. The effects of the graded composition and thickness on the reflection and transmission coefficients were then quantitatively evaluated, and the suppression effect of electromagnetic noise was discussed.

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