In metal matrix particulate composites, factors such as the volume fraction of the particulate phase, particle size and interfacial bonding on influence the crack propagation behavior. In this study, the effects of the volume fraction of the particulate phase and heat treatment on the relationships between crack propagation rate da/dN and the stress intensity factor range ΔK, crack pass profiles and crack opening displacement COD are examined using two kinds of Al₂O₃/Al alloy composites and Al alloy. At the low ΔK level, da/dN decreases with the increase of the volume fraction, but with increasing ΔK level, the tendency disappears. This is mainly due to crack deflection and roughness-induced crack closure due to the presence of particles. A unique relationship is obtained between da/dN and CTOD irrespective of heat treatment and volume fraction. Thus, it can be concluded that the main factor which controls da/dN is CTOD.

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This study examines the effect of surface modification by tufftriding on fatigue strength behaviors of SM490A material. We used non-tufftrided, tufftrided and anti-tufftrided specimens made of SM490A and measured their hardness distribution. mechanical properties and fatigue strength. Is terms of the fatigue behaviors, we investigated the relationship between the crack propagation rate da/dN, the stress intensity factor range ΔK, da/dN and the effective stress intensity factor range ΔK_eff, as well as the fatigue fracture cross-section of a specimen. The set of result supports that tufftrided specimen is effective in the prevention of tatigue crack intiation, and anti-tufftrided specimen is effective in the prevention of fatigue crack propagation.

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In order to clarify the simple shear strength of solder joint, we carried out static strength tests, fatigue tests, fatigue crack growth tests and creep crack growth tests on Cu/60Sn·40Pb/Cu joint under simple shear stress. Major conclusions obtained in this study are summarized as follows : 1) The maximum simple shear stress increased with the increase in the simple shear strain rate. 2) The effect of the width of the solder on the fatigue strength were not observed. 3) The fatigue cyclic crack growth rates were governed by neither the stress intensity factor range nor the maximum stress intensity factor. 4) The fatigue and creep loading time crack growth rates were governed by the modified J integral. 5) The fatigue and creep crack growth behaviors depended on the process zone (small scale creep zone) at the crack tip.

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Rotating bending fatigue tests were carried out on carbon steels and a nickel-based super alloy, Inconel 718, for investigation of the effect of CBN wheel grinding on the fatigue strength at room temperature and 500°C. The results are discussed from several view points, including surface roughness, residual stress and work hardening or softening due to grinding. The fatigue strength increased upon CBN wheel grinding at room temperature, primarily because of generation of compressive residual stress due to the CBN wheel grinding. However, this marked increase in the fatigue strength due to CBN wheel grinding tended to disappear at elevated temperature.

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Rotating bending fatigue tests were performed using smooth and precracked 0.25%C annealed steel specimens. The initiation and propagation of fatigue cracks were successively observed by the replication method, and the cumulative fatigue damage under two-step loading was investigated. Precracked specimens with four different precrack lengths, 150, 300, 450 and 700μm, were examined and the S-N curves for the precracked specimens with arbitrary crack lengths were estimated. The fatigue damage defined by Miner's rule under two-step loading was estimated from the crack propagation curve, the S-N curve of the smooth specimen and the estimated S-N curve for the precracked specimen. The estimated average value of the lower limit was 0.97, but it was 0.60 when the scatter of the experimental data in each specimen was considered.

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Fatigue crack growth tests under Hi-Lo two-step loadings were carried out on a 3% silicon iron in a scanning electron microscope, using the specially designed servo-hydraulic fatigue loading system. Fatigue crack growth behavior was discussed based on direct, real-time observation and microscopic quantitative analysis of principal shear strain distribution near the fatigue crack tip. which was obtained by a newly developed image processing technique. It was found that the delayed retardation behavior of crack growth occurred under Hi-Lo two-step loadings and the crack growth rate decreased as the frequency of crack branching increased. At the lowest growth rate, the interval of crack branching was found to be only about 4∼10μm. Principal shear strain distribution exhibited that the preferred slips occurred actively at not only the main crack tip but also the branched crack tips. Decentralization of the crack driving force may account for the retardation of crack growth rate.

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Fatigue crack growth tests under single overloads were carried out on a 3% silicon iron in a scanning electron microscope (SEM), using the specially designed servo-hydraulic fatigue loading system. Fatigue crack growth behavior under single overloads is discussed based on direct, real time observation and microscopic quantitative analysis of the principal shear strain distribution near the crack tip. It was found that the fatigue crack tip was remarkably blunted by an overload, and two fatigue cracks reinitiated along the preferred slip directions (±55°) at the root of the blunted crack tip within 300 load cycles after the overload and grew simultaneously, which resulted in the retardation of the crack growth rate. When one of the branched cracks arrested and the other grew by itself, the recovery of the crack growth rate was observed and followed by another retardation. The second retardation was due to the frequent branching and deflection of the main crack, the mechanism of which was identical to that of the delayed retardation observed in Hi-Lo two-step loading tests. The measured principal shear strain distribution represented that the preferred slips occurred actively at not only the main crack tip but also the branched crack tips. Such decentralization of the crack driving force was observed during the period of retarded fatigue crack growth.

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Most of the fatigue life is spent by the growth life of a small crack, and the growth rate of a small crack is expressed by the small crack growth law. Therefore, the fatigue life can be predicted approximately by the crack growth law. In the present study, a convenient method of prediction of the fatigue life for plain specimens based on the small crack growth law using the tensile strength and the cyclic stress strain curve when the type of loading is different is proposed. The validity of the proposed method is confirmed using several steel samples.

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The fatigue reliability of recycled advanced fiber reinforced thermo plastic (FRTP) resin was examined. In particular, the effects of the mesoscopic factor on the fatigue crack propagation (FCP) orientation and length of resin matrix on the FCP property of recycled FRTP is remarkably different among PEEK (Poly-Ether-Ether-Ketone). PPS (Poly-Phenylen-Sulfide) and PA·MXD6 (Poly-Amide-MXD6). (2) From fractography using SEM, it was found that the triple structure of recycled materials was different among these resin matrixes. Thus, it could be interpreted that the influence of the recycling process for each resin on the FCP property was caused by the different fiber orientation and length. (3) It was found that controlling the mesoscopic structure of the recycling process would improve the decline in the FCP property of recycled materials.

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The fatigue reliability of recycled advanced fiber-reinforced thermoplastic (FRTP) resin was examined, with a focus on the effects of the mesoscopic factor on the Fatigue Crack Propagation property. The main results were as follows : (1) In spite of the low weight percentage of carbon fiber, the rate of decreace the FCP property of PPS/ZW+CF materials was similar to that for PPS/GF materials with high weight percentages of glass fibers. The rate of decrease of the mechanical property of PA46/AF materials were low, but the rate of decrease of the FCP property of PA46/AF materials was very high remarkably. (2) The carbon fibers in PPS/ZW+CF materials were not oriented in one direction because of the three dimensimality of the zinc oxide whiskers in the molding process, and effective orientation of the carbon fibers appeared on FCP resistance. (3) The value of da/dN was constant on the FCP property of PPS/ZW+CF materials at low stress intensity factor range (ΔK) because of microcrack initiation. (4) Aramide fibers (AF) were not broken and not unidirectionally oriented because of their flexibility during molding at high temperatures. The FCP property of recycled PA46/AF materials was influenced by the winding shape of the AF.

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A fiber-matrix cylinder with a circumferential crack in the matrix is formulated within elastostatic scope. The problem is considered by means of integral transforms and a singular integral equation with a dominant generalized Cauchy kernel is obtained. Following the numerical solution technique developed by Erdogan, Gupta and Cook, the singular integral equation is reduced to a system of linear equations. By solving the linear equations, the stress intensity factor associated with the depth of the crack length and the material properties is calculated and discussed. The solutions presented in this study are found to be general, including those obtained as special cases of the present formulation for a homogeneous solid cylindrical bar and a thick-walled shell with an outer circumferential crack.

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Mesomechanical analysis of the elastic stress distribution near the tip of a delamination crack in fiber-reinforced plastics (FRP) was conducted using the boundary element method. FRP composites were modeled by a two-dimensional laminated structure composed of an isotropic matrix and orthotropic fiber. A mode I crack was induced in the matrix parallel to the fiber direction. The stress intensity factor, K₁, and the energy release rate, G₁, were calculated for the above inhomogeneous model and compared with those for a homogenized model. For long cracks, the energy release rate for the inhomogeneous model was equal to that obtained for the homogeneous model. For short cracks, the energy release rate was larger for the inhomogeneous model than for the homogeneous model. The characteristics of the elastic stress distribution ahead of the crack tip in the matrix were compared with the stress distribution for the homogeneous model.

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The boundary element method was used to determine the elastic stress distribution near the tip of a delamination crack in fiber-reinforced plastics (FRP). FRP composites were modeled by a two-dimensional laminated structure composed of an isotropic matrix and orthotropic fiber. A mode II crack was induced in the matrix parallel to the fiber direction. The stress intensity factor. K₁₁, and the energy release rate, G₁₁, under mode II in-plane shear loading were calculated for the above inhomogeneous model, and compared with those for a homogeneous model. For long cracks, the energy release rate for the inhomogeneous model was equal to that obtained for the homogeneous model. For short cracks, the energy release rate was larger for the inhomogeneous model than for the homogeneous model. The characteristics of the elastic stress distribution ahead of the tip of a mode II crack in the matrix were compared with those of the elastic stress distribution for a mode I crack.

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The main strengthening mechanisms for Al-Zn-Mg-Cu system alloys include the solid solution and precipitation. In this study, we evaluated tensile properties of the 7475 aluminum alloy whose grain size was changed, and discussed the mechanisms of solid solution and precipitation strengthening on the 0.2% proof stress. In this paper, we discuss the precipitation mechanism based on accompanying theories. The main results obtained were as follows : (1) The precipitate particle, η'-MgZn₂ phase dispersed in the aluminum matrix was investigated by use of the transmission electron microscope. The average radius and the center to center spacing of the η'phase were 3.1 and 10.5nm, respectively. As a result, the volume fraction of the η'phase was 10.8% after heat treatment. (2) The precipitation strengthening was estimated from the cut-through mechanism proposed by Brown and Ham. As a result, the energy for the deformation of the interface was 106 mJ/m². (3) The relationship between the dispersion appearance of particles and the precipitation strengthening was estimated using the cut-through mechanism proposed by Gerold and Haberkorn. In this material, the experimental result of the precipitation strengthening agreed with the theoretical one. Furthermore, this theory was effective in estimating the precipitation strengthening of the fine particles. (4) The Orowan mechanism did not applied to the fine particle, η'phase, in the 7475 aluminum alloy.

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The stress corrosion cracking (SCC) resistance of two types of Al-Zn-Mg-Cu system alloys, one of which contains a superplastic material of fine grain structure prepared by thermo mechanical treatment and the other commercial materials of coarse grain structure prepared by conventional process, was evaluated. The SCC resistance of the two materials were markedly different ; Al-Zn-Mg-Cu system alloy with coarse grains was superior to that with fine grains. In this study, the effect of X-ray residual stress and random strain on the SCC resistance in the two alloys was discussed on the basis of experimental results. The main results obtained in the present work are as follows. (1) The macro residual stress in these alloys with fine grains and coarse grains measured by X-ray diffraction method. These alloys had compressive stress, and SCC life of these alloys increased with increasing compressive stress. (2) The random strains were estimated by X-ray diffraction method. The random strain values of the alloy with fine grains were larger than those of the alloy with coarse grains. The SCC life of the alloy increased with decreasing random strain. (3) The difference in SCC threshold stresses in L and T directions in the alloys with fine and that with coarse grains agreed with the difference in sum stress of macro and micro residual stresses from random strain. Furthermore. SCC threshold stress in both materials was determined from the total stress which is the sum of the macro and the micro residual stresses and the applied stress. (4) The SCC resistance of the materials can be estimated from the residual stress and the random strain by X-ray analysis.

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In this work, stress concentration factors (SCFs) of a round bar with a circular-arc or V-shaped notch K_t are considered on the basis of exact solutions for special cases and accurate numerical results. First, for the limiting cases of deep and shallow notches, the body force method is used to calculate the SCFs ; then, the formulas are obtained as K_td and K_ts. On the one hand. upon comparison of K_t and K_td. it is found that K_t is nearly equal to K_td if the notch is deep or blunt. On the other hand. if the notch is sharp or shallow, K_t is mainly controlled by K_ts and the notch depth. The notch shape is classified into several groups according to the notch radius and depth ; then, the least squares method is applied for calculation of K_t/K_td and K_t/K_ts. Finally. a set of convenient formulas useful for any shape of notch in a round test specimen is proposed. The formulas yield SCFs with less than 1% error for any shape of notch.

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Effects of the number of screw revolutions in an injection molding machine and the notch shape of molded specimens on fracture mechanisms of notched FRPP are investigated by means of the acoustic emission (AE) technique and scanning electron microscopy. The relationship between the number of screw revolutions and the fiber orientation in the molded specimen is determined. It is found that the usual AE characteristics are affected by the fiber orientation and radius of curvature at the notch tip. It is estimated from the AE frequency analysis that the damage modes are also affected by the fiber orientation and the radius of curvature at the notch tip. The estimation of damage modes are compared via microfractographs at the notch tip.

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Elastic moduli along the three major axes of FRP honeycomb core sandwich panel have been calculated using a unit model in 3D-FEM analysis, which was considered from a regular array of honeycomb core in the panel. In the analysis, computing conditions were determined considering compatibility of displacement and equilibrium of force at each node in the unit model keeping continuity at nodes surrounded by those with the same shape and size. Effects of geometric parameters of the unit model such as thickness of the skin and thickness and height of the honeycomb core were evaluated in the study. Almost all the elastic moduli were expressed nearly as liner relations to V₈ (volume of the skin material) and V_c (volume of the core material) in the practical geometrical size of FRP honeycomb core sandwich panel and the deviation from the regular honeycomb core size varied the elastic moduli.

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The present paper discusses a thermoelastic problem in an isotropic structural plate to which a piezoelectric ceramic plate of crystal class 6mm is perfectly bonded. When an unknown thermal load acts on the free surface of the isotropic plate, the combined plate is deformed and then an electric field is induced in the piezoelectric ceramic plate. First the unknown thermal load is inferred from the electric potential measured on the free surface of the piezoelectric ceramic plate. Next we derive a distribution of electric potential on the free surface of the piezoelectric ceramic plate which gives the prescribed normal elastic displacement on the free surface of the isotropic structural plate. Finally, numerical results are illustrated graphically.

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Shear banding is considered as localized necking where multiple solutions can exist on the necking plane comprising the boundary between the shear band and its surroundings. Therefore, shear banding is identical with localized necking though it is investigated under plane strain. On the necking plane the discontinuity of velocity gradient can be permitted. Hill and Hutchinson [J. Mech. Phys. Solids, 23 (1975), 239-264] investigated shear band without considering the discontinuity, but their method is methodically equivalent to that which takes into account the discontinuity. In previously published analyses of shear banding, it is assumed that the regions separated by the necking plane keep contact each other during the onset of shear banding, and the equilibrium of forces is maintained on the plane. However, it is proven that this assumption cannot provide useful information for determining the deformation when shear banding begins to occur. Furthermore, the assumption does not allow the formation of a common boundary condition imposed on both regions separated by the necking plane. When shear banding occurs, the spin rate of the regions differs because of multiple solutions. The criterion for determining the occurrence of shear banding can be deduced by imposing a rigid spin to make the spin rates identical. It is found that this criterion agrees with one of the universal criteria obtained from considering the occurrence of multiple solutions under the common boundary condition on the surface of a body.

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This study is concerned with a new boundary element method for two dimensional anisotropic thermoelasticity in steady heat conduction. The governing differential equations of the displacement and temperature fields are transformed into a set of boundary integral equations which include the unknown quantities of displacement, temperature, traction, and heat flux on the boundary. They are discretized by means of the standard boundary element method, and solved under the given boundary conditions. A set of fundamental solutions are derived by the Hormander method. Mathematical formulations are presented in detail for two dimensional thermoelasticity in anisotropic bodies. The proposed solution procedure is applied to some typical examples, and its usefulness is demonstrated through discussion of the results obtained.

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A homogenization theory for rate dependent deformation such as creep and viscoplastic deformation of composites with periodic internal structures is described. The first-order perturbation of displacement rate is decomposed into elastic and viscous parts. Then, a constitutive equation between macro-stress and strain rates and an evolution equation of micro-stress are expressed in terms of Y-periodic functions appearing in the elastic and viscous parts, and two-unit cell problems for determination of the Y-periodic functions are formulated. An incremental formulation of the theory is also given. The theory is effective for problems in which either macro-stress or macrostrain, or a mixture of the two, is prescribed. As an application of the theory, transverse creep of metal matrix composites reinforced unidirectionally with continuous fibers is analyzed by solving the unit cell problems discretized with finite elements.

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A high-velocity oxygen-fuel (HVOF) system in air has been established for producing coatings that are extremely clean and dense. It is thought that the HVOF-sprayed MCrAlY (M is Ni, Co or both) coatings can resist oxidation and corrosion in the hot section of gas turbines. Also, it is known that in order to improve the residual stress coatings thicker than those from other thermal spraying systems can be sprayed. However, residual stress characteristics of HVOF coatings remain to be clarified. In this paper, the residual stress characteristics were analyzed using the deflection measurement technique and the X-ray technique. It was confirmed that the residual stress of HVOF coatings was reduced by the shot-peening effect. The generation mechanism of residual stress was investigated from the measurement results of deflection of cantilever specimens during HVOF spraying.

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By examining the stress strain relationship in a film made of shape-memory polymer of polyurethane series through cyclic loading at and above the glass transition temperature T_u, the properties of energy dissipation and storage were investigated. The results are summarized as follows. (1) Although yield stress decreases and irrecoverable strain appears after the initial loading at and above T_g, stress-strain curves vary slightly thereafter. Therefore, in order to obtain constant cyclic deformation properties in practical applications, mechanical training with one cycle is effective. (2) The rate of energy dissipation is 0.6∼0.7 in the case of loading at T_g. Therefore, its capacity as a damping material is excellent at T_g. The higher the strain rate and the maximum strain, the larger the dissipated work. (3) The energy storage efficiency is 0.7∼0.8 in the case of loading above T_g. Therefore, the performance as a energy storage material is high above T_g. The amount of recoverable strain energy is almost the same at and above T_g. (4) The performance as a damping and energy storage material is effective if the polymer element is of a large scale and is subjected to large deformation.

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There are two main methods to calculate the temperature dependence of electrical resistivity. The first one known as the Ziman method is based on relaxation time calculations. The second, known as the correlation function method, is one of many methods used to arrange Kubo expressions into a new formula is very simple to use to calculate transport properties. In this work, we applied these two methods to electron-ion interactions of simple metals which can be described by a local pseudopotential. There the temperature dependence of the electrical resistivity of the simple metals was calculated. The results were compared with experimental data over a wide range of temperatures and agreement was found to be good for both methods. Compared with Ziman method, correlation function method is more appropriate for calculating the electrical resistivity of high Debye temperature metals. Also, the relationship between the electrical and mechanical properties of metals is discussed. Particularly, we outline a method to evaluate the temperature dependence of sound velocity and elastic constant by calculating electrical resistivity.

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The microstructure of silicon thin films deposited onto the (001) surface of silicon substrates and the intrinsic stress present in them were studied using three-dimensional molecular dynamics simulation. The Tersoff potential was used to represent the interaction among the silicon atoms. Simulation results show that such thin films have crystalline structures at deposition temperatures T/T_m>0.45 (T : absolute temperature, T_m : melting temperature) while they are amorphous at T/T_m<0.45. The pair correlation function and bond angle distribution for amorphous silicon obtained from our simulations agreed well with experimental results. The simulation results show that the tensile stress in amorphous silicon films increases and that the variations in stress caused by the difference in the positions at which deposited atoms impinge become larger when the substrate temperature decreases. It was verified that the intrinsic stress in silicon thin films depends strongly on the microstructure of the films.

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Molecular dynamics simulations of energetic SiH₃ ion particles of up to about 150 eV incident on a-Si : H film surfaces have been performed. The influence of the incident kinetic energy on the surface temperature, and behavior of the SiH₃ particles entering the surface layer were then studied. As a result of the simulations, it was found that when the incident kinetic energy exceeds about 10 eV. an average surface temperature during 0.5 ps after incidence reaches more than 1000 K. with the bulk temperature of the film kept at 450 K. In addition, it was found that although the incident SiH₃ particles of up to about 10 eV stay on the surface. Si atoms of SiH₃ particles with energies of 10-20 eV start to migrate into the surface layer, and that when the incident energy exceeds 100 eV. the Si entering depth increases rapidly, and it becomes 13.52 A in the case of 150 eV. It is thought that it is necessary to control the ion bombardment energy in plasma CVD process in order to improve a-Si : film.

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When a hard steel sphere over a range of impact velocities (80-100 m/s) and impact angles (15-90°) is projected obliquely onto three ductile metal targets, the shapes of the plastic craters and the softening or hardening of the craters were measured. Their variations with impact angle were experimentally obtained. It is observed that a pronounced lip is formed at the end of the crater for an impact angle of 45°in the three targets. It can be assumed that such a large lip will be easily detached during abrasive grit-blasting. The hardness at the crater periphery except for the lip and the interior of the crater were measured by means of a micro-vickers hardness tester. The hardness of a mild steel crater at an impact angle of 15°is less for the residual tensile deformation due to the tangential component of the oblique impact than for the virgin specimen. The hardness of the craters of other soft metal targets except for steel increase with the impact angle. Cracks in the piling-up were observed using SEM. The impact and rebound angles of the sphere projectile were also measured using a CCD camera.

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This paper presents the closed-form solutions of a two-dimensional anisotropic elastic medium (matrix) containing isotropic elastic multilayered elliptic ring inclusions under uniform out-of-plane shear stresses at infinity. This analysis is based on the complex variable method using a conformal mapping technique and analytical continuations, and allows some sliding boundary conditions among the elastic rings, inner inclusion and the matrix. Using these solutions, we demonstrate the effects of the number, elastic properties and sliding parameters of various multilayered isotropic elastic rings on the distribution of stresses and displacements.

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The flat-wise hard and soft body impact resistance of two kinds of carbon fiber/PEEK systems were evaluated using drop weight (mass=2.5 kg, 1 to 3 m/s), aluminum bullet (mass=1.9 g, 50 to 100 m/s), and gelatin projectile (mass=3 g, 90 to 190 m/s) impact tests. Tested systems were AS4/PEEK (APC-2/AS4) and AS4/PEEK+IL, which consist of APC 2 prepreg and PEEK film inserted between layers as an interleave. For investigation of the effects of the stacking sequence on resistance, the fiber angle and lamina thickness were varied as experimental parameters. The projected damage area was measured using an ultrasonic C Scan. The impact resistance was assessed in terms of the value of DA/IE, which is the ratio of the damage area (DA) to the impact energy (IE). The effects of the stacking sequence on impact resistance can be assessed in terms of the proposed nondimensional stacking parameter βT2. The relationship between DA/IE and βT2 was linear, and the value of (DA/IE)/βT2 indicated impact resistance of the tested material with dependence on neither fiber angle nor lamina thickness. The effects of the impact conditions, i. e., low/high impact velocity and hard/soft body impact, on impact resistance were discussed.

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A creep constitutive equation in Hastelloy XR was developed at 900 and 950°C, following the previous report at 850°C. In the equation, the inelastic strain rate is written in the form of a flow equation of the Norton-Bailey type and the hardening during deformation under various loads is induced by an internal stress which is subdivided into back stress and friction stress. Parameters were determined by the deformation properties for creep under constant stress conditions at each temperature. In order to confirm the validity of these constitutive equations deformation curves and/or strain rate under creep, stress dip, stress relaxation and tensile tests were compared with the calculated results. The results showed good agreement at 900 and 950°C, respectively. Finally the temperature dependence of two internal parameters q₀ and λ defined as a function of applied stress was discussed to determine those properties given to Hastelloy XR whose boron content was controlled to improve the creep resistance at high temperatures.

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In this paper, we developed a new method for evaluating the adhesive strength of paint film on a concrete surface. The peel test for paint film was carried out. A reinforcement plate was attached to the paint film so that it would not be damaged during the peel test. The critical energy release rate (G_c value) was obtained by using peel load and the displacement of the loading point measured during the peel test. G_c values were not affected by the thickness of the reinforcement plate and the peel length. Therefore, it was clear that G_c values could be used to evaluate the adhesive strength of the paint film. Furthermore, the influence of the environment on paint films was elucidated by obtaining the G_c value.

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A tensile creep specimen with projections was designed to measure the creep displacement by means of the laser beam displacement meter at temperatures elevated beyond 1000°C. Stress/strain concentrations, however, occur around the root of projections in this specimen. The high-temperature creep strain was determined form the measurement of tensile displacement between the two projections by correcting influence of the projections. The procedure used to determine the steadystate creep constitutive equation of Si₃N₄ ceramics was proposed by combining a high-temperature creep test using the speciment with projections and the finite-element method (FEM) calculations for the specimen. Furthermore, the method for designing the optimum creep specimen with projections was proposed via the FEM calculations using the steady-state creep constitutive equation.

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The problem of the effect of thermal loads on buckling strength is important in buckling research for fast breeder reactors, because axial temperature gradient is produced in the main vessel and a significant thermal stress is induced at the surface level of sodium. In this paper, we focus on two types of reactor vessels (loop-type and pool type) and investigate the effect of thermal loads accompanied by an axial temperature change near the sodium surface level. In addition, the reduction of the buckling strength due to the thermal loads is quantitatively evaluated.

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This paper deals with a method of generating a multiple connected region and shape optimization for reducing the weight and stress concentration of mechanical structural components. Structural components often contain some holes for the purpose of reducing their weight. It is a difficult task to determine the optimum number, position and shape of holes under various constraints in the conceptual phase of design. In this study, we propose a method of shape generation for obtaining minimum weight and maximum stiffness for clastic structural components using a genetic algorithm. We describe in detail how to apply the genetic algorithm to determine the multiple connected region and its optimization. We show some results of typical problems to demonstrate the effectiveness of the proposed method.

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Shape optimization is applied to dissimilar material joints to decrease free-edge singular stress using a CAE system of finite element-based shape optimization programs. The optimum shape of a joint with an interlayer is similar to the case of that without an interlayer. It is revealed that the free-edge singular stress decreases in the optimum shape. Shape optimization is a useful method for designing dissimilar material joints from the point of view of decreasing singular stress.

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In this paper, we describe a methodology for three-dimensional structural design for reinforcement that determines both layout and cross-sectional shape. Considering the difference in scale between the design variables for the layout design and those for the design of a cross-sectional shape. we separate the design problem into two sub-problems. One can be called a macroscopic design problem, and the other a microscopic one. The proposed design method takes the correlation between the sub-problems partially into account by using a new parameter to construct a feedback loop. The effectiveness of this method has been proved through simple numerical examples.

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