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Article type: Cover
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Published: August 22, 2001
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Article type: Appendix
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Published: August 22, 2001
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Article type: Appendix
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Published: August 22, 2001
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Article type: Appendix
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Published: August 22, 2001
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Article type: Index
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Published: August 22, 2001
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Shigenobu OGATA, Yoshinari HATANAKA, Naoto HIROSAKI, Hiroshi KITAGAWA
Article type: Article
Session ID: K-0101
Published: August 22, 2001
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The ideal tensile strength of beta silicon nitride were determined by first-principle molecular dynamics method based on density functional theory with local density approximation. From evaluated stress-strain curves, we found that the tensile strength along c-axis 75GPa is slightly larger than that along a-axis 72GPa. The calculated elastic constants from the stress-strain curves, C_11 and C_33, are in good agreement with the previous theoretical and experimental results.
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Masanori KOHYAMA
Article type: Article
Session ID: K-0102
Published: August 22, 2001
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The tensile strength and fracture of the polar and non-polar interfaces of the {122}Σ=9 tilt boundary in cubic SiC have been examined through the behavior of electrons and atoms using the ab initio tensile tests. The strength of these interfaces is very large because of reconstructed interfacial bonds. However, the interfacial C-C and Si-Si bonds have serious effects. For the non-polar interface with both C-C and Si-Si bonds, the fracture starts at the back Si-C bond of the C-C bond because of local stress concentration, and the fracture proceeds rather continuously. The P-type polar interface with Si-Si bonds has larger tensile strength with no remarkable local stress concentration because of highly symmetric configuration, and the fracture occurs rather catastrophically. There exists the general critical bond stretching for the Si-C bond breaking.
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Tokuteru UESUGI, Masanori KOHYAMA, Kenji HIGASHI
Article type: Article
Session ID: K-0103
Published: August 22, 2001
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The light weight and high specific strength magnesium alloys are important as structural materials. However, magnesium and magnesium alloys have low plastic formability. It is important to understand the deformation mechanism to improve their plasticity. In the behaviors of slip deformation and dislocation motions, the critical and effective parameter is the generalized stacking fault (GSF) energy. The GSF energy is identified with the energy necessary to ideal slip, and shear strength of real materials should increase as the GSF energy increases. In this work, the GSF energies on basal plane and prismatic plane in magnesium are calculated by ab initio pseudopotential method. Especially, we investigate the effect of the relaxation of strain normal to slip plane using periodic model and slab model.
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Yoshitaka UMENO, Takayuki KITAMURA
Article type: Article
Session ID: K-0104
Published: August 22, 2001
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In recent years, manufactureing of devices with nanostructure has been attempted with the advent of the nano-processing technique. In this study, an ab initio molecular dynamics simulation in tension of Si/Al interface is conducted in order to clarify the mechanism of its deformation in atomic level. Al atoms are precipitated on the Si-(001) surface and then one Al atom is pulled in the direction perpendicular to the surface. The range of effect of the tension is within 3 atomic layers from the surface. The tensile strength of the Al atom on the surface is estimated as 1.3nN, which is close to that of the tensile strength of Al atomic chain.
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Akiyuki Takahashi, Naoki Soneda, Genki Yagawa
Article type: Article
Session ID: K-0105
Published: August 22, 2001
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Energy minimum configuration and binding energy of vacancy-copper cluster in α-Fe are evaluated using lattice Monte Carlo method and molecular dynamics method. In the energy minimum configuration, vacancies are concentrated at the center region of the cluster and copper atoms are located around the vacancy concentration. By the effect of copper atoms, binding energy of vacancy cluster becomes higher then that of pure vacancy cluster, and the cluster becomes more stable.
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Tomoyasu AIHARA, Takanori NAKAZAWA
Article type: Article
Session ID: K-0106
Published: August 22, 2001
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Dissociation of molecular hydrogen to solid alloy consists of two phenomena. First is an essential hydrogen absorbability of the alloy, which are affected by chemical component and crystal structure. Second is a catalytic reaction at the surface of the alloy. Experiments could not separate both phenomena clearly. The former information of the alloy is important for screening of high performance hydrogen storage alloy. In present work, analyses of properties of Ti-Cr and their hydrides were performed by FLAPW (Full Potential Linearized Augumented Plane Wave) calculation.
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Satoshi IZUMI, Shinsuke SAKAI
Article type: Article
Session ID: K-0107
Published: August 22, 2001
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Molecular dynamics simulation have been performed for the 50-5000 eV Ar bombardment of Si {100} surface using Tersoff potential in order to investigate the nano-scale damage. The dependences of the number of interstitials and etched atoms on the ion energy, substrate strain and the polar angle of the incident Ar were investigated. As a result, the number of intersitials was found to be a linear function of the damage energy, and its slope showed good agreement with the Kinchin-Pease model. The number of etched atoms had little correlation with that of interstitials. In addition, the number of interstitials increased as the strain was increased, and decreased as the polar angle of incident Ar was increased. The effect of the polar angle was small at the angles of 0-30 degrees.
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Koichiro YAMADA, Kyoji HOMMA
Article type: Article
Session ID: K-0108
Published: August 22, 2001
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Numerous micro-cutting simulations have been proposed by using molecular dynamics (MD), in which the temperatures of an outer boundary are kept constant by assuming a steady state. Present paper investigates the treatment of temperature distributions of the boundary in the vicinity of the tool edge comparing between steady and unsteady, in the case of cutting force per unit width, morphology of chip deformation and temperature distributions. As a result, giving unsteady temperature distribution to the boundary is more desirable to the analysis than steady one. In the case, temperature distributions in the vicinity of the tool edge under unsteady boundary condition agreed well to the results under broad boundary condition.
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Yoshihiro AONO, Yoji SHIBUTANI, Keishi YAMANAKA
Article type: Article
Session ID: K-0109
Published: August 22, 2001
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Nano-indentation of silicon is analyzed using the molecular dynamics simulation with an initial configuration deformed by the elastic solution in order to diminish the computational time. Comparing the usual procedures with the perfectly undeformed initial configuration, almost similar internal structural change of occurrence of amorphous-phase and emission of a dislocation loop are observed. From the crystallographic analyses to determine a Bergers vector, a dislocation loop is found to be formed by combining the 60 degree dislocation with the screw dislocation.
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Tadao FUKUTA, Yasuhiro AKAHOSHI, Shoji HARADA
Article type: Article
Session ID: K-0110
Published: August 22, 2001
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We focus on nanoscale copper-rich precipitates and try to clarify the effect of the nanoscale copper-rich precipitates on embrittlement of reactor pressure vessel steels. Our final goal is to evaluate such embrittlement from microscopic viewpoint based on atomistic simulation. In this study, we simulate interaction between motion of an edge dislocation and copper precipitates using Molecular Dynamics (MD) method with a periodic boundary condition, where uniform shear strain is applied to the boundaries parallel to the slip plane (112) in the system. Comparing motions of the edge dislocation among models with copper precipitates in different diameter, it is found that the larger the copper precipitates are, the more decelerated the motion of the edge dislocation is by copper precipitates.
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Haruo NAKAMURA, Sonoko MAEDA, Yasuhiro SAKURAI, Hideo KOBAYASHI
Article type: Article
Session ID: K-0111
Published: August 22, 2001
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In a multi-layered structure such as laminated metallic thin firms, it is known that hydrogen atmosphere causes functional degradation near interfaces. In this study, the molecular dynamics (MD) was applied to multi-layered structures with various crystal orientations and structures to investigate the micro mechanisms of deformation near interfaces and mechanical properties. Three-layered thin films which are composed of ductile and brittle crystals were analyzed. It was found that their mechanical property depends mainly on that of the laminar at a center position. Then, to obtain better properties, the mechanism of hydrogen invasion from a free surface was also investigated.
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Masato NAITO, Kisaragi YASHIRO, Yoshihiro TOMITA
Article type: Article
Session ID: K-0112
Published: August 22, 2001
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The dislocation behavior at γ/γ' interface in Ni-based superalloy is studied in terms of the molecular dynamics technique. It is observed that an edge dislocation is dissociated at an edge of γ' precipitate after showing dislocation pinning, as well as that a superdislocation, which is composed of a pair of dislocations and anti-phase boundary, is nucleated and propagates from an edge of γ' precipitate.
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Tomoyuki HIROYASU, Mitsunori MIKI, Tamaki OKUDA, Shinya WATANABE
Article type: Article
Session ID: K-0201
Published: August 22, 2001
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In this paper, a new algorithm of Genetic Algorithm for Multi objective Optimization Problems, called Distributed Cooperation model of MOGA (DCMOGA), is proposed. In the proposed algorithm, there are some sub populations. One of them is finding a Pareto optimum set and the other is finding an optimum solution of one of objectives. These sub populations sometimes exchange their searching information respectively. The proposed algorithm is applied to three types of knapsack test problems. Comparing to the conventional multi objective optimization methods, the proposed model found the good and widespread Pareto solutions.
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Mitsunori MIKI, Tomoyuki HIROYASU, Yoshiaki NAGAYA, Yashumasa OGAWA
Article type: Article
Session ID: K-0202
Published: August 22, 2001
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We propose a new network collaboration system, named DIGA (Distributed Interactive Genetic Algorithm), where IGA is extended to Parallel and Distributed Model. By using DIGA we can realize an IGA-based design system with many people at the same time. DIGA is aimed to solve problems of making creative plans and making agreement within a group. We developed a proto-type system and applied the proposed approach to make good plans for selecting the colors of three furniture (sofa, curtain, and carpet). The experiment shows the effectiveness of the method.
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Masao ARAKAWA, Yamato UTSUNOMIYA, Hiroshi ISHIKAWA, Ichiro MIURA
Article type: Article
Session ID: K-0203
Published: August 22, 2001
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These days, small factories are required to make so many kinds of different items within short terms. They are really troubled with handling their requirements, however, it is too expensive to buy commercial software of those programs. In this paper, a new type of Genetic Algorithms (GA) for optimal product process management is developed. Basis vector is introduce for decoding and its update system is proposed. Through out numerical example of real data, we will show the effectiveness of the proposed method.
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Yasunari MIMURA, Tomonari FURUKAWA, Shinobu YOSHIMURA
Article type: Article
Session ID: K-0204
Published: August 22, 2001
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This paper presents fundamental system design and implementation of the parametric optimization module for large scale parallel finite element analyses. Issues to be next-generation general-purpose computational mechanics system are (1) high parallel performance in MPPs, (2) portability among various parallel and distributed environments ranging from PC cluster to MPPs, and (3) Uni-phenomenon analysis, coupling analysis and design analysis in an efficient and flexible manner. To solve these issues simultaneously, an advanced general-purpose computational mechanics system for large-scale analysis and design, named "ADVENTURE" is begin developed, implementing high-performance and soft computing technology. The ADVENTURE system employs module-based architecture. Currently, we have developed preprocessor, solver, and visualizer for parallel and distributed environments. The parametric optimization module developed here works together with other ADVENTURE modules.
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Koji SAITO, Takuya YOSHIMURA, Akira SUTO, Nobuo AIZAWA
Article type: Article
Session ID: K-0205
Published: August 22, 2001
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To reduce the span of automotive development a new optimum design method considering vibration properties is presented in this paper. It is important to have prospects for complex structures like automotive bodies having good vibration properties in the early stage of design. In order to accomplish this, hierarchical optimization of complex structures is investigated. The relationship between the substructure's natural frequencies and those of the whole structure is derived by using substructure synthesis approach. By the presented method natural frequencies of substructures are assigned to achive the certain natural frequencies of the whole structure.
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Qiang Yu, Naoki Adachi, Masaki Shiratori
Article type: Article
Session ID: K-0206
Published: August 22, 2001
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If the buckling mode of the main side members can be kept in a good mode, it is possible to get a stead deceleration characteristic, and to reduce the weight. In this study, the authors proposed a new mode controlling approach to control the buckling mode of the side member. The results of the optimized design given by the new approach showed that not only can this new design method reduce the weight of the side member at the geometric design step, but also it can improve the basic characteristic of the energy absorbing behavior of side member.
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Naoyuki YAMAMOTO, Hideyuki AZEGAMI, Masatoshi SHIMODA
Article type: Article
Session ID: K-0207
Published: August 22, 2001
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This paper presents a numerical analysis method for shape optimization problems of cross section in three dimensional frame structures made of thin plate. The beam theory was applied for frame segments. Cross section was assumed as rectangle with height and width. The distribution functions of the height and the width defined on frame structures were chosen as design variables. With respect to stiffness maximization problem, numerical analysis method of shape gradient function was presented by applying the adjoint variable method. Using the shape gradient function, a program for three dimensional frame structures based on the gradient method was developed. The performance was demonstrated with some numerical results for three dimensional frame structures.
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Kenzen TAKEUCHI, Hideyuki AZEGAMI
Article type: Article
Session ID: K-0208
Published: August 22, 2001
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This paper presents an improvement of the traction method that was proposed as a solution of shape optimization problems of domain boundaries in which boundary value problems of partial differential equations are defined. Using the theory of the gradient method in Hilbert space the principle of the traction method is presented. Based on the principle a new method is proposed by selecting another bounded coercive bilinear form from the previous method. The proposed method obtains domain variation with solution of a boundary value problem with the Robin condition using the shape gradient. With respect to a three-dimensional bar problem with notch that was not solved with the previous method the proposed method obtained smooth convergence.
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Shou KANEADA, Takefumi KAMITAMARI, Qiang YU, Masaki SHIRATORI, Keiichi ...
Article type: Article
Session ID: K-0209
Published: August 22, 2001
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In many mechanical structures, structural design for noise reduction is becoming increasingly important. Noise reduction is often achieved through structural modifications. However, it is hard to predict the effectiveness of noise reduction by typical approaches. This paper presents an optimal design approach for reducing sound power from a vibrating plate by its curvature design. The method couples an optimization technique based on a genetic algorithm (GA) with the shape representation technique, vibration analysis and acoustic radiation analysis. It is shown that the curvature design of the plate obtained by using this method can achieve effective reductions in radiated sound power. Finally, the robustness of the optimized design candidates obtained is studied by using stochastic simulations in order to find the candidate which is least sensitive to changing design parameters.
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Hidehisa SAKAI, Masaki SHIRATORI, Qiang YU, Masahide Kaneko
Article type: Article
Session ID: K-0210
Published: August 22, 2001
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In this paper, prediction methods of solder joint shape, such as solder joint height and contact angle, for EGA package, which is effective on high density packaging, are studied. Various calculation methods to predict the melting solder joint shape are studied, and results of the calculation are compared to experimental results to confirm the validity of each calculation methods. Approximate polynomial of solder joint shape, such as solder joint height and contact angle are calculated by combining a numerical differential method and the design of experiment method.
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Takashi MIYAJIMA, Seiichi KUDOH, Masayuki NAKAMURA, Mitsuyuki KOBAYASH ...
Article type: Article
Session ID: K-0211
Published: August 22, 2001
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The design value of a silicon wafer polishing machine such as radius ratio, rotational velocity ratio, attachment position, rocking cycle and rocking amplitude has great effect on planarization of the silicon wafer. Relative velocity is one of factors which determines polishing quantity. The purpose of this study is optimization of the design value of polishing machine for planarization of the silicon wafer. In this paper, relative slide distance was substituted for polishing quantity and it was investigated how design value influenced relative slide distance.
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Masayuki NAKAMURA, Mitsuyuki KARASAWA, Kazunori KOBAYASHI, Mitsuyuki K ...
Article type: Article
Session ID: K-0212
Published: August 22, 2001
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Multilayer coatings are widely used to various optical parts, for example, multimode optical fibers, beam splitters, antireflection coatings. For another applications, multicoated thin films on the solar panel have capabilities to control the solar energy by means of the spectrum transmittance and reflectance control. In this paper, we discuss the specifications and the functions of solar panel coatings. In the design of optical multilayer coatings, refractive index and thickness of each layer must be determined in accordance with the specifications on a spectral reflectance. The solar spectrum, the culmination altitude and conditions of the production process for coatings must be considered. To solve the problem, our developed design system is used for optimum design. Some optimum design results for restricted design specifications are shown.
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Koetsu YAMAZAKI, Tomokazu KATOH, Yoshiaki ONDA
Article type: Article
Session ID: K-0213
Published: August 22, 2001
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When car traffic accidents occur, it is important to absorb much crushing energy by a car body. For the development of lighter and more crushable structure , the crushing experiment of aluminum honeycomb structure with two kinds of cell sizes is carried out and crashworthiness and impact phenomena are observed. The finite element simulation by DYNA3D is also implemented and the numerical results are compared with that of experiment. The simulation results coincide well with the experimental results.
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Eisuke KITA, Tetsuya TOYODA
Article type: Article
Session ID: K-0214
Published: August 22, 2001
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This paper describes the structural optimization scheme based on the concept of the cellular automata (CA) simmulation. The optimization process is carried out with the local rule. This paper presents the new rule which not only deletes cells but also adds cells near the stress concentration points. Finally, the present scheme is applied to the shape optimization of the continuum structures.
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[in Japanese], [in Japanese], [in Japanese]
Article type: Article
Session ID: K-0215
Published: August 22, 2001
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Immune system in mammals plays a significant role on the survival in the case with attacking of various bacteria. This system seems to equip the mechanism eliminate the various vacteria. From the view point of information mechanism, this system could offer the designs that are considered with the environmental situation, for example, wind loads, deterioration and so on. Especially, immune algorithms are considered as the optimization algorithms. However, the immune algorithms are not fully established becase various algorithms are considered and fully investigated. In this study, from above point of view, we will propose the immune algorithm that treates the "antibody-antigen reaction". Through some numerical examples, we will show the effectivenews of th proposed algorithm.
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Hisatoshi NEYA, Naoyuki KUBOTA, Fumio KOJIMA
Article type: Article
Session ID: K-0216
Published: August 22, 2001
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This paper deals with a coevolutionary algorithm (CEA) for a crack shape identification problem where the number of shapes is unknown. In the case of problem with unknown factors, we should perform optimization and environmental identification at the sometime. A CEA Including two populations of candidate shapes and candidate combination is proposed. Furthermore, simulation results show the proposed method can obtain the number of cracks and identify their shapes simultaneously.
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Osamu OKUDA
Article type: Article
Session ID: K-0217
Published: August 22, 2001
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There are three distinct categories of structural optimization as follows: (1) Shape optimization, (2) Size optimization, (3) Topology optimization. Each one has a different solution strategy. The third method shows rapidly new development with approximate discretization method of the partial differential equation such as FEM, BEM and FDM. The object of topology optimization is to have no restriction on the final form of the structure. The self-organization method is based on the simple concept that by removing under-stressed materials and simultaneously adding newly surrounding materials to over-stressed materials. The effectiveness of the present simulation method is demonstrated by the numerical examples of the topology optimization problem.
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Koetsu YAMAZAKI, Masuhito TANAKA, Xiao Hong DING
Article type: Article
Session ID: K-0218
Published: August 22, 2001
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In ecological system, various kinds of branching tree patterns such as plant roots and branches of trees, arterial tree can be observed. These branching trees are regarded as one of the structural systems that supply or gather uniformly energy and materials, from and into a specified three-dimensional space field. This paper suggests how to construct computer models of such branching trees that can be applied to the system optimization.
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Nobuhiro YOSHIKAWA
Article type: Article
Session ID: K-0914
Published: August 22, 2001
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A new concept of structural reinforcement for compressed natural gas vehicle fuel containers is presented with formulation of structural optimization. The reinforcement is done by net, whereas the conventional composite containers are fabricated with continuous filament winding. The production efficiency is aimed at by the net reinforcement with high structural reliability ensured by means of structural optimization technique. The net is modeled as truss structure contacting with the surface of the metallic liner, which is modeled as elastic solid finite elements. The geometrical nonlinearity with the finite rotation of net members raises the shape finding of the net. The position of connection node is analyzed on the basis of principle of minimum strain energy with the iterative solution finding. The cylinder part of the container is relatively simple structure, so that the net reinforcement of spherical dome is taken into consideration. The optimum length of net member is determined so as to realize uniform strain net. A formulation of the sensitivity analysis is derived to constitute the governing equation of the optimum length, which is summarized in linear simultaneous equations. An optimum configuration of the net is searched for through the numerical example.
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Akihiro Horide, Shuichi Wakayama
Article type: Article
Session ID: K-0915
Published: August 22, 2001
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The effects of FW-FRP ring thickness on the strength, which was evaluated by simplified strength test methods, were investigated. The deformation of ring specimen was analyzed by using a finite element analysis. Two types of ring strength test, i.e. NOL ring tensile test and ring burst test were carried out in this study. As the results of strength tests, the fracture stress was decreased as increasing a thickness of specimen in NOL ring tensile test. On the other hand in ring burst test, the fracture stress was almost constant independently of thickness. It was confirmed by FE analysis that the degree of uniform deformation in FRP ring influences the above result. Although in a NOL ring tensile test the unbending stress concentrated at the edge of split disk, in ring burst test the hoop stress was uniform through the thickness.
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Eiichi Aoyama, Tsutao Katayama, Toshiki Hirogaki, Kazuya Sugimura, Jun ...
Article type: Article
Session ID: K-0916
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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The plastic gear is used in various fields. However, the development of FRP gear of the high-stiffness and high-strength must be carried out, because it is weak in the impact load. Then, we investigated mechanical property and vibration characteristic in driving of the FRP gear using laminated material of the woven cloth phenolics of which formability and impact resistance were good. As the result, it was proven that the FRP gear was more effective than the metal gear for the reduction in the housing vibration in the low torque. And, it was possible that the strength of the gear could be improved by changing the lamination composition.
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Osamu KUWAZURU, Nobuhiro YOSHIKAWA
Article type: Article
Session ID: K-0917
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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Plain-weave fabrics have complex and nonlinear mechanical property which violates the assumption of continuum and linear elastic body. The discontinuity and heterogeneity permitting finite rotation of the threads are main reason for the property. The pseudo-continuum model proposed by authors is defined so as to represent such mechanical and geometrical properties of the fabric by a new strain-displacement relationship. The mechanical anisotropy and nonlinearity of plain-weave fabrics are clarified by the proposed model throuth the finite element analyses of uniaxial tensile tests.
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Kayo SATO, Nobuhiro YOSHIKAWA
Article type: Article
Session ID: K-0918
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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The trade-off between high reliability and weight reduction should be adequately handled for the design of FRP composite pressure vessels such as fuel tank for the compressed natural gas vehicles. Therefore, the detailed analysis based on the finite element method is indispensable for the design of the vessels. Conventionally, the solid elements are utilized for the finite element analysis of the vessels regardless of disability for bending deformation. In this study, we examine the solid elements in comparison with the shell elements for the purpose of warning the abuse in the finite element analysis of the vessels.
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Naoki TAKANO, Masaru ZAKO, Toru OKAZAKI
Article type: Article
Session ID: K-0919
Published: August 22, 2001
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The authors have presented so far the effectiveness of the microstructure-based process simulation for textile reinforced polymer matrix composites. In this study, the permeability tensor, which is an important parameter in RTM process, is calculated by the mathematical homogenization theory. The proposed analysis gives us not only the macroscopic permeability but also other important information on the microscopic flow characteristics and flow field. The sheared woven fabric after performing in RTM process is studied in this paper.
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Yoshinobu SHIMAMURA, Yosuke YAMAMURA, Akira TODOROKI, Hideo KOBAYASHI
Article type: Article
Session ID: K-0920
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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Recently, applications of integrated large composite structures have been attempted to many structures of vehicles. In order to improve the cost performance and reliability, it is necessary to judge the structural integrity of the composite structures. Fracture simulation techniques using FEM have been developed for the purpose. Influence of the element size on damage growth process is well know but appropriate element size to obtain more accurate results and less calculation time is not investigated in detail. In this study, analytical damage growth process and load-displacement relationship are compared with experimental ones for various mesh sizes. As a result, it is shown that the appropriate mesh division is required for the fracture simulation.
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Naoki TAKANO, Masaru ZAKO, Toru OKAZAKI
Article type: Article
Session ID: K-0921
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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There have been many reports on the numerical analysis of damage propagation in woven fabric composite materials. However, most of them studied the behaviors under in-plane loading conditions including tension, compression and shearing. Because composite materials are often used as plates and shells, their out-of-plane bending behaviors are important. To study the micro- or mesoscopic damage propagation under bending, the consideration of micro-macro coupling is a critical issue. A small region to consider the microscopic behavior is subject to macroscopic non-uniform strain field under bending. Therefore, the conventional homogenizing technique is not applicable. In this paper, we propose a new computational method named finite element mesh superposition method to solve this problem. A two-dimensional example of plain woven fabric composites is shown in this paper.
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Hideo Awaji, Eisuke Yagi, Seong-Min Choi
Article type: Article
Session ID: K-0922
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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Toughening and strengthening mechanisms in nanocomposites were clarified based on the energy equilibrium between energy release rate and fracture energy rate (known as Griffith's equilibrium), and residual stresses around second-phase nano-particles dispersed in matrix grains. The residual thermal stresses around a spherical dispersed particle within a concentric sphere of a matrix grain were specifically analyzed to clarify the effects of residual stresses on the toughening mechanism in the frontal process zone involving microcracks. The analytical results revealed that the ratio of the thermal expansion coefficients of the particle and matrix has a greater effect on residual stresses than the ratio of the Young's moduli, and that the estimated residual stresses were of sufficient magnitude to generate lattice defects around the particle. The toughening and strengthening mechanisms for nanocomposites were also discussed based on the analytical results and explained schematically.
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[in Japanese], [in Japanese], [in Japanese], [in Japanese]
Article type: Article
Session ID: K-0923
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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Increased use of Carbon/Carbon (C/C) composites necessitates fabrication of complex structures, which require high temperature secondary bonding. Secondary bonding of C/C interfaces provides design flexibility and also alleviates complicated fabrication problems. In this study, resin-carbonizaition process was applied for the bonding of C/C composites. In this process, C/C composites were bonded with phenolic resin and the cured resin was then heat-treated to carbonize. Bonding strength of thus bonded layers was evaluated by a double-ends-notched method at elevated temperatures up to 2000℃ in vacuum. The results revealed that bonding-strength increase with increasing temperature. Since strength of graphite is known to be affected by absorbed gas, out gas test was also performed. Absorbed gas is shown to lower bonding strength. Therefore it is concluded that this effect was shown to be one of major factors for the strength enhancement at elevated temperatures.
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Kazunari SHIBUYA, Ken GOTO, Hiroshi HATTA, Yasuo KOGO
Article type: Article
Session ID: K-0924
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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Fracture behavior of three-dimensional reinforced C/C disk was investigated to establish design criteria for high temperature turbine disk. Fly-out objects were detected from the rotation speed of 3000 r.p.m and the vibration amplitude increased with increase of rotation speed. The observation of the surface after high speed rotation revealed that the object flown-out from the disk was θ-directional fiber bundles. The vibration increasing behavior was predicted with simplified model and the result agreed well in tendency.
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Yutaka Sato, Yasumasa Hamaguchi, Ippei Susuki
Article type: Article
Session ID: K-0925
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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The mechanical behaviors of bolted joint of titanium and heat-resistant composites are investigated in this study. The finite element numerical analysis for a multi-fastener joint model, in which the frictional contact is fully taken into consideration, was carried out, and the effect of the friction on the load distribution ratio for each fastener was evaluated. Furthermore, the advanced measurement system using a laser extensometer, which enables us to measure the fastener hole deformation rather directly than a conventional method, was also proposed and the availability of the method was demonstrated through the experimental evaluation of the load distribution ratio.
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Farid El-Tantawy, Kenichi KAMADA, Hisaichi OHNABE
Article type: Article
Session ID: K-0926
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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Positive temperature coefficient (PTC) thermostats are widely used in electronics for its switching and power limiting ability. It can also be used for sensing of different parameters through accurate measurement of temperature. For this, controlled the structure and stability of epoxy matrix with metallic doping is required at a very degree of accuracy for technical point of view. In this study, the effect of Aluminum (Al) particles on the structure and electrical properties of conductive carbon black/epoxy resin composites was investigated in details. Dynamic percolation curves in epoxy matrix were examined at various annealing temperature. The activation energy was calculated as a function of dynamic annealing temperature and various content of Al particles.
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Kohji MINOSHIMA, Kazuto TANAKA, Witold GRELA, Yuji ARAKI, Kenjiro KOMA ...
Article type: Article
Session ID: K-0927
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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Single fiber pull-out tests were carried out to investigate the influence of water absorption on the interfacial properties of aramid/epoxy composite. Interfacial strength is severely weakened after 7-week immersion in hot water. In-situ observations of interfacial crack propagation by video microscope were performed and acoustic emission (AE) signals were analyzed at the same time. AE signals obtained during the pull-out process classified into four types of fracture processes: crack propagation, stick and slip, final unstable crack propagation and fiber breakage.
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Yoshihide HAYASHI, Satoshi SOMIYA
Article type: Article
Session ID: K-0928
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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On the research of fracture process on AFRP debonding and delamination are very important phenomenon. It is said that the fracture process on AFRP is changed by the structure of composite. The fracture sound for two sorts of AFRP, unidirectional and plain woven, was measured on tensile loading. The delamination between layers was occurred intentionally on bending loading and the fracture sound of delamination was measured. Both fracture sounds were compared by AE method. It was pointed that the frequency characteristic distribution of fracture sound corresponding to delamination and debonding is almost same in spite of the structure of composite.
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