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Article type: Cover
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Cover1-
Published: July 31, 2000
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Article type: Appendix
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App1-
Published: July 31, 2000
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Article type: Index
Pages
Toc1-
Published: July 31, 2000
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Katsutoshi Kobayashi, Nobuyuki Taniguchi, Toshio Kobayashi
Article type: Article
Pages
1-2
Published: July 31, 2000
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A non equilibrium fixed parameter subgrid scale model obeying with the near wall asymptotic constraint was proposed by Yoshizwa. In this research Yoshizawa model with two model constants which were optimized by using 2nd order finite difference scheme, was re assessed by using 4th order finite difference scheme proposed by Morinishi. And Yoshizawa model with the optimized model constants was applied to channel flows R_τ = 180,395,590. 4th order finite difference scheme improved the accuracy of numerical simulation in Streamwise mean velocity and GS turbulent intensity. And Yoshizawa model was better in the accuracy of numerical simulation than Smagorinsky model in 4th order finite difference scheme.
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Nobuyuki ABE, Shinichi TASHIRO
Article type: Article
Pages
3-4
Published: July 31, 2000
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Large Eddy Simulation (LES) with dynamic mixed subgrid-scale model is expected to be the most effective method to represent the inverse transfer of turbulent energy from unresolved small size eddies to resolved large ones (the backscatter). We get instantaneous turbulent properties by using LES. By phase-averaging these properties, the principal features of periodic phenomena can be extracted. In this paper, we compare two kinds of ways of phase-averaging to evaluate the energy transfer. Especially we focus on the relations between phase averaged energy transfer and turbulent properties.
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Masayoshi OKAMOTO, Nobuyuki SHIMA
Article type: Article
Pages
5-6
Published: July 31, 2000
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A third-order nonlinear K-ε model proposed by the authors is applied to turbulent flow through an asymmetric diffuser including separation and reattachment. The numerical results show that the nonlinear model predicts profiles of the turbulent quantities better than a representative linear eddy-viscosity model but does not reproduce the flow separation. The model is improved by incorporating a strain-convection effect derived from a theoretical analysis into the Reynolds stress to capture separation and reattachment.
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Kangbin LEI, Nobuyuki TANIGUCHI, Toshio KOBAYASHI
Article type: Article
Pages
7-8
Published: July 31, 2000
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The paper presents a dynamic SGS model of Two Way Coupling for Large Eddy Simulation of particle-laden turbulent flow, which based on Yuu's model (2000). The advantage of this new model is that the coefficient of proposed SGS model can be decided by Germano's (1991) dynamic procedure. Then, the numerical simulation was performed with Van Driest wall function model and the present dynamic SGS model, for downward particle laden turbulent flows at Re=644 in a vertical channel. The present dynamic SGS model has been verified through comparison of statistical properties of particle-laden turbulent flow.
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Hiroyuki ISHII, Takeshi MIYAZAKI, Kiyoshi YAMAMOTO
Article type: Article
Pages
9-10
Published: July 31, 2000
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The interaction between a columnar vortex (Lamb-Oseen vortex) and initially isotropic homogeneous turbulence (produced by a DNS of decaying turbulence) is investigated numerically. After a columnar vortex is introduced, the intense vortices are wrapped around the vortex core. The velocity field of small scale eddies near the vortex core becomes statistically axisymmetric, within a period of two or three revolutions of the columnar vortex (t ≈ 2). The axial velocity dominates near the core surface ('blocking' effect) but the radial velocity dominates away from the vortex core. The linear rapid distortion theory explains well the statistics of turbulence if t < 2,whereas it fails for larger times. The two-point velocity correlation functions saturate t ≈ 5 and decay for t > 6. Bending waves of large amplitude are excited on the columnar vortex, which seems to induce its destruction.
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Naoya TAKAHASHI, Kiyoshi YAMAMOTO
Article type: Article
Pages
11-12
Published: July 31, 2000
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We analyse transition mechanism and visualize vortical structure in the transition regions of the Blasius boundary layer directly simulated on a parallel-super computer. The simulation started with a initial flow given as the basic flow plus small disturbances. When the disturbance amplitude is smaller, the transition is induced by the well-known Tollmien-Schlichting wave instability. In this case. A vortices induced by the nonlinear mechanism appear and produce peak-valley structures on the Tollmien-Schlichting wave, which have been observed in the experiments. On the other case starting with a larger disturbance amplitude than the threshold value, transient growth of streamwise vortices becomes to be dominant. Then, the amplified streamwise vortices collapse to three-dimensional vortices by the nonlinear mechanism.
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Youhei MORINISHI, Shinji TAMANO, Kouichi NAKABAYASHI
Article type: Article
Pages
13-14
Published: July 31, 2000
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Direct numerical simulation (DNS) of wall-bounded compressible turbulence is performed. Our main objective of this study is to clarify compressible effects on turbelence near adiabatic and isothermal walls. Compressible supersonic turbulent flow simulations in a plane channel between isothermal walls, and between isothermal and adiabatic walls are performed. The governing equations of compressible fluid flow are solved using B-spline collocation method in the wall normal direction with Fourier Galerkin method in the periodic directions. As a typical result, the peak value of streamwise velocity fluctuation near the adiabatic wall becomes smaller than one near the isothermal wall in wall coordinates.
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Hiroshi KAWAMURA, Takahiko SAKAKI, Keisuke HONMA
Article type: Article
Pages
15-16
Published: July 31, 2000
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With an aid of the recent development of computers, various direct numerical simulations (DNS) of turbulence were performed. Although the turbulence itself is unsteady in nature, the mean flow is assumed steady in most of the DNS's. This is because the DNS of the turbulence with an unsteady mean flow requires more computational effort to obtain a stable statistical average. In the present study, a pulsating flow driven by pressure gradient is imposed on the turbulent channel flow. The each period is divided into a number of phases and statistical average is obtained for various turbulence quantities.
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Mamoru TANAHASHI, Daigo FUJIMURA, Toshio MIYAUCHI
Article type: Article
Pages
17-18
Published: July 31, 2000
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Direct numerical simulations of MHD turbulent channel flow with a uniform magnetic field in the transverse direction are conducted to investigate the effects of the magnetic field on the turbulence structure and drag. By applying the magnetic field, turbulence intensity and the number of fine scale eddies decrease. Drag increases for the case of intense magnetic field, whereas drag does not increase for the moderate magnetic field case. In the moderate magnetic field case, the fine scale eddies near the wall are sustained even though their rotating motions are weakened by Lorentz force.
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Yasunori TAKAHASHI, Oaki IIDA, Yasutaka NAGANO
Article type: Article
Pages
19-20
Published: July 31, 2000
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The flow in the planetary atmosphere and ocean is influenced by both the effects of Coriolis force and the buoyancy. The effect of vertical and horizontal temperature gradients is also important in a global weather phenomenon, such as thermal wind, i.e., a jet generated on upper atmospheric stratum. In this study, the effect of the horizontal temperature gradient on the sense of the rotation in the vertical vortices is investigated by using direct numerical simulation in the homogeneous shear flow under the effects of rotation and stable stratification. As a result, it is found that in the thermal wind with the horizontal temperature gradient, the cyclons with the same sense of the rotation as the earth, become dominant. On the other hand, in the case without horizontal temperature gradient, the anticyclonic vortices are enhanced.
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Masataka TOKUDA
Article type: Article
Pages
21-22
Published: July 31, 2000
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Meso-plasticity which incorporates directly the micro-mechanism of deformation and the structural characteristics have a possibility to reproduce the plastic deformation of engineering materials in a practically reasonable accuracy and reliability. The related scientific research activities are vitally going on now. In this paper, the history. the present situation and the expectations of this Meso-plasticity are discussed.
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Shokichi KANNO, Koichi ITO, Jun NITTA, Yoshihiro KAMADA, Taketoshi SAG ...
Article type: Article
Pages
23-24
Published: July 31, 2000
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We performed numerical analyses, based on crystalline plasticity, of the formation and development of localized shear bands in ductile single crystals in order to establish a fundamental basis for predicting the forming limit of sheet metals. The critical condition and direction of the development of shear bands are predicted by using bifurcation theory. For the post-bifurcation analysis, we introduce a hypothetical 13th slip system into elements that satisfy the bifurcation conditions. Results of numerical analyses applied for plane strain compression demonstrate that an envelope line connecting shearing directions of elements penetrates the metal in the thickness direction.
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JUN Nitta, KOICHI Itoh, SHOKICHI Kanno, YOSHIHIRO Kamata, TAKETOSHI Sa ...
Article type: Article
Pages
25-26
Published: July 31, 2000
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Shear band is the band-like region with concentrated shear strain under large deformation state. In this study, prediction of onset of shear band in ductile single crystal is discussed based on crystal plasticity. Rate dependent crystal constitutive relation is applied to 3D fcc crystal model and shear band instability analysis is performed. The results show the effects of rate sensitivity m and latent hardening. Besides, the dependence for given constraints in shear band deformation is showed too.
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Tetsuya OHASHI
Article type: Article
Pages
27-28
Published: July 31, 2000
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Toshihiro KAMEDA
Article type: Article
Pages
29-30
Published: July 31, 2000
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Based on a three dimensional multiple slip crystalline formulation with dislocation density and computational scheme, the characteristics of grain boundaries (G.B.) of Ni_3Al are studied. To analyze the G.B. behavior in polycrystal, the direction of the most active slip system and its immobile dislocation density are considered at each G.B. It is shown that the fraction of some G.B.s orientation is one of the dominant issues to determine fracture mode of polycrystalline materials. The results show the polycrystal which includes Σ17b G.B. causes intergranular fracture more likely than the polycrystal which contains Σ33α G.B.
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Tadashi HASEBE, Yutaka IMAIDA
Article type: Article
Pages
31-32
Published: July 31, 2000
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This paper proposes constitutive model for dislocation substructure evolution within the framework of crystal plasticity where cell formation and dislocation pile-ups at the cell boundary are considered. A concept of imaginary cell size representing chracteristic length scale of the evolved substructures are introduced. Recovery model based on activation energy of cross slip are also developed. The model is applied to several loading conditions.
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Shigeo KOTAKE, Yasuyuki SUZUKI, Masafumi SENOO
Article type: Article
Pages
33-34
Published: July 31, 2000
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Probability density of stress on valence electron, called electron stress σ, at slip plane of metals, K and Al, with one-axial deformation is studied in compariosn with former dislocation theory. σ is calculated from the wave function by using pseudo-potential method. Distributional change on σ indicates the different properties on the critical shear stress in bcc and fcc metals. The direction of the local minmum density of σ from an atom coinsides with the slip direction of bcc and fcc metals. We also examine the force between ion and electron from σ by concerning the electron screening effects on ion. Although these calculations are the analysis on the perfect crystal, σ can explain the phenomena on plastic deformation in metal.
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Yasuko MOTOYASHIKI, Atsushi SUGETA, Yoshihiko UEMATSU, Masahiro JONO
Article type: Article
Pages
35-36
Published: July 31, 2000
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The discrete dislocation dynamics (DDD) method is known as a mesoscopic computer simulation procedure which can represent each dislocation movement. In this paper, the 2-dimension DDD simulation was carried out in order to investigate dislocation movement near a fatigue crack tip in bcc iron. Cyclic plastic strain at the crack tip, including compressive one due to the reverse slip during unloading, was obtained and the shape of plastic region was similar to that observed in the grain-oriented 3% silicon iron by an atomic force micro scope. Since cyclic plastic strain is considered to be a primary factor of fatigue damage, DDD approach is valuable method to simulate the fatigue crack propagation.
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Yuji SHIMIZU, Yoji SHIBUTANI, Takashi MAEDA
Article type: Article
Pages
37-38
Published: July 31, 2000
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Self-organization due to dynamics of dislocation network leads the macroscopic hardening of materials and inhomogeneous localization of deformation. Discrete Dislocation (DD) methodology has been add-ressed as one of the prospective mesoscopic simulations to model its process. One DD which describes the crystallographic local rule between dislocations by the Cellular Automata (CA) is here proposed and then the mechanism on dipole generation or annihilation in the dislocation network under the external stress is investigated.
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Kanto KIKUCHI, Kazuyuki SHIZAWA
Article type: Article
Pages
39-40
Published: July 31, 2000
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A model of self-organization of collective dislocations is proposed on the basis of geometrical descriptions of crystal defects and thermodynamics of complexity. The simultaneous reaction-diffusion equations expressing interactions between GN dislocation density and incompatibility are derived rigorously. Furthermore, the evolution process of PSBs is investigated by the linear stability and bifurcation analyses.
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Tadashi HASEBE, Yutaka IMAIDA
Article type: Article
Pages
41-42
Published: July 31, 2000
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This paper discusses cell formation process based on the gauge field theory of dislocations. Dislocation theoretical first principle (FP) Hamiktonian for dislocation field is derive where interaction with the background elastic field. Annihilated field is introduced as an order parameter and effective Hamiltonian is evaluated from the FP Hamiktonian by using the quantum field theoretical method. Further mechanism of cell formation is extensively discussed.
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Makoto OHTSUKA, Hiroki CHIBA, Minoru MATSUMOTO, Kimio ITAGAKI, Toshiyu ...
Article type: Article
Pages
43-44
Published: July 31, 2000
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The Ni-Mn-Ga films were deposited on a poly-vinyl alcohol substrate with a radio-frequency magnetron sputtering apparatus using Ni_<50>Mn_<25>Ga_<25> and Ni_<52>Ga_<24> targets. After separating from the substrates, the films were annealed at several temperatures for 3.6ks. The chemical composition of the films depended on the radio-frequency generating power, however, there was no dependence on the heat treatment temperature. Each deposited film has a columnar grain structure. After heat treatment, the width of columnar grains widened and then became indistinct with increasing heat treatment temperature. At more than 1073 K, the precipitation of MnO was observed clearly. The films showed he most crystallinity at 1073 K. The martensitic transformation temperature increased with increasing nickel content of films, while the Curie temperature decreased. The film obtained at 200 W using the Ni_<52>Mn_<24>Ga_<24> target after heat treatment at 1073 K showed one-way shape memory effect through the reverse martensitic structural transformation during heating.
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Hisashi Naito, Yuji Matsuzaki
Article type: Article
Pages
45-46
Published: July 31, 2000
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In our previous work, introducing a concept of interaction energy for phase transformation, we proposed a one-dimensional constitutive model of Shape Memory Alloys(SMA), which can express the deformation behavior caused by martensitic transformation. In this paper, we extend our model as to be able to express the behavior due to R-phase transformation. Here, we newly introduce free energies and interaction energies with respect to the R-phase transformation. Stress-strain-temperature relationships calculated using the proposed model are in good agreement with available experimental data including R-phase transformation. The result suggests that the proposed model is useful for the analysis of the behavior of SMA.
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Masato ENDOU, Hisaaki TOBUSHI, Shunichi HAYASHI, Kazuyuki TAKATA, Kayo ...
Article type: Article
Pages
47-48
Published: July 31, 2000
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The thermomechanical properties of polyurethane-shape memory polymer foam were investigated. The main results are summarized as follows. (1) Strain is recovered at temperatures around he glass transition temperature during heating. The temperature at which strain is recovered decreases with an increase in maximum strain. (2) The rate of strain recovery is 99% and does not change under cyclic deformation. (3) The rate of strain fixity is 100%. (4) Stress diminished during cooling. Stress decreases markedly at temperatures below the glass transition temperature. (5) Because large deformation and large variation in volume are obtained in shape-memory polymer foam, shape-memory polymer foam has excellent functional performance for large elements of mechanics and structures.
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Yuuki NAGAO, Satoru MATSUMURA, Michihiko NAKAGAKI, Yadong WU
Article type: Article
Pages
49-50
Published: July 31, 2000
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A macroscopic constitutive law was develped for an intelligent composite material with dipersed particle/fiber inclusions that consist of a Shape memory Alloy. The model uses the equivalent inclusion method with the Self-consistent Compliance method for the mixing. Localized Rigidity Method(LRM) is used to take into account of the phase transformation occurring in the meso-local domain in the composite. The numerical results of the model are demonstrated for a particle dispersed composite with SMA, and are compared with that of a meso-mechanics analysis by a finite element procedure.
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Kentarou TAKASHINA, Hiromasa YABE, Kazuya OGURI, Yoshitake NISHI
Article type: Article
Pages
51-52
Published: July 31, 2000
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We have studied an actuator function of a pair of different glasses, bi-ceramic glass, which is shape memory effect. The reversible shape memory effect (RSME) was found near glass transition temperature. We conclude that the bi-ceramic glass is a new concept of the actuator that can be operated in corrosion environment.
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Go MURASAWA, Keiichiro TOHGO, Hitoshi ISHII
Article type: Article
Pages
53-54
Published: July 31, 2000
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Composites containing NiTi shape memory alloy long-Fiber, short-fibers or Ti long-fiber in a Polycarbonate matrix have been fabricated by the injection molding technique. In the shape memory alloy (SMA) composites, two kind of NiTi fibers showing the shape memory effect (SME) and the psuedoelasticity (PE) at room temperature are used. Fracture behaviro under uniaxial tension and deformation behavior under thermo-mechanical loading are examined on the composites. The obtained results are as follows : (1) The stress-strain relation up to the final fracture of the SMA composites showed the repeated up-and-down of the stress which corresponds to the necking of the specimen, fiber fracture and matrix fracture. (2) The strain for the initiation of necking and the strain for the fiber or matrix fracture in the SMA composites were higher than those in the Ticomposite. This is attributed to the unique stress-strain relations accompanied by the stress-induced martensitic transformation of the SMA fibers. (3) The SMA composite containing PE fiber exhibited the psuedoelastic deformation under tensile loading-unloading. (4) The SMA composite containing SME fiber exhibited the contraction by heating after tensile loading-unloading, but the compressive residual stress in the matrix expected in this process was not remarkable.
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Toshiyuki TAKAGI, Yun LUO, Hirokazu NAKAMURA, Shintaro AMAE, Tomoyuki ...
Article type: Article
Pages
55-56
Published: July 31, 2000
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This paper describes the development of a shape memory alloy (SMA) actuator as an artificial sphincter. The artificial sphincter is expected to enable the active bowel movement of patients without the function due to inborn intestinal atresia or medical operations of an artificial anus. The actuator has the functions of a valve; keeping the artificial anus closed at the body temperature and opening it by heating the SMAs. Investigations on thermomechanical properties of the actuator have been carried out. The actuator has also been subjected to clinical tests on animals, and exhibits complete functions of an artificial sphincter.
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Soichi SUGINO, Masataka TOKUDA, Tadashi INABA
Article type: Article
Pages
57-58
Published: July 31, 2000
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The two-way shape memory effect is caused by the internal stresses induced by the thermo-mechanical cyclic loading called "training". The training by combined loading induces some complex internal stress, while the training under simple loading like a uniaxial tension causes simple internal stress states. Therefore the two-way shape memory behaviors trained by combined loading may be quite different from those obtained by simple loading. We have been experimentally investigating the two-way shape memory behaviors trained under combined loading by applying the combined loads of axial force and torque to the thin-wall tube specimen of Cu-based shape memory alloy. In this paper, some of experimental results are shown and discussed from a viewpoint of developing the new functional actuator.
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Masahiko Kawase, Goichi Ben, Hitoshi Yoshida
Article type: Article
Pages
59-60
Published: July 31, 2000
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This paper presents a fabrication method of the unidirectional composite material, in which shape memory alloy (Ti-Ni alloy) fibers and Epoxy resin are used as reinforced fibers and matrix, respectively. In order to be recovered the memorized shape, this new composite is heated by current and its responsive temperature is measured. Furthermore, the flexural properties of new composite is also examined.
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Masayuki OKUGAWA, Minoru SASAKI
Article type: Article
Pages
61-62
Published: July 31, 2000
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This paper addresses the vibration control and the motion control of a cantilever by using a bimorph piezoelectric actuator, based on the concept of smart materials and structures, and discusses the method of how to separate a sensing output signal from measured data include control input signal. The input-output relationship of a self-sensing system on the cantilever using piezoelectric actuator can be described by the state space expression with a direct part. Adopting observer theory is proposed in order to control estimated state vectors with a state feedback controller such as the LQ or H_∞ controller, and to separate measured data. Calculated simulation result by identified model using the subspace state space identification method shows that the proposed method can be achieved to suppress the vibration and separate sensing output without using the bridge circuit.
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Mamoru SHIMAZAKI, Takafumi FUJITA, Yasuhiro MATSUI, Masayoshi TATSU
Article type: Article
Pages
63-64
Published: July 31, 2000
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We have tested the fundamental properties of magnetostrictive actuators. In order to apply the smart structures to large-scale structures on the earth such as buildings, actuators which can produce much larger forces are required. Whether the smart structures can be applied to actual buildings or not, depends on performance and costs of large-scale magnetostrictive actuator. In this study, to investigate the performance, a large-scale magnetostrictive actuator which consists 10 magnetostrictive plates of a φ 30×(12)^H mm outer size is tested. Static and dynamic tests were carried out for the large-scale magnetostrictive actuator, showing fundamental properties of the actuator.
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Mamoru SHIMAZAKI, Takafumi FUJITA, Yasuhiro MATSUI, Masayoshi TATSU
Article type: Article
Pages
65-66
Published: July 31, 2000
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In order to apply the smart structures to large-scale structures on the earth such as buildings, actuators which can produce much larger forces are required. For the smart structure used for buildings, magnetostrictive actuators might be more suitable ones than piezoelectric actuators, because magnetostrictive actuators are far stronger than piezoelectric actuators which are slightly brittle ceramics. In this study, static and dynamic tests were carried out for the magnetostrictive actuator, showing fundamental properties of the actuator.
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Yun LU, Mitsuji HIROHASHI, Ryohta HAYASHI
Article type: Article
Pages
67-68
Published: July 31, 2000
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A processing technique was developed to improve conductivity of SiC/Al composite electrical heating actuator. Response characteristics such as electrical resistance, temperature and curvature were measured and discussed. The results showed that the conductivity of SiC/Al compostie electrical heating actuator was improved by the present processing technique. The actuator temperature goes up with supplying electrical power. The reproducibility of the relationship between the temperature and the electrical power was confirmed by repeating to heat and cool the actuator.
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Toshihiro HIRAI, Jianming ZHENG, Masashi WATANABE
Article type: Article
Pages
69-70
Published: July 31, 2000
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Non-ionic polymer gel of poly(vinyl alcohol)(PVA) swollen with a dielectric solvent, dimethyl sulfoxide (DMSO) was found to be bent by applying an electric field. The gel was prepared by chemically crosslinking a physically crosslinked PVA gel. The gel has homogeneous structure. Bending at the field of 500 V/mm reached the bending angle of over 90° within 60 ms. The size of the gel was 10 (length)x5 (width)x2 (thickness) in mm. With increasing the field strength the bending curvature was proportional to the square of the electric field. The strain induced in the deformation was suggested over 100%. The gel also showed a crawling motion, when it was placed on an array of the electrodes fixed on a glass plate. The mechanism of the deformation was suggested to be explained by the charge injected solvent drag. Solvent drag induced the pressure distribution in the gel which leads the bending deformation. The nonionic gel and the method proposed can be a possible way for the practical artificial muscle.
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Takashi HOSAKA, Osamu HAGA, Hiroshi ASANUMA, Hideo KOYAMA
Article type: Article
Pages
71-72
Published: July 31, 2000
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The purpose of this study is to create a shape controllable structural material and to develop its control method. The unsymmetric lamination plates composed of Aluminum alloy CFRP and KFRP sheets were used as the testing material. It was clarified that thermal control of the material was possible by the PID control method by using Joule heating characteristics obtained with the step response method. The shapes of the test pieces at the optional temperature were measured experimentally, and they were compared with the calculation results obtained by the classical lamination theory. There was considerable difference between the two. therefore it is difficult to estimate the relationship between the two. therefore it is difficult to estimate the relationship between the shape and the temperature of the testing material using classical lamination theory.
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Hiroshi ASANUMA, Junichiro OHIRA, Toshiyuki SATO, Osamu HAGA
Article type: Article
Pages
73-74
Published: July 31, 2000
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Thispaper describes fabrication of higher performance CFRP/aluminum laminate actuators by investigating various factors such as mechanical properties of aluminum plate, bonding strength between FRP prepreg and aluminum plate, and glass transition temperature of the matrix resin. According to the experimental results, the follwing conclusions were obtained. (1) Curvature of the actuator increases with increasing proportional elastic limit of the aluminum plate in the experimental range. (2) In order to maintain high bonding strength between the aluminum plate and the FRP prepreg up to higher temperature range, roughness must be given on the aluminum plate or the matrix resin must be replaced with higher glass transition temperature one. (3) The force generated by an actuator made of higher temperature (453K) cure type epoxy linearly increases with increasing temperature up to higher temperature range compared with that of lower temperature (393K) one and the maximum force reaches about 1.5 times that of lower temperature one.
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Toshihiko SHIRAISHI, Shin MORISHITA, Yong Kong AHN
Article type: Article
Pages
75-76
Published: July 31, 2000
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The viscosity variation of a suspension due to applied electric field strength is called Electrorheological(ER) effect, and several kinds of ER fluid have been developed so that it may be applied to mainly semi-active devices in mechanical engineering field. ER fluid generally consists of solid particles suspended in dielectric liquid. The particles in the liquid build up chain structures between electrodes in the direction of the applied electric field, whose tensile strength causes yield shear stress variation of ER fluid. In the present paper, the cluster formation of particles in ER fluid under an electric field was simulated by Cellular Automata(CA) and ER effect was quantified.
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Ismail YUKSEK, Yoshihiro KIKUSHIMA, Selim SIVRIOGLU, Nobuo TANAKA
Article type: Article
Pages
77-78
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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This paper deals with cluster control to suppress structural vibrations occurring on viaduct roads because of movement of vehicles. A viaduct road is modeled using finite element method and structural modes of road element are obtained. Based on the finite element model of the flat road part, a cluster control method is studied. It is verified that cluster actuation and sensing based control suppress considered structural modes in any case without any control and observation spillover effects.
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Yoshihiro KIKUSHIMA, Ismail YUKSEK, Selim SIVRIOGLU, Nobuo TANAKA
Article type: Article
Pages
79-80
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Recently, highway roads have been constructed as steel structures instead of concrete because of their lightweight after Hanshin Great Earthquake caused big damages on concrete highway roads. While earthquake-resistance of a steel road structure increases, vibration and low frequency noise on such structures becomes a major problem due to flexibility. There is an increasing demand especially in populated areas to suppress vibration and noise in highway roads for reducing noise related environmental pollution. This study proposes cluster filtering which classifies vibration modes into the certain mode groups and cluster actuation, which excites only certain modes as a reliable and effective approach to suppress vibration on viaduct roads. In the previous reports, the cluster control is studied for a clamped-clamped simply supported plate. In this study, the previous results are experimentally verified and the cluster control is applied to a viaduct road using moment actuators, which generate absolute forces inside the structure.
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Koichi EGAWA, Masato KUSHIHASHI, Makoto NAKAMURA
Article type: Article
Pages
81-82
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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The researches on vibration suppression in structural health monitoring are doing many places for the purpose of preventing fracture of structures by cyclic loading and structural resonance. In intelligent structural study, the researches are done by using optical fiber and other sensors for detecting large amplitude and at the same time, PZT and other actuators for suppressing the vibration with connecting logical circuit. Many researches of this category are done on cantilever beams as the simplest model of a helicopter blade. When we are trying to materialize the concept of intelligent structures and/or structural health monitoring (SHM) in Japan, the targets are not helicopters and other weapos, but consumers goods and these intellectualized ones are expected to be cost-effective. So, sometimes we can not make large, complex intelligent/SHM system. Then, as an example, a magnetic damper was adopted here. It has simple shape and composition, and cheap. The details will be explained in the presentation.
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Masanori Ohori, Takafumi Fujita, Minoru Ohiraki
Article type: Article
Pages
83-84
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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This study aims to develop systems to measure maximum strains for structural health monitoring. In this study steels having TRIP effects are tested for maximum strain sensors. For the first step, a stainless steel (SUS304) was tested to make clear its characteristics. We showed relations between strain and magnetic permeability by simple axis tension test, and by two types of cyclic 3 points bending tests. These results showed possibility to for the maximum strain sensor.
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Xin Zen LI, Shiro TAKADA
Article type: Article
Pages
85-86
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Stimulated Brillouin Scattering (SBS) is utilized in the optical fiber sensor distributed measurement system. BOTDA (Brillouin Optical Time Domain Analyzer), one of these devices, shows a capability to obtain strain and temperature simultaneously with high precision over a distance of tens' kilometers. This makes BOTDA an expectable candidate device to realistic FOBSS (Fiber Optic Based Smart Structure). The present paper suggests a computer based tomography method to enhance the spatial resolution of BOTDA which can be solved to an artificially specified segment of centimeter order or less; this is one or two orders smaller than the present art of view. The presented result is considered as an important progress towards widely commercial applications.
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Kazuro Kageyama, Isao Kimpara, Hideaki Murayama, Akiyoshi Shimada, Hir ...
Article type: Article
Pages
87-88
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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In this paper, we describe a structural health monitoring system using fiber optic strain distributed sensors. This system was applied to International America's Cup Class (IACC) yachts and we used a Brillouin optical time domain reflectometer (BOTDR) in order to measure strain distributions of the yachts. Nippon Challenge syndicate that entered in America's Cup 2000 built two IACC yachts (Asura and Idaten) for the races. These yachts were equipped with sensing fibers to monitor deformation and to detect degradation or damage. We successfully measured strain distributions of the yachts on shore and undertook a health monitoring using the strain distribution data. The results had been used for daily maintenance, structural reinforcement and race strategy until the races was over.
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Akira TODOROKI, [in Japanese], Hiroshi SUZUKI, Yoshinobu SHIMAMURA, Hi ...
Article type: Article
Pages
89-90
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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The present paper employs electric resistance change method for detections of delamination crack of CFRP laminated plates. The method is applied to embedded delamination crack of quasi-isotropic laminates. The delamination cracks are created by static indentation tests. Response surface methodology is adopted as a tool for solving inverse problems. As a result, the present method is successfully detected delamination crack location and size.
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Takaomi INADA, Yoshinobu SHIMAMURA, Akira TODOROKI, Hideo KOBAYASHI
Article type: Article
Pages
91-92
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Recently CFRP laminated structures have been applied to many structures of vehicles. Interlaminar strength of laminated structures is relatively low, and delamination can be induced easily by an impact load or a cyclic load. Since delamination degrades stiffness of the structures, it is need to identify delamination nondestructively. Natural frequencies have been adopted to identify delamination of CFRP laminated beams. Identification of delamination location, however, is difficult, and another parameters that can identify delamination location are needed. In the present study, an identification method of delamination for a CFRP laminated beam using the change of natural frequencies and anti-resonance frequencies. Effectiveness of the present method is evaluated in delamination identification analysis of a cross-ply beam.
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Atsushi Iwasaki, Akira TODOROKI, Yoshinobu SHIMAMURA, Hideo KOBAYASHI
Article type: Article
Pages
93-94
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Delamination cracks are invisible and cause decrease of compression strength of laminated composites. Therefore, health monitoring system is required for laminates. The present study adopts an electric potential method for health monitoring of graphite/epoxy laminated composites, the electric potential method does not cause strength reduction and can be applied existing structures by low cost. The present study focuses on the applicability of the electric potential method for identification of delamination crack size. Multi points measurements of electric voltage are adopted for the identification. FEM analyses are conducted to investigate the applicability. The present paper employs Mahalanobis distance adopted in discriminant analysis for identifications of delamination crack. As a result, it was shown that this method is effective for identification of delamination crack.
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