宇宙飛翔工学研究系

佐藤 英一

サトウ エイイチ  (Eiichi Sato)

基本情報

所属
国立研究開発法人宇宙航空研究開発機構 宇宙科学研究所 宇宙飛翔工学研究系 教授 (プログラムディレクター)
東京大学 大学院工学系研究科 教授
学位
工学博士(1989年12月 東京大学)

連絡先
satoisas.jaxa.jp
研究者番号
40178710
ORCID ID
 https://orcid.org/0000-0001-7397-3477
J-GLOBAL ID
200901078153204966
researchmap会員ID
1000144501

外部リンク

主要な論文

 235
  • Amit Patel, Eiichi Sato, Takeshi Takagi, Naohiro Shichijo
    Journal of the European Ceramic Society 42(10) 4121-4132 2022年8月  
  • Fei Shen Ong, Ryotaro Nishi, Hirobumi Tobe, Eiichi Sato
    Journal of the European Ceramic Society 42(6) 2707-2717 2022年6月  査読有り
    A novel two-step bonding of Ti-6Al-4V/Si3N4 joint was developed with Nb interlayer as residual-stress reliever via low-pressure transient-liquid-phase bonding (TLPB) of Ti-6Al-4V/Nb side prior to active-metal brazing of Nb/Si3N4 side. While 1.75 mass% of Ti in a 50-µm-thick CUSIL-ABA® filler was sufficient for sound bonding at Nb/Si3N4 side when brazed at 1103 K for 10 min, one-step-brazed joints with bonding area of 10 × 10 mm2 were prone to failure at the Ti-6Al-4V/Nb side due to brittle Cu-Ti intermetallic compounds (IMCs). Replacing brazing of Ti-6Al-4V/Nb side with TLPB using pure Cu and Ni foils as filler at 1213 K for 180 min eliminated the formation of brittle IMCs via homogenization of (α + β)-Ti; bending strength increased to 193 MPa with residual-stress-induced failure from Si3N4 ceramics. Finally, effectiveness of stress-accommodation via Nb interlayer and filler's plastic flow was quantitatively verified with reasonable fidelity by finite-element analysis incorporating temperature-dependent elasto-plastic properties.
  • Hirobumi Tobe, Shunsuke Kojima, Eiichi Sato
    Acta Materialia 229 117811-117811 2022年5月  査読有り
  • Hiroshi Masuda, Eiichi Sato
    Acta Materialia 197 235-252 2020年9月  査読有り
  • Hirobumi Tobe, Yuichi Matsuki, Shinsuke Takeuchi, Eiichi Sato
    MATERIALS TRANSACTIONS 61(1) 68-71 2020年  査読有り
    A novel deployable rocket nozzle utilizing superelasticity was proposed in this study. Ti-4.5Al-3V-2Fe-2Mo alloy (SP-700) sheets were heat-treated to have appropriate alpha/beta ratio so that the sheet shows superelasticity at room temperature. A miniature nozzle model was fabricated through thinning, cutting, and welding processes of the sheets. Folding-deployment tests of the model were conducted in addition to finite element analyses of its folding behavior. The feasibility of the new concept of superelastically-deployable sheet structure was successfully verified.
  • Hiroshi Masuda, Hirobumi Tobe, Eiichi Sato, Yoshito Sugino, Shigeharu Ukai
    Acta Materialia 176 63-72 2019年  査読有り
  • 長野 幹雄, 川合 伸明, 長谷川 直, 北薗 幸一, 佐藤 英一
    日本機械学会論文集 84(863) 19-00012 2018年  査読有り
  • 比金健太, 増田紘士, 戸部裕史, 北薗幸一, 佐藤英一
    軽金属 67(6) 228-233 2017年  査読有り
  • Masaya Deguchi, Hirobumi Tobe, Eiichi Sato
    INTERNATIONAL JOURNAL OF FATIGUE 87 351-358 2016年6月  査読有り
    This paper describes a characteristic damage propagation mechanism in low-cycle creep-fatigue of Cu-0.7Cr-0.09Zr (mass%), as investigated by creep-fatigue tests including strain controlled fatigue and stress-holding type creep, and following microstructural observations by scanning electron microscopy (SEM). The total stress-holding time until rupture in the creep-fatigue test was shorter than one-tenth of the rupture life in the simple creep test, and the rupture life of the specimen in the creep-fatigue test was shorter than half of that in the simple fatigue test. The SEM images suggest that the connection between fatigue crack propagating along grain boundaries and intergranular creep voids rapidly accelerates crack propagation. Crown Copyright (C) 2016 Published by Elsevier Ltd. All rights reserved.
  • Tetsuya Matsunaga, Tatsuya Kameyama, Kohei Takahashi, Eiichi Sato
    MATERIALS TRANSACTIONS 50(12) 2858-2864 2009年12月  査読有り
    This paper reports creep tests on three kinds of polycrystalline hexagonal close-packed metals, i.e. commercially pure titanium, pure magnesium, and pure zinc, in the vicinity of ambient temperature even below their 0.2% proof stresses. These materials showed significant steady state creep rates around 10-9 s(-1) and had stress exponents of about 3.0. Arrhenius plots in the vicinity of ambient temperature indicate extremely low apparent activation energies. Q, of about 20 kJ/mol, which is at least one-fourth of the Q of dislocation-core diffusion. Ambient-temperature creep also has a grain-size effect with an exponent of 1.0. These parameters indicate that ambient-temperature creep is a new creep deformation mechanism in h.c.p. materials. [doi:10.2320/matertrans.M2009223]
  • Y. Motoyashiki, S. Hasegawa, K. Okudaira, E. Sato
    INTERNATIONAL JOURNAL OF IMPACT ENGINEERING 35(12) 1666-1671 2008年12月  査読有り
    A new advanced ceramic thruster made of monolithic silicon nitride (Si(3)N(4)) is under development for the next interplanetary probe of PLANET-C Venus exploration mission in Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA). In order for secure operation of a spacecraft with a ceramic component onboard a real mission, the reliability against micrometeoroid impacts on the ceramic component has to be investigated in addition to the quasi-static mechanical and thermal analyses and verifications. First, the risk probability of the micrometeoroid impacts was evaluated by using an interplanetary flux model, and the risk evaluation in terms of impact energy was proposed by combining the velocity distribution with the flux model. The probability of impacts on the ceramic thruster during the mission was estimated with this model. Second, hypervelocity impact tests were performed with a two-stage light-gas gun. Three types of failure were observed: one was only a crater formed on the impact surface. Another type was crater formation on the front-face and spall fracture on the back-face and in the last type a perforation was formed in addition to cratering and spalling. The samples did not either shatter or breakdown for the impact energies tested in this study. The impact failure morphology observed in this study showed dependency on the plate thicknesses and the projectile kinetic energy. The energy-based risk evaluation together with the series of the hypervelocity impact tests indicated that the silicon nitride ceramic thruster onboard the interplanetary probe would have only a local damage and survive during the mission term. (C) 2008 Elsevier Ltd. All rights reserved.
  • E. Sato, K. Kawabata, K. Kitazono, K. Kuribayashi
    Materials Transactions 45(7) 2295-2303 2004年  査読有り
    Composite creep deformation was analyzed, based on a continuum plasticity representation of the matrix, in an ideal composite at high temperatures in the case of negligible interfacial diffusion and sliding. A general formula of the steady-state creep strain rate was derived for a composite consisting of an ellipsoidal rigid reinforcement and a creeping matrix with a stress exponent of one. A closed-form solution was then derived for a composite with a cylindrical reinforcement under pure shear deformation in a two-dimensional analysis. The resultant creep deformation satisfies the requirements of impotency, volume conservation and interfacial continuity. Traces of two types of edge dislocations were analytically drawn; they show that dislocations climb over the reinforcement, retaining no dislocations either in the matrix or at the interface. Also, two types of dislocations simultaneously climb up and down at any portion in the matrix through dislocation core shuffling without long-distance diffusion. Finally, it was concluded that plastically-accommodated creep is characterized by two types of dislocations that simultaneously climb over a reinforcement, generating a heterogeneous creep strain increment without long-distance diffusion.
  • K Kawabata, E Sato, K Kuribayashi
    ACTA MATERIALIA 51(7) 1909-1922 2003年4月  査読有り
    A steady-state creep model of a metal matrix composite was proposed considering the accommodation processes of the misfit strain between the matrix and reinforcements in order to comprehensively explain dispersion strengthening, composite strengthening and composite weakening. The proposed model was verified experimentally using the model composites, Ti/TiB in situ composites of 5, 15 and 20vol.%TiB, which have a good interfacial bonding, suitable size and aspect ratio of TiB for a moderate diffusional accommodation rate, and no fine oxides. A sigmoidal curve in a double-logarithmic scale of stress and strain rate was observed in the creep of Ti/15TiB at 1123 K and was classified into a complete-diffusional-accommodation region corresponding to composite weakening, a diffusional-accommodation-controlled region and a plastic-accommodation-controlled region corresponding to composite strengthening with increasing stress. The activation energies in the three regions were close to those of the volume, interface and volume diffusion of Ti, respectively. In the plastic-accommodation-controlled region, the strain rate decreased with increasing volume fraction, while near the complete-diffusional-accommodation region, the strain rate scarcely changed. The strain rate of the transverse creep was ten times that of the longitude creep in the plastic-accommodation-controlled region, while the difference was scarcely observed near the complete-diffusional-accommodation region. (C) 2003 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.
  • K Kawabata, E Sato, K Kuribayashi
    MATERIALS TRANSACTIONS 43(7) 1647-1652 2002年7月  査読有り
    The steady-state creep behavior of metal matrix composites was analyzed via consideration of two accommodation processes, diffusion and plastic, which are inevitable for the materials to continue creep deformation. The creep experiments were performed using a model material, in situ TiB fiber-reinforced pure alpha-Ti matrix composite, which has a good interfacial bonding, a moderate diffusional-accommodation rate and no fine oxide dispersions. A sigmoidal curve of strain rate and stress relation in a double logarithmic plot was observed, indicating the presence of three deformation regions: plastic-accommodation-control region, diffusional-accommodation-control region and complete diffusional-accommodation region, at high, middle and low stresses, respectively. The activation energies in the three regions were close to those of volume, interface, and volume diffusion of alpha-Ti, respectively.
  • K Kitazono, R Hirasaka, E Sato, K Kuribayashi, T Motegi
    ACTA MATERIALIA 49(3) 473-486 2001年2月  査読有り
    A theoretical model of internal stress superplasticity is developed in a single-phase polycrystalline material with an anisotropic thermal expansion. Quasi-steady state creep equation during a thermal cycle is derived quantitatively based on continuum micromechanics. The model assumes that the generated mismatch strain is accommodated simultaneously by the plastic flow of the material. The linear creep deformation. which corresponds to internal stress superplasticity, is obtained at low applied stress region. and the creep rate depends on the crystallographic texture of the material. The validity of the model is experimentally verified using polycrystalline zinc which is a typical metal having large anisotropy in thermal expansion. The calculated strain rates using the texture information and the isothermal creep equation agree quantitatively well with the experimental results. The apparent activation energy of thermal cycling creep reveals 1/n (n: stress exponent of isothermal creep) of that of isothermal creep, which is one of the characteristics of internal stress superplasticity. Except for the factors attributable to the material geometry, the thermal cycling creep equation in the polycrystalline material is identical to that in a metal matrix composite. (C) 2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.
  • E. Sato, K. Kawabata, K. Kitazono, K. Kuribayashi
    Materials Transactions 45(7) 2295-2303 2000年  査読有り
    Composite creep deformation was analyzed, based on a continuum plasticity representation of the matrix, in an ideal composite at high temperatures in the case of negligible interfacial diffusion and sliding. A general formula of the steady-state creep strain rate was derived for a composite consisting of an ellipsoidal rigid reinforcement and a creeping matrix with a stress exponent of one. A closed-form solution was then derived for a composite with a cylindrical reinforcement under pure shear deformation in a two-dimensional analysis. The resultant creep deformation satisfies the requirements of impotency, volume conservation and interfacial continuity. Traces of two types of edge dislocations were analytically drawn; they show that dislocations climb over the reinforcement, retaining no dislocations either in the matrix or at the interface. Also, two types of dislocations simultaneously climb up and down at any portion in the matrix through dislocation core shuffling without long-distance diffusion. Finally, it was concluded that plastically-accommodated creep is characterized by two types of dislocations that simultaneously climb over a reinforcement, generating a heterogeneous creep strain increment without long-distance diffusion.
  • K Kitazono, E Sato, K Kuribayashi
    ACTA MATERIALIA 47(5) 1653-1660 1999年3月  査読有り
    Three main theoretical models of internal stress superplasticity proposed by Greenwood and Johnson [Proc. R. Soc. A, 1965, 283, 403], Sherby ct al. [Mater. Sci. Technol., 1985, 1, 925], and Sate and Kuribayashi [Acta metall. mater., 1993, 41, 1759] have been expanded to include the temperature dependence of the average strain rate. It is revealed that the constitutive equations of these models are equivalent regarding the thermally activated kinetics, and that the apparent activation energy of internal stress superplasticity is equal to 1/n (where n is the stress exponent of isothermal power-law creep) times that of isothermal power-law creep. This theoretical prediction has been experimentally verified by the thermal cycling creep tests using the same temperature profiles with several equivalent temperatures in a Be particle-dispersed Al matrix composite. The obtained apparent activation energy was 22 kJ/mol, which is approximately 1/7 limes that of isothermal creep. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Science Ltd All rights reserved.
  • E Sato, T Ookawara, K Kuribayashi, S Kodama
    ACTA MATERIALIA 46(12) 4153-4159 1998年7月  査読有り
    The stress relaxation in an inclusion bearing material at high temperatures under an external load has been examined. Independently from the analysis by Mori ct al. (Acta mater., 1997, 45, 429), it has been ascertained that the material reveals steady-stare creep even with only matrix plastic flow (multiaxial power-law creep) operating, through both variational principles analysis and finite element method (FEM). The characteristic of nonuniform stress distribution, which brings about steady-state creep, has been discussed. The dependence of the steady-state creep rate on inclusion aspect ratio and volume fraction has been also obtained through FEM anlaysis. (C) 1998 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.
  • E SATO, K KURIBAYASHI
    ACTA METALLURGICA ET MATERIALIA 41(6) 1759-1767 1993年6月  査読有り
    A new theoretical model is proposed to explain internal stress superplasticity under a simultaneous applied stress during thermal cycling. The analyzed material is an elastically uniform body containing an elastic spherical inclusion, surrounded by a plastic matrix obeying a power law creep. It is assumed that only relaxation by interface diffusion is significant. At first it is shown that an inclusion dilatation can be counterbalanced by a certain matrix plastic flow. Assuming a certain stress distribution for this condition, a stationary flow on heating or cooling results. Typical behavior of this stationary flow is analyzed for the specific cases of high or low applied stresses. Under a low applied stress, the internal stress by an inclusion dilatation strongly accelerates the flow in the direction of the applied stress, which is in proportion to the applied stress, to the heating or cooling rate and to the inclusion volume fraction.
  • E SATO, K KURIBAYASHI
    ISIJ INTERNATIONAL 33(8) 825-832 1993年  
    Superplastic deformation, especially in quasi-stable fine equiaxied grain structures, is accompanied by grain growth whose rate exceeds that which can occur without deformation. The deformation induced component of the grain growth stabilizes the deformation itself through an increase in the flow stress. An empirical expression for the grain growth is demonstrated which describes the behavior of microduplex and second-phase dispersed alloys. Finally, a new deformation model of superplasticity is proposed to explain the grain growth.
  • 佐藤英一, 栗林一彦, 堀内良
    日本金属学会誌 55(2) 151-157 1991年  査読有り
  • 佐藤英一, 栗林一彦, 堀内良
    日本金属学会誌 52(11) 1043-1050 1988年  査読有り

主要なMISC

 40

書籍等出版物

 3

共同研究・競争的資金等の研究課題

 23

産業財産権

 14