宇宙飛翔工学研究系

松宮 久

マツミヤ ヒサシ  (Hisashi Matsumiya)

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 助教
学位
博士(工学)(2024年3月 京都大学)

ORCID ID
 https://orcid.org/0000-0001-7109-1497
J-GLOBAL ID
202301018520225697
researchmap会員ID
R000056622

受賞

 1

論文

 5
  • 岡田和歩, 柴田曉伸, 松宮久, 辻伸泰
    鉄と鋼 110(11) 890-898 2024年9月1日  査読有り
  • Kazuho Okada, Akinobu Shibata, Taisuke Sasaki, Hisashi Matsumiya, Kazuhiro Hono, Nobuhiro Tsuji
    SCRIPTA MATERIALIA 224 2023年2月  査読有り
    This study challenged to improve the resistance against hydrogen embrittlement by increasing the concentration of carbon segregated at prior austenite grain boundary (PAGB), XPAGB, in low-carbon martensitic steels. The specimens with/without carbon segregation treatment (Non-seg and Seg specimens, respectively) had almost the same microstructure, other than higher XPAGB in the Seg specimen. While the uncharged Non-seg and Seg specimens exhibited similar mechanical properties, the maximum stress of the hydrogen-charged specimen was much higher in the Seg specimen than that in the Non-seg specimen even when diffusible hydrogen contents were almost the same. In addition, the fraction of intergranular fracture surface was much smaller in the Seg specimen. Based on these results, we conclude that the segregated carbon suppressed the accumulation of hydrogen around PAGB by site competition and increased cohesive energy of PAGB, leading to the significantly improved resistance against hydrogen-related intergranular fracture.
  • Hisashi Matsumiya, Akinobu Shibata, Yoshiaki Maegawa, Kazuho Okada, Nobuhiro Tsuji
    ISIJ INTERNATIONAL 62(10) 2089-2094 2022年  査読有り
    The present study investigated the hydrogen-related fatigue fracture under various test frequencies in low-carbon martensitic steel. In the hydrogen-charged specimen, although the number of cycles to failure decreased with decreasing test frequency, the time to failure was almost the same regardless of the test frequency. Observation of fracture surface revealed that the transgranular surface was a main component in the uncharged specimen, while the intergranular surface was often observed especially at the lower test frequency in the hydrogen-charged specimen. In addition, for the transgranular fracture, cracks often propagated across the laths regardless of test conditions. The high-strained region was observed over a relatively wide area in the uncharged specimen. On the other hand, the hydrogen-related fatigue-crack propagation was accompanied by intense localized plastic deformation, which could accelerate crack growth. The intergranular cracking and high localization of plastic deformation could be the possible reasons for decreasing the fatigue life by the presence of hydrogen.
  • Kazuho Okada, Akinobu Shibata, Hisashi Matsumiya, Nobuhiro Tsuji
    ISIJ INTERNATIONAL 62(10) 2081-2088 2022年  査読有り
    A typical hydrogen-related transgranular fracture, namely quasi-cleavage fracture, is usually accompanied by serrated markings on the resultant fracture surfaces in steels with body-centered cubic phases. The present paper investigated the microscopic three-dimensional morphology and crystallographic feature of serrated markings in a 2Mn-0.1C steel mainly composed of ferrite microstructure. The serrated markings corresponded to the corners of the step-like morphologies which consisted of microscopic {011} facets whose longitudinal directions were almost parallel to < 110 > or < 112 > direction. In addition, the microscopic {011} quasi-cleavage facets had the largest inclination angle from tensile axis among six crystallographically equivalent {011} planes, suggesting that resolved normal stress imposed on the {011} plane is an important factor for the hydrogen-related quasi- cleavage fracture. We propose that not only the slip deformation enhanced by hydrogen but also the coalescence of vacancies / voids induced by hydrogen-enhanced plastic deformation should be considered for understanding the mechanism of the hydrogen-related quasi-cleavage fracture along the {011} planes.
  • Hisashi Matsumiya, Akinobu Shibata, Kazuho Okada, Nobuhiro Tsuji
    INTERNATIONAL JOURNAL OF HYDROGEN ENERGY 46(75) 37509-37517 2021年10月  査読有り
    This study investigated the hydrogen-related fatigue fracture in 2Mn-0.1C steel having a lath martensite microstructure. The presence of hydrogen significantly reduced the fatigue life. The transgranular surface was a main component in each stress range of the uncharged specimen, while the intergranular surface was frequently observed in the hydrogen-charged specimen. The crystallographic orientation analysis by electron back scattering diffraction revealed that the cracks mainly propagated along {011} planes regardless of the presence of hydrogen. Compared with the uncharged specimen, however, plastic deformation was localized near the fatigue crack in the hydrogen-charged specimen. According to the reconstructed fracture process by fracture surface topography analysis, the hydrogen-related fatigue fracture was discontinuous and composed of isolated nucleation of intergranular cracks and quasi-cleavage crack propagation initiated at the pre-existing intergranular cracks. (c) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

講演・口頭発表等

 13

共同研究・競争的資金等の研究課題

 1