著者
作井 誠太 中村 正久 布村 成具 藤原 達雄
出版者
The Iron and Steel Institute of Japan
雑誌
鉄と鋼 (ISSN:00211575)
巻号頁・発行日
vol.49, no.4, pp.672-679, 1963-04-01 (Released:2010-10-12)
参考文献数
7
被引用文献数
3

The effect of the specimen width on the Charpy test was studied with specimens of hotrolled mild steel and quenched-and-tempered medium carbon steel, by recording the load-time relations under impact bending. Results obtained were summarized as follows:(1) The energy absorption in the ductile range was influenced by the specimen-width smaller than 4mm-the smaller the width, the lower the energy absorption per unit sectional area and it was found that the law of similarity was not satisfied in this case. On the contrary the maximum fiber fracture strength was almost constant for all the specimens, showing the applicability of the law of similarity.(2) Maximum fiber bending stress in fracture was the largest in the temperature range where the absorption energy was decreased almost to minimum value and the load-time curve of type I designated by the authors in the previous papers was obtained. (Tetsu-to-Haganeé 46 (1960) p. 141, 1538; Tetsu-to-Haganeé Overseas, 1 (1961) p. 38).(3) The brittle specimens tempered at a rather lower temperature after quenching, showed the type I or 11 load-time curves over all the testing temperature, and thus fractured thoroughly with only a crack, once started. It was found that in these tests the fracture strength scattered considerably.(4) The notch shape had an influence on the absorption energy for ductile fracture of the less ductile specimens with tempered martensite. It was concluded that the above effect was mainly due to the difference of the amount of deformation produced until the crack formation.(5) The transition temperature showed the same tendency to the changes of specimenwidth under any definition, rising as the width increased. However, the change of the transition temperature for the specimen-witdh larger than 6mm showed the considerablly different tendency from that of the specimen smaller than 4mm. Therefore, in the application of subsize specimen, it is desirable to use the specimen-width larger than 6mm. The effect of specimen-width on transition temperature was affected markedly by the types of the steels and their microstructures.
著者
作井 誠太 中村 正久 布村 成具
出版者
The Iron and Steel Institute of Japan
雑誌
鉄と鋼 (ISSN:00211575)
巻号頁・発行日
vol.48, no.1, pp.28-34, 1962-01-01 (Released:2010-02-22)
参考文献数
7
被引用文献数
4 1

This paper describes of the influences of deformation rate of wide range on the tensile impact properties of several steels by using a high-speed impact-tensile testing machine with a large rotary disk. The deformation rate was varied from static region to 80m/s, and the testing temperature from room temperature to 800°C. The results obtained were summarized as follows:(1) Blue brittleness was observed clearly in mild steel and two alloy steels, and temperature range of blue brittleness shifted to higher temperature with increasing rate of deformation. This shift was conspiquous up to a speed of deformation of 10m/s, but was decreased beyond this speed. Moreover, at the speed of 40m/s the blue brittleness temperature was decreased on the contrary.(2) The similar dependence on deformation rate was also made clear, with regard to the brittleness of 18-8 stainless steel which was due to the effect similar to that causing blue brittleness as well as the brittleness of pure copper at elevated temperature.(3) At higher temperature over 600°C, the critical impact velocity was not observed so distinctly as obtained at room temperature. Tensile strength was lowered with a larger scattering as the deformation rate was increased, while, correspondingly, the value of elongation or reduction of area showed tendency to be rather larger. This phenomenon, named by the authors as “high-rate deformation softening”, was discussed in relation to the loadtime curves observed experimentally.
著者
中村 正久 高瀬 稔
出版者
広島大学
雑誌
一般研究(C)
巻号頁・発行日
1994

両生類の性腺分化は、組織・形態学的には、変態前、変態最盛期、あるいは変態後のいづれかの時期に起きることが知られている。本邦産のカエルに性ホルモンを投与すると種によっては機能的な性の転換(性巣⇔卵巣)が見られる。本研究は両生類の性分化に係る遺伝子を人為的に発現させ、それらの遺伝子を解析することによって哺乳類をふくめた脊椎動物の性分化のしくみを明らかにすることを目的としている。研究材料のツチガエルは性ホルモンで性が転換(雌→雄)することから、当初、ステロイドホルモンの合成及び代謝酵素が性腺分化に関与していると考え、3β-ヒドロキシデヒドロゲナーゼ5α-レダクターゼの遺伝子の単離を試みた。二つのcDNA(ヒト、ニジマス、ラット等)をプローブとしてスクリーニングを行ったところ、いくつかの陽性クローンを得たので、塩基配列を決定し、ホモロジー検索を行ったが、目的とする遺伝子ではなかった。そこで、哺乳類で性腺及び副腎の分化を支配すると考えられているAd4BP遺伝子が両生類の性腺分化においても重要であると考え、この遺伝子の単離を試みたところ、2.1kb Ad4BP全長cDNAを得た。現在、その全塩基配列の決定及び発現時期を決定している。また、テストステロン処理個体から全RNAを既に得ているので、テストステロン処理個体のAd4BP遺伝子の発現に変化があるかどうかも検討している。更に、二つのCa^<2+>結合蛋白、カルレティキュリンとカルネクシンcDNAを得、全塩基配列も決定した。この二つのCa^<2+>結合蛋白遺伝子の発現は組織によって著しく異なり、前者が分化時卵巣で強く発現するが、後者は発現しない。カルレティキュリン蛋白をカエル肝臓から精製後、マウスに免疫して抗体を作成し、カエル卵巣を用いて免疫染色を行ったところ特異的分布パターンを示したことから、カルレティキュリン蛋白が卵形成に密接に係っている可能性があること、また、カルレティキュリン遺伝子の発現はテストステロン処理個体で著しく抑制されることから、性の転換に重要な働きをしている可能性もあることが分かった。