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■■■■■■■■■■■■■■■■■■■ 川崎製鉄技報 KAWASAKI STEEL GIHO Vol.3 (1971) No.4 ■■■■■■■■■■■■■■■■■■■ |
| 鋼の塑性変形挙動と音波吸収 Deformation Characteristics and Dislocation Damping of Steels and other Metals 今中 拓一(Takuichi Imanaka) 佐野 謙一(Kenichi Sano) 藤元 克己(Katsumi Fujimoto) |
| 要旨 : 結晶塑性の研究において，音波吸収の実験のもつ意義を明らかにし，その実験から得られる数々の情報は，物質の強度と直接結びついて重要であることを述べた。さらに，音波吸収の理論や実験の現状にも言及し，鋼を含むbcc金属における問題点を指摘した。また，著者らのグループが最近開発した，塑性変形中に，音波吸収や音速の変化を応力，歪と同時に測定する技術および，実際にこの測定法を用いて，軟鋼，18％Cr-14％Ni不銹鋼や銅（単結晶）などについて行なった実験の結果について述べ，この方法の鋼の降伏や低温靱性の問題についての応用をも併せて検討した。 |
| Synopsis : The simultaneous measurement of stress, strain and attenuation in metals and alloys during plastic deformation gives quantitative information on the instantaneous density and segment length of mobile dislocations. Recent progress in both theory and experiment on dislocation damping is critically reviewed, Also, the effect of bias stress on damping and the interpretation of the damping in bcc metals are discussed. The attenuation-changes during plastic deformation have been measured with composite piezoelectric resonator technique at 70kHz in polycrystalline low carbon steel and stainless steel samples, and with pulse echo technique at 9 to 225MHz in copper monocrystals. The microyield characteristics of these samples have also been investigated. In the low carbon steel, the attenuation has remained almost unchanged in a microyield region, increasing beyond a macroscopic yield point. On the other hand, in the stainless steel, the attenuation has increased through a conspicuous peak in a microyield region. Such attenuation changes are found to be closely related to the microyield characteristics of these samples. In copper monocrystals, the initial stage of plastic deformation has been studied both by continuous recording of attenuation changes at 27MHz and by measurement of overdamped resonance at various steps of deformation. The frequency dependence of attenuation has been found to agree well with that calculated by the Granato-Lucke theory. The attenuation has increased through two stages, the boundary of which being a macroscopic yield point. These observations are reasonably interpreted in terms of segment length change and multiplication of mobile dislocations which participate in plastic flow. The applicability of these experimental techniques to studies of micro-and macro-yield behaviour and low temperature ductility of steel is suggested. |
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