Recent Progress of Experimental and Measuring Technology. Changes of Ultrasonic Attenuation and Microstructure Evolution in Crept Stainless Steels.

OHTANI Toshihiro, OGI Hirotsugu, HIRAO Masahiko

doi:10.1299/kikaia.67.454

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実験計測技術の新展開　　ＳＵＳ３０４ステンレス鋼のクリープ損傷に伴う超音波減衰と材料微視組織の変化
SUS 304 ステンレスコウノクリープソンショウニトモナウチョウオンパゲンスイトザイリョウビシソシキノヘンカ

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Abstract

We studied the ultrasonic attenuation change during creep tests on austenitic stainless steel (JIS-SUS 304). We applied to tensile stresses to the materials at 973K and measured ultrasonic attenuation using electromagnetic acoustic resonance (EMAR) . EMAR is a contactless resonant method with an EMAT and is free from extra energy losses in the attenuation measurement, resulting in the measurement of intrinsic attenuation in solids. We launched polarized shear wave in the thickness direction of the plate specimen to obtain the ultrasonic velocity from the resonant frequency and the attenuation coefficient from the ringdown curve at the resonance. Attenuation exhibits much larger sensitivity to the damage accumulation than the velocity. Approaching to the rapture, it becomes ten times as large as the initial value, which is attributed to the microstructural changes, especially, dislocation mobility. This is supported by the TEM observations for dislocation structure. This technique has a potential to assess the damage advance and to predict the creep life of metals.

Journal

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series A

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series A 67 (655), 454-461, 2001

The Japan Society of Mechanical Engineers

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