非線形超音波法を用いたCr-Mo-V 鋼のクリープ損傷評価

概要

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A nonlinear acoustic measurement is studied for creep damage evaluation. An electromagneticacoustic transducer (EMAT) magnetostrictively couples to a surface-shear-wave resonance alongthe circumference of a cylindrical specimen during creep of Cr-Mo-V steels. Excitation of the EMATat half of the resonance frequency caused the standing wave to contain only the second-harmoniccomponent, which was received by the same EMAT to determine the second-harmonic amplitude.This measured surface-wave nonlinearity showed the peaks at 30% and the minimum at 50% of thetotal life. We interpreted these phenomena in terms of dislocation mobility and restructuring, withsupport from the SEM and TEM observation. This noncontact resonance-EMAT measurement canmonitor the evolution of the surface-shear-wave nonlinearity throughout the creep life and has apotential to assess the damage advance and to predict the creep life of metals.
2012-03-31