著者

石井 優 草なぎ 祐紀 大谷 俊博 仲庭 正義

出版者

The Japanese Society for Non-Destructive Inspection

雑誌

非破壊検査 (ISSN:03675866)

巻号頁・発行日

vol.64, no.4, pp.179-183, 2015

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In this study, we apply non-contacting nonlinear resonant ultrasound spectroscopy (NNRUS) to the evaluation of fatigue damage in pure copper. NNRUS is a combination of a contactless transducer, electromagnetic acoustic transducer (EMAT), and nonlinear resonant ultrasound spectroscopy (NRUS). The NRUS technique is exploits the significant nonlinear behavior of damaged materials. The resonant frequency of an object is studied as a function of its excitation level. As the excitation level increases, the elastic nonlinearity is manifested by a shift in the resonance frequency. The change in nonlinearity rapidly increases from 80% of fatigue life and is synchronized with the change in the attenuation coefficient with fatigue progression. This novel phenomenon is interpreted in terms of change in dislocation mobility and the dislocation rearrangement. TEM (Transmission Electron Microscope) observations supported this view. This technique has the potential to assess the level of damage and to predict the fatigue life of metals.