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

---

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.

著者

大谷 俊博 荻 博次 平尾 雅彦

出版者

一般社団法人日本機械学会

雑誌

評価・診断に関するシンポジウム講演論文集

巻号頁・発行日

vol.2006, no.5, pp.73-77, 2006-11-29

著者

大谷 俊博

出版者

湘南工科大学

雑誌

湘南工科大学紀要 (ISSN:09192549)

巻号頁・発行日

vol.42, no.1, pp.1-10, 2008-03-18

---

The microstructural evolution of the Cr-Mo-V ferritic steel, JIS-SNB16, subjected to a tensile creep test at 923 K wasstudied by monitoring the shear wave attenuation and velocity with electromagnetic acoustic resonance (EMAR). Thisstudy revealed an attenuation peak independent of the applied stress and the type of EMAT (electromagnetic acoustictransducer) used at around 30% of the creep life and a minimum value at 50%. This novel phenomenon is interpreted asresulting from microstructural changes, including strain hardening and dislocation recovery. This interpretation is supportedby TEM observations of dislocation structure. The relationship between attenuation change and microstructureevolution can be explained with the string model for dislocation vibration. EMAR is shown to possess the potential toassess the progress of creep damage and predict the remaining creep life of various metals.