Title: Pitting damage imaging by non-linear ultrasonic technique: comparison between resonance and non-resonance modes

Authors: Tao Wan; Takashi Wakui; Takashi Naoe; Masatoshi Futakawa; Koichiro Kawashima; Katsuhiro Maekawa

Addresses: Graduate School of Science and Engineering, Ibaraki University, 4-12-1, Nakanarusawa, Hitachi 316-8511, Japan ' J-PARC Center, Japan Atomic Energy Agency, 2-4 Shirane, Shirakata, Tokai-mura, Ibaraki 319-1195, Japan ' J-PARC Center, Japan Atomic Energy Agency, 2-4 Shirane, Shirakata, Tokai-mura, Ibaraki 319-1195, Japan ' J-PARC Center, Japan Atomic Energy Agency, 2-4 Shirane, Shirakata, Tokai-mura, Ibaraki 319-1195, Japan ' Nonlinear Ultrasonic Laboratory, Hazama 4, Nagoya 466-0062, Japan ' College of Engineering, Ibaraki University, 4-12-1, Nakanarusawa, Hitachi 316-8511, Japan

Abstract: A non-linear ultrasonic method was applied for evaluating the cavitation damage, so-called pitting damage, in the mercury target of the Japan Spallation Neutron Source (JSNS). First, pitting damage was imposed on disk specimens in mercury using the magnetic impact testing machine (MIMTM) with various numbers of impacts (0, 10⁴, 10⁵, 10⁶, 10⁷ and 10⁸). The pitting damage was imaged with resonance and non-resonance modes, respectively, by employing a non-linear acoustic imaging system. Waveform attenuation and generation of higher harmonics, which have high relevance to the degree of pitting damage, were useful for the imaging. Combined with the attenuation phenomenon, the resonance mode imaged the micropits with higher harmonics more effectively with higher harmonics, compared with the non-resonance mode.

Keywords: mercury target; cavitation damage; pitting damage; nonlinear acoustics; ultrasonics; acoustic imaging; resonance mode; non-resonance mode; magnetic impact testing; waveform attenuation; higher harmonics; liquid metals; spallation neutron sources.

DOI: 10.1504/IJMPT.2013.056299

International Journal of Materials and Product Technology, 2013 Vol.46 No.2/3, pp.141 - 154

Received: 25 Jun 2012
Accepted: 31 Mar 2013
Published online: 21 Jun 2014 *

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