title: A Method Using Optical Contactless Displacement Sensors to Measure Vibration Stress of Small-Bore Piping.
abstract: In nuclear power plants, vibration stress of piping is frequently evaluated to prevent fatigue failure. A simple and fast measurement method is attractive to evaluate many piping systems efficiently. In this study, a method to measure the vibration stress using optical contactless displacement sensors was proposed, the prototype instrument was developed, and the instrument practicality for the method was verified. In the proposed method, light emitting diodes (LEDs) were used as measurement sensors and the vibration stress was estimated by measuring the deformation geometry of the piping caused by oscillation, which was measured as the piping curvature radius. The method provided fast and simple vibration estimates for small-bore piping. Its verification and practicality were confirmed by vibration tests using a test pipe and mock-up piping. The stress measured by both the proposed method and an accurate conventional method using strain gauges were in agreement, and it was concluded that the proposed method could be used for actual plant piping systems.
authors.affiliation: e-mail:  maekawa@inss.co.jp.
authors.forename: Akira
authors.initials: A
authors.lastname: Maekawa
authors.affiliation: e-mail:  tsuji.takashi@inss.co.jp.
authors.forename: Takashi
authors.initials: T
authors.lastname: Tsuji
authors.affiliation: e-mail:  takahashi.tsuneo@inss.co.jp Institute of Nuclear Safety System, Inc. , 64 Sata, Mihama-cho , Mikata-gun, Fukui 919-1205, Japan.
authors.forename: Tsuneo
authors.initials: T
authors.lastname: Takahashi
authors.affiliation: Kansai Electric Power, Co., Inc. , 13-8 Goichi, Mihama-cho , Mikata-gun, Fukui 919-1141, Japan e-mail:  noda.michiyasu@c4.kepco.co.jp.
authors.forename: Michiyasu
authors.initials: M
authors.lastname: Noda
keywords: LED; light emitting diode; maintenance engineering; optical measurement; piping vibration problem; small-bore piping; structural health diagnostics; vibration fatigue; vibration measurement