Basic study of monitoring for vibration, crack generation and propagation

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PNC TJ9602 97-001, 19 Pages, 1997/03

PNC-TJ9602-97-001.pdf:0.73MB

Failure of machine and structure has to be prohibited to avoid the leak of liquid natrium. The technology of detection of pre-existing phenomena before final failure becomes very important. In this basic study, the laser based ultrasonic sensor technique which is one of promising methods was invernstigated to summarize its principle and current status and to know the applicability of this method. Firstly the importance of non-destructive evaluation (NDE) method and the history of laser based NDE were reviewed. The technological basic of the non-contact generation of elastic wave by laser radiation and the non-contact defection of ultrasonic wave by laser interference technique. The difference of two modes of generation of elastic wave, that is, thermal stress mode and ablation mode, was reviewed. The detection methods of ultrasonic wave by laser interference such as homodyne interferometer, time-delay interferometer and confocal Fabry-Perot interferometer were investigated and their principle and characteristics were compared. Finally, examples of application of these methods for rough surface samples and high temperature materials were considered. It was concluded that these laser based NDE techniques were able to be used in practical applications.