Abstract
Nondestructive evaluation (NDE) of a pipe-shaped specimen was performed by the use of the acoustic resonance of an open-pipe. A modulated laser beam irradiates an inner surface of the specimen. An acoustic wave was generated by the photoacoustic (PA) effect. Modulation frequency was tuned across a resonant frequency of the pipe. Since a defect of the inner surface of the pipe decreases a Q-factor of the acoustic resonance, tuning characteristic of the pipe showed the existence of the inner surface of the pipe. The PA imaging of the specimen was also demonstrated by attaching a PA cell on x-y slide-stages. Relation between acoustic resonance of the pipe-shaped specimen and that of a PA cell was also discussed. The applications of the present method to NDE of structured materials with a pipe-shaped structure was discussed with a special attention to that of a variable-orifice nozzle (VON) used for the injection of diesel engines.
