Basic Research on the Nondestructive measurement and inspection method by the use of resonant photoacoustic instrumentation scheme

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In this research subject, a new resonant photoacoustic spectroscopy (R-PAS) method was proposed. And the excitation of the resonant acoustic mode of the solid specimens with open and close structures was performed.In the year 2001, modulation frequency of the laser beam was tuned to the resonance frequency 975Hz for a metal tube with the length and inner diameter of 170mm and 6 mm, respectively. The Q-value for the resonance was about 10. On the other hand, The Q-value of the acoustic resonance for the open pipe with an artificial surface defect was decreased up to about 4. The imaging experiment was also performed by scanning with the slide stages with a fixed modulation frequency of the laser beam.In the year 2002, ultrasonic range experiments were carried out in addition to those performed in 2001. Experiments by the use of capacitive transducers were not sufficiently done, because it is not commercially sold. However, the feasibility of precise measurement of the length of the specimen was shown by exciting an inner wall of the tiny pipe-shaped object with a modulated laser beam at the ultrasonic frequency of 40KHz. Furthermore, the feasibility of the method to apply to detect the finished size of the small pipe-shaped specimen nondestructively, such as fuel injection nozzle, was also demonstrated.