Development of NDE Apparatus for Dry/Wet Surface Defects with Photo acoustic and Photo thermal effects.

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In this research project, we paid an attention to the fact that a photothermal electrochemical (PE) detection is based on the accumulation and modulation of a electrochemical reaction by the laser beam so that the improvement of the reproducibility was most considered. In the academic year 1998, three-terminal (3T) method was adopted instead of two-terminal (2T) method. In the 3T scheme, a reference electrode was added between cathode and anode in order to stabilize a potential between cathode and anode. As a result, 3T method improves the reproducibility of the PE signal. Furthermore, it was verified that the chemical etching of the pitting corrosion hole was accumulated so that it generated a PE signal. On the other hand, however, the rest metal specimen was almost kept without pitting by chemical reaction, if the voltage applied to the reference electrode was adjusted slightly below the corrosion potential of the metal specimen. The same surface defect was measured by PA method for … More comparison. The result showed that the PE method was comparable to PA method in spatial resolution. Group of investigator Hiwatashi tried to made actual pitting corrosions and measured them with PAM.. Group of investigator Endoh measured actual cracks occurred in a metal plate with PAM..Their works made advance in NDE with PAM as actual applications.In the academic year 1999, remarkable development of PAM was by the practical use of fine slide stages controlled by the software Lab VIEW. The above research results were presented at the domestic and international conferences (SPIE, Yokohama/IEEE, Nevada).As described above, in this research project, a new PE method, which was proposed by the head investigator, was shown to be a new tool, which is capable to measure corrosions or tiny pitting holes occurred in small distributing pipes in an electrolyte liquid environment, in which a conventional gas-microphone PA method was unable to be applied. Furthermore, driving system of PAM was also done so that applications of the PAM to actual NDE was realized. Less