抄録
We monitored AEs from a self-fracture of atmospheric rust produced on circular steel plates (SS400) welded in a SUS304 bottom plate of a 820mm diameter water-storage cylindrical tank. The tank was set on the tar-sand base and exposed to outdoor weathering for 61 days. AEs were monitored as Lamb waves using four resonant-type AE sensors (PAC, type-R6I with center frequency of 60kHz) mounted on the dog-running surface of the bottom plate. AE monitoring at 20dB amplification for one day recorded AE events with large amplitude and higher S/N ratio. AE event counts increased after 15 days exposure and were correctly located to the circular steel plates which suffered higher wall reduction by atmospheric corrosion. Next we monitored AEs from a tank exposed for 80 days at 60dB amplification for one hour using the R6I sensors mounted on the dog-running surface of the bottom plate and shell wall. AE events monitored by the bottom-plate sensors were located correctly in the heavily corroded carbon steel plates, while location accuracy of AE events by the shell-wall sensors was poor.
