Inner surface peening for long and narrow helical pipe using acoustic cavitation

Abstract

The inner surface peening of helical pipes is highly challenging due to the inaccessibility of the inner surface. To the end, we propose to peen the inner surface by introducing acoustic cavitation inside the pipe. We also provide a theory to account for how the inner surface peening can be achieved by the acoustic cavitation for a long helical pipe. We evaluate the validity of theory with experiments conducted on helical pipe specimens. The experimental results well agree with the theorical predictions. Also, it was found that a significant amount of compressive residual stress was achieved by the acoustic cavitation on the inner surface. The experimental results imply that the acoustic-cavitation-generation of compressive residual stress is effective regardless of pipe length, which promises that the present peening method will be applicable for a wide range of helical pipe length.