Detection of cavitation erosion through acoustic emissions techniques

Abstract

Cavitation erosion on propellers and rudders remains a problem in the marine industry. The consequences of failing to detect the risk of erosion damage during the design phase, and early in the service life of a vessel, include reducing the speed of the vessel, unscheduled dry-dockings and repairs or replacement of the propellers or rudders. The associated costs are borne by the builder and owner and may harm their reputations within the industry. Lloyd's Register has developed and tested a unique measurement system, based on acoustic emission techniques, which is capable of detecting the onset of erosion damage on propellers and rudders. The system uses high frequency transducers to quantify the impulsive energy transmitted from imploding cavitation events through the material paths of rudder, propeller and shafting configurations. The acoustic emission signals from such events have been synchronised with visual observations using high speed video equipment and borescopes.