Fatigue failure in marine propeller blades of Ni-Al-bronze was investigated. Calculations of alternating stress imposed on the propeller blades were carried out by unsteady lifting surface theory and the results were applied to the analysis of fatigue failure of blades. Fatigue tests in seawater were carried out by using unnotched and notched specimens taken from practical propellers and the fatigue life up to crack initiation was estimated with obtained fatigue curves and stress frequency-curve already known. Fatigue crack propagation tests were carried out in synthetic seawater with WOL type specimens taken from a propeller fractured in service, and crack propagation lives of two propeller blades were estimated with the help of fracture mechanics. It was clarified that estimated fatigue lives were approximately in good agreement with those of blade fractured in service.

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