Failure analysis of propeller blade

A failure of marine propeller blade used to be very rare occurrence. In recent year, however, we have reported one or two failures of the propeller blade of pure car-carrier (P.C.C.) in a year. Not only working stress condition but also technical transition of manufacturing method are thought to contribute as a triger of the failure more in this case than that of the other types of ship. A failure analysis of the propeller blade is carried out from a viewpoint of preventing similar failures. In this report, the analysis is presented and some problem that should be solved are described. Furthermore, a few important parameter such as working stress amplitude, resistance of fatigue crack propagation, fracture toughness and capability of the non-destructive testing (so called NDT), all of which are considered to influence the reliability of the propeller blade, are discussed herein.