Abstract
In the recent years, some damages of propeller blades due to fatigue were experienced on the liner ships, which make a demand to develop the strength evaluation method of the propeller blade considering the alternative stress, instead of the traditional methods bosed on the mean stress.
There are a few methods to calculate the alternative stress on the propeller blade. However, these methods are inconvenient to discuss comparatively the strengthes of many propellers, because they are based on the flow around the propeller which can only be calculated numerically using rather large computer.
In this paper, a formula for calculating blade stress using few parameters is led from Schoenherr's thrust equation, and the results are compared with the ones of a computer calculation based on the lifting surface theory and with the measured stresses on several actual ship propellers.
Further, a practical design formula to calculate the blade thickness is presented, considering the sea states or the condition under which ship is operated, and the allowable stress of propeller materials provided from the latest fatigue test results.
