THE PROPELLER BLADE STRUCTURAL PROBLEM AND ITS SOLUTION BY FINITE ELEMENT METHODS

The ever-increasing use of large diameter, skewed propellers on large and/or high-powered ships and a number of recent blade failures in service have directed renewed attention to the problem of blade structural behavior. A brief discussion is first given of methods for predicting blade loadings, earlier approaches to blade stressing and the need for realistic design criteria. Using a consistent formulation of blade geometry, a finite-element model of the blade structure is then displayed. A description is given of DYNAPROP, a special-purpose computer program that has been developed for the routine prediction of blade natural frequencies and mode shapes, stress distributions, blade deflections and fatigue life. Computed results are given for a plate, a destroyer propeller that has been tested in the model scale and a moderately skewed blade. The paper concludes with lessons learned from the use of this method and with the nature of several related problems that demand early solution.