Hub-Blade Interaction in Propeller Strength

Stresses in monobloc propeller blade and hub normally are calculated separately. In the blade stress calculation, for which nowadays the finite element method is generally prefer red, the hub is assumed to be rigid. On the other hand the blade is completely ignored if hub strength is considered. The finite element program, the author used for the blade, also allows the examination of the interference between the stress conditions in both parts since it enables three-dimensional elastic analyses. Moreover, detailed experimental data, obtained in strain gauge measurements on a full scale blade, proved the validity of the chosen element type and mesh for application on propeller blades. Therefore strong tools are available to shift the disturbing boundary conditions from the blade root to the hub-shaft interface and obtain reliable information about the blade root loading and its resolution in the hub. Results of comparative calculations show the strong influence of the hub elasticity on the stress distribution in the blade root section.