| Résumé | The complexity of loading on ice class propellers, involving high levels of in- and out-of-plane bending as well as severe blade torsion, means that for final design a detailed numerical stress analysis must be done on the propeller blade structure. The paper outlines an interaction equation, linking the main limit states, to be applied at the design point (the position of maximum principle stresses). The approach allows explicitly for both steady and unsteady loading components arising from ice and hydrodynamic loads and the structural response in the form of direct stresses, fatigue loadings and existing residual stresses. For initial design there is a requirement for sizing the blade thicknesses and a method to do this is described. Again the main limit states described in the first paragraph are explicitly accounted for, but here the design point is assumed to be the maximum thickness locations at the root section and the section at the 0.6 radius fraction. Results are presented using this method and these are compared with the blade thicknesses of several existing ice class propellers. Exceptional loads arising from impact loads from ice on stopped blades are considered as a separate limit state. |
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