Strength considerations in controllable pitch propeller design¹

Article type: Research Article

Authors: Beek, G.H.M. | Heidemans, J.

Affiliations: Lips B.V., Drunen, The Netherlands

Note: [1] Paper read before the 3rd Lips Propeller Symposium, Drunen, The Netherlands.

Abstract: Strength calculations for propellers are usually made using nominal static load values with fluctuations due to circumferential wake field variations superimposed. The allowable load is determined by applying experimentally obtained material properties (Smith/Goodman – diagrams) on the computed stress pattern. Moreover dimensions of propeller blades have to satisfy the requirements of the involved classification society. For special purpose applications (ice breakers, warships) discussion is mostly dominated by a compulsory strengthening of some components aiming at a higher survival rate in unpredictable conditions. Poor engineering judgment in applying these heavy duty requirements can lead to constructions where strength levels at several critical spots are badly harmonized. This can lead to severe damage to propeller, shaftline, gear box or even the hull. While accepting that damage caused by excessive shock loads (grounding, extreme ice load) cannot always be avoided it is possible to restrict it by a suitable distribution of local strength over all the parts concerned. For a controllable pitch propeller the replacement of a single blade is a relatively simple operation, so the strengthening of other threatened parts in order to withstand the maximum load of a collapsing blade is an obvious consequence. This publication compares results of this philosophy with the classification societies’ rules. Stress calculations performed with the aid of modern numerical methods contributed to obtaining detailed information about stress conditions in complex shaped and loaded parts.

DOI: 10.3233/ISP-1976-2326602

Journal: International Shipbuilding Progress, vol. 23, no. 266, pp. 329-341, 1976