Finite element analysis of shafts under combined loads

Abstract

The trend for aeroengines with increasing thrust capacities requires the development of shaft technology to deal with this greater power transmission, while still restricting their dimensions and weight. Thin-walled designs can assist in achieving this objective, but are limited by their torsional collapse behaviour. By improving the understanding of the torsional buckling behaviour of shafts, this will enable improved shaft designs able to deal with the increase load capacities required. Until recently the prediction of buckling failures of such thin-walled shafts was by empirical and theoretical equations, which are, in general, unnecessarily conservative. A previous publication described the development and validation of an accurate and versatile finite element-based analysis technique for predicting the torsional buckling behaviour of thin-walled shafts. Although for a typical aeroengine drive shaft the dominant loading mode, under normal conditions, is torsion, aeroengine drive shafts will also experience bending and axial loading. The aim of this paper is to prove that the previously developed finite element buckling methodology can be used for buckling analyses of shafts under combined load situations. This paper presents validation cases for which experimental test results are compared with the results of finite element analyses, under various loading modes; it shows that the behaviour of shafts under combined loads can be accurately predicted using the finite element method.