The development and applications of the helically symmetric boundary conditions in finite element analysis

Helically symmetric structures such as helical springs, machine screws and wire rope strands are commonly used structural items. When they are subject ed to axial loads (tensile and torsional), these structures may still exhib it the helically symmetric characteristic after loading. If this is the cas e this feature can be used to substantially simplify the analysis of these structures in numerical simulations. In this paper, the formulation of heli cally symmetric boundary conditions for finite element (FE) modelling is pr esented. The helically symmetric relationship is ensured by using constrain t equations which relate the displacements of the corresponding nodes on th e corresponding artificial boundaries of the model. The application of thes e helically symmetric equations renders it possible to reduce the finite el ement model size greatly and improve the accuracy of the results. Examples of a simple circular cross-section bar and wire rope strand are presented w hich demonstrate the validity of the formulation. Copyright (C) 1999 John W iley & Sons, Ltd.