ABSTRACT
A finite deformation and infinitesimal strain formulation of the problem of axial extension and torsion of helicoidal shells is deduced from a general nonlinear shell theory for infinitesimal strain problems. A consistent application of the infinitesimal strain assumption further simplifies the relevant boundary value problem effectively to a linear problem; only the unknown stretch and twist parameters appear nonlinearly. The effects of finite deformations are clearly shown by examining the perturbation solutions for slightly pretwisted strips and (shallow) shells with a small pitch. In the presence of the core of the helicoid, the Poincaré-Lighthill perturbation technique is needed to avoid the spurious singularity associated with the regular perturbation solution.
