Abstract: Based on the analytical models which describe axial extension on both ends of superelastic shape memory alloy (SMA) helical structures and the simplified constitutive model of SMA materials, in this paper, the equivalent-transformed method is applied to establish the relationship between the shrinkage of helical springs undergoing uniform radial pressure and the axial extension deformation, with the purpose of satisfying the practical application of helical structures made of SMA. The validity is proved through finite element method (FEM) and then this analytical model is generalized to braided stents for inter interventional therapy. The possibility of this application and error analysis are discussed through parametric analysis and comparison between results of analytical model and FEM. This model can be applied to analyze the deformation behavior of radial compression of SMA helical springs in an analytical way, and its computational efficiency is obviously superior to FEM, so that it is more convenient to adjust parameters to achieve the desired deformation in earlier stage of helical structure design.

Key words: helical structure, shape memory alloy (SMA), superelastic, analytical model, radial pressure