Influence of surface energy on the stiffness of nanosprings

When the cross-sectional size of structural elements reduces to nanometers, surface effects become quite important in their mechanical behaviors. In this letter, a theoretical model is proposed to account for surface effects through both surface energy and core-shell model. Through the principle of minimum potential energy, a refined analytical solution is derived for the stiffness of nanosprings. It is shown that surface energy evidently affects the stiffness of nanosprings. The present model provides an efficient tool to analyze the mechanical performance of various nanosized helixes and is also helpful to design nanospring-based devices.