A study of the deformation of helical springs under eccentric loading

Abstract

Much analysis has been done to date on the deformation of helical springs due to normal loadings. The aim of this study is to design a helical spring that will deform under eccentric loading a desired amount due to a given force. Under the assumptions of linear stress strain relationships, the spring will be designed in terms of its material properties and its geometry. The deformation of the spring will be made possible utilizing a Shape Memory Alloy (SMA) active element that undergoes phase transformation upon heating above a certain temperature. Two models for spring deformation have been considered. In the first model we study the differential compression of a spring using SMA wire actuators, and in the second model we investigate the bending of an SMA rod placed inside the spring. Our efforts were a first step towards the development of a structural skeleton for a minimally invasive surgical manipulator