Investigation of Torsion Springs by Considering the Friction and the End Effect

In this study, the nonlinearity in moment and angular displacement of torsion springs is studied analytically and experimentally. It is shown that the inclined angles at both ends have direct effects on the nonlinearity of a constant-pitch torsion spring. Also, an algorithm for determining the friction between the spring coils in close-wound torsion springs is proposed. From the comparison to experimental data, it is found that the spring rates are different at forward and backward strokes. The dynamic equations for the close-wound torsion spring is also derived by considering the friction between the spring coils, and two different natural frequencies are found in simulation.