An improved model for predicting effective Young's modulus of the twisted structure under cyclic loading: taking into account the untwisting effect

Twist structures have diverse applications, ranging from dragline, electrical cable, and intelligent structure. Among these applications, tension deformation can't be avoided during the fabrication and working processes, which often leads to the twist structure rotation (called untwisting effect) and twist pitch increasing. As a consequence, this untwisting behavior has a large effect on the effective Young's modulus. In this paper, we present an improved model based on the classical Costello's theory to predict the effective Young's modulus of the basic structure, twisted by three same copper strands under cyclic loading. Series of experiments were carried out to verify the present model taking into account the untwisting effect. The experimental results have better agreements with the presented model than the common Costello's model.