Mechanism exploration and effective analysis method of shear effect of helically wound structures

Helically wound structures are widely used in practical engineering due to its excellent mechanical property, such as the steel rope, the reinforced armor layer of the marine flexible pipe/cables. The shear stiffness plays an important role in exactly predicting the mechanical response of the helically wound structure, especially for the short structure. There has been no general methodology to directly calculate the shear effect of this type of structure because of the geometrical complexity. This paper introduces and modifies a novel implementation of asymptotic homogenization method so-called NIAH to effectively calculate the shear property of the helically wound structure. This modification of NIAH is derived based on the strain energy equivalence of the macroscopic structure and the microscopic structure so-called the microscopic unit cell, which can be used to quickly calculate the effective stiffness and effective stress. In this paper, the effective stiffness is only discussed. The mechanical mechanism of the shear effect of helically wound structures is firstly explained, and then taking into account the shear effect, a quickly effective analysis method of the mechanical response for the helically wound structure is proposed. The efficient and accurate finite-element model of the unit cell which is used in the numeric implementation of the effective analysis method, is determined through the sensitivity analysis of meshing methods and periodic boundary conditions. Considering the practical application, the implementation of this method is validated for helically wound structures with equal-scale subcomponents and non-equal-scale subcomponents. The influence of the slenderness ratio on the shear effect is also explored in this work. This study provides a meaningful reference for the loading analysis and structural design of helically wound structures.