Analysis Method And Mechanical Behaviors Of Strands And Hierarchical Helix Cables

The hierarchical helix structures are wildly used in the engineering,there are abundant mechanical behaviors because of the complex internal interacts of each strand and subcables,such as the internal contact and friction effects.In this paper,the theoretical modeling and numerical analysis are carried out to predict the effective properties of the hierarchical structure,and the purpose of this paper is to study the theoretical analysis method and the influence of various factors on the prediction results,and to provide theoretical support and reference for optimizing the design of cable.In this paper,based on the existing theory,the following aspects are mainly studied:Firstly,helix strand is the basic unit of cable structure which is usually a composite material composed of various materials.In this case,the study of the basic properties of the helix strands becomes the first problem to be solved.Based on the existing theory of micromechanics,a generalized Mori-Tanaka method to predicting the effective properties of composite structures of strands in the complex environment of force,heat,electricity and magnetic field is presented.At the same time,the finite element model is proposed to predict the effective thermal properties of the composite material by using the finite element software Comsol.The numerical examples show that the results obtained by the theoretical prediction method and the finite element method are in good agreement,and it is is proved our method could be applicable to a larger range of helix angle.Secondly,the influence of the contact deformations between the strands and the friction forces is analyzed in detail in the triplets.An analytical method of step loading is established,and the complex nonlinear problem is decomposed into two relatively simple nonlinear problems,the influence of contact deformation and friction are added gradually.In this paper,by introducing the influence of the contact deformation between the strands to the influence of the helix radius of triplets,a method to analyzing the performance of the tripltes is proposed.On the basis of the above analysis,and the influence of the friction force on the performance of the helix is considered.Based on this model,the analysis of the effects of contact deformation,friction,internal force components and the distribution of stressed under different helix angle are given in detail.Based on the finite element analysis software ABAQUS,the finite element model of triplets structure is established to verify the theoretical results,and the results are in good agreement with the theoretical results.It is found that the contact deformation and friction will affect the prediction of the o structure mechanical properties.Thirdly,on the basis of the above analysis,the influence of the contact deformation of the double-helix structure on the overall performance is analyzed in detail.There are two kinds of contact in the double-helix structure,one is the contact between the three tuples,and the other is the contact between the inner helix of the three tuple.Under the condition of neglecting the friction force,the contact force between the components of the two double-helix structure is analyzed.Influence of contact deformations are all considered by introduce the Poisson's ratio of the helix radius due to the contact displacement.The analysis method considering a line contact deformation affects the mechanical properties of the cable and analyzes on the different helix angle.The study found the influence of the contact deformation act an important role in the analysis of the double-helix structure when the helix angle are in a smalle case.Finally,a method for analyzing the mechanical properties of hierarchical cable is established.The existing theoretical analysis methods for the effective mechanical properties of cable structures mainly focus on single-helix or double-helix twisted structure.An analysis mehod to predicted the effective mechanical properties of hierarchical cable structure is propsed which neglecting the Poisson effect and cable internal contact deformation.A recursive relations of the center line displacement of each level are given,and then the centerline deformations get and rotation angles are derived step by step recursion.In the small deformation assumption,according to the transformation relation of the cross section and the main axis coordinate frames,the relationship between the degree of bending and torsion of the strands and the rotation angle of each direction and the strain of each point on the strand are obtained.Then the whole force and torque are obtained by the equivalent method.We calculate the effective properties of the triplet-wire structure and the 3×3 structure cable and compare the results with the existing methods.