Research On Numerical Simulation Of Wind-induced Fatigue Of Steel Strand Based On Multi-scale Model

As a kind of light high-strength engineering components,steel cables have been widely used in space structures.However,the complex working environment of steel cables makes them exposed to wind load,rain effect and other alternative loads.As a result,the fatigue problems of steel cables have become the critical point for controlling their working life.The fatigue problems for steel cables can be mainly categorized into two types: fretting fatigue and corrosion fatigue.In particular,the fretting fatigue appears more frequently in the steel cables manufactured by skein twisting such as the widely used steel strand cables,and thus shorten the working life of these components.Consequently,based on the steel strand cables,this dissertation explored the fretting fatigue characteristics inner steel strand cables,and the details are illustrated as follows:1.Firstly,this dissertation reviewed recent literature on fretting fatigue,and summarized the current research system of fatigue life prediction methods,especially the analysis methods of multiaxial fatigue and fretting fatigue.2.Secondly,a global finite element model of the cable was established.Moreover,based on the wind speed curve obtained by Kaimal wind speed spectrum,the dynamic analysis of the cable model was carried out to acquire the characteristics of the dynamic response of the cable under the pulsating wind as well as the wind-induced fatigue load spectrum under different wind speed.3.Thirdly,The multi-scale refined finite element model of steel strand cable,including an overall model and contact sub-model,were established by using the commercial finite element software ABAQUS and its parametric method.Next,a series of analyzes were implemented based on the refined finite element model.First of all,the static load analysis was utilized for analyzing the stress state of steel strand cables under the axial force.In the second place,the analyze of fatigue characteristic of steel strand cable under cyclic tensile load,cyclic bending load and cyclic torsional load was executed.Also,the SWT critical plane method was utilized to predict the working life of steel cables when suffering fretting fatigue under different working conditions.Then,in order to simulate the actual stress condition of the cable more precisely,this dissertation analyzed the fretting fatigue characteristics of the steel strand cable under two combined work conditions,tensile-bending and tensile-torsion,and analyzed the changing law of stress field in the contact area under different loading paths to find the most unfavorable loading condition for the steel strand cable.Finally,by comparing the predicted fatigue working life under the combined working condition with that under the single working condition,the former was founded significantly reduced.4.Last but not least,taking advantage of parametric modeling,several parameters such as average stress,stress amplitude,friction coefficient,wire diameter and twist angle were changed respectively to analyze the influences of each parameter on the working life of the steel strand cable under fretting fatigue.Additionally,some significant conclusions about construction were given.