Analysis Of Damage Evolution Of Bridge Cables Under The Combined Effects Of Fretting Fatigue And Corrosio

Cable is one of the most important stress-bearing components in the bridge structure,and its safety redundancy is small.The local mesoscopic damage of a single steel wire inside the cable can easily lead to the domino effect of "individual breaking" of the structure.Numerous studies have shown that due to the influence such as its own structure and wind and rain excitation,fretting fatigue and its induced fretting wear behavior often occur near the anchoring end of the cable beam and tower,as well as the electrochemical corrosion behavior which caused by rain erosion and oxygen infiltration.Engineering examples have proved that the joint action of fretting fatigue and corrosive medium is one of the typical failure modes of the cable wire near the anchorage end.The region where fretting fatigue occurs is often in a complex multiaxial stress state.The alternating loads such as vehicles and wind will cause the performance of the area to gradually deteriorate,and the corrosion fatigue behavior based on the interaction of electrochemical and mechanical processes also accelerates the performance degradation process.For some simple structure,the fretting fatigue life can be directly obtained through force analysis and the analytical method where the uniaxial fatigue analysis methods is mostly used.However,this analytical formula is not suitable for estimating the multi-axial fatigue life of a complex stress system,let alone the interaction and mutual promotion of the force-electrochemical process.Under different cyclic loading cycles,the continuous evolution of microscopic material fatigue damage will lead to continuous deterioration of macroscopic structural mechanical properties for complex stress systems.How to visualize the damage evolution process of materials under the combined action of environment and load through effective modeling strategies and implementation steps,so that engineers can grasp and track the deterioration process of structural performance at any time,is a hot research topic in the current engineering community.In view of this,starting from the fretting fatigue mechanism of the cable wire,the fretting fatigue damage constitutive model considering the multi-axis effect and the corrosion pit evolution constitutive model are established.Then,the user material subprogram UMAT for damage evolution analysis and the wear subprogram UMESHMOTION_Wear for wear morphology evolution analysis are written to realize the visualization of the damage evolution process of the cable wire under the action of fretting fatigue considering the evolution of wear morphology,and predicts the fatigue life.Further,starting from the corrosion mechanism,a constitutive model of corrosion pit evolution considering the coupling effect of force and electrochemistry is established,and a user subroutine UMESHMOTION_Wear_Corrosion that considers both wear and corrosion morphology evolution analysis is written to realize the visualization of the damage evolution process of the cable wire under the action of fretting fatigue considering the evolution of wear morphology and corrosion morphology,and predict the cable life.Finally,considering factors such as different tensile loads,different normal contact forces,and different bending effects,the fretting fatigue characteristics and damage evolution process of cable wires are studied.Based on the above research process,the main contents and research results of this paper are as follows:(1)Based on the multiaxial fatigue theory of the critical plane,the critical plane damage parameters suitable for the fretting fatigue of the cable wire are selected,and the multiaxial fatigue damage evolution constitutive models that do not considering the evolution of wear morphology,considering the evolution of wear morphology,and considering the changes of wear and corrosion morphology are established respectively.Finally,the failure criterion suitable for the fretting fatigue analysis of cable wire is determined.(2)Using the commercial finite element software ABAQUS,a mesoscopic model between the cable wires is established,and the material subprogram UMAT is written according to the damage constitutive relationship,which realizes the visualization of the cumulative damage of the cable wire under different load cycles and obtains the fretting fatigue life.Then,the simulation data and fretting fatigue experimental data were compared to verify the rationality of the material subroutine in simulating the damage evolution process under uniaxial and multiaxial conditions.The correlation between the mechanical properties of the contact zone,the crack initiation position,and the damage evolution law is analyzed,and the effects of different normal contact forces,different bending stresses and other factors on the damage evolution and life are also studied.(3)Based on the contact theory,a user subprogram UMESHMOTION_Wear is written to simulate the evolution of the wear profile of the contact surface.Cooperating with the material subprogram UMAT,the damage evolution process of the cable wire under the action of fretting fatigue considering the evolution of wear morphology is realized in the commercial software ABAQUS.Based on the numerical simulation results,the difference of the damage evolution and fatigue life is studied between whether to consider the evolution of wear morphology,so as to study the wear effect on the performance deterioration of the cable wire under the action of fretting fatigue.(4)Based on the electrochemical nature of metal corrosion,a corrosion pit evolution model under the coupling action of force loading and electrochemical is constructed,and a user subroutine UMESHMOTION_Wear_Corrosion that considers both wear and corrosion topography evolution analysis is written to simulate the surface topography evolution under the combined action of wear and environmental corrosion.Combined with the material subroutine UMAT,the visualization of damage evolution considering both the evolution of the wear morphology and corrosion morphology is realized and the fatigue life is predicted in the commercial software ABAQUS.Based on the numerical simulation results,the difference of the damage evolution and fatigue life is studied between whether to consider the evolution of corrosion morphology,so as to study the accelerated effect of the corrosion effect on the performance deterioration of the cable wire.The research method in this paper can fully consider the fretting fatigue effect caused by fretting wear and friction between the wires at the anchoring end of the cable beam,which makes up for the existing research that use bridge cables as macroscopic uniaxial tensile members and have the insufficient of only consider tensile strength and fatigue strength of a single cable.At the same time,through the fretting wear program and damage evolution program,the visualization of the mechanical damage on the surface of the cable wire is realized,and the influence of the mechanical damage of wear on the fretting fatigue damage evolution is obtained.In addition,this paper considers the mutual promotion and acceleration effect between mechanics and electrochemistry,and fully studies the damage evolution of cables under the combined action of fretting fatigue and corrosive media,which provides a reference for the research on the performance degradation process of engineering structures under the coupling action of force-electrochemical multi-physics.The research conclusions can provide theoretical support for the mechanical performance degradation and accurate life assessment of bridges with cable-supported systems.