Study On Corrosion Fatigue Damage Mechanism And Failure Safety Reliability Assessment Of Cables During Service

The research conducted a series of experiments focusing on the corrosion fatigue behavior of in-service steel wires and the wire’s corrosion evolution inside a cable with sheath breakage.Decoupled analysis was conducted to understand the degradation mechanisms of steel wires under the coupled effect of fatigue loads and corrosive environments.The study explored the corrosion morphology characteristics of steel wires inside a cable under the influence of multiple environmental factors.A probability model for the wire’s corrosion evolution inside a cable was established with Bayesian theory,the research studied the spatial distribution characteristics of wire’s corrosion evolution inside a cable,and provided the calculation method for the material properties of wires inside a cable.A cellular automaton model with dynamically parameters was established to simulate the wire’s corrosion evolution inside a cable under the coupled effects of fatigue loads and corrosive environments.The variation of permanent life reliability and operational limit state reliability of cables were studied through Monte Carlo simulations.The conclusions of the paper are as follows:(1)The decoupled analysis of the corrosion fatigue behavior of high-strength steel wires under the coupled effect of fatigue loads and corrosive environments was achieved by comparing fatigue load-corrosion environment coupled experiments with accelerated corrosion experiments without fatigue loads.The study parameters included the maximum corrosion depth of the wire,mechanical properties,and fatigue performance.In the study,an equivalent characterization of corrosion environment intensity was established to investigate the correlation between the corrosive environment and the corrosion behavior of the steel wires.The load effect was introduced to describe the influence of fatigue loads,and the variation of the load effect were analyzed.(2)The research focused on the corrosion morphology characteristics of highstrength steel wires under the coupled effect of fatigue loads and corrosive environments.The study conducted the research on the temporal variations in the uniform corrosion behavior of the wires and the statistical characteristics of pit corrosion behavior.A probability calculation model was constructed with comprehensive corrosion environment scores(including temperature,humidity,chloride concentration,and stress amplitude)as inputs and characteristic parameters of uniform corrosion behavior of steel wires as outputs.a probability calculation model was established with comprehensive corrosion environment scores and corrosion duration as inputs,and characteristic parameters of pit corrosion behavior of steel wires as outputs.(3)The shortest effective path of the corrosion medium based on the artificial potential field method and the corrosion duration were identified as key parameters to establish the probability model for the wire’s corrosion evolution inside a cable,aiming to study the spatial distribution characteristics of wire’s corrosion evolution inside a cable.The wire’s corrosion evolution along the length direction of the wire inside a cable was studied with the effective corrosion length.The wire’s corrosion evolution in the radial direction inside a cable was examined by investigating the furthest corrosion distance.Furthermore,the analysis of the spatial distribution of corrosion characteristic indices,mechanical properties,and fatigue performance of the steel wires inside a cable was conducted.(4)The cellular automata model was established based on the salt spray accelerated corrosion test on the cable and the coupled fatigue load-corrosive environment experiment to simulate the wire’s corrosion evolution inside a cable under the coupled effects of fatigue loads and corrosive environments.The cellular automata model considered the wire’s position inside a cable,corrosion probability,and fatigue loads,allowing for a more accurate simulation of the wire’s corrosion evolution inside a cable.The key parameters in the model could be adjusted according to the cable conditions and the corrosive environment,taking into account the dynamic changes in the cable conditions and the uncertainty of the corrosive environment.According to the Monte Carlo results of the cellular automata model and the critical conditions for wire cracking and fracture,the calculation models were established for the risk of wire cracking and fracture inside a cable under the fatigue loads.The study investigated the variation of the permanent life reliability and operational limit state reliability of the cable with sheath breakage.It utilized the limit corrosion duration to describe the critical points where the reliability of permanent life and operational limit state reach 0.Further exploration was conducted into the relationship between the two limit corrosion durations and fatigue load.