Reserch On Stray Current Corrosion Fatigue Evolution And Numerical Simulation Of Reinforced Steel Bar

The subway has been widely used to alleviate the increasingly heavy urban traffic pressure because of its large passenger capacity and fast speed.Stray current will be produced during the operation of the subway.And then the stray current is easy to couple with the fatigue load which will cause the occurrence of stray current corrosion damage.This phenomenon will lead to premature damage for the structure,a serious threat to the subway structure durability and service life.This paper relies on the National Natural Science Fund Project "Research on the failure mechanism and damage of subway interface reinforced concrete multi scale corrosion fatigue"(Project ID: 51478183).The evolution law,damage mechanism and life prediction of the tensile corrosion fatigue damage of the stray current of the metro steel was studied based on the method of combining theoretical research and numerical simulation.The main work and research results are as follows:(1)Based on the tensile test of corroded steel bar,the damage law of stray current corrosion damage of subway steel bar was studied.The results show that the stray current causes serious pitting of the steel bar,which leads to the serious degradation of the mechanical properties of the steel bar,and the greater the stray current intensity,the more serious the corrosion of the steel bar,the yield strength,the tensile strength,the elastic modulus and other mechanical properties The more serious degradation.(2)Based on the theory of modern electrochemical corrosion fracture mechanics,the main factors influencing the crack propagation under the coupling of stray current corrosion and tensile fatigue load of metro steel are analyzed,and the crack propagation rate equation The results show that the main factors influencing the fatigue crack propagation of the stray current corrosion of metro steel are stray current intensity,fatigue load stress level and service time.(3)Based on the observation of the microstructure of the tensile fracture of the corroded steel bar,the finite element numerical simulation method was used to study the fatigue crack propagation process and the damage mechanism of the stray current corrosion and the damage evolution model.The results show that with the increase of the stray current intensity and the stress level of the fatigue load,the greater the fatigue crack growth rate of the stray current corrosion.The main reason is that stray current causes serious pitting of steel bar not only to reduce the mechanical properties of steel bars,but also to form fatigue crack source under tensile fatigue load,so as to accelerate the corrosion damage of subway steel.(4)The effects of stray current intensity and fatigue load stress on the residual life of metro steel bar under the coupling of stray current corrosion and tensile fatigue load are studied.The results show that the residual life of the stray current of the metamaterials is decreasing with the increase of the stray current intensity and the stress level of the fatigue load.When the fatigue load stress level is 0.5,when the stray current intensity increases from 0V to 30 V,the remaining life from 56260 times to 3664 times.When the stray current intensity is 15 V,the residual life is reduced from 25891 times to 23577 times when the fatigue load stress level increases from 0.1 to 0.6.