| The rail is widely laid in China and its service conditions are complex.Under the environment of corrosion,the fatigue fracture caused by corrosion fatigue seriously affects the service life of rail.Nowadays,the research on corrosion fatigue is mainly about aluminum alloy for aviation and high strength steel of offshore drilling platform,and few of them are concerned about corrosion fatigue of rail.In order to study the influence of corrosion and fatigue on fatigue performance and fracture behavior,and describe the interaction of corrosion on rail fatigue life and fatigue on rail corrosion damage,and to explore the attenuation law of fatigue life and mechanical properties of rail under the interaction of corrosion and fatigue,this paper takes U75 V rail as the research object to formulate pre corrosion fatigue The two experimental schemes of pre fatigue corrosion fatigue are used to simulate the alternate effect of corrosion and fatigue during the service of the rail.Through the corrosion test,tensile test and fatigue life test of U75 V rail,the surface morphology and roughness change after corrosion are characterized,the fracture appearance of fatigue and tensile test is analyzed under the two experimental schemes,The corrosion resistance,mechanical properties and fatigue life of U75 V rail with corrosion cycle of 48-120 h and stress condition of 200-360 MPa are discussed.The results show that the number of pits in the two experimental schemes decreases with the increase of corrosion cycle;The corrosion is intensified because of the surface micro damage such as resident slip zone and extrusion,which makes the pre fatigue corrosion fatigue mass loss and corrosion rate greater than that of U75 V rail;As for the crater morphology,the pre fatigue pit has a more gentle mechanism of preferential solution,and there is no V-shaped pit with steep wall which is easy to stress concentration.The results show that the loss rate of mechanical properties parameters such as yield strength,tensile strength and elongation rate are rising from 48 h to 120h;Under each corrosion period,the loss rate of mechanical properties of U75 V rail is greater,and the loss rate of yield strength and tensile strength is 17.8% and 15.83% respectively when the corrosion period is 120h;The fracture forms of tensile after corrosion are brittle fracture.Through fatigue life test and fracture morphology analysis,it can be seen that with the increase of stress and corrosion cycle,the cycle times have been decreased.When the conditions are 360 MPa and 120 h,the fatigue life of corroded samples is 115042 times;The corrosion fatigue life of the samples under alternating action is related to the stress and cycle times,that is,the presence of the persistent slip zone;The fracture morphology is consistent,and there are corrosion pits in the crack source area which cause fatigue fracture.The expansion area has fatigue striations,and the only corroded samples have larger striations spacing.The transient fracture area has typical cleavage morphology,cleavage surface,river pattern,steps,etc.In conclusion,the corrosion rate of U75 V rail with pre fatigue corrosion fatigue is faster than that of pre corrosion fatigue and the mass loss is more;However,due to the action of the optimal solution mechanism,the corrosion pits of the pre fatigue U75 V rail are more gentle and stress concentration is not easy to occur.The attenuation of mechanical properties and fatigue life of the steel rail is slower than that of U75 V rail. |
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