Experimental Study On Sliding Friction And Wear Properties Of Four Rigid Catenary Wire-pantograph Strip Couples With Direct Current

China’s urban rail transit is in the period of rapid development,and the subway has become the main mode of urban transportation.With the continuous expansion of the urban center area,the subway running distance increases,and the demand for the train speed is getting higher and higher.As the main power supply device of electrified locomotives,pantograph-catenary systems encounter great challenges,which are mainly reflected in the severe wear of contact strips,serious arc discharge,unstable current-carrying quality,and so on.The research work on how to make the catenary/pantograph system run more stably is of great significance to the safe and punctual operation of trains.In this thesis,Cu-Ag alloy contact wire rubbing against four metal-impregnated strips were taken as the research objects.The current-carrying friction and wear characteristics of four pantograph strips against the contact wire were studied experimentally using a ring-on-block high-speed current-carrying friction and wear test machine.The wear characteristics of different metal-impregnated strips against the contact wire were compared.The results can be drawn as follows:(1)Under the low-voltage direct current,the discharge forms between the metal-impregnated strip and the contact wire are mainly electric spark discharge and short-arc discharge.The discharge form has a great relationship between the electric current and the normal load.(2)When the current increases,the arc discharge energy,the Joule heat and the temperature increase,the current-carrying efficiency decreases.Increasing the normal load can restrain the arc discharge to some extent,lower the running temperature of the contact strip,and increase the current-carrying efficiency.(3)The wear of metal-impregnated strips increases with the increase of current,and the friction coefficient decreases with the increase of current.The increase of current will make the surface ablation of the strip material more serious,and the softening of the material will lead to the increase of the strip wear.Under the current-carrying condition,arc heat and Joule heat will produce the metal oxide film with lubrication function on the surface of the catenary wire and reduce the friction coefficient.(4)Under current-carrying friction and wear,melting and ablation pits,cracks,peeling,scratches and pitting are mainly found on the surface of metal-impregnated materials.Under a low normal load less than 20 N,there were many large melting ablation pits and obvious electrical wear on the strip sliding surface.Under high normal load larger than 25 N,the number of ablation pits on the strip sliding surface decreases obviously.In this case the electrical wear of strips is inhibited,but the mechanical wear is enhanced.(5)The current-carrying wear performances of different metal-impregnated strips were compared.Strip A has poor heat resistance and the highest average operating temperature.In severe high temperature,the strip material will fall seriously,thus increases the wear loss of the strip.Strip C has fine heat dissipation,and relatively low average operating temperature,but the maximum wear.Strip B has the best comprehensive performance.(6)Based on the orthogonal test method,four-factor including strip type,normal load,current,sliding speed and four-level orthogonal test scheme was established.The wear mass loss of pantograph strips was analyzed.It was found that current was the most important factor affecting the wear performance of contact strips.