Material Preparation And Sliding Friction Finite Element Analysis Of Copper-based Grounding Brush

Graphite/Cu self-lubricating friction collector materials have been widely used in electric friction devices,such as the pantograph slide plate and the electric brush,which are the common accessory materials for the electric traction system of the high-speed train.However,the continuous improvement of train running speed has put forward higher requirements for the application in this field.New friction collector material is prepared to study its friction and wear properties,which can provide reference for the development of grounding device materials that meet the safety operation guarantee of the train.In this paper,copper-based self-lubricating composites with different graphite content were prepared by powder metallurgy.The effects of graphite content on the structure,physical properties and friction and wear properties of the composites were studied respectively,and the variation of wear mechanism was also discussed.In addition,the finite element simulation was carried out for the sliding friction process of grounding brush carrier friction pair.The imported grounding brush material is graphite/copper composite composed of copper,graphite and SiO₂.Graphite and SiO₂ were evenly distributed in the copper matrix,which was reticulated.The structure and composition of the brush were not the key factors causing abnormal wear and can be used as a basis for the preparation of the composite.The prepared graphite/copper composites were relatively uniform and compact,and the relative density can reach about 96%.The graphite content can affect the distribution state of graphite in the copper matrix,and when the content reached to 20 wt.%,graphite particles were connected and there was a network distribution in some parts.With the increase of the graphite content,the density and relative density of the composites decreased,the porosity increased,and when the graphite content was more than 15 wt.%,the relative density decreased obviously.The hardness and conductivity decreased with the increase of graphite content.With increasing graphite content,the friction coefficient and wear rate of the composites decreased first and then increased,reaching to the lowest value at 15 wt.%.When the graphite content was below 15 wt.%,the main wear forms were adhesive wear and abrasive wear.The wear surface damage was relatively light at 15 wt.%graphite.When the graphite content reached to 20 wt.%,the wear forms were mainly adhesive wear and fatigue wear.Under the condition of 40 N,600 r/min and 60N,400 r/min,the friction coefficient of the composites in the friction process was more stable,the surface damage was smaller,and the friction and wear performance was better.ANSYS Workbench was used for modeling analysis and the temperature and stress distribution of the ring-brush friction pair was obtained.The high-temperature region of the friction pair appeared in the friction contact position,and it was a gradient distribution from internal to external.The high temperature region of the grounding brush was biased towards the friction outlet.The stress field changed and interacted with the temperature field.The addition of electric current increased the temperature and stress of the friction pair and did not change the distribution state of temperature and stress field.