Study On Influences Of Friction,Lubrication And Reinforcement Components On The Braking Performance Of Copper Based Friction Materials For High-speed Trains

With the continuous increase of running speeds of high-speed railway trains,higher safety and reliability requirements have been put forward for the train braking system.This thesis takes copper-based powder metallurgy friction materials as the research object.Various types of copper-based friction materials are prepared by adjusting different friction,lubrication and strengthening components.The physical and mechanical properties of the materials are tested.The friction and braking performance are evaluated under simulated actual braking conditions of high-speed railways.It provides reference for improving the performance and reliability of highspeed train braking systems.Specifically,this study optimizes the friction,lubrication and strengthening components of copper-based friction materials to enhance their physical and mechanical properties,improve the braking stability,and reduce wear rates.It makes friction materials more in line with the growing braking requirements of high-speed trains.(1)In the design of friction component schemes,the addition of kyanite can significantly reduce the material wear rate.Its function is,at low speeds,kyanite acts as a primary platform to effectively prevent debris from being carried away and significantly improve the material’s ability to resist wear.At high speeds,kyanite is crushed and mixed into the mechanical mixing layer to help form a tribo-film.This tribo-film is a double-layer structure composed of a mechanical mixing layer and an oxide layer.It can strongly improve lubrication,reduce wear of the friction surface,and protect the integrity of the substrate at the same time.(2)In the design of lubrication component schemes,the research has shown that the lubricating effect of molybdenum disulfide is weaker than that of copper-plated graphite or carbon fiber.In addition,the friction material containing both copper-plated graphite and carbon fiber has the best comprehensive performance.During the braking experiment,carbon fiber and copper-plated graphite synergistically work as the thirdbody lubrication.At the initial stage of braking,partial carbon fibers fall off and are compacted on the worn surface.As the braking continues,the carbon fibers enter the grooves left by the peeling copper-plated graphite to reduce the wear rate and maintain the stability of the friction coefficient.(3)In the design of strengthening components,the nano iron powder has a stronger strengthening effect on the copper substrate than that of micro iron powder.Nanoparticles of iron powder can reduce the sensitivity of the friction coefficient of copper-based friction materials to the braking speed,and increase the strength of the tribo-film,thereby reducing the wear rate.After adding nano iron powder,the main form of wear on the friction surface is adhesive wear,effectively reducing the delamination wear on the friction material containing micro iron powder.This study uses powder metallurgy methods to prepare copper-based brake pad samples,and investigates the effects of friction,lubrication and strengthening components,as well as their synergistic effects and friction wear mechanisms.It provides theoretical and technical support for improving the performance of brake pads for high-speed trains in China.