| The key technology of high-speed train braking system is one of the nine core technologies of high-speed train,which is related to the safety,smoothness and comfort of train operation.The train braking system is mainly composed of brake disc and brake disc.The train braking is realized by the friction between brake disc and brake disc.The tribological performance between disc and brake disc directly affects the braking performance of the train.With the increase of high-speed train speed,the problem of high temperature wear of friction block on brake plate becomes more and more prominent.High temperature friction and wear of brake interface involves the changes of physical,chemical and mechanical properties of material surface,which play an important role in the transition of friction block from slight wear to severe wear.Although scholars have done a lot of research on the damage behavior of friction blocks,the research on the wear mechanism at different temperatures is not sufficient,and the research on the friction and wear behavior of friction blocks with different shapes at high temperatures is still few.With the increase of high-speed train speed and the opening of complex service lines,it is urgent to study the high-temperature friction and wear behavior of brake system.This study based on multi-mode vehicle braking performance simulation test bench,to high-speed train stationary friction block as the research object,to explore the damage behavior of friction block under different temperature and different friction block shape on the brake interface tribology behavior,the influence of the tribology,the Angle of material science in this thesis,the friction and wear mechanism of the friction block under different temperature,High temperature and friction block shape on the lower surface contact state,pressure distribution,the wear behavior and the influence of thermal distribution of tribological behavior,at the same time,using the finite element simulation software of friction in the braking process,to simulate the wear process and analysis of braking contact pressure in the process of evolution,wear area evolution,the phenomenon such as surface area evolution,In order to help reveal the high temperature friction and wear mechanism of friction block in braking process.The main conclusions are as follows:1.Different drag braking time will lead to significant difference in the surface temperature distribution of brake disc.In the early stage of braking,the temperature of disc braking system is low,and the contact state between friction block and brake disc is poor,resulting in local high temperature hot ring on the friction surface of brake disc.With the increase of temperature,the softening of the interface and the wear of the friction block make the contact state between the disc become better,which makes the local high temperature splitting phenomenon on the friction surface of the brake disc weaken.2.Friction block wear mechanism is different at different temperatures.When the interface temperature reaches 183℃,the abrasive particles disperse on the friction interface,and the main wear form of friction block is abrasive wear.When the interface temperature reaches 305℃,oxidation occurs on the friction interface of the friction block,and many small scratches appear,and the furrow depth is shallow,which is the result of the combined effect of abrasive wear and oxidation wear.When the interface temperature reaches 456℃,the interface sofens and a large spalling pit appears,which is caused by adhesive wear.3.Temperature has a great influence on friction coefficient.At the initial stage of braking,the contact state of the braking interface is poor and the friction coefficient is small.With the braking and temperature rise,the contact state becomes better and the friction coefficient increases gradually.With the increase of temperature,the surface of the friction block appears softening and plastic flow,which reduces the friction coefficient.Under the working condition adopted in this test,the friction coefficient begins to decline rapidly after 410℃,indicating that serious plastic flow begins to occur at this time,serious adhesive wear occurs at the interface of friction block,and the braking effect begins to deteriorate.Therefore,the temperature of the friction interface of the braking system should be controlled to improve its service life.4.The shape of brake disc friction block of high-speed train mainly affects its contact pressure distribution and heat distribution,and thus affects its wear behavior.For the fixed type of friction block,the circular friction block will make the brake disc surface temperature distribution is more uniform,pentagonal and hexagonal friction block due to the hole on both sides of the arc length is longer,so that the disc surface has obvious heat aggregation phenomenon;The arc edge of the circular friction block can alleviate the stress concentration phenomenon at the cutting end,and make the friction block contact with the brake disc better,and the friction block wear is uniform and the degree of partial wear is low.The edge of pentagonal and hexagon intensifies the stress concentration of the cutting tip and makes the cutting tip damage more serious.5.This study has a certain understanding of the friction and wear behavior of brake friction block at high temperature,has preliminarily revealed the friction and wear mechanism of brake friction block at different temperatures,and analyzed the influence of the shape of friction block on the friction and wear behavior at high temperature,which has certain guiding significance for the design of train brake friction block. |
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