Simulation Analysis And Wear Mechanism Research Of Synthetic Brake Pads For New Type Of Quasi-High Speed Trains

With the vigorous development of science and technology,the transportation volume of railway passenger and freight cars has increased rapidly.Therefore,increasing the speed of trains has gradually become the inevitable choice and the only direction for development.The primary goal of high-speed railway construction and operation is to improve train-related technology to ensure safe and reliable operation.The key to achieving this goal is to improve the basic braking device of trains.Which means that the brake material in the basic brake device will have higher quality requirements.At present,when the electrical braking system of high-speed train fails,it is mainly based on the emergency friction braking system.At this time,the contact surface of the brake pads and the brake disc will be subjected to thermal shock.Therefore,the study of higher-performance brake pads one of the important contents of research in the field of high-speed railway technology.Based on the high-speed train brake friction material of the basic physical properties and the ability of friction and wear,this thesis conducts the design and preparation of the resin matrix synthesis of quasi high speed train brake friction materials.Furthermore,the friction and wear performance test and microstructure characterization,as well as on brake under emergency braking conditions of the distribution of temperature field and thermal stress field and the change rule are investigated for optimizing the structure of the braking system and improving the stability of the brake system performance to realize the safe and stable operation of the high-speed train.The main research work and results of this paper are as follows:1.Through the hydrolysis reaction to reducing graphene oxide(RGO)and copper oxide(CuO)nanocomposite materials were manufactured.Then,polyimide(PI)composites filled with this RGO/CuO on were successfully prepared.By XRD,scanning electron microscope(SEM)and FTIR analysis methods,the nature of the functional groups on the surface and structure were investigated.The friction morphology and wear mechanism were further discussed.2.The effects of different filler content and different loads on the performance of the friction material were studied by the MM-2000 friction testing machine.It can be seen from the experiment results that when the mass fraction of RGO/CuO filler increases,the porosity in the friction material is significantly reduced,the accumulation of wear debris is less,and the wear performance is gradually improved.When the mass fraction of the filler in the material remains unchanged,the porosity of the brake pad material continues to decrease as the applied pressure increases.The traces of wear gradually become smooth while the accumulation of wear debris is reduced,and the wear performance is improved.3.Through the mechanical and thermal performance analysis of the self-developed RGO/CuO/PI brake pad friction material,some physical properties of the material are obtained,which proposes that this material is feasible as a brake pad material.RGO/CuO filler can effectively improve the mechanical properties of polyimide resin-based brake pads.The heat resistance of the brake pad material is higher than that of pure PI,which reduces the thermal decay of the brake pads and improves the stability of the coefficient of friction and wear rate.In addition,the addition of RGO/CuO filler makes the friction performance of the brake pads more stable.4.In the simulation,the uneven temperature distribution during the braking process causes the stress field to change,and the change of the stress field causes the thermal deformation of the contact surface.Therefore,it can be seen that the temperature field and the stress field of the composite brake pad are highly coupled during the braking process.Finally,select the RGO/PI friction material and RGO/CuO/PI friction material in the friction unit to compare the temperature field and the stress field through a broken line graph.It is found that the maximum temperature of the RGO/PI friction material is increased by about 25℃ as compared with the RGO/CuO/PI friction material,and its peak pressure is about 6MPa high than that of RGO/CuO/PI friction material.RGO/CuO/PI friction material has larger heat capacity and better thermophysical properties,so it is more suitable for brake pads material.