| SiCp/A356 brake disc has the advantages of light weight,fast heat conduction and heat dissipation,which meets the requirements of lightweight braking parts of urban rail trains with frequent braking.At present,the applicable speed of SiCp/A356 brake disc is lower than 120 km/h,and its heat capacity does not meet the braking requirements of 160km/h municipal vehicles.Based on the project of SiCp/A356 brake disc of a municipal vehicle in Wuhan,through the combination of simulation and test,this paper carries out the research on the structure and process design of SiCp/A356 wheel mounted brake disc of 160 km/h municipal vehicle.The main research contents are as follows:The analysis model of brake disc flow field was established by using Star-CCM+software,and the influence of the friction surface thickness of wheel mounted brake disc on the flow field is analyzed.The simulation shows that the increase of the friction surface thickness will increase the convective heat transfer coefficient between brake disc and air and reduce the convective heat flux.According to the brake disc interface and the influence law of various structural elements of the brake disc on ventilation and heat dissipation,the structural design of the brake disc is completed.Using the thermal fluid solid coupling three-dimensional simulation calculation method and ANSYS software,the influence of the thickness of the friction surface on the temperature field and stress field of the brake disc at the initial speed of 160 km/h is analyzed.The simulation results show that reducing the thickness of the friction surface will significantly improve the maximum temperature rise of the friction surface of the brake disc.Considering the temperature rise and heat dissipation comprehensively,the thickness of the friction surface is determined as 32 mm.Under each simulation condition,the heat capacity of the brake disc meets the requirements,that is,the braking temperature rise is lower than 350 ℃,and the braking thermal stress is lower than the strength of the material at the same temperature.In view of the poor fluidity of SiCp/A356 composites,SiCp/A356 brake disc adopts the low-pressure metal mold forming method and completes the casting design.The casting forming process simulation of brake disc is carried out by using Pro CAST casting simulation software,the defect free process and parameters inside the casting are obtained,and the casting mold design is completed.After heat treatment and machining,the braking test of the brake disc is completed on the ZF 1:1 braking power bench.The test results show that the friction surface of the brake disc is in good condition and the friction coefficient is stable.The temperature rise of the brake disc under two emergency braking conditions of 160 km/h is the highest,reaching 342 ℃,and the temperature rise of the friction surface under other braking conditions is significantly lower.The temperature rise of the friction surface under all working conditions is lower than the allowable temperature of SiCp/A356 Composite by350 ℃.In addition,by comparing the test temperature measurement data and simulation temperature data at the same position,they have good consistency.The results of this paper can promote the lightweight and localization of basic braking parts of urban and intercity trains during the 14 th Five Year Plan period,and have good engineering application value. |
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