Simulation Research Of Structural Integrity Of Carbon Fiber Composite Ceramic Brake Disc

The disc brake of high-speed train is a kind of basic brake mode which can ensure the safety of train after the failure of electric brake.As the key component of railway vehicle foundation braking,brake disc is of great significance to ensure the basic safety of drivers and passengers.Carbon fiber composite ceramic brake disc is low density,high temperature resistance and good thermal stability,which has an excellent application prospect in high-speed train braking.Due to the anisotropic material properties of carbon fiber composite ceramic and the bolted connections among carbon ceramic part and metal parts,there is a complex thermal mechanical coupling behavior during the braking process of carbon fiber composite ceramic brake disc system.Therefore,the research on the structural integrity of the carbon ceramic brake disc system during the braking process has important engineering application value for the design and application of the brake disc.In this thesis,the thermal mechanical coupling finite element model of the wheel mounted carbon ceramic brake disc system in the emergency braking of 400km/h initial speed is established to study the temperature,stress and deformation characteristics of the brake disc and the axial load variations of the connecting bolts.Combined with the user damage subroutine,the damage evolution characteristic of the brake disc is also analyzed.The highest temperature of the brake disc measured by the brake disc bench test is in good agreement with the simulation result during the braking,which verifies the accuracy of the finite element model.Therefore,through the finite element model,the complex thermal mechanical coupling behavior of the carbon ceramic brake disc can be analyzed in more detail.The simulation results show that the distribution of surface temperature and out of plane displacement of brake disc are non-uniform.The edges of the small bolt holes of the brake disc along the radial direction of the brake system are the weak positions of crack initiation.The thermal mechanical damage of the disc occurs at the edges of the small bolt holes,and evolves along the fiber direction which has the shortest distance from the center of the small bolt holes in the inner ring to the inner edge of the disc.Therefore,when designing the fiber laying direction of the brake disc,the angles between the two fiber directions and the radial direction of the brake disc at the center of inner ring small bolt holes should be both as close as 45°.During the braking,the differences of thermal deformation among bolts and connectors causes the variations of bolt axial loads.The axial loads of the connecting bolts among the wheel and the support bodies increase continuously during the braking process.The axial loads of the connecting bolts between the brake disc and the support body decrease greatly in the braking process.In the second stage of the braking,the plastic deformation of these bolts is produced by the uncoordinated radial deformation of the brake disc and the support body,which also affects the variation of bolt loads.At the end of braking,the axial loads of the connecting bolts between the brake disc and the support body are less than half of the preload.Increasing the diameter of the mounting holes of the brake disc can effectively reduce the plastic deformation of the connecting bolts.Moreover,the support material and connecting bolt material with lower coefficient of thermal expansion should be selected to avoid the plastic deformation.There are 77 figures,14 tables and 51 references.