| The braking system is an important component of ensuring the safe operation of highspeed trains,and the brake disc is the core component of the braking system,playing a crucial role in the braking process.During braking,the train generates a large amount of heat,causing the temperature of the brake disc to rise,which seriously affects the braking performance of the train,and thus affects the safety of train operation.Therefore,improving the heat dissipation performance of the brake disc is extremely important for enhancing the braking ability of the braking system.A well-designed heat dissipation structure that can dissipate heat in a timely manner is an effective way to improve the heat dissipation performance of the brake disc.However,due to the limitations of traditional manufacturing processes,the heat dissipation rib structures designed for brake discs are relatively simple,and their heat dissipation efficiency is low.Additive manufacturing technology can break through the limitations of traditional manufacturing processes in brake disc structural design.This paper takes the trailer brake disc of CRH5 high-speed train as the research object,and studies and tests its heat dissipation rib structure and additive manufacturing process parameters.The main contents are as follows:(1)Based on the principles of heat transfer and finite element analysis software,numerical simulation was used to calculate and analyze the temperature field and thermal stress field of the brake disc during an emergency braking process.Following the principle of model simplification(balancing physical realism and mathematical feasibility),a reasonable simplified 3D model of the brake disc was established.The heat generated during an emergency braking process when the CRH5 high-speed train was traveling at a speed of 250km/h was calculated using the energy conversion method,and the heat flux density was obtained as the thermal load for the finite element analysis.Different convective heat transfer models for the friction surface,circumferential surface,and heat dissipation ribs of the brake disc were established to obtain the forced convection heat transfer coefficients as the boundary conditions for the finite element analysis,and the temperature field and thermal stress field of the brake disc were calculated and analyzed.The results showed that the temperature of the brake disc reached its highest point at around 66 seconds into the braking process,with a maximum temperature of 472.3℃ located on the friction surface of the brake disc and showing a step-like distribution;at around 81 seconds into the braking process,the maximum thermal stress of the brake disc was 195.9 MPa,located at the inner edge of the brake disc.(2)Based on the analysis results of the temperature field and thermal stress field,and drawing inspiration from the highly efficient heat dissipation structures in nature,three types of brake disc structures with arc-shaped groove heat dissipation ribs(Type A),rectangular groove heat dissipation ribs(Type B),and V-shaped groove heat dissipation ribs(Type C)were designed.Finite element thermal analysis and static strength evaluation were carried out for the three new types of brake discs.The results showed that all the new types of brake discs could effectively suppress the temperature rise and reduce the stress peak during emergency braking,and met the requirements for static strength.Among them,Type B brake disc had the best effect,with the highest temperature of the friction surface being reduced by 12.7°C compared to the traditional brake disc,and the stress peak being reduced by 24.3 MPa.(3)Considering the structural characteristics of the new brake disc’s cooling fins and the advantages of additive manufacturing technology,simulations,process parameter optimization,and solid forming of the new brake disc were carried out using additive manufacturing.A fivefactor four-level orthogonal test design was used,with laser power,scanning speed,laser diameter,layer thickness,and base plate temperature as the experimental factors.Ansys Additive software was used to simulate the additive manufacturing process of the new brake disc,and residual stress and deformation were used as the evaluation indexes for the forming quality of the additive manufacturing.Range analysis was used to analyze the simulation results,and an optimal set of process parameters that resulted in better forming quality was obtained:laser power of 100 W,scanning speed of 2500mm/s,laser diameter of 110μm,layer thickness of 40μm,and base plate temperature of 70℃.The residual stress of the brake disc formed under this set of process parameters was reduced by 18.3% compared to the average value of the overall experiment results,and the deformation was reduced by 10.9%.The three newly designed brake discs in this study all showed improved heat dissipation performance compared to traditional brake discs,with the disc featuring rectangular grooved heat dissipation ribs showing the most significant improvement.Due to its relatively complex structure,additive manufacturing technology was considered for the fabrication of this brake disc.Simulation was used to validate the optimized process parameter combination,which greatly improved the quality of the brake disc fabrication.Subsequently,a prototype was successfully produced. |
