Simulation Study On Preparation Technology Of Powder Metallurgy Brake Pads

In recent years,with the rapid development of trains towards high speed and heavy load,the stability and reliability of their braking devices and brake materials have gradually attracted public attention.Compared with traditional brake pads,powder metallurgy brake pads have stable friction coefficient,higher heat resistance,thermal conductivity,economic efficiency and environmental adaptability.Traditional preparation methods are usually designed based on"experience",with long production cycles and high costs.Therefore,this study uses a combination of computer simulation and experiments to investigate the influence of process parameters on the performance of brake pads,and to optimize the best process parameters.The specific research contents are as follows:1)The mechanical and chemical parameters of Cu and Fe powders,preparation methods,and performance testing methods were obtained by consulting literature.The process simulation of formulation and pressing stages was carried out using the Multi-Particle Finite Element Method(MPFEM)with the selected powders.The preset mass ratio of binary powder particles in the formulation was generated using the Discrete Element Method(DEM)software EDEM,and the particle model was filled into the mold cavity to form a combined body in Solid Works.Then,the combined body was imported into the finite element software ABAQUS,and the four-node tetrahedral element mesh was automatically generated,with fixed boundary conditions set and material properties defined.This approach enabled the construction of a particle packing model that closely resembled the actual filling state,making the simulation model more similar to the actual production situation.2)During the formulation stage,a simulation model was used to study the influence of different Cu/Fe mass ratios on the particle flow,deformation,stress,and velocity vector distribution inside the compact under the same process environment.The results showed that the Fe mass ratio had a significant impact on the feasibility of compact processing.Different experimental schemes were designed to measure the density of the compact and sintered body,verifying the accuracy of the simulation and obtaining the optimal Cu/Fe mass ratio in the formulation.3)During the pressing stage,a simulation model was used to numerically simulate the optimal particle model in terms of pressing pressure,pressing speed,pressing mode,friction coefficient,and holding pressure process.The results showed that pressing pressure and friction coefficient had a significant impact on the compact density,and pressing speed had a large influence on the uniformity of compact density distribution.Bi-directional pressing could promote particle flow deformation and uniform density distribution.Extending the pressing time could effectively improve the concentration of internal stresses in the compact,prevent demolding,and avoid cracking during sintering due to stress concentration.Different experimental schemes were designed under various pressing pressures to verify the accuracy of the simulation and obtain the optimal pressing process parameters.4)During the sintering stage,a Cu/Fe two-phase cellular automaton sintering simulation model was constructed.The fixed Q-value assignment method and model initialization method were improved.The simulation results showed that Fe particles formed agglomerates in the compact,which affected the growth of Cu particles,and there were many Cu particles encapsulating Fe particles.Based on the simulation model,an experimental scheme for the sintering process was designed,and the optimal sintering process parameters were obtained through a single-factor comparative experiment.Samples were prepared accordingly.The measurement results showed that the powder metallurgy brake pads had high density,hardness,friction coefficient,and other properties.Various industrial software were used for modeling and simulation,simulating the entire preparation process,making the simulation results closer to actual production,greatly improving the design efficiency,and reducing resource consumption.In the study of the preparation process of powder metallurgy brake pads,combining numerical simulation calculations with experimental analysis can effectively summarize the quantitative impact of factors on performance at each stage.The deviation between the simulation results and experimental results was within an acceptable range,which has theoretical guidance and practical reference value.