Study On Grinding Mechanism Of Particle Reinforced Cu-matrix Braking Composites Based On Simulation And Experiment

Particle reinforced Cu-matrix composite brake are the main types of brake pads for high speed trains in China.This kind of brake block is prepared by powder metallurgy method.After pressing,sintering and shaping process,it can be used to achieve the desired size and surface integrity of the product by grinding.Because the particles are randomly distributed in the copper matrix,and their different characteristics,the surface defects of the grinding process are serious,and the machining mechanism is more complicated.This paper studies the grinding mechanism of particle reinforced Cu-matrix braking composite by simulation and experiment:The simulation model of particle reinforced Cu-matrix braking composite was established by coupling finite element method and smoothed particle hydrodynamics method.The finite element model of particle phase is established by using the method of random segmentation,and it is randomly distributed in the copper matrix with smooth particle description.The coupling between the two is realized by defining the solid contact.And verify the accuracy of the coupling method.The results show that the coupling between the finite element mesh and SPH particles can be effectively and accurately coupled.Based on the simulation of single abrasive cutting process,the process of cutting deformation and chip morphology of particle reinforced copper based brake materials were studied.The effects of cutting parameters,particle content,relative cutting force and cutting heat were analyzed.Research shows that: the cutting deformation of particle reinforced Cu-matrix braking composite is completed by the plastic deformation of the copper alloy matrix and the movement of the particle phase and the crushing of the lubricating phase;The increase of cutting depth and particle content will lead to the increase of cutting force,cutting speed increases the cutting force is reduced;With the increase of cutting speed and particle content,the cutting temperature increases,and the cutting depth has little influence on the cutting heat;The large size of the lubricating phase results in a reduction in the cutting force and a decrease in the cutting temperature.An experimental platform of single diamond abrasive particle reinforced Cu-matrix braking composite was built on the MM7125 type surface grinder.The cutting forces were measured under different cutting depths,and the surface morphology and defect characteristics were observed by microscope,scanning electron microscope and profilometer.The results showed that with the increase of cutting depth,cutting force increases;The surface morphology of the scratch is formed by the plastic deformation of the copper matrix,the breakage of the graphite and the falling of the particle phase.The fragmentation of graphite and particles is the main cause of surface defects.The conclusions in this paper have important guiding significance for revealing the formation mechanism of the surface of particle reinforced Cu-matrix braking composite,In order to give full play to the performance of brake block to provide theoretical basis and technical support.