Drilling Force Modeling And Hole-making Damage Study Of SiCp/Al Composites Considering Particle Damage

As one of the key light metal matrix composites(MMC),SiC particle reinforced aluminum matrix(SiCp/Al)composite are widely used in aerospace,electronic instruments and other high-end manufacturing fields due to its high specific strength,specific modulus,wear resistance and low thermal expansion coefficient.Although SiC particles can significantly improve material properties,they can also degrade machining performance.The reinforced particles with high hardness will cause serious hole making defects,such as burr,edge breakage and tear,which will seriously affect the hole making quality and service performance of the composite.However,compared with homogeneous metal materials,SiCp/Al composites have great differences in material removal mechanism,damage formation mode and other aspects.Therefore,in this paper is systematically studied the SiCp/Al composite drilling force model,hole damage mechanism and multi-objective optimization.The main contents are as follows:(1)An analytical model of drilling force of SiCp/Al composite material considering particle damage characteristics was established.Three kinds of particle damage characteristics including particle break,particle debonding and particle squeezing were studied.At the same time,the main cutting edge,the second chisel edge and the extrusion zone of twist drill are characterized respectively based on the oblique cutting theory,orthogonal cutting theory and slip line field theory.In order to verify the correctness of the model,drilling experiments with different material parameters and machining parameters were carried out.The experimental results show that the average error between the predicted drilling force and the experimental drilling force is 6.55%.Compared with the drilling force model in the existing literature,the drilling force predicted by particle model in this paper is more accurate.Based on the model,the energy ratio in drilling of SiCp/Al composite material was analyzed,and the results showed that the energy ratio of particle action was about 8.2% to 13.6%.(2)The drilling machinability investigations and surface integrity of SiCp/Al composites were systematically investigated.The results show that the burr damage occurred at the entrance of pores with different particle volume fraction.Burr(15%)and edge breakage(30% and 45%)were found at the exit.The damage characteristics of the pore wall were studied,and the matrix damage(groove,microcrack,matrix tear,cavity and scratch damage)and particle damage(particle extrusion,particle peel,particle crack,particle cut)were found.Serious damage defects were also found on the subsurface of the pore wall,including particle agglomeration,matrix deformation and matrix ablation.The subsurface microhardness of SiCp/Al composite was studied and analyzed,and the subsurface damage of SiCp/Al composite was about 180μm-220μm.(3)Based on genetic algorithm-Pareto optimization,the key parameters of SiCp/Al composite drilling process were studied,and the parameters were analyzed according to analysis of variance(ANOVA)and response surface.The range of optimized parameters was obtained by genetic algorithm,and appropriate processing parameters were selected by Pareto optimization,which was verified through experiments,providing theoretical support for low-damage hole making of SiCp/Al composite materials.