| The high volume fraction aluminum-based silicon carbide composite(SiCp/Al)has the characteristics of low density,high specific strength,good thermal conductivity,fatigue resistance,wear resistance,creep resistance and corrosion resistance.Therefore,it is widely used in aerospace,transportation,military medicine fields.However,in the cutting process of SiCp/Al composite materials,there are problems such as low processing efficiency,severe tool wear,and low precision of processed parts and poor surface quality.Based on the Hopkinson pressure bar(SHPB)dynamic compression test data of SiCp/Al composites and the constitutive equations of high volume fraction composites are established through the shear hysteresis model,effective medium approximation method;and the two-dimensional and composite materials are established.Three-dimensional cutting simulation model to study the cutting force and cutting surface quality of composite materials.The main research contents are as follows:(1)Through the separate Hopkinson pressure bar dynamic compression test,the aluminum-based silicon carbide particle-reinforced composite material(SiCp/2024Al)with a volume fraction of 45% was studied at large strain rates(6400s-1-8500s-1)and Thermal deformation behavior in the range of deformation temperature(300K-690K).The influence of thermal deformation parameters(deformation temperature and strain rate)on the flow stress is analyzed.The study found that the deformation temperature and strain rate have a significant effect on the flow stress,compressive strength,and elastic modulus of composite materials.The compressive strength and elastic modulus decrease with the increase of deformation temperature,and the inflection point appears with the increase of strain rate.The original material and the micrograph of the composite material after compression are observed through the Keyence ultra-depth stereo microscope.It is found that the SiC particles in 45%-SiCp/2024 Al are only arranged in an orderly manner after compression and there is no obvious breaking phenomenon,but shear bands are found on the micrograph of SiCp/2024 Al after compression.(2)The shear lag model is used to calculate the yield point,and then the stress-strain relationship in the elastic deformation stage is obtained,and then the effective medium approximation(EMA)method is used to obtain the stress-strain relationship in the plastic deformation stage.Under the quasi-static condition,the volume fraction is 45%-the stress-strain function relationship of the SiCp/Al composite,and then the obtained quasi-static constitutive model is combined with the strain rate sensitivity function and the thermal softening function to make the constitutive model It can calculate the stress-strain curve under different temperature-different strain rate.Finally,the constitutive model is applied to the cutting simulation,and finally the simulated cutting force is consistent with the experimental cutting force,which proves that the constitutive model calculated in this chapter is correct.(3)In Digimat-FE,three-dimensional models with different shapes of reinforced particles(spheres,ellipsoids,cubes)and randomly distributed are established,and the established models are imported into Abaqus/Explicit finite element software for cutting simulation and adjusting the cutting depth So that the tool can cut on different positions of the SiC particles.Then,by comparing the surface morphology of the SiC particles cut by the tool at different relative positions,the influence of different cutting relative positions on the surface morphology is obtained.The cross-sectional view shows the fracture and removal mechanism of SiC particles.In the model,you can see the fracture and removal of SiC particles at different relative positions,such as slightly broken top of the particles,burrs around the cavity,and severely deformed shallow cavities.And compared with the experimental graph of the milling surface,it proves the correctness of the simulation. |
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