| Particle reinforced aluminum matrix composites,with excellent physical and mechanical properties,have gradually replaced traditional metal and alloy materials in extreme environmental fields such as impact,wear and high temperature.However,as a typical difficult to machine material,how to improve its machinability is the main problem faced by the industry.Since ultrasonic vibration assisted cutting(UVAC)technology was proposed,it has been widely used in difficult to machine materials and composites with intermittent contact characteristics and friction reversal characteristics,and some valuable research results have been obtained.At present,the research of particle reinforced aluminum matrix composites during UVAC is mainly in single vibration assisted cutting,and mainly based on experimental research,lack of relevant research on material removal mechanism of 2D UVAC.Aiming at ultrasonic vibration assisted cutting of particle reinforced aluminum matrix composites(taking SiCp/Al composites as an example),this paper carries out finite element characterization,removal mechanism,cutting force modeling and prediction,pseudo "All plastic" surface generation and experimental verification,and the main research contents include:(1)A two-dimensional microscopic finite element model is proposed to characterize the cutting removal process of particle reinforced aluminum matrix composites.Based on the actual microstructure of SiCp/Al composites,the effects of material physical properties(metal matrix,reinforced particle and particle-matrix interface),geometric properties(volume fraction,size and distribution)and interaction are comprehensively considered.Combined with particle fracture behavior,chip morphology,cutting force and surface morphology,the accuracy of the model is verified through cutting experiments.At the same time,the influence of different particle modeling methods on the simulation results is analyzed to provide an optimal scheme for the finite element characterization of the cutting removal process of particle reinforced aluminum matrix composites.(2)Explore the removal mechanism of SiCp/Al composites in 2D ultrasonic vibration assisted machining,and focus on the influence of elliptical tool path on material removal mechanism,particle deformation behavior and surface morphology.Considering the effects of cutting depth,radius of cutting edge and particle position,the influence law of tool path on particle removal behavior is analyzed,and the surface improvement mechanism of vibration assisted cutting particle reinforced aluminum matrix composites is revealed.(3)The cutting force prediction model of SiCp/Al composites during ultrasonic vibration assisted cutting is established.Dynamic cutting characteristics in the mechanical removal process of SiCp/Al composites are mathematically characterized based on the shear deformation theory,tool chip contact friction characteristics and the ploughing effect of the flank.The dynamic cutting force is decomposed into chip forming force,tool-chip-workpiece interaction force and ploughing force.Combined with the vibration assisted cutting characteristic function,the cutting force prediction model of SiCp/Al composites during ultrasonic vibration assisted cutting is proposed,and the correctness of the cutting force prediction model is verified by experiments.In addition,by designing single factor cutting experiments,the effects of cutting speed,cutting depth,feed rate and particle volume fraction on the cutting force of SiCp/Al composites during UVAC are revealed,which provides theoretical guidance for the process optimization of mechanical removal of particle reinforced aluminum matrix composites.(4)The concept of pseudo "All plastic" surface of SiCp/Al composites is proposed,and the critical cutting parameter model of plastic surface generation is established and verified.According to the material deformation behavior,the machined surface of SiCp/Al composites is divided into plastic deformation of Al matrix and surface defects caused by particle deformation.By analogy with the brittle-plastic transformation of brittle materials,the pseudo "All plastic" surface dominated by plastic deformation is defined,and the integrity transformation corresponds to the proportion of the two surface forms.Based on specific cutting energy criterion,the prediction model of critical cutting parameters for surface integrity transformation of SiCp/Al composites in ultrasonic vibration assisted cutting is established.Two kinds of scratching tests(equal cutting depth and variable cutting depth)are used to explore the key factors affecting the surface integrity transformation,so as to provide theoretical guidance for improving the machinability and machining process optimization of particle reinforced aluminum matrix composites. |
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