Research On Material Removal And Surface Finish In Ultrasonic Vibration Grinding Of SiCp/Al Composites

Superior properties make silicon carbide particle reinforced aluminum matrix composites(SiCp/Al composites)being widely used in defense industry and national economic field.However,the addition of SiC particles makes SiCp/Al composites hard to be manufactured due to its extreme abrasive properties.Ultrasonic vibration assisted grinding is a combination of two ordinary material remove processes,i.e.grinding and ultrasonic machining.Compared with other traditional machining methods,this machining method has many advantages,such as lower grinding force and temperature and is suitable for machining of difficult-to-machine materials.Thus,fundamental research on the material removal mechanism and surface finish of SiCp/Al composites in ultrasonic vibration assisted grinding process is of great significance to the further application of this kind of composite materials.The material removal process of SiCp/Al composites is a result of synergetic deformation and interactions among Al matrix,SiC particles and interface under a certain process condition.The non-homogeneity of microscopic mechanical properties due to the inherent polyphase heterogeneity of SiCp/Al composites will directly affect the removal mechanism and surface finish in the machining process.In order to investigate the influence of non-homogeneity of SiCp/Al composites on the microscopic mechanical properties,based on the nanoindentation test,the micromechanical properties of the SiCp/Al composite materials were tested and the deformation behavior was analyzed.On the basis of this,the tradit ional scratch and ultrasonic vibration assisted scratch tests were carried out to analyz scratch force,friction coefficient and curve surface morphology,and investigate the effect of ultrasonic vibration on the material removal mechanism of SiCp/Al compo sites.All of these provide the basis for subsequent research on the influence of the ultrasonic vibration on surface finish.In order to study the heterogeneity properties and the influence of the deformation behavior on the surface defects of SiCp/Al com posites,based on the research of material removal mechanism of SiCp/Al composites,a micromechanics finite element model of SiCp/Al composites was established,in which Al matrix,SiC particles and interface were modeled respectively by using ABAQUS softw are and python language.The formatin mechanism of defects on machined surface and the influence of ultrasonic vibration on the material removal process of SiC particles were simulated by the use of this model.The simulation results show that there were three kinds of material removal modes for SiC particles,including rolled and pulled in Al matrix,fractured and pulled out.As a result of SiC particles being fractured and pulled out,the pit was the main defect on the machined surface.The defects of the machining surface in the scratch tests were analyzed by scanning electron microscopy,and the validity of the simulation model was verified.The results provide a basis for the subsequent evaluation and optimization of the surface finish of SiCp/Al composites.The results provide a basis for the exploration of technical measures to improve the surface finish of SiCp/Al compositesGrinding force has a great effect on the material removal process and machined surface finish.Based on the research of material removal mechanism of SiCp/Al composites and kinematics analysis of ultrasonic vibration assisted grinding,considering the chip forming characteristics of two phase materials,predictive force model in ultrasonic vibration assisted grinding of SiCp/Al com posites is established and verified,which is consist of side grinding force model and end grinding force model.And then,the influence of process parameters on grinding force are investigated,which provides evidence for the selection of process paramete rs in the research on the surface finish.On the basis of above research,the machined surface finish is experimental studied in ultrasonic vibration assisted grinding of SiCp/Al composites.The machined surface topography is evaluated by three dimensional surface roughness and fractal dimension.The relationship between surface roughness,surface defect and fractal dimension,and the influence of process parameters on machined surface are investigated.Finally,setting a new parameter which reflects the ch aracteristics of the machined surface of SiCp/Al composites as the optimization objective,process parameters are optimizated by using nondominated sorting genetic algorithm(NSGA-II),and the experimental results agree well with optimization results.The results of the study provide evidence for the selection of process parameters in ultrasonic vibration grinding of SiCp/Al composites.