Modeling Of SiCp/Al Composite Cutting Subsurface Damage Depth And Its Effect On Mechanical Properties

Silicon carbide particle-reinforced aluminum matrix(SiCp/Al)composite materials have been widely used in key manufacturing fields such as aerospace and military industry due to SiCp/Al composite materials outstanding characteristics such as high strength,low weight,high wear resistance and low thermal expansion.The tool-particle-matrix interaction in the machining of SiCp/Al composites leads to severe subsurface damage to the workpiece material.This not only exacerbates the initiation and propagation of cracks,but also greatly reduces the fatigue performance of the material and limits its reliability application.Therefore,the research on the cutting sub-surface damage characteristics of SiCp/Al composites and their influence on the mechanical properties of the material is of great significance for improving the reliability of the material parts in key areas.In this paper,an analytical model for predicting the depth of cutting subsurface damage in cutting of SiCp/Al composite materials was established.The model comprehensively considered the effects of SiC reinforced particle characteristics,tool wear,and thermal-mechanical stress coupling.Firstly,based on the slip line field theory,a prediction model of the chip forming force in the orthogonal cutting of the material was established;according to the two-body wear friction and three-body rolling friction theory,the characterization model of tool-particle-chip interface friction was modeled;based on the flank wear stress equation,an analytical model of the tool-workpiece interface friction was constructed.Then,by establishing a parabolic mechanical load distribution model and a thermal load temperature field model,the mechanical stress and thermal stress at any point of the cutting subsurface were predicted.Finally,the mechanical stress and thermal stress were coupled and superimposed,and the von Mises yield criterion was introduced to predict the depth of the subsurface damage of the SiCp/Al composite.In order to verify the correctness of the prediction model of cutting subsurface damage depth proposed in this paper,orthogonal cutting experiments of SiCp/Al composite with different feed rate and different tool wear were carried out.The subsurface damage depth is evaluated as a measure of variation in microhardness along the depth normal to the cross-section of the machined surface.The results show that the average error of the prediction model is 7.8%.The influence of cutting parameters,tool wear,and strain rate coefficient in the constitutive model on the depth of subsurface damage of SiCp/Al composites was systematically analyzed.The results show that the subsurface damage depth of SiCp/Al composite increases with the increase of feed rate and tool wear,and decreases with the increase of cutting speed;the strain rate coefficient in the constitutive model has little effect on the subsurface damage depth of SiCp/Al composite.Based on the model,the influence rules of mechanical stress and thermal stress on the cutting subsurface damage depth of SiCp/Al composite were revealed.The results show that mechanical stress is the main factor affecting the ctting subsurface damage depth of SiCp/Al composites compared with thermal stress.The mechanism of subsurface damage in SiCp/Al composite cutting was analyzed.The particles broke under the action of shear stress,resulting in cracks at an angle of about 45°to the machined surface;the particles rotated and moved due to the plastic deformation of the material.The effect of cutting subsurface damage depth on mechanical properties of materials was studied.The results show that the tensile strength of SiCp/Al composites decreases with the increase of the cutting subsurface damage depth.Based on digital image correlation(DIC)technique,the global strain field of tensile specimens with different cutting subsurface damage depths was analyzed.Both the maximum negative strain of?_xx and the maximum positive strain of?_yyincrease with the increase of the depth of cutting subsurface damage.The maximum normal strain of?_yy only shows sensitivity to the depth of cutting subsurface damage under high stress.The fracture morphology of the tensile specimen was analyzed.It is found that the aluminum alloy matrix presented ductile fracture,SiC particles presented brittle fracture,and SiC particle dense area presented quasi cleavage fracture morphology.