Research On Theoretical Model Of Surface Formation And Surface Roughness Of Turned Engineering Ceramics

Engineering ceramics have excellent chemical stability and play an indispensable role in many fields such as high-precision equipment,medical equipment,large-scale aviation,and navigation.At present,there are relatively few researches on the processing mechanism of engineering ceramics at home and abroad.Therefore,brittle materials are studied.The removal mechanism of cutting is very much needed.Surface roughness is an important parameter to characterize surface quality,which can affect the mechanical properties,fatigue strength,fit properties,corrosion resistance and lubricity of mechanical parts.However,ceramic materials have low fracture toughness,are sensitive to defects and cracks,have poor surface quality,low material removal rate,and high tool wear rate.As a typical hard and brittle material,engineering ceramics study its turning surface forming mechanism,determine the influence of cutting parameters and tool geometry on roughness,establish a theoretical model of roughness,and control the surface quality,improve the processing efficiency,and reasonably optimize the cutting parameters.And reducing processing costs are of great significance.In this paper,by studying the removal mechanism of brittle materials of engineering ceramics,a theoretical model of engineering ceramics surface roughness is established,and the selection of cutting tools and cutting parameters are discussed.The main work is as follows:1.By studying the micro-crack and fracture mechanism of engineering ceramics,the mechanism of surface formation in cutting is analyzed,and the effect of cutting force on the removal of crushing is studied to determine the crack propagation path,crack propagation length and crack propagation angle.There are three stages of brittle evolution:crack formation,crack propagation,and chip fracture.2.Through the first batch of cutting experiments,study the three elements of cutting and the influence of tool wear on surface roughness.3.By studying the formation mechanism of tool wear,determine the different tool wear forms and corresponding surface quality,through the engineering ceramic cutting force theory,combined with Griffith strength theory,taking into account the joint influence of the tool rake face and the tool flank at the same time,the establishment The contact stress model between the tool and the workpiece is combined with the stress intensity factor,considering that the surface of the workpiece is formed into a non-ideal arc in the actual machining process,and the surface damage factor is proposed.4.Through single factor experiment and orthogonal experiment,the cutting speed,feed speed and depth of cut were verified on the crack propagation angle,crack propagation length and surface roughness model.The study found that the surface roughness increased with the cutting speed and The increase of the feed rate decreases first and then increases,and gradually increases with the increase of the cutting depth.According to the orthogonal experiment,the primary and secondary order of the factors affecting the surface roughness is analyzed.The largest is the feed rate and the smallest is the cutting speed.