Study On Micro-ground Tip Induced Brittle Fracture Cutting Performance Of Hard And Brittle Materials

The precision cutting of high-performance chip materials such as single crystal silicon carbide,sapphire and quartz glass due to the brittle-ductile removal transformation needing mechanical feed of micro and nano unit,leads to low processing efficiency and exists environmental problems such as materials removal and waste cutting fluid.Therefore,it is proposed the method of cutting high performance chip materials through micro-ground tip induced micro-crack propagation.First,the high precision and smooth straight microgroove is processed on the surface of hard-brittle chip substrate using diamond wheel micro-tip by precision dressing.Then,the loading rod is loading on the upper of substrate leading to the stress concentration at the micro-groove tip.The material zero removed dry cutting of chip materials is accomplished through microgroove tip induced generating micro-crack and precision propagation on chip materials.In this study,the micro-indentation tip micro-crack propagation is experimental studied on chip materials.Grinding performance of straight microgroove tip and cutting mechanism of dynamic and static load of chip materials are researched.The precision cutting feasibility of hard-brittle chip materials is discussed.(1)The relationship model between micro-indentation tip micro-crack extension length and micro-indentation diagonal length and indentation force is established through the micro-indentation experiment using diamond cone.It is shown that the order of the strength of hindering micro-indentation induced micro-crack propagation is quartz glass,single crystal silicon carbide,sapphire and single crystal silicon.In grinding micro-groove tip on chip surface,the micro-grinding processing quality is consistent with the strength of hindering micro-crack propagation of chip materials.Moreover,the micro-tip grinding force of single crystal silicon carbide is 38.9%,10.8%and 46.8%less than the ones of sapphire,single crystal silicon and quartz glass,respectively.(2)In micro-indentation array tip micro-crack induced cutting chip materials,the strength of hindering micro-crack propagation can be used to predict its severability.Single crystal silicon carbide has the best severability,and the cutting force,cutting time and cutting form errors are about 80%,43%and 84%less than ones of sapphire,respectively,about 99%,82%and 81%less than the ones of single crystal silicon.Moreover,the indentation force of single crystal silicon carbide can be used to control the cutting force,efficiency and accuracy.The cut surface roughness is 22~35 nm.The micro-indentation and cutting time is within 25 s and high efficient and smooth cutting processing can be realized.(3)The smooth cutting surface with no edge damage can be obtained through micro-groove tip induced cutting quartz glass compared with the mechanical roller cutting.When critical loading rate is less than 20~60 mm/min,dynamic cutting transforms to static cutting with different mechanism.The static cutting model of cutting force related to tip radius has been experimentally verified.Moreover,static cutting force and time are about 2times and 9 times than dynamic cutting,however,the cut surface form error and roughness is reduced about 36%and 12%and reach 16.3μm/mm and 19.7 nm,respectively.(4)In the cutting of single crystal silicon carbide and sapphire,when the loading rate reach the critical value 40~60 mm/min which leads to dynamic and static cutting transformation,the cut surface quality is best.In addition,the cutting force and cutting time gradually decrease to a stable value.The cut form error in static cutting was 52.9%and 33.5%less than the ones in dynamic cutting,respectively.In the static cutting,the cutting time of single crystal silicon carbide is greater than the one of sapphire and reach 0.2~0.3 s.But the cut form error of single crystal silicon carbide is less than about 10 times than the one of sapphire and the cut surface roughness reach 43~47 nm.Moreover,the straight microgroove is processed along the crystal orientation<1~-21~-0>,which can reduce the cutting force and the cutting time.