Numerical Simulation Study On Vibration-Assisted Single Abrasive Grain Scratching Silicon Carbide Crystals

With the development of optoelectronics and microelectronics technology,Single crystal silicon carbide has been widely used and highly valued as a third-generation semiconductor material.The single crystal silicon carbide has high hardness and high brittleness,and is a typical extremely difficult material to be processed.Therefore,diamond abrasive grain processing is its main processing method.However,the current abrasive grain processing method has room for further improvement in various aspects.A large number of studies have shown that ultrasonic assisted grinding processing can effectively improve the processing efficiency and the surface quality of the workpiece.Therefore,this paper proposes a vibration-assisted scratch simulation experiment on single crystal silicon carbide to study the mechanism of ultrasonic assisted grinding.In this paper,the molecular dynamics and finite element simulation software LS-DYNA was used to simulate the single-crystal silicon carbide ultrasonic assisted single-grain scratch.By comparing the processing phenomenon and processing effect with or without ultrasonic vibration,the removal mechanism of ultrasonic vibration assisted grinding is revealed in essence.It mainly includes the following parts:(1)Plastic deformation removal caused by ultra-fine grain grinding wheels in ultra-precision grinding.According to the basic ideas and principles of molecular dynamics,a simulation model of vibration assisted single abrasive grain rubbing silicon carbide was established.The changes of scratching force,amorphous layer,stress and dislocation in the presence or absence of vibration were compared.It was found that the scratching force and the maximum stress value were reduced after the vibration was added,the scratching force is reduced by about 40%,the thickness of the amorphous layer is reduced by 2 nm,and the dislocations disappear.(2)Molecular dynamics simulation was used to study the effect of scratch parameter changes on the scratching process.It is found that both the average tangential force and the average normal force decrease with increasing frequency and amplitude,and increase with the increase of depth of cut;the thickness of amorphous layer decreases with increasing frequency,and the width of amorphous layer It increases as the amplitude increases.(3)Based on the finite element software LS-DYNA,a simulation model was established for the brittle fracture caused by the coarse-grained grinding wheel.The smooth particle hydrodynamics(SPH)method was used to study the scratch force,the crack propagation and the stress change when there was vibration.It was found that the friction force decreased after the vibration was added,and the maximum expansion depth of the crack was reduced.Constantly becomes an alternating stress field,but the maximum equivalent stress is essentially constant.(4)The influence of scratch parameter changes on the scratching process was studied by finite element simulation.Both the average tangential force and the average normal force show a decreasing trend with increasing frequency and amplitude,and increase with the increase of the depth of cut.The maximum expansion depth of the crack decreases with increasing frequency,and as the amplitude increases,more minute lateral cracks are generated inside the workpiece.(5)The effect of interference in vibration-assisted scratching was quantitatively studied.It is found that the interference has a significant effect on the reduction ratio of the scratching force.The interference ratio increases with the increase of the frequency and amplitude,and decreases with the increase of the speed.In molecular dynamics,the reduction ratio of the scratching force increases to about 75% with the increase of the interference effect;in the SPH method,as the interference increases,the reduction ratio of the tangential force increases to 45%.The reduction ratio of the normal force has increased to about 20%.