Cutting characteristics of monocrystalline silicon in elliptical vibration nano-cutting using molecular dynamics method

Abstract

Based on the molecular dynamics method, the model of monocrystalline silicon in elliptical vibration nano cutting (EVNC) is established. The effects of amplitude ratio (ratio of amplitude in parallel cutting direction to amplitude in vertical cutting direction) on the mechanical properties, thermal properties, crystal phase transition and morphology are systematically investigated. The results show that with the amplitude ratio increasing from 0.0 to 3.0, the hydrostatic compressive stress during cutting in the contact area decreases from 12.31 GPa to 8.31 GPa, and the tensile stress on the machined surface decreases from 5.23 GPa to 3.07 GPa. The depth of tensile stress layer after cutting is reduced from 12.02 Å to 4.8 Å. During cutting the maximum temperature of the machined surface decreases from 1419 K to 1236 K, and the chip maximum temperature increases from 1730 K to 2994 K. The number of diamond structures (bond length is 2.35 Å) is reduced during the cutting process, and the moderately increasing in the amplitude ratio can inhibit the formation of the bct-5 phase. After cutting, the number of diamond structures (bond length 2.35 Å) on the workpiece surface increases. The scratch morphology quality is effectively improved. With increasing amplitude ratio, the extrusion impact of the tool increases, resulting in the length and direction of the atomic displacement vector in the cutting area changing periodically, and the atomic kinetic energy and potential energy also change periodically, which may be the reason for EVNC to obtain better surface integrity. The research results provide theoretical reference for the application of ultrasound vibration assisted process in the field of atomic or near-atomic scale manufacturing.