Fundamental investigation on partially overlapped nano-cutting of monocrystalline germanium

Molecular dynamics simulations on partially overlapped nano-cutting of monocrystalline germanium with different feeds are carried out to investigate the surface topography, cutting force and subsurface deformation. The results indicate that the side-flow material piling up on the edges of tool marks is a decisive factor for the surface topography with the machining parameters in this study, ignoring the tool wear and machining vibration. In the partially overlapped nano-cutting, the lateral force is more affected by nominal depth of cut than by pitch feed with the value of feed being in some range. The atomic sights on the subsurface deformation show that the thickness of deformed layer after machining is much thinner than that after single cut with the same nominal depth of cut. Laser micro-Raman spectroscopy and cross-sectional transmission electron microscopy are used to detect the subsurface deformation of monocrystalline germanium after eccentric turning. The crystalline structure with defects rather than the amorphous germanium is observed in many areas of machined surface. Both molecular dynamics simulation and experimental results indicate that the amorphous-damage-less and even amorphous-damage-free machined surface can be achieved by partially overlapped nano-cutting.