Study Of Nanometric Cutting Mechanism Based On A Scanning Electron Microscope

Nano-cutting technology has been developing rapidly in recent years. The reveal of nano-cutting extrusion mechanism makes the research field of cutting theory much broader. A series of explorations of the core problems based on the new cutting mechanism have become an important issue to be solved in the manufacture area. Currently, the approaches for studying the nanometric cutting mechanism mainly focus on ultra-precision cutting using cutting tools, nanometric scratching using atomic force microscope, molecular dynamics simulation, and experimental study using specially developed devices. However, these methods have many shortcomings for deeply understanding the nanometric cutting mechanism. Therefore, a new nanometric cutting platform is developed in this study. Based on this device, a series of experiments are carried out, including the following aspects:(1) A in-situ nano-cutting system was developed based on a scanning electron microscope. Multi-degrees of freedom(DOF) cutting such as straight line cutting、tapper cutting、sinusoidal cutting can be carried out with online observation, which is suitable for studying the nanometric cutting mechanism intuitively. Focused ion beam(FIB) technology was used to fabricate single crystal diamond cutting tools with different edge radii.(2) The positioning accuracy, stiffness, repeatability, creep drift characteristics and the cutting abilities of the nano-cutting system were tested using different methods. A closed-loop control method was proposed using image processing means for correcting the creep drift. When the command depth of cut was 10 nm, 50 nm and 100 nm, the actual depth of cut was 10.6 nm, 54.9 nm and 100 nm respectively. The results indicated that the nano-cutting system is of nanoscale precision and it is able to satisfy the requirements during the nano-cutting process.(3) The effects of the depth of cut on the single crystal copper chips morphology were studied. It was found when the depth of cut was less than 40 nm, there was no shear zone existing in the cutting. Nevertheless, when the depth of cut was between 50 nm and 100 nm, both the shear and extrusion were found on the chips, showing a transitional depth of cut. The effects of different crystal orientation、edge radius and cutting speed on the critical depth of brittle-ductile transition were analyzed. The influences of cutting speed and edge radius on cutting deformation were studied according to the chips deformation coefficient. Moreover, the minimum depth of cut under different edge radius was studied. It was found that the minimum depth of cut increases as the increasing of the edge radius. The ratio of the minimum depth of cut and edge radius is about 0.36–0.51.(4) The surface integrity of monocrystalline silicon was analyzed by micro-Raman spectroscopy. It was found that both transition of crystalline state and phase transformation occurred during the nano-cutting process. Moreover, the result of Raman spectrum on the chip indicates that the chip is a mixture of polycrystalline silicon and amorphous silicon, of which the former is dominant. The influences of cutting parameters on the monocrystalline copper and silicon were studied, including the thickness of sub-surface damage layer, residual stress, transition of crystalline state and phase transformation.