Genyu Chen

Study on three-dimensional laser cutting technology in auto-body panel

In this paper, three-dimensional cutting test of auto-body panel was carried out by CO2 laser on the five-axis linkage numerical control cutting machine. First, the advantage of adopting 3D laser cutting method to process Auto-body Panel was summarized, and the essential factor in cutting quality was discussed. Then, the technical difficulty in three-dimensional laser cutting was addressed, and several experiments and theory analysis on problems such as collision and overburning at upslope, downslope, and corner were conducted, with corresponding improvement methods and solutions proposed. Finally, the cutting quality was evaluated with respect to kerf width, surface roughness, and the size of heat affected zone (HAZ). The experimental results indicated that to obtain three dimensional cutting workpiece with superior cutting quality and high cutting precision, the incident angle changed with the pose of cutting head should be limited to 20°. Narrow kerf (0.28~0.50mm), smooth surface (2.68μm~7.22μm) and small heat affected zone (appr. 70μm) can be obtained under the condition of appropriate technological parameters. Besides, overburning can be eliminated effectively at upslope, downslope and corner by decreasing laser power, adopting pulse laser, or using the air as assisting gas alternatively.

Influence of laser nanostructured diamond tools on the cutting behavior of silicon by molecular dynamics simulation

In this study, a series of large-scale molecular dynamics simulations have been performed to study the nanometric cutting of single crystal silicon with a laser-fabricated nanostructured diamond tool. The material removal behavior of the workpiece using a structured diamond tool cutting is studied. The effects of groove direction, depth, width, factor, and shape on material deformation are carefully investigated by analyzing normal stresses, shear stress, von Mises stress, hydrostatic stress, phase transformation, cutting temperature, cutting force and friction coefficients. Simulation results show that a cutting tool groove orientation of 60° produces a smaller cutting force, less cutting heat, more beta-silicon phase, and less von Mises stress and hydrostatic stress. Moreover, tools with a smaller groove orientation, groove depth and groove width, and larger groove factor lead to more ductile cutting and an increased material removal rate. However, a cutting tool with a smaller groove width results in more heat during the nanoscale cutting process. In addition, the average temperature of the subsurface increases as groove factor increases, showing that a tool groove accelerates heat dissipation to the subsurface atoms. Furthermore, this V-shape groove cutting is shown to improve material removal ability in nanoscale cutting.

Molecular dynamics simulation of subsurface damage mechanism during nanoscratching of single crystal silicon

Three-dimension molecular dynamics (MD) simulation is employed to investigate the nanoscratching process of monocrystalline silicon with diamond tools. The effects of tool geometry on subsurface damage and scratching surface integrity are investigated by analyzing phase transformation, chip, defect atoms, hydrostatic stress, von Mises stress and workpiece deformation. In addition, a theoretical analytical model to study the subsurface damage mechanism by analyzing the zone size of phase transformation and normal force with diamond tools at different half-apex angles on silicon surfaces is established. The results show that a bigger half apex angle causes a higher hydrostatic stress, a larger chip volume, a higher temperature and a higher potential energy, and increases subsurface damage. The results also reveal that the evolution of crystalline phases is consistent with the distribution of hydrostatic stress and temperature. In addition, tip scratching with a bigger half-apex angle would result in a larger scratching force and a bigger phase transformation zone, which is in good agreement with the results of the theoretical analytical model.