Papers by Author: Zhi Guo Wang

Abstract: Wear of diamond tool is also very serious, which affects the surface quality of the machined work material, even if ductile mode where an undeformed chip thickness is at a nanoscale is used. During the cutting process, the crystal structure in the cutting zone is destroyed under the high pressures applied by the diamond tool. The silicon atoms adhering to the tool surface reconstruct to be in a crystal state under the effect of adhesion and pressures.

Abstract: Under atmospheric pressure diamond is a metastable phase of carbon, which on heating can spontaneously transforms into a thermodynamically stable phase of carbon, graphite. No matter in diamond and in graphite, the six-fold ring is the smallest ring structure; they are very simillar in shape. The graphitization occurs when the rings of {111} plane are flattened. The {111} plane of diamond is the one that would graphitize preferentially and the (001) planes are most resistant to high temperature thermal graphitization.

Abstract: To study the removal mechanism of materials during nano cutting, molecular dynamics method is adopted to simulate single crystal copper nanomachining processes, and subsurface defects evolvements and chip forming regulation are analyzed by revised centro-symmetry parameter method and the ratios of the tangential cutting force and the normal cutting force. The results show that there are different defects under different cutting depths. When cutting depths is shallower, there are dislocation loop nucleation in the subsurface of the workpiece beneath the tool; however, when the cutting depths is deeper, there are dislocations nucleation and slipping along {101} plane and (111) plane. In addition, both tangential cutting force and the normal cutting force decrease as the cutting depths decreasing. When the ratios of the normal cutting force and the tangential cutting force is below 0.9, the chip will be formed.

Abstract: Molecular dynamics simulations of the single crystal silicon nanoscale cutting with a diamond tool in ductile mode are carried out to investigate the adhesion phenomenon. After relaxation the silicon atoms on the surface reconstruct to make the potential decrease. The silicon atoms close to the diamond tool have the lowest potential (<-5.5 eV) and form a stable structure with surface atoms on the tool surface.

Abstract: In order to investigate the mechanical properties of single crystal Cu nanorod with preset defects, the multiscale unixial tension simulation models of nanorods with two different crystallographic orientations are established. In two orientations, the dislocations are emitted firstly from the notch tip. The results show that the defect evolution, stress-strain curves and train energy vary with different crystallographic orientations. In setup, the deformation is ductile mode and it is fracture fashion in the setup.