Three-dimensional molecular dynamics simulation of nanostructure for reciprocating nanomachining process

Three-dimensional molecular dynamics simulations are conducted to investigate the effect of reciprocating nanomachining process on the subsurface damaged layers, surface integrity, cutting force, stress variation of subsurface, and changes of energy and defects in the workpiece. Results show that there is no obvious shear zone ahead the tool during nanomachining. Dislocation nucleations are near the free surface ahead the tool and the interface of the tool and the workpiece and propagate in the surface and downward in the workpiece. There are the generations of dislocation jog and dislocation loops ahead the tool during the reciprocating cutting. The values of the reciprocating cutting force for the (111) orientation and (100) orientation under offset distance of 0 a₀ are not zero but 11.756 and 13.0498 nN, respectively. When the offset distance of the tool is up to 10 a ₀, the ratio of primary cutting force to reciprocating force is nearly 90%. The shape of the machined groove in the (111) orientation remains better than that in the (111) orientation in cases of both the primary cutting process and the reciprocating process. Reciprocating cutting with the offset distance of 5 a₀ of the tool results in the pile-up atoms filling in the primary machined groove and forming the order lattice by surface reconstruction. Primary cutting force decreases with the reduction of workpiece sizes, which shows the size effects. With the increasing cutting depths, average primary cutting force and average reciprocating force increase. It is noted that reciprocating cutting force in the case of the (111) workpiece is larger than that of the (100) orientation except for the offset distance of 0 a ₀. With the increasing offset distance of the tool, the residual shear stress increases in the subsurface of the workpiece, and the order degree of subsurface atoms of the workpiece decreases in the cases of both the (111) orientation and (100) orientation. It is denoted that, with the offset distance at 5 a₀, the peak of the average shear stress is highest during the reciprocating cutting. Meanwhile, the order degree of subsurface atoms in the case of the (111) orientation is better than that of the (100) orientation.