M.D. Simulation of nanometric cutting of single crystal aluminum–effect of crystal orientation and direction of cutting

Abstract

Molecular Dynamics (MD) simulation of nanometric cutting was conducted on single crystal aluminum in specific combinations of crystal orientation {(111), (110), and (001)} and cutting direction 〈[1̄10], [2̄11], and [100]〉 and with tools of different positive rake angles (0°, 10°, and 40°) to investigate the nature of deformation and the extent of anisotropy of this material. When the aluminum crystal was oriented in (111) plane and cut in [1̄10] direction, plastic deformation ahead of the tool was accomplished predominantly by compression along with shear in the cutting direction. Also, the deformation in the work material (underneath the depth of cut region) was found to be along the cutting direction. In (001) [1̄10] combination, the dislocations were found to be generated parallel to the cutting direction. These were relieved from the uncut region into the work material underneath by elastic recovery. While there was some reorganization, yet some disorder of the atoms was observed in the machined surface in the amount close to the depth of cut. In contrast, in (110) [001] combination, the dislocations were generated normal to the cutting direction, which was rather unusual in machining. In the case of (110) orientation and [1̄10] cutting direction, the dislocations were found to be parallel as well as perpendicular to the cutting direction. In contrast, for (001) [100] combination, extensive dislocations motion at ∼45° to the cutting direction was seen. Similarly, for (111) [2̄11] combination, the dislocation motion was observed to be at ∼60° to the cutting direction. In both cases, the material in the shear zone was deformed at an angle (equivalent to a shear angle), which is the mirror image of the dislocations generated in the work material, i.e., ∼45° (clockwise) in the case of (001) orientation and [100] cutting direction and ∼60° (clockwise) in the case of (111) orientation and [2̄11] cutting direction. The variation of the cutting forces, the ratio of thrust to cutting force, the specific energy (energy required for removal of unit volume of work material), and the nature of deformation ahead of the tool as well as the subsurface deformation of the machined surface with crystal orientation and direction of cutting were investigated.