MD Simulation of nanometric cutting of single crystal aluminum-effect of crystal orientation and direction of cutting

Molecular Dynamics (MD) simulation of nanometric cutting was conducted on s ingle crystal aluminum in specific combinations of crystal orientation {(11 1), (110), and (001)} and cutting direction ([(1) over bar 10]. [(2) over b ar 11], and [100]) and with tools of different positive rake angles (0 degr ees, 10 degrees, and 40 degrees) to investigate the nature of deformation a nd the extent of anisotropy of this material. When the aluminum crystal was oriented in (111) plane and cut in [(1) over bar 10] direction, plastic de formation ahead of the tool was accomplished predominantly by compression a long 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 cu tting direction. In (001) [(1) over bar 10] combination, the dislocations w ere found to be generated parallel to the cutting direction. These were rel ieved From the uncut region into the work material underneath by elastic re covery. 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 c ut. In contrast, in (110) [001] combination, the dislocations were generate d normal to the cutting direction, which was rather unusual in machining. I n the case of (110) orientation and [(1) over bar 10] cutting direction, th e dislocations were found to be parallel as well as perpendicular to the cu tting direction. In contrast, for (001) [100] combination, extensive disloc ations motion at similar to 45 degrees to the cutting direction was seen. S imilarly, for (111) [(2) over bar 11] combination, the dislocation motion w as observed to be at similar to 60 degrees to the cutting direction. In bot h cases, the material in the shear zone was deformed at an angle (equivalen t to a shear angle), which is the mirror image of the dislocations generate d in the work material, i.e., similar to 45 degrees (clockwise) in the case of (001) orientation and [100] cutting direction and similar to 60 degrees (clockwise) in the case of (111) orientation and [(2) over bar 11] cutting direction. The variation of the cutting forces, the ratio of thrust to cut ting 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 orienta tion and direction of cutting were investigated. (C) 2000 Elsevier Science S.A. All rights reserved.