Nanocutting: A Comparative Molecular-Dynamics Study of Fcc, Bcc, and Hcp Metals

Background: The so-called orthogonal cutting process constitutes a well-defined and transparent example of machining. Modern applications require an understanding of the defect formation processes occurring in nano-manufacturing. Methods: Molecular-dynamics simulation is employed to study the cutting of metals by a rigid tool made of C atoms. Fe, Al and Ti are selected as examples of bcc, fcc and hcp metals. We choose single-crystalline workpieces oriented such that multiple slip systems are activated. Atomistic analysis tools provide information on the crystal-plasticity effects induced by the cutting process. Results: The quantitative evolution of the forces needed to cut through the materials is similar for the three metals studied. However, the chip form and the roughness of the cut surface are quite distinct in the three metals, and reflect the different plastic processes occurring inside the material. Conclusion: The form of the cut depends on the details of the plastic processes proceeding in the interior. The form of the chip itself is strongly influenced by the constant arrival and absorption of dislocations at its surface; similarly the roughness of the cut surface stems from the emission of dislocations from the cutting edge.