Analysis of Micro-cutting Mechanisms using Continuum-Mechanics-Controlled Molecular Dynamics

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1. A method of simulation to study atomistic scale mechanism existing in a shear deformation of a monocrystal copper has been proposed based on the hierarchical coupling of molecular dynamics and the analytical expression of the displacement field around a mode-II crack.2. The result of the simulation shows that there is a critical state at which a shear deformation changes its nature from that caused by an external force to that progressing by itself. This result agrees well with the description of the slip deformation theory of a monocrystal and/or the Piispanen card model for microcutting.3. During, the process before the critical state, cross slips occur in many places in a material repeatedly, each time increasing their magnitute. These cross slips block a macroscopic shear slip.4. A macroscopic shear slip occurs at the critical state where the area composed of disordered atomic arrangement has stretched from one end to the other end of a crystal. The resultant macroscopic shear occurs in the directions of the slip planes in a crystal because the area above mentioned develops only to those directions.5. Controlled molecular dynamics has been applied to micrometer-scale Hertz indentation using the analytical displacements derived on the basis of the Hertz contact theory.6. Defects that will cause a ring crack can be initiated during indentation even in monocrystalline silicon with no preexisting defect.7. Defects are initiated by the coupling of the dynamic force transmitted from an amorphous area in the specimen with the static tensile stress on the specimen surface. The coupled forces slowly loosen the crystal structure on the surface and triggers cross slips, which result in valley-like defects on the surface.