Material deformation mechanism of polycrystalline tin in nanometric cutting

The surface generation and subsurface deformation mechanisms of polycrystalline tin in nanometric cutting are investigated using molecular dynamics. Subsurface deformations such as amorphization, phase transformation, grain boundary migration, and grain rotation during machining are observed. The distribution of hydrostatic stress and the evolution of the crystal structure are analyzed to determine the causes of cutting force fluctuations. The effects of undeformed chip thickness and cutting speed on material removal and subsurface deformation are also examined. Results show that the propagation of deformation is suppressed by the grain boundaries, and the grain boundary steps on the machined surfaces are expanded by deformation recovery. In addition, the removal behavior of polycrystalline tin is remarkably affected by the grain size and crystal orientation.