MOLECULAR DYNAMIC SIMULATION OF CRACK PROPAGATION BEHAVIOR IN NANO SIZE HCP CRYSTALS

摘要

A crack propagation behavior of nano size hcp crystal (13nm x 24nm x 4.6nm) has been simulated by molecular dynamics method using Lennard-Jones type potential. In a case of model crystal with initial notch plane and direction were (1010), [1210], the crack propagated parallel to notch plane and two sets of prismatic slips were occurred at the crack. Therefore, the crack in this crystal is deduced to extend by alternating shear on two intersecting {1010}< 1210 > prismatic slip systems. In a model crystal with (0001), [1010] initial crack, {1011} first order pyramidal slip occurred at crack tip and following {1012} twin was also observed. In the model crystal with (1010)[0001] initial crack, the crack propagated parallel to initial crack plane with two prismatic slips in front of the crack. To understand strength of nano size titanium crystals as MEMS materials, stress intensity factor, K of each model crystals were also estimated from stress-strain curves obtained from these simulations.