Molecular dynamics simulation on crack growth in amorphous metal
Nakatani Keiko; Nakatani Akihiro; Kitagawa Hiroshi; Sugiyama Yoshihiko
Abstract:Fractures in amorphous metal usually occur in a brittle manner. The metal is, however, essentially a ductile material, for it demonstrates high deformability, despite having a high yield strength. These two facts seem to conflict with each other at first glance. In this paper an atomistic simulation is carried out to resolve this apparent contradiction. The molecular dynamics (MD) method is applied to a cracked amorphous structure containing 102356 atoms with mode I loading. Crack growth begins at the time when a stress wave arrives at the crack tip. The amount of crack extension increases with increase in the crack-tip opening displacement, and potential energy is changed to kinetic energy with the crack growth. From an investigation of the atomic arrangement and structure of the defect atoms (which is defined by a local density), it is demonstrated that crack growth occurs with atomic deformation that takes place in a ductile manner in a local area, but in a brittle manner in a macroscopic view. Moreover, it is shown that the interaction between the crack and the void, which develops in front of the crack tip, plays some important roles during crack growth. Key Words:Computational mechanics, Fracture mechanics, Molecular dynamics, Fe amorphous metal, Viscous flow, Mode I crack