3D molecular dynamic simulation of fracture behavior of bcc iron

The fracture behavior of bcc iron is investigated by means of 3D molecular dynamic simulation with EAM potential. The crack propagation is studied under the condition of specific temperatures and loading. The results show that the formation of dislocation is different according to the strain rates. The temperature has a significant effect on the crack profile and dislocation. Slip on (110) plan is observed in the crack process. Introduction Iron is an important material for vehicle. It is a strong metal used widely with good deformation and alloying property. Understanding the process of crack and fracture of iron is essential to safe utilization of them in various structures. The basic fracture mechanics is the linear elastic fracture mechanics (LEFM), which is an ideal approach to dealing with linear elastic materials. SK Chan i.e. proposed the finite element method of linear fracture mechanics to compute crack tip stress intensity factors. Beside of continuum approaches to studding fracture, molecular dynamic method is another means of investigation of fracture at the atomic scale. Since the first molecular dynamic simulation of crack propagation was reported in 1976 by Ashurst and Hoover, [1] the fracture of iron has been studied widely by the means of MD simulation. The simulations were small (1000~10000 atoms) 2D systems at the early stage for the limitation of the computing power. In order to deal with the crack propagation in small geometry of system various boundary conditions were introduced. DeCelis, Argon, and Yip proposed a constant-stress boundary condition [2] to eliminate some of the difficulties of dealing with the transmission of the dislocation emitted from the crack. Cheung and Yip reported that dislocations are emitted form crack tip, when they used the constant-force boundary condition in their small (3000 atoms) 3D system to study the brittle to ductile transition of bcc iron. [3] Many studies with the MD approach are 2D system or small 3D system. We report our 3D simulation to investigate the crack process in a system at nanometer scale which consisted of 60080 atoms by means of parallel computing.