Investigation of Crack Initiation and Propagation and its Instability Condition using Molecular Dynamic Simulation

Modeling and simulation techniques are able to throw new insights in the science and mechanics of materials. Predictability of fracture and failure are becoming more certain and these are now compared with experimental observation. In this work, the authors have investigated the fracture behavior of a single crystal alpha-iron having a mode-I edge crack. Using small-scale Molecular Dynamics Simulation (MDS) and proper choice of interatomic potential and boundary conditions, the authors have shown agreement in the prediction of crack initiation and propagation using Griffith fracture criteria, and crack instability condition from material’s fracture resistance in the atomic scale. The simulation shows that the crack does not initiate or propagate until the stress intensity value reaches the stress intensity factor equivalent to Griffith fracture stress for the material. The fracture resistance and crack opening displacement (COD) were measured using the simulated results, similar to that of continuum fracture mechanics. The point of initiation of stable and unstable crack was delineated using the principle of plane stress fracture toughness testing. The results indicated inelastic deformation in the early stage of the application of load when crack propagates.