Modeling Plastic Fracture by Stillinger-Weber Potential-Embedded Discretized Virtual Internal Bond

The failure of material always involves with the plastic deformation and fracturing process. For the plastic deformation, the continuum plastic mechanics can competently deal with the plastic deformation through a yield function and the flow rule. However, the continuum mechanics method has some limitations in dealing with the fracture problem due to that it cannot account for the microstructure of the material. The lattice model can simulate the fracture problem very well, but it is inadequate in dealing with plastic deformation. To unify the plasticity and the fracture together on the bond level, the present paper employed the Stillinger-Weber potential-based discretized virtual internal bond (SW-DVIB) method. DVIB is a kind of lattice model. It considers material to consist of bond cells. Each bond cell can take any geometry with any number of bonds. In original DVIB, the interaction between particles in a cell is characterised by an interatomical bond potential, which intrinsically contains the microfracture mechanism. However, because the interatomical potential only accounts for the effect of the bond stretch, the Poisson ratio it represents is fixed. To remedy this drawback, in the SW-DVIB the SW-potential is adopted to characterise the energy of a bond cell. Due to that, the SW-potential can simultaneously account for the bond angle and stretch effect; the SW-potential can represent the variable Poisson ratio. In this paper, the SW-DVIB is adopted to model the elastoplastic fracture. The plasticity is considered in the two-body potential. That is before the bond reaches its yielding point, this bond is linear elastic. After it reaches the yielding point, the bond enters the ideal plastic state. The irreversible deformation is reflected by following different loading-unloading paths. The bond does not rupture until its deformation reaches the limit value, which is related to the bond cell size and the macro fracture energy of the material. The three-body potential is kept linear elastic until the normal bond is ruptured. By this method, several examples were simulated. It is suggested that the irreversibility feature of the plastic deformation can be well captured. It can simulate the fracture propagation of material with the conservation of the fracture energy. The present paper provides an efficient approach to the elastoplastic fracture simulation.