Application of Multiscale Process Zone Model to Simulate Fracture in Polycrystalline Solids

In this work, an early proposed atomistic-based multiscale process zone model is revised and employed to simulate crack propagation and spall fracture in polycrystalline solids. The multiscale process zone model is capable of describing heterogenous materials by incorporating the effect of inhomogeneities such as grain boundaries, slip lines and inclusions. A consistent depletion potential resulting from fundamental principles in colloidal physics is used to describe the cohesive laws for both the grain interfaces and process zones in bulk materials, which provides microstructure-based interface potentials in both normal and tangential directions with respect to finite element boundary separations in contrast to conventional cohesive methods. The polycrystalline microstructure are generated by using the Voronoi tessellations. Two different approaches of treating the process zone are proposed. The multiscale process zone model is implemented in a Lagrange framework based on the Galerkin weak form formulation. In addition, to eliminate the zero-energy modes and avoid shear locking in the interphase elements, a reduced integration technique is adopted in simulations. Numerical simulations on crack propagation in materials with various cohesive strengths have been carried out, and they can describe both inter-granular and trans-granular fractures. Finally, the spall-fracture of a specimen under high-impact load is captured using the proposed multiscale process zone model.