Hyperdynamics accelerated concurrent atomistic-continuum model for developing crack propagation models in elastic crystalline materials

S Chakraborty and S Ghosh, COMPUTATIONAL MATERIALS SCIENCE, 154, 212-224 (2018).

DOI: 10.1016/j.commatsci.2018.07.064

Concurrent multiscale models that couple atomistic and continuum calculations are useful for extending the spatial limitations of atomistic models, as well as for deriving effective continuum models. This paper develops a concurrent atomistic-continuum computational model with an embedded crack in the atomistic domain. Molecular dynamics (MD) simulations are conducted in the atomistic domain, while the continuum domain is modeled using the finite element (FE) method. A major limitation of concurrent models is the time-scale mismatch between the continuum and atomistic domains that causes the two sub-domains to experience different strain-rates. To bridge the time scale difference, the MD model is augmented by a novel strain-boost hyperdynamics accelerated time marching scheme. The concurrent model is used to study strain-rate and temperature effects on crack propagation in a nickel single crystal. The continuum domain uses a nonlinear anisotropic elasticity constitutive model. Crack propagation rate is represented by a parametric continuum model, whose strain-rate and temperature dependencies are investigated. Finally, the concurrent model is used to evaluate the free energy density function for phase field modeling of crack propagation. Validation studies elucidate the potential of the concurrent model as a modeling tool for large scale continuum fracture models.

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