Micromechanical Analysis of Fragmentation using ALE-AMR

Professor David J. Benson

Fragmentation is a fundamental process that naturally spans micro to macroscopic scales. Recent advances in algorithms, computer simulations, and hardware enable us to connect the continuum to microstructural regimes in a real simulation through a heterogeneous multiscale mathematical model.

We apply this model to the problem of predicting how targets in MegaJoule-class laser chambers dismantle, so that optics and diagnostics can be protected from damage. The mechanics of the initial material fracture depend on the microscopic grain structure. In order to effectively simulate the fragmentation, this process must be modeled at the subgrain level with computationally expensive crystal plasticity models.

However, there are not enough computational resources to model the entire laser target at this microscopic scale. In order to accomplish these calculations, a hierarchical material model (HMM) is being developed. The HMM allows fine-scale modeling of the initial fragmentation using computationally expensive crystal plasticity, while the elements at the mesoscale can use polycrystal models, and the macroscopic elements use analytical flow stress models. The HMM framework is built upon an adaptive mesh refinement (AMR) capability. Figure: Fragmentation of a cooling ring in an inertial confinement fusion experiment using the ALE-AMR code.