Hybrid FE-DE Simulation of Dynamic Fracture Processes

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Falk Wittel
Dr. Falk K. Wittel

The simulation of dynamic fracture and fragmentation processes sill pose a challenge for the computational accessibility. Interestingly often the experimental studies of these processes are limited by technical reasons too.

One way of looking inside of the material are in-silico fracture and fragmentation experiments. Simulation techniques like the Discrete Element Method (DEM) proved to be successful to simulate dynamic fracture of brittle, heterogeneous materials. DEM involves the repulsive, cohesive and frictional interaction of thousands of particles of different shapes and sizes, representing a sample of material.

One of the advantages of the DEM lies in its full physical access. However, the large number of particles required to represent a specimen or real structure are disadvantageous. Fortunately only a small number of elements is located in the damage zone while the majority represent its elastic foundation. DEM can be used for the discretization of the  damage zone, while the Finite Element Method (FEM) is utilized to model the surrounding domain.

Snapshot from a breaking system with the crack tip in the notch. On the left and right are the FEM domain, while the fracture zone is modeled with packings of spheres interconnected by beam elements. Colors represent magnitudes of accelerations.

The FEM domain is solved with an explicit integration scheme, while the DEM domain uses a predictor-corrector scheme. Domain edge coupling was found to be sufficient for this example. We show this technique on a 3D simulation of a notched bar impact test. Theses systems are used to obtain a better understanding of dynamic fracture processes with respect to crack roughnesses, velocities, energies and macroscopic properties with respect to microscopic ones of the model.

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