NUMERICAL MODELING OF SPALLING PHENOMENON ON ALUMINA BY DISCRETE ELEMENT METHOD.

The numerical Discrete Element Method (DEM) approach has already proven its legitimacy to represent the behaviour of brittle or quasi-brittle materials such as ceramics at quasi-static regime. The present study investigates the DEM approach in reproducing the dynamic behaviour of an AL23 ceramic under dynamic spalling tests. Elastic microscopic parameters of the DEM model are calibrated using quasi-static uniaxial tensile tests in order to match the macroscopic elastic behaviour of an AL23 ceramic. The DEM model is then used to simulate the stress waves propagation, interactions and fracture mechanisms generated during spalling damage tests. Rear face velocity profiles have been measured and compared to the numerical results. The strain-rate sensitivity of the spalling stress of AL23 ceramic has been observed experimentally. The anisotropic DFH (Denoual-Forquin-Hild) damage model is implemented in DEM to take into account the strain rate sensitivity. Several methods to manage anisotropy in DEM are tested.
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