Development of a numerical protocol for the very high strain rate dynamic fragmentation of porous-brittle materials at the microstructure scale

The discrete element method is used to study the influence of strain rate on the fracture behavior of porous brittle materials. Dynamic uniaxial tensile tests are simulated on 2D idealized samples. In such high strain rate simulation, initial and boundary conditions must be chosen carefully to achieve a uniform loading of the sample and initial conditions in order to interpret properly the results obtained. A new initial condition is developed by using an initial velocity field in accordance with the heterogeneous microstructure. High strain rates ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>&gt;</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mn>6</mml:mn> </mml:msup> <mml:mspace width="0.166667em"/> <mml:msup> <mml:mi mathvariant="normal">s</mml:mi> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> ) condition have been achieved while ensuring force equilibrium. The numerical results show an increase of the maximum stress at failure, as well as the transition from single to multiple fragmentation, which are inline with experimental observations. Cracks path and stress field are also analyzed to understand the transition from single to multiple fragmentation, and an obscuration phenomenon linked to the microstructure is successfully identified.