Abstract
We investigate the fragmentation process of solid materials with
crystalline and amorphous phases using the the discrete element method.
Damage initiates inside spherical samples above the contact zone in a
region where the circumferential stress field is tensile. Cracks
initiated in this region grow to form meridional planes. If the
collision energy exceeds a critical value which depends on the
material's internal structure, cracks reach the sample surface resulting
in fragmentation. We show that this primary fragmentation mechanism is
very robust with respect to the internal structure of the material. For
all configurations, a sharp transition from the damage to the
fragmentation regime is observed, with smaller critical collision
energies for crystalline samples. The mass distribution of the fragments
follows a power law for small fragments with an exponent that is
characteristic for the branching merging process of unstable cracks.
Moreover this exponent depends only on the dimensionally of the system
and not on the microstructure.
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