 |
| Titel |
Transition from straight to fractal cracks due to projectile penetration |
| VerfasserIn |
Ferenc Kun, Zoltán Halász, Frank van Steeden |
| Konferenz |
EGU General Assembly 2014
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250092252
|
| Publikation (Nr.) |
 EGU/EGU2014-6583.pdf |
|
|
|
|
|
| Zusammenfassung |
| We investigate the fracturing of heterogeneous materials due to the penetration of a rod with
conical shape. A two-dimensional discrete element model of a disc shaped specimen is
worked out coupling randomly shaped convex polygons by cohesive beam elements.
Computer simulations are carried out of the process when a rod with a conical nose is pushed
perpendicularly into a disc shaped sample. Cracks are generated in the sample by the
successive breaking of beams.
Varying the speed of penetration simulations revealed a rich dynamics of the system: In the
limit of very slow loading straight cracks are formed along which the sample falls apart.
Increasing the loading speed first the number of cracks increases, while above a threshold
speed cracks start to branch and form fractal structures. The fractal dimension of three-like
branching cracks proved to increase with the speed of loading from Df - 1.0 toDf - 1.65 .
When the speed of penetration surpasses a second threshold value the fractal cracks merge
forming a network and the specimen breaks up into a large number of fragments. The
fragmentation pattern is mainly controlled by the interference of elastic waves generated
by the energetic loading and by the reflection at the free external boundary of the
disc. The size distribution of fragments determined by the crack structure proved
to be a power law with an exponent close to 1.9. Analyzing the simulated data
we deduce scaling relations which characterize the straight crack - fractal crack -
fragmentation transition. The theoretical results are confronted with experimental findings. |
|
|
|
|
|