Probabilistic damage model for the crack propagation in Si3N4 ceramics

0450459 - ÚFM 2016 RIV ES eng A - Abstract
Chlup, Zdeněk - Tatarko, P. - Hadraba, Hynek - Petráš, Roman - Kozák, Vladislav - Dlouhý, Ivo
Probabilistic damage model for the crack propagation in Si3N4 ceramics.
14th International Conference European Ceramics Society. Toledo: ECERS, 2015. ISBN 978-84-606-9257-7.
[ECERS 14 - International Conference of the European Ceramic Society /14./. 21.06.2015-25.06.2015, Toledo]
R&D Projects: GA MŠMT(CZ) ED1.1.00/02.0068
Institutional support: RVO:68081723
Keywords : damage model * crack propagation * silicon nitride
Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass

The microstructural constitution of silicon nitride possesses the ability to enhance fracture propert ies by changing the grain shape parameters and change the glassy phase composition. The composition of the glassy phase plays significant role in the grain formation. Usually, the elongated beta silicon nitride grains homogeneously distributed within the m icrostructure formed from equi - axed grains creates significant obstacle for propagating crack. There are few mechanisms that acts during the fracture process and led to enhanced fracture resistance of the material. First one is the crack bridging, where op ening of existing crack is constrained by the elongated grain in elastic regime. The second is the grain trans - granular fracture where the elastically loaded bridging grain is fractured and this grain fracture consumes some portion of accumulated energy st ored in the system. The third mechanism can be seen when the crack is somehow forced to change its direction and use delamination between grains (inter - granular fracture out of the main fracture direction) to overcome the elongated grain. The first two mec hanisms described acting dependently to each other and can be merged to one having two phases. The both basic reinforcing mechanisms act together based on the number of factors. The obstacle in modelling based on physical principles of the crack behaviour is the determination of material parameters as the grain de - cohesion energy dependence on glassy phase or single - crystal strength as well as rather complicated local stress state around the crack tip. The suggested approach tries to eliminate outlined diff iculties by simplification of necessary independent variables with addition of probabilistic approach necessary for realistic results.
Permanent Link: http://hdl.handle.net/11104/0252774