Simulations of microcracking in the process region of ceramics with a cellmodel

Authors
Citation
E. Johnson, Simulations of microcracking in the process region of ceramics with a cellmodel, INT J FRACT, 111(4), 2001, pp. 361-380
Citations number
20
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Mechanical Engineering
Journal title
INTERNATIONAL JOURNAL OF FRACTURE
ISSN journal
0376-9429 → ACNP
Volume
111
Issue
4
Year of publication
2001
Pages
361 - 380
Database
ISI
SICI code
0376-9429(200110)111:4<361:SOMITP>2.0.ZU;2-#
Abstract
Microcracking around a macrocrack and the consequential toughening in polyc rystalline ceramics are simulated. The objective is to check the hypothesis that the Suppression mechanism for opening of off-side microcracks does no t work in certain ceramic materials because cracks open up, assisted by res idual stresses, at a much reduced load in some grains, while, still encount ering a high resistance to crack growth at the grain boundaries. A two-dime nsional cell model of a polycrystalline material is investigated. Each cell represents one grain. The load-deformation law for the cell is assumed to contain two load peaks. The first peak is associated with microcrack nuclea tion in the grain, while the second peak is related to the resistance that the microcrack meets at the grain boundary. The cells are included in a fin ite element model. Grain to grain variations, for instance due to residual stresses, are taken into account by a Weibull distribution of the first loa d peak. Results from the simulations show that variations of the propensity for microcrack nucleation between different g-rains constitute a major fac tor responsible for the generation of microcrack clouds. Such cloud formati on would otherwise he impeded by unloading effect,, from central microcrack s. In addition, and in accordance with observations, the simulations also s how high fracture energies (compared to what would be expected for a typica lly brittle material), as well as a period of stable crack propagation.