@article{oai:kumadai.repo.nii.ac.jp:00022988,
 author = {Mori, Kazuya and Noguchi, Hiroshi and 森, 和也 and 野口, 博司 and Tabarrok, Berouz},
 issue = {572},
 journal = {日本機械学會論文集. A編},
 month = {Apr},
 note = {application/pdf, 論文(Article), It is well known that the fracture strength of ceramics with small defects is lower than the strength estimated by linear fracture mechanics, based on the strength of a large defect. This phenomenon can be explained by the increase in the crack resistance with crack propagation. This R-curve behavior is caused mainly by grain bridging in the wake of the crack. Recently the grain-bridging stresses for alumina and silicon nitride have been measured experimentally. In this study, the fracture strength is estimated by numerical simulation, based on grain-bridging stresses. In the simulation, the effective stress intensity factor at the crack tip, K_<tip>, and the effective fracture toughness at the crack tip, (K_<tip>)_c, are used for the conditions of stable and unstable crack propagation. It is found that the fracture toughness for long cracks, K_<Ic>, depends on specimen geometries, and the maximum values of K_c approach (K_<tip>)_c as the initial crack length approaches the width of the specimen. Furthermore a convenient method to evaluate (K_<tip>)_c experimentally is discussed., http://ci.nii.ac.jp/naid/110002371861@@@http://www.jsme.or.jp},
 pages = {984--991},
 title = {数値シミュレーションによる欠陥を有するセラミックスの破壊強度評価 : 第1報,基礎理論とアルミナセラミックスへの応用},
 volume = {60},
 year = {1994}
}