DEPENDENCE OF STRENGTH ON SIZE OF FLAW DOMINATING FRACTURE IN CERAMICS

概要

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Bending tests using a silicon nitride and an alumina were carried out under 4-point bending to clarify the relation between the strength and the size of flaw observed at a fracture origin. When the fracture originated from a smaller flaw, the strength was confirmed to be lower than that expected from the fracture toughness criterion. A convenient procedure using the mean strength and the fracture toughness was proposed to estimate the strength degradation depending on flaw size. A new model was also developed assuming the stable cracking caused by the separation per one grain ahead of a flaw prior to the final unstable fracture. A Monte Carlo simulation based on the proposed model was made to explain the anomalous behavior of small flaw. The relation of strength vs.crack length simulated by taking account of grain-size distribution showed good agreement with the experimental result. The lower bound in scatter of strength depending on flaw-size was suggested to be estimated by using the size of the largest grain expected in a material.
社団法人日本材料学会の論文
1995-06-15