セラミックスの破壊強度に及ぼすブリッジング特性の影響

概要

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The influence of bridging characteristics on the fracture strength of ceramics was investigated by numerical simulation. Factors influencing the fracture strength of ceramics include the defect size, bridging characteristics and the fracture toughness. The relationship between defect size and fracture strength has been studied by many researchers. However, there are few reports on the relationship between bridging characteristics and fracture strength, though this relationship is important for materials development. The purpose of the present investigation was to reveal the relationship between the bridging characteristics and the fracture strength of ceramics by numerical simulation. In the numerical simulation, the stress intensity factor at crack tip and the fracture toughness were used for the fracture criterion. It is assumed that the crack propagates when the crack-tip stress intensity factor reaches the fracture toughness. The effect of bridging on the toughening is not expected when the defect size as an equivalent crack length is smaller than 20 to 50 μm. The reason is that the stable crack extension with bridging before a catastrophic fracture is very short for defects smaller than 20 to 50 μm.
1996-09-01