Study on the Failure Assessment Diagram of Ceramics

结果表明，定量评价陶瓷的断裂特性是可能的，并得出以下结论：1)采用相同的材料，考察了断裂应力--σ_F和断裂韧性K_(？)2)在室温至1200ﾟ℃范围内，断裂应力SiHMA_F随温度的升高而减小。3)用线断裂力学方法无法评价短裂纹陶瓷的强度性能。陶瓷的断裂应力与裂纹长度有关。所提出的工艺区域尺寸准则可以作为陶瓷断裂行为的一种合理的评价方法。此外，还对过去五种其他类型的陶瓷进行了检测。可以定量评估缺口尖端半径断裂韧性与其他三种陶瓷材料的相关性。5)基于概率概念和工艺区域尺寸准则，提出了陶瓷材料的失效评定图。通过这种方法，可以容易地和保守地评估陶瓷的可靠性。

Fracture behaviour of ceramics was examined in the range at a room temperature to 1200^ﾟC. Based on these results, a process zone size criterion for ceramics was proposed. In results, it was possible to assess the fracture characteristics of ceramics quantitatively, and gave following conclusions.1)Using the same material, the statistical properties of fracture stress-sigma_F and fracture toughness K_<1C> was examined. In results, the dispersion characteristics of sigma_F and K_<1C> evidently conformed to the Weibull distribution. And the value of shape parameter alphafor K_<1C> is large than that for sigma_F.2)In the range at a room temperature to 1200^ﾟC, fracture stress sihma_F tend to decreased with a gain of temperature. On the other hand, fracture toughness K_<1C> tend to increased.3)It was impossible to evaluate the strength properties for ceramics with short crack by linear fracture mechanics. Fracture stress of ceramics show dependence on crack length. The proposed process zone size criterion can be accepted as a rational evaluation method for the fracture behaviour of ceramics. Furthermore, the past five other types of ceramics was examined. those data agreed fairly well process zone size criterion.4)A evaluation method for notched material was also proposed based on process zone size criterion. It was possible to assess the dependence of fracture toughness for notch tip radius quantitatively on three other types of ceramics.5)A failure assessment diagram for ceramics was proposed based on probabilistic concept and process zone size criterion. In this way, it was possible to assess the reliability for ceramics easily and conservatively.