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STUDY OF FRACTURE SURFACE BRIDGING EFFECT IN CERAMICS

陶瓷断裂表面桥联效应的研究

基本信息

批准号：
11450248
负责人：
NISHIDA Toshihiko
金额：
$ 5.82万
依托单位：
Kyoto Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2001
项目状态：
已结题

项目摘要

Some toughness reinforced ceramic-based composites )polycrystalline aluimina containing a few vol% stainless-steel particles, β-spodumene glass ceramics containing 30.vol% Ni or Co metal, and silicon nitride ceramics reinforced with 20 vol% silicon carbide whisker , etc.) were prepared. We tried to clarify the toughening mechanism by 1) Spectroscopic techniques at micro scale, 2) R-curve evaluation, and 3) Crack profile observation. The R-curve behavior and crack opening displacement (COD) profiles for those composites were evaluated and mechanism for fracture resistance was examined. Those composites showed remarkable R-curve behavior within short crack extension of 1 mm. The results were discussed, associated with microstructural features and fracture surface geometry of those composites. For COD profile observation in glass or ceramic single crystals, the interaction between fracture surfaces was not observed. In the COD profiles of toughness reinforced ceramic-based composites on the other hand, the experimental value was lower than the theoretical one (Irwin parabola) near the crack tip, resulting in the enhancement of the fracture surface interaction. Especially, it was obvious that external stress shielding effects acted more strongly near the crack tip in highly toughened composite. The increase in matrix grain size and addition of metal powder or whisker were found to enhance the interaction between fracture surfaces. The relationship between the applied stress intensity and the stress intensity at the tip of crack as a function of K(appl)/K(tip) indicate that the agents for reinforcement acted as elastic bridging elements in the toughness reinforced ceramic-based composites. The size of bridging zone in COD profile for each specimen was clarified to correspond to that of rising extension in R-curve characteristics.

一些韧性增强的陶瓷基复合材料)多晶铝含有少量体积%的不锈钢颗粒，β-锂辉石玻璃陶瓷含有30%。制备了体积% Ni或Co金属，以及体积%碳化硅晶须增强的氮化硅陶瓷等。我们试图通过1)微观尺度的光谱技术，2)r曲线评价和3)裂纹轮廓观察来阐明增韧机理。评估了复合材料的r曲线行为和裂纹张开位移（COD）曲线，并对其抗断裂机理进行了研究。复合材料在短裂纹扩展1 mm范围内表现出显著的r曲线行为。讨论了复合材料的微观组织特征和断口几何形状。对于玻璃或陶瓷单晶的COD剖面观察，没有观察到断裂面之间的相互作用。另一方面，韧性增强陶瓷基复合材料的COD曲线在裂纹尖端附近的实验值低于理论值（Irwin抛物线），导致断口表面相互作用增强。在高增韧复合材料中，裂纹尖端附近的外应力屏蔽效应更为明显。基体晶粒尺寸的增大和金属粉末或晶须的加入增强了断口间的相互作用。外加应力强度与裂纹尖端应力强度的关系(K（appll)/K(tip)）表明，增强剂在韧性增强陶瓷基复合材料中起弹性桥接元件的作用。澄清了各试样COD剖面中桥接带的大小与r曲线特征中上升延伸的大小相对应。