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.

一些韧性增强陶瓷的成分）多晶藻氨基酸胺，其中包含几％的不锈钢颗粒，含有30.Vol％Ni或Co Metal的β-辛氨基玻璃陶瓷，以及氮化硅陶瓷，并准备了20 vol％的碳化物碳水化合物晶须等。我们试图通过微观尺度，2）R-Curve评估和3）裂纹概况观察来阐明1）光谱技术。评估了这些组合物的R曲线行为和裂纹打开位移（COD）剖面，并检查了断裂抗性的机制。这些组合物在1 mm的短裂纹延伸中显示出显着的R-Curve行为。讨论了结果，与这些成分的微观结构特征和断裂表面几何形状有关。对于玻璃或陶瓷单晶中的鳕鱼曲线观察，未观察到断裂表面之间的相互作用。另一方面，在韧性增强基于陶瓷的组合物的COD曲线中，实验值低于裂纹尖端附近的理论值（Irwin抛物线），从而增强了裂缝表面相互作用。尤其是，很明显，外部应力屏蔽效应在高度强化的复合材料中的裂纹尖端附近更强烈。发现基质晶粒尺寸的增加以及金属粉末或晶须的添加可增强断裂表面之间的相互作用。裂缝尖端的施加应力强度与应力强度与K（appl）/k（尖端）的函数之间的应力强度之间的关系表明，加固的试剂在韧性增强基于陶瓷的组合物中充当弹性桥接元素。阐明了每个标本中COD轮廓中的桥接区的大小，以对应R-Curve特征中延伸的延伸。