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.

一些韧性增强陶瓷基复合材料）含有少量vol%不锈钢颗粒的多晶氧化铝、含有30.vol%Ni或Co金属的β-锂辉石玻璃陶瓷、以及用20vol%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 曲线评估和 3）裂纹来阐明增韧机制。对这些复合材料的 R 曲线行为和裂纹张开位移 (COD) 曲线进行了评估，并检查了这些复合材料在 1 毫米的短裂纹扩展内表现出显着的 R 曲线行为。另一方面，对于玻璃或陶瓷单晶的 COD 剖面观察，在韧性增强陶瓷基复合材料的 COD 剖面中没有观察到与这些复合材料的微观结构特征和断裂表面几何形状相关的相互作用。值低于裂纹尖端附近的理论曲线（欧文抛物线）导致断裂表面相互作用增强，特别是，在高韧化复合材料中，外部应力屏蔽效应在裂纹尖端附近的作用更加强烈。发现添加金属粉末或晶须可以增强断裂表面之间的相互作用。施加的应力强度和裂纹尖端的应力强度之间的关系是 K(appl)/K(tip) 的函数，表明这些试剂。用于加固，充当弹性桥接元件明确了每个样本 COD 轮廓中桥接区的尺寸，以对应于 R 曲线特性中上升延伸的尺寸。