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Direct Measurement of Fatigue Damage Accumulation in Ceramics and Elucidation of Its Mechanisms

陶瓷疲劳损伤累积的直接测量及其机理的阐明

基本信息

批准号：
07650119
负责人：
HORIBE Susumu
金额：
$ 1.54万
依托单位：
Waseda University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07650119/
关键词：
cyclic fatigue static fatigue crack growth silicon nitride ceramics conductive film-potential method 繰り返し疲労疲労応力比 Grain Bridging き裂開口

项目摘要

There have been "Crain-bridging degradation model" and "Grack resisting-reactivating model" (or "Wedging microcracking model" ) proposed to explain the fatigue crack growth behavior in ceramic materials. The significant difference between the two models is that in the former the crack propagates during loading only but in the latter it should do both during loading and unloading. Paying attention to this point, we tried to elucidate the mechanism of fatigue damage in ceramics.The basic data on fatigue crack growth in silicon nitride and alumina were measured so that the effects of microstructural factors (grain size and aspect ratio), stress ratio and crack closure on crack growth behavior were made clear. Unsteady crack growth was examined in relation to the microstructure. Afterwards, the crack extension during loading and unloading processes in silicon nitride was precisely measured by using the conductive film-potential method. As a result, it has been found that the crack growth occurs not only during loading process but also during unloading process and the fraction of the crack advancement during unloading increases with increase of frequency. Judging from these results, it was concluded that the "Crack resisting-reactivating" or "Wedging microcracking" mechanism should be dominantly operative in the cyclic fatigue in silicon nitride ceramics.

陶瓷材料的疲劳裂纹扩展行为有“裂纹桥接退化模型”和“抗裂纹再活化模型”（或“楔状微裂纹模型”）。两种模型的显著区别在于前者裂纹只在加载过程中扩展，而后者裂纹在加载和卸载过程中都应扩展。针对这一点，我们试图阐明陶瓷材料的疲劳损伤机理，测定了氮化硅和氧化铝材料的疲劳裂纹扩展的基本数据，阐明了微观结构因素（晶粒尺寸和长径比）、应力比和裂纹闭合对裂纹扩展行为的影响。非稳态裂纹扩展的微观结构进行了检查。然后，用导电膜电位法精确测量了氮化硅中裂纹在加载和卸载过程中的扩展。结果表明，裂纹不仅在加载过程中扩展，而且在卸载过程中扩展，卸载过程中裂纹扩展的比例随频率的增加而增加。从这些结果可以看出，氮化硅陶瓷的循环疲劳机制主要是“抗裂-再活化”或“楔入微裂纹”机制。