Degradation of Crack Shielding in Toughened Ceramics in Cyclic Fatigue

循环疲劳中增韧陶瓷裂纹屏蔽的退化

• 批准号: 9412691
• 负责人: Dinesh Shetty
• 金额: $ 22.57万
• 依托单位: University of Utah
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-01-01 至 1998-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9412691&HistoricalAwards=false
• 关键词: Degradation; Crack; Shielding; Toughened; Ceramics

9412691 Shetty Toughened ceramics, including transformation-toughened zirconia based ceramics and whisker-and fiber-reinforced ceramic composites, are susceptible to true cyclic fatigue phenomena. The associated high subcritical crack-growth rates in cyclic loading can arise from either extrinsic (degradation of crack shielding) or intrinsic (crack-tip damage) mechanisms. The research proposed will investigate the origins of cyclic fatigue in ceria partially stabilized zirconia/alumina and self-reinforced silicon nitride by separating the contributions of the extrinsic and the intrinsic mechanisms via direct measurements of crack shielding using Roman microprobe spectroscopy. Critical comparison of the measured shielding with the theories of crack shielding and direct examination of the transformation or bridging zones via Transmission and scanning electron microscopes techniques are also the important elements of the proposed research. %%% The proposed research will investigate the origin of cyclic fatigue in ceria-partially stabilized zirconia/alumina and self reinforced silicon nitride by means of Roman spectroscopy and electron microscope. ***

9412691 Shetty增韧陶瓷，包括相变增韧氧化锆基陶瓷和晶须和纤维增强陶瓷复合材料，对真正的循环疲劳现象敏感。 在循环加载中，相关的高亚临界裂纹扩展速率可能来自外在（裂纹屏蔽的退化）或内在（裂纹尖端损伤）机制。 提出的研究将调查循环疲劳的起源，在氧化铈部分稳定的氧化锆/氧化铝和自增强氮化硅分离的贡献的外在和内在的机制，通过直接测量裂纹屏蔽使用罗马微探针光谱。 临界比较的测量屏蔽与理论的裂纹屏蔽和直接检查的转换或桥接区通过透射和扫描电子显微镜技术也是拟议的研究的重要内容。 本研究将利用罗马光谱和电子显微镜研究氧化铈部分稳定氧化锆/氧化铝和自增强氮化硅的循环疲劳起源。 ***