Microstructural mechanisms of cyclic fatigue-crack propagation in grain-bridging ceramics☆
Microstructural mechanisms of cyclic fatigue-crack propagation in grain-bridging ceramics☆
复制标题
晶桥陶瓷循环疲劳裂纹扩展的微观结构机制☆
DOI：
10.1016/s0272-8842(96)00048-x
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发表时间：
1997
影响因子：
5.2
通讯作者：
R. Ritchie
中科院分区：
文献类型：
--
作者：
C. Gilbert;R. Dauskardt;R. Ritchie
本文研究了单块热压氧化铝和氮化硅的循环疲劳裂纹扩展的微观结构基础。在这两种材料中，亚临界裂纹在循环载荷下的增长率被观察到是许多数量级的速度比相应的增长率单调加载下，在相同的应力强度水平。这种行为是由于减少裂纹尖端屏蔽循环载荷下所造成的退化的晶粒桥接区在裂纹尖端的后与摩擦磨损在晶粒/基体界面;减少屏蔽作用局部提高裂纹尖端的驱动力在循环疲劳。这个过程的微观力学模型被证明是一致的断口和原位裂纹轮廓分析。微观结构和力学变量对裂纹扩展速率的影响进行了研究，在这种机制。
The microstructural basis of cyclic fatigue-crack propagation in grain-bridging ceramics is investigated for monolithic, hot-pressed alumina and silicon nitride. In both materials, rates of subcritical crack growth under cyclic loads are observed to be many orders of magnitude faster than corresponding growth rates under monotonic loading at equivalent stress-intensity levels. This behaviour is attributed to diminished crack-tip shielding under cyclic loads caused by a degradation of the grain-bridging zone in the wake of the crack tip associated with frictional wear at the grain/matrix interface; the reduced shielding acts locally to enhance the crack-tip driving force in cyclic fatigue. Micromechanical modelling of this process is shown to be consistent with fractographic and in situ crack-profile analyses. The effect on crack-growth rates of microstructural and mechanical variables are examined in light of this mechanism.