CRACK-PROPAGATION IN CERAMICS UNDER CYCLIC LOADS
CRACK-PROPAGATION IN CERAMICS UNDER CYCLIC LOADS
复制标题
DOI：
10.1007/bf01233107
复制
发表时间：
1987-04-01
影响因子：
4.5
通讯作者：
SURESH, S
中科院分区：
文献类型：
--
作者：
EWART, L;SURESH, S
在室温、湿空气环境和真空条件下，观察到多晶氧化铝缺口板在完全压缩远场循环载荷作用下的稳定裂纹扩展。疲劳裂纹沿缺口平面沿宏观上与压缩轴垂直的方向以逐渐减小的速度扩展。从远场压应力作用下的缺口端损伤、微裂纹、微裂纹的摩擦滑动和张开以及裂纹闭合等方面分析了导致这种效应的主要破坏事件。这种I型裂纹扩展的一个重要贡献来自缺口尖端局部产生的残余拉伸应力，当从最大名义压应力卸载时，缺口尖端过程区域内的变形留下永久应变。结果表明，在循环压缩应力作用下，裂纹扩展现象在宏观上表现出相似的行为，在很大范围内的材料中，从延展性很强的金属到极脆的固体，尽管这种效应的微观力学在不同类别的材料之间非常不同。将陶瓷的疲劳机制与金属系统中更常见的远场循环压缩下裂纹扩展的例子进行了比较和对比，并强调了陶瓷-金属复合材料和相变增韧陶瓷复合材料断裂的意义。对这一现象的一些重要应用提出了建议，用于研究断裂机制和测量脆性固体的断裂韧性。
Stable crack growth is observed in notched plates of polycrystalline alumina subject to fully compressive far-field cyclic loads at room temperature in a moist air environment andin vacuo. The fatigue cracks propagate at a progressively decreasing velocity along the plane of the notch and in a direction macroscopically normal to the compression axis. The principal failure events leading to this effect are analysed in terms of notch-tip damage under the far-field compressive stress, microcracking, frictional sliding and opening of microcracks, and crack closure. An important contribution to such Mode I crack growth arises from the residualtensilestresses induced locally at the notch-tip when the deformation within the notch-tip process zone leaves permanent strains upon unloading from the maximum nominal compressive stress. It is shown that the phenomenon of crack growth under cyclic compressive stresses exhibits a macroscopically similar behaviour in a wide range of materials spanning the very ductile metals to extremely brittle solids, although the micromechanics of this effect are very different among the various classes of materials. The mechanisms of fatigue in ceramics are compared and contrasted with the more familiar examples of crack propagation under far-field cyclic compression in metallic systems and the implications for fracture in ceramic-metal composites and transformation toughened ceramic composites are highlighted. Strategies for some important applications of this phenomenon are recommended for the study of fracture mechanisms and for the measurement of fracture toughness in brittle solids.