Modeling Slow Crack Growth Behavior of Glass Strengthened by a Subcritical Tensile Stress Using Surface Stress Relaxation
Modeling Slow Crack Growth Behavior of Glass Strengthened by a Subcritical Tensile Stress Using Surface Stress Relaxation
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使用表面应力松弛模拟亚临界拉伸应力强化玻璃的缓慢裂纹扩展行为
DOI：
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
M. Tomozawa
中科院分区：
文献类型：
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作者：
Jared H. Seaman;P. J. Lezzi;T. Blanchet;M. Tomozawa
在水蒸气或液态水存在下，玻璃在低于断裂韧性的应力强度下表现出缓慢的裂纹生长。几位作者已经观察到，当具有大裂纹的氧化物玻璃在室温水蒸气或液态水中保持在亚临界应力强度（其中不发生缓慢的裂纹生长）下时，在重新加载到更高的应力强度时，在可测量的裂纹延伸之前观察到有限的重新启动时间。这种明显的强化现象或裂纹止裂现象被归因于裂纹尖端的腐蚀溶解、裂纹尖端钝化或水扩散以及随后裂纹尖端周围材料的膨胀等概念。最近，一个新观察到的表面应力松弛过程，是由分子水扩散的帮助下，被用来提高玻璃纤维的机械强度，并解释在离子交换强化玻璃中观察到的亚表面压缩应力峰。这里采用相同的过程来解释这些延迟的缓慢裂纹扩展数据。一个简单的数学模型已经开发利用水辅助表面应力松弛和断裂力学。使用该模型预测的重新启动时间与发表的实验数据一致，表明表面应力松弛是负责异常延迟缓慢裂纹扩展行为。
Glasses exhibit slow crack growth under stress intensities below the fracture toughness in the presence of water vapor or liquid water. It has been observed by several authors that when an oxide glass with a large crack is held under a subcritical stress intensity (where no slow crack growth occurs) in room-temperature water vapor or liquid water, upon reloading to a higher stress intensity, a finite restart time is observed prior to measurable crack extension. This phenomenon of apparent strengthening, or crack arrest, has been attributed to concepts such as corrosive dissolution of the crack tip, crack tip blunting, or water diffusion, and subsequent swelling of the material around the crack tip. Recently, a newly observed surface stress relaxation process that is aided by molecular water diffusion was used to improve the mechanical strength of glass fibers and to explain the subsurface compressive stress peak observed in ion-exchange strengthened glasses. The same process is employed here to explain these delayed slow crack growth data. A simple mathematical model has been developed utilizing water-assisted surface stress relaxation and fracture mechanics. Predictions of restart times using the model agreed well with published experimental data, indicating that surface stress relaxation is responsible for the anomalous delayed slow crack growth behavior.