The role of surface forces in environment-enhanced cracking of brittle solids
The role of surface forces in environment-enhanced cracking of brittle solids
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DOI：
10.1016/j.jmps.2022.105162
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发表时间：
2022-12
影响因子：
5.3
通讯作者：
Mehdi Eskandari-Ghadi;S. Nakagawa;Hang Deng;S. Pride;Benjamin Gilbert;Yida Zhang
中科院分区：
文献类型：
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作者：
Mehdi Eskandari-Ghadi;S. Nakagawa;Hang Deng;S. Pride;Benjamin Gilbert;Yida Zhang
脆性材料中的断裂起始和扩展在表面反应（吸附）环境中得到促进，这一现象被称为亚临界裂纹扩展（SCG）。实验室测量的裂纹扩展速度与应力强度因子的关系通常表现出高度非线性，多阶段的特性，是敏感的环境因素，如吸附浓度和温度。出于实际目的，经验关系（例如，幂律）被用来描述这种复杂的现象。然而，如何出现的整体SCG行为的基本过程附近的裂纹尖端，如相互作用的裂纹表面分离只有几个纳米和质量传输内的纳米有限的空间，仍然没有很好地理解。本文发展了一种基于表面力的断裂理论，它将表面力模型、流体输运模型和线弹性断裂力学相结合，定量地解释了脆性固体中SCG的多阶段特性。数值模型的基础上SFFT和解决通过隐式分区计划的效率和模块化。Wiederhorn的数据在钠钙玻璃在较宽的相对湿度水平范围内的裂纹扩展的结果进行了验证。我们表明，第一次，整个范围的SCG曲线可以捕获一个单一的物理为基础的模型。预测的SCG曲线表明，发展的排斥分离压力后，裂纹尖端可以负责在吸附环境中的表观断裂韧性降低。SCG曲线的形状及其相对于环境的变化严重依赖于假设的传输模型。
Fracture initiation and propagation in brittle materials is promoted in surface-reactive (sorptive) environments, a phenomenon known as subcritical crack growth (SCG). Laboratory measured crack-propagation velocity vs. stress intensity factor relationships typically exhibit highly nonlinear, multi-stage characteristics that are sensitive to environmental factors such as adsorbate concentration and temperature. For practical purposes, empirical relationships (e.g., a power law) have been used to describe this complex phenomenon. However, how the overall SCG behavior emerges from the underlying fundamental processes near the crack tip, such as the interaction of the crack surfaces separated by only a few nanometers and mass transport within the nano-confined space, is still not well understood. This paper develops a mechanistic, surface-force-based fracture theory (SFFT) which integrates surface force models, fluid transport models, and linear elastic fracture mechanics to quantitatively explain the multi-stage characteristics of SCG in brittle solids. A numerical model is developed based on SFFT and solved through an implicit partitioned scheme for efficiency and modularity. The results are validated by Wiederhorn's data on crack propagation in soda-lime glasses at a wide range of relative humidity levels. We show that, for the first time, the entire range of an SCG curve can be captured by a single physics-based model. The predicted SCG curves reveal that the development of repulsive disjoining pressure behind the crack tip can be responsible for the reduced apparent fracture toughness in a sorptive environment. The shape of the SCG curve, and its changes with respect to the environment, is found to critically depend on the assumed transport models.