Department of Civil Engineering, The University of Tokyo, Tokyo 113-8656, Japan.
Department of Geological Engineering, Nanjing Tech University, Nanjing 211800, China.
Ultrasonics. 2019 Nov;99:105962. doi: 10.1016/j.ultras.2019.105962. Epub 2019 Jul 13.
Particle breakage has been recognized as a crucial factor affecting the mechanical behavior of stressed granular assemblages. To understand such underlying micro-mechanical behavior, Acoustic Emission (AE) technique that is capable of continuously diagnosing the deterioration and failure process of stressed materials was employed into single particle compression tests on silica sands. Regardless of different particle sizes, the fracturing process could be highly featured by AE characteristics, in which AE hit rate and peak frequency characteristics were analyzed to evaluate the intensity and mode of micro-mechanical behaviors, respectively. "Early warning omens" regarding the impending failure of the stressed particle is revealed in terms of the initiation and rapid increase of high-frequency AE components, as well as the rapid increase of AE hit rate. The effect of "prehistory of failure" on the stressed particle is sensitively featured by the highly emitted AE events after the catastrophic failure. Furthermore, a frequency-based method is suggested to distinguish different modes of micro-mechanical behaviors associated with particle readjustment, asperity abrasion, and microcracking. Further employment of the present result is expected to continuously evaluate the intensity and mode of particle interactions in stressed granular assemblages.
颗粒破碎已被认为是影响受应力颗粒集合体力学行为的关键因素。为了理解这种潜在的微观力学行为，采用能够连续诊断受应力材料劣化和破坏过程的声发射 (AE) 技术，对硅砂进行了单颗粒压缩试验。无论颗粒尺寸如何，破碎过程都可以通过 AE 特征高度来描述，分别分析 AE 撞击率和峰值频率特征，以评估微力学行为的强度和模式。通过高频 AE 分量的起始和快速增加以及 AE 撞击率的快速增加，揭示了受应力颗粒即将失效的“预警迹象”。此外，通过灾难性失效后高度发射的 AE 事件，敏感地描述了“失效前史”对受应力颗粒的影响。此外，建议采用基于频率的方法来区分与颗粒调整、粗糙度磨损和微裂纹相关的不同微力学行为模式。进一步应用本研究结果有望持续评估受应力颗粒集合体中颗粒相互作用的强度和模式。
