In-situ synchrotron characterisation of fracture initiation and propagation in shales during indentation
In-situ synchrotron characterisation of fracture initiation and propagation in shales during indentation
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DOI：
10.1016/j.energy.2020.119161
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发表时间：
2020-10
期刊：
影响因子：
9
通讯作者：
Lin Ma;A. Fauchille;M. Chandler;P. Dowey;K. Taylor;J. Mecklenburgh;P. Lee
中科院分区：
文献类型：
--
作者：
Lin Ma;A. Fauchille;M. Chandler;P. Dowey;K. Taylor;J. Mecklenburgh;P. Lee
在压痕试验中，同步加速器成像技术在有效表征页岩裂缝起裂和扩展方面的可行性和优势已得到证实。这些技术包括1)裂缝起裂的快速（分钟尺度）和高分辨率（μm尺度）成像，2)裂缝发育的同步时空信息（4D）， 3)裂缝发生前页岩变形的量化和建模。对代表页岩微观结构3个关键变量的4个不同层状和成分的页岩样品进行了成像实验。随着时间的推移，裂缝的开始和扩展成功地在3D中被捕获，并使用数字体积相关（DVC）生成应变图。随后，实验后的裂缝几何形状在纳米尺度上使用互补的扫描电镜成像进行表征。表征结果强调了微观结构和各向异性变化对页岩力学性质的影响。在宏观尺度和微观尺度上，由于变形不相容，在两种不同织构的界面处，裂缝都倾向于扭结。平均成分似乎对硬度和起裂载荷起主要控制作用；而材料的织构和层理压痕的方向共同控制着断裂的扩展方向和几何形状。这种对页岩裂缝发育的更好理解在清洁能源应用中具有潜在的重要意义。
The feasibility and advantages of synchrotron imaging have been demonstrated to effectively characterise fracture initiation and propagation in shales during indentation tests. These include 1) fast (minute-scale) and high-resolution (μm-scale) imaging of fracture initiation, 2) concurrent spatial and temporal information (4D) about fracture development, 3) quantification and modelling of shale deformation prior to fracture. Imaging experiments were performed on four shale samples with different laminations and compositions in different orientations, representative of three key variables in shale microstructure. Fracture initiation and propagation were successfully captured in 3D over time, and strain maps were generated using digital volume correlation (DVC). Subsequently, post-experimental fracture geometries were characterised at nano-scale using complementary SEM imaging. Characterisation results highlight the influence of microstructural and anisotropy variations on the mechanical properties of shales. The fractures tend to kink at the interface of two different textures at both macroscale and microscale due to deformation incompatibility. The average composition appears to provide the major control on hardness and fracture initiation load; while the material texture and the orientation of the indentation to bedding combine to control the fracture propagation direction and geometry. This improved understanding of fracture development in shales is potentially significant in the clean energy applications.