While we fundamentally understand the dynamics of simple cracks propagating in brittle solids within perfect (homogeneous) materials, we do not understand how paths of moving cracks are determined. We experimentally study strongly perturbed cracks that propagate between 10% and 95% of their limiting velocity within a brittle material. These cracks are deflected by either interaction with sparsely implanted defects or via an intrinsic oscillatory instability in defect-free media. Dense high-speed measurements of the strain fields surrounding the crack tips reveal that crack paths are governed by the direction of maximal strain energy density, even when the near-tip singular fields are highly disrupted. This fundamentally important result may be utilized to either direct or guide running cracks.

中文翻译：

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脆性固体中的快速裂纹如何选择其路径

尽管我们从根本上理解了在完美（均质）材料中脆性固体中传播的简单裂纹的动力学特性，但我们不了解如何确定运动裂纹的路径。我们通过实验研究了在脆性材料中扩展速度在极限速度的10％到95％之间的强烈扰动的裂纹。这些裂纹通过与稀疏植入的缺陷相互作用或在无缺陷介质中固有的振荡不稳定性而发生偏转。对裂纹尖端周围应变场的密集高速测量表明，即使近尖端奇异场受到极大破坏，裂纹路径也受最大应变能密度方向的控制。根本上重要的结果可用于引导或引导运行裂纹。