Single crystalline silicon fractures on low-energy cleavage planes such as (111) and (110). The crack propagation cannot accurately be predicted by linear elastic fracture mechanics since it does not account for small scale and inelastic phenomena such as atomic lattice trapping. Here we show that, under pure bending load, (110) cleavage in silicon single crystal rapidly accelerates to 3700 m/s without crack path deviation or crack branching, contrasting previous observations. We highlight that the crack front shape involves strong velocity dependence and presents a curvature jump during very high-speed crack growth. In addition, we observe special marks—a kind of periodic surface undulation—that exclusively arise on the rapid fracture surfaces, and we suggest that they are front wave traces resulting from an intrinsic local velocity fluctuation. This finding gives insight to the wavy nature of the crack front in the absence of material asperity.
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机译：单晶硅在低能分裂平面（例如（111）和（110））上断裂。裂纹扩展不能通过线性弹性断裂力学准确预测，因为它不能解决小规模和非弹性现象（例如原子晶格俘获）的问题。在这里，我们表明，在纯弯曲载荷下，单晶硅中的（110）裂解迅速加速至3700 m / s，而没有裂纹路径偏差或裂纹分支，这与以前的观察结果相反。我们强调指出，裂纹前部形状涉及强烈的速度依赖性，并且在非常高速的裂纹扩展过程中会出现曲率跳跃。此外，我们观察到特殊标记（一种周期性的表面起伏）仅在快速断裂表面上出现，我们建议它们是由固有的局部速度波动引起的前波迹线。该发现使洞察在没有材料粗糙的情况下裂纹前沿的波浪性质。
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