The transition from subsonic to supersonic cracks
The transition from subsonic to supersonic cracks
复制标题
从亚音速裂纹到超音速裂纹的转变
DOI：
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
M. Marder
中科院分区：
文献类型：
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作者：
C. Behn;M. Marder
本文给出了脆性三角形晶格中平面内裂纹稳态运动的完整解析解。这允许对非常大的系统进行快速数值评估，便于与连续介质断裂理论进行比较。在连续介质理论中，传播速度超过瑞利波速度的裂纹被认为是不允许的，但在晶格系统中却明显存在。利用我们的分析方法，我们详细研究了裂纹尖端周围原子的运动，裂纹速度从亚音速到超音速的变化。亚音速裂纹的位移场特征与应力强度因子一致。对于超音速裂纹，应力强度因子消失。亚音速裂纹的特征是原子沿裂纹线垂直位移的小振幅高频振荡，而超音速裂纹的特征是原子沿裂纹线垂直位移的大振幅低频振荡。因此，虽然超音速裂纹的物理性质并不亚于亚音速裂纹，但微观和宏观行为之间的联系必须以不同的方式进行。这就是过去认为不存在超声速张力裂纹的原因之一。
We present the full analytical solution for steady-state in-plane crack motion in a brittle triangular lattice. This allows quick numerical evaluation of solutions for very large systems, facilitating comparisons with continuum fracture theory. Cracks that propagate faster than the Rayleigh wave speed have been thought to be forbidden in the continuum theory, but clearly exist in lattice systems. Using our analytical methods, we examine in detail the motion of atoms around a crack tip as crack speed changes from subsonic to supersonic. Subsonic cracks feature displacement fields consistent with a stress intensity factor. For supersonic cracks, the stress intensity factor disappears. Subsonic cracks are characterized by small-amplitude, high-frequency oscillations in the vertical displacement of an atom along the crack line, while supersonic cracks have large-amplitude, low-frequency oscillations. Thus, while supersonic cracks are no less physical than subsonic cracks, the connection between microscopic and macroscopic behaviour must be made in a different way. This is one reason supersonic cracks in tension had been thought not to exist.