Understanding the dynamics of shear band propagation in metallic glasses remains elusive due to the limited temporal and spatial scales accessible in experiments. In micron-scale molecular dynamics simulations on two model metallic glasses, we studied the propagation of a dominant shear band under uniaxial tension with a macroscopic strain of 3-5%. For both materials, the shear band can be intersonic with a propagation speed exceeding their respective shear wave speeds. The propagation exhibits intrinsic instability that manifests itself as microbranching and considerable fluctuations in velocity. The shear strain singularity ahead of propagating shear band tip scales as 1/r (r is the distance away from the tip), independent of the macroscopic tensile strain. In addition, we studied the intersection of two shear bands under uniaxial tension, during which path deflection, speed slowing-down, and temperature rise at the junction region were observed. The dynamics of propagating shear band shown here indicate that shear band in metallic glasses can be viewed as shear crack under the framework of weakly nonlinear fracture mechanics theory.

由于实验中可用的时间和空间尺度有限，了解金属玻璃中剪切带传播的动力学仍然难以捉摸。在两种模型金属玻璃的微米级分子动力学模拟中，我们研究了在宏观应变为 3-5% 的单轴拉伸下主剪切带的传播。对于这两种材料，剪切带可以是音速间的，传播速度超过它们各自的剪切波速度。传播表现出内在的不稳定性，表现为微分支和相当大的速度波动。传播剪切带尖端之前的剪切应变奇异性比例为 1 / r ( r是距尖端的距离），与宏观拉伸应变无关。此外，我们研究了单轴拉伸下两个剪切带的交点，在此过程中观察到交界处的路径偏转、速度减慢和温度升高。这里显示的传播剪切带的动力学表明，在弱非线性断裂力学理论的框架下，金属玻璃中的剪切带可以被视为剪切裂纹。