脆性薄板中裂纹的形核
Nucleation of cracks in a brittle sheet
摘要：
本文用分子动力学研究了无裂纹二维材料中裂纹的成核过程。我们研究了剪切模量为零和非零的模型。在这两种情况下，裂纹形成所需的时间服从阿耳忒弥斯定律，从中提取的能量障碍和前置因子为不同的系统尺寸。对于大系统，特征时间的破裂被发现减少系统的大小，与经典的威布尔理论。在剪切模量为零的情况下，抵抗破裂的能量被确定为单个原子层的破裂。在非零剪切模量的情况下，热激活断裂只能在非常高的应变下在合理的时间内进行研究。在这种情况下，能量势垒涉及几个层内的键的拉伸，与零剪切模量的情况相比，导致高得多的势垒。在绝热模拟中可以理解这种势垒。
英文摘要：
We use molecular dynamics to study the nucleation of cracks in a two dimensional material without pre-existing cracks. We study models with zero and non-zero shear modulus. In both situations the time required for crack formation obeys an Arrhenius law, from which the energy barrier and pre-factor are extracted for different system sizes. For large systems, the characteristic time of rupture is found to decrease with system size, in agreement with classical Weibull theory. In the case of zero shear modulus, the energy opposing rupture is identified with the breakage of a single atomic layer. In the case of non-zero shear modulus, thermally activated fracture can only be studied within a reasonable time at very high strains. In this case the energy barrier involves the stretching of bonds within several layers, accounting for a much higher barrier compared to the zero shear modulus case. This barrier is understood within adiabatic simulations.
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