论文部分内容阅读
为了估算几个物理因素对动态裂纹稳定性的影响,进行了一系列分子动力学模拟。这些因素是由各种实验潜势模拟得到的晶体结构和原子间的相互作用。对于低温下脆性裂纹的扩展,我们发现稳态裂纹的速度被限制在一个易于达到的数值区间内。当增加过载并且远远超过 K_(Ic)时,裂纹以稳态速度扩展并迅速达到终止速度,即约为0.4个瑞利波速度。终止速度的幅值可能与原子间相互作用的非线性有关。进一步增加过载并未显著地改变稳态速度,却明显地增加了来自裂纹尖端的声发射幅度。受载裂纹进而失稳,其形式可为劈裂、位错辐射或分岔。裂纹的失稳与由键裂事件产生的局部相干的声子场的建立紧密相关。失稳的形式主要取决于晶体结构和裂纹系的结晶学产状,但也可能与易于产生的位错运动有关。
In order to estimate the influence of several physical factors on the dynamic crack stability, a series of molecular dynamics simulations were carried out. These factors are crystal structures and atomic interactions simulated by various experimental potentials. For the propagation of brittle cracks at low temperature, we find that the steady-state crack velocity is limited to an easy-to-reach numerical range. When overload is added and far exceeds K_ (Ic), the crack propagates at a steady state speed and reaches the termination speed, which is about 0.4 Rayleigh wave speed. The magnitude of the termination velocity may be related to the nonlinearity of the interaction between atoms. A further increase in overload does not change the steady-state speed significantly but significantly increases the amplitude of acoustic emission from the crack tip. Loaded cracks and then instability, the form of cleavage, dislocation radiation or bifurcation. Crack instability is closely related to the establishment of locally coherent phonon fields due to the splintering event. The form of destabilization depends primarily on the crystallographic appearance of the crystal structure and the crackline but may also be related to the easy-to-produce dislocation motion.