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Nanoscale void nucleation and growth and crack tip stress evolution ahead of a growing crack in a single crystal

机译：纳米级空洞形核和生长以及裂纹尖端应力在单晶裂纹扩展之前演化

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摘要

A constrained three-dimensional atomistic model of a cracked aluminum single crystal has been employed to investigate the growth behavior of a nanoscale crack in a single crystal using molecular dynamics simulations with the EAM potential. This study is focused on the stress field around the crack tip and its evolution during fast crack growth. Simulation results of the observed nanoscale fracture behavior are presented in terms of atomistic stresses. Major findings from the simulation results are the following: (a) crack growth is in the form of void nucleation, growth and coalescence ahead of the crack tip, thus resembling that of ductile fracture at the continuum scale; (b) void nucleation occurs at a certain distance ahead of the current crack tip or the forward edge of the leading void ahead of the crack tip; (c) just before void nucleation the mean atomic stress (or equivalently its ratio to the von Mises effective stress, which is called the stress constraint or triaxiality) has a high concentration at the site of void nucleation; and (d) the stress field ahead of the current crack tip or the forward edge of the leading void is more or less self-similar (so that the forward edge of the leading void can be viewed as the effective crack tip).
机译：裂纹的铝单晶的约束三维原子模型已被用来研究具有EAM势的分子动力学模拟的纳米级裂纹在单晶中的生长行为。这项研究的重点是裂纹尖端周围的应力场及其在快速裂纹扩展过程中的演变。以原子应力表示了观察到的纳米级断裂行为的模拟结果。模拟结果的主要发现如下：（a）裂纹扩展以裂纹尖端之前的空核，扩展和聚结的形式出现，因此类似于连续尺度上的韧性断裂; （b）空洞成核发生在当前裂纹尖端之前的一定距离处，或者在裂纹尖端之前的前导空洞的前边缘; （c）在空核成核之前，平均原子应力（或等效地与冯·米塞斯有效应力之比，称为应力约束或三轴性）在空核成核位置处具有很高的浓度; （d）当前裂纹尖端或前导空隙的前边缘之前的应力场或多或少是自相似的（因此前导空隙的前边缘可被视为有效裂纹尖端）。

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