Shear transformation (ST), as the fundamental event of plastic deformation of amorphous solids, is commonly considered as transient in time and thus assumed to be an equilibrium process without inertia. Such an approximation however poses a major challenge when the deformation becomes non-equilibrium, e.g., under the dynamic and even shock loadings. To overcome the challenge, this paper proposes a dynamic mesoscale model for amorphous solids that connects microscopically inertial STs with macroscopically elastoplastic deformation. By defining two dimensionless parameters: strain increment and intrinsic Deborah number, the model predicts a phase diagram for describing the inertia effect on deformation of amorphous solids. It is found that with increasing strain rate or decreasing ST activation time, the significant inertia effect facilitates the activation and interaction of STs, resulting in the earlier yield of plasticity and lower steady-state flow stress. We also observe that the externally-applied shock wave can directly drive the activation of STs far below the global yield and then propagation along the wave-front. These behaviors are very different from shear banding in the quasi-static treatment without considering the inertia effect of STs. The present study highlights the non-equilibrium nature of plastic events, and increases the understanding of dynamic or shock deformation of amorphous solids at mesoscale.

中文翻译：

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非晶态固体变形的惯性效应：一种动态的中尺度模型


剪切变换 （ST） 作为非晶态固体塑性变形的基本事件，通常被认为是时间上的瞬态，因此被认为是没有惯性的平衡过程。然而，当变形变得不平衡时，例如在动态甚至冲击载荷下，这种近似值会带来重大挑战。为了克服这一挑战，本文提出了一种非晶态固体的动态中尺度模型，该模型将微观惯性 ST 与宏观弹塑性变形联系起来。通过定义两个无量纲参数：应变增量和内禀 Deborah 数，该模型预测了一个相图，用于描述惯性对非晶态固体变形的影响。研究发现，随着应变率的增加或 ST 激活时间的减少，显着的惯性效应促进了 ST 的激活和相互作用，从而导致塑性的早期产生和较低的稳态流动应力。我们还观察到，外部施加的冲击波可以直接驱动 STs 的激活，远低于全局产额，然后沿波前传播。这些行为与不考虑 STs 惯性效应的准静态处理中的剪切带有很大不同。本研究强调了塑性事件的非平衡性质，并增加了对中尺度上非晶态固体动态或冲击变形的理解。