Scaling of relaxation and excess entropy in plastically deformed amorphous solids
Scaling of relaxation and excess entropy in plastically deformed amorphous solids
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DOI：
10.1073/pnas.2000698117
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发表时间：
2020-06-02
影响因子：
11.1
通讯作者：
Arratia, Paulo E.
中科院分区：
文献类型：
--
作者：
Galloway, K. Lawrence;Ma, Xiaoguang;Arratia, Paulo E.
当受到足够的应力时，固体材料通过微观成分的重组而产生塑性变形。实际上，通过合理地施加应力来改变材料的微观结构是可能的，这是一种在实践中用于提高金属机械性能的经验过程。然而，理解这些非平衡状态下塑性流动和微观结构的相互依赖性仍然是一个重大挑战。在这里，我们实验研究这种关系，在塑性变形过程中的松弛动力学和无序胶体固体的微观结构之间。我们施加振荡剪切固体胶体单分子层和研究其颗粒的轨迹作为剪切速率的函数在塑性区。在这些情况下，应变速率、与塑性流动相关的松弛速率以及样品微观结构一起振荡，但具有不同的相位。有趣的是，实验表明，在时间t与塑性流动相关的弛豫速率与应变速率和样品的微观结构，分别在较早和较晚的时间测量。在这种非平稳条件下，弛豫率表现出幂律、剪切稀化行为，并与样本过剩熵呈指数级关系。因此，样品静态结构（过剩熵）的测量提供了有关应变速率和组分重排动力学在样品中在较早的时间洞察。
When stressed sufficiently, solid materials yield and deform plastically via reorganization of microscopic constituents. Indeed, it is possible to alter the microstructure of materials by judicious application of stress, an empirical process utilized in practice to enhance the mechanical properties of metals. Understanding the interdependence of plastic flow and microscopic structure in these nonequilibrium states, however, remains a major challenge. Here, we experimentally investigate this relationship, between the relaxation dynamics and microscopic structure of disordered colloidal solids during plastic deformation. We apply oscillatory shear to solid colloidal monolayers and study their particle trajectories as a function of shear rate in the plastic regime. Under these circumstances, the strain rate, the relaxation rate associated with plastic flow, and the sample microscopic structure oscillate together, but with different phases. Interestingly, the experiments reveal that the relaxation rate associated with plastic flow at time t is correlated with the strain rate and sample microscopic structure measured at earlier and later times, respectively. The relaxation rate, in this nonstationary condition, exhibits power-law, shear-thinning behavior and scales exponentially with sample excess entropy. Thus, measurement of sample static structure (excess entropy) provides insight about both strain rate and constituent rearrangement dynamics in the sample at earlier times.