Necking and failure of a particulate gel strand: signatures of yielding on different length scales.
Necking and failure of a particulate gel strand: signatures of yielding on different length scales.
复制标题
颗粒凝胶链的颈缩和失效：不同长度尺度上的屈服特征。
DOI：
10.1039/d3sm00681f
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发表时间：
2023
期刊：
影响因子：
3.4
通讯作者：
Thijssen K
中科院分区：
文献类型：
--
作者：
Thijssen K
具有短程吸引力的“粘性”球体是从原子尺度到颗粒尺度的各种材料的基本模型。粘球所表现出的复杂现象之一是形成远非平衡的动态捕获网络，该网络由密集排列的粒子“股”组成。考虑到模型的简单性，这种凝胶在载荷下的老化和失效是一个非常具有挑战性的问题，因为它涉及多个长度和时间尺度，使得单一方法无效。在这里，我们通过结合多种方法解决单链的失败来解决这一挑战。我们用数值和解析两种方法研究了模型成胶机单链对变形的力学响应。在伸长的情况下，钢绞线因颈部不稳定而断裂。我们在三个不同的长度尺度上分析这种行为：整个链的流变连续体模型；颗粒结构和动力学的微观分析；和局部应力张量。将这些不同的方法结合在一起，就形成了一幅颈缩和失败的连贯画面。链具有无定形的局部结构，从初始化开始就具有较大的残余应力。我们发现颈部的形成与塑性流动的增加、局部结构稳定性的降低和残余应力的降低有关；这表明系统失去了固体特性，开始表现得更像粘性流体。这些结果将为更详细的模型的发展提供信息，这些模型包括颗粒凝胶的异质网络结构。
“Sticky” spheres with a short-ranged attraction are a basic model of a wide range of materials from the atomic to the granular length scale. Among the complex phenomena exhibited by sticky spheres is the formation of far-from-equilibrium dynamically arrested networks which comprise “strands” of densely packed particles. The aging and failure of such gels under load is a remarkably challenging problem, given the simplicity of the model, as it involves multiple length- and time-scales, making a single approach ineffective. Here we tackle this challenge by addressing the failure of a single strand with a combination of methods. We study the mechanical response of a single strand of a model gel-former to deformation, both numerically and analytically. Under elongation, the strand breaks by a necking instability. We analyse this behaviour at three different length scales: a rheological continuum model of the whole strand; a microscopic analysis of the particle structure and dynamics; and the local stress tensor. Combining these different approaches gives a coherent picture of the necking and failure. The strand has an amorphous local structure and has large residual stresses from its initialisation. We find that neck formation is associated with increased plastic flow, a reduction in the stability of the local structure, and a reduction in the residual stresses; this indicates that the system loses its solid character and starts to behave more like a viscous fluid. These results will inform the development of more detailed models that incorporate the heterogeneous network structure of particulate gels.