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arXiv 1605.09447cond-mat.soft
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软固体中弹性驱动的间歇微观动力学

Elastically driven, intermittent microscopic dynamics in soft solids

Mehdi Bouzid, Jader Colombo, Lucas Vieira Barbosa, Emanuela Del Gado

摘要:

具有可调机械响应的软固体是新材料技术的核心,但应用的一个关键限制是它们随着时间的推移而逐渐老化,这极大地影响了它们的功能。普遍接受的范例是,这种老化是渐进的,并且其起源是慢于指数的微观动力学,类似于过冷液体或玻璃中的那些。尽管如此,时间和空间分辨的测量提供了对比的证据:动态比指数快,不稳定性和突然的结构变化。在这里,我们使用微观模型的3D计算机模拟来揭示分别通过热波动和弹性恢复来控制应力松弛的时间尺度是老化动力学的关键。当热波动太弱时,凝固时冻结的应力不均匀性仍然可以通过弹性驱动的波动部分地松弛。这种波动是间歇性的,因为强相关性在实验或模拟的时间尺度上持续存在,导致比指数动态更快。

英文摘要:

Soft solids with tunable mechanical response are at the core of new material technologies, but a crucial limit for applications is their progressive aging over time, which dramatically affects their functionalities. The generally accepted paradigm is that such aging is gradual and its origin is in slower than exponential microscopic dynamics, akin to the ones in supercooled liquids or glasses. Nevertheless, time- and space-resolved measurements have provided contrasting evidence: dynamics faster than exponential, intermittency, and abrupt structural changes. Here we use 3D computer simulations of a microscopic model to reveal that the timescales governing stress relaxation respectively through thermal fluctuations and elastic recovery are key for the aging dynamics. When thermal fluctuations are too weak, stress heterogeneities frozen-in upon solidification can still partially relax through elastically driven fluctuations. Such fluctuations are intermittent, because of strong correlations that persist over the timescale of experiments or simulations, leading to faster than exponential dynamics.

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