We present a version of soft glassy rheology that includes thermalized strain degrees of freedom. It fully specifies systems' strain-history-dependent positions on their energy landscapes and therefore allows for quantitative analysis of their heterogeneous yielding dynamics and nonequilibrium deformation thermodynamics. As a demonstration of the method, we illustrate the very different characteristics of fully-thermal and nearly-athermal plasticity by comparing results for thermalized and nonthermalized plastic flow.
School of Physics and Astronomy, Shanghai Jiao Tong University（上海交通大学物理与天文学院）；College of Physics, Chengdu University of Technology（成都理工大学物理学院）；Med-X Research Institute and School of Biomedical Engineering, Shanghai Jiao Tong University（上海交通大学Med-X研究院与生物医学工程学院）；School of Physics, East China Normal University（华东师范大学物理系）；Jiangsu First-Imaging Medical Equipment Co., Ltd.（江苏首影医疗设备有限公司）；State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu University of Technology（成都大学地质灾害防治与地质环境国家重点实验室）
Yield stress fluids display a rich rheological phenomenology. Beyond the defining existence of a yield stress in the steady state flow curve, this includes in many materials rather flat viscoelastic spectra over many decades of frequency in small amplitude oscillatory shear; slow stress relaxation following the sudden imposition of a small shear strain; stress overshoot in shear startup; logarithmic or sublinear power law creep following the imposition of a shear stress below the yield stress; creep followed by yielding after the imposition of a shear stress above the yield stress; richly feat…
Glassy solids may undergo a fluidization (yielding) transition upon deformation whereby the material starts to flow plastically. It has been a matter of debate whether this process is controlled by a specific time scale, from among different competing relaxation/kinetic processes. Here, two constitutive models of cage relaxation are examined within the microscopic model of nonaffine elasto-plasticity. One (widely used) constitutive model implies that the overall relaxation rate is dominated by the fastest between the structural ($α$) relaxation rate and the shear-induced relaxation rate. A dif…
We study the emergence of critical dynamics in the steady shear rheology of fluidized soft glassy materials. Within a mesoscale elasto-plastic model accounting for a shear band instability, we show how an additional noise can induce a transition from phase separated to homogeneous flow, accompanied by critical-like fluctuations of the macroscopic shear rate. Both macroscopic quantities and fluctuations exhibit power law behaviors in the vicinity of this transition, consistent with previous experimental findings on vibrated granular media. Altogether, our results suggest a generic scenario for …
Rheological properties of soft-glassy flows from hydro-kinetic simulations
基于软玻璃材料的晶格动力学模型的数值模拟，我们描述了一个致密的乳液状系统的全局流变学，在三个代表性的负载条件下：Couette流，时间振荡应变和Kolmogorov流。结果发现，在所有情况下的流变学描述的赫歇尔-Bulkley（HB）的关系，$σ= σ_{Y} + A S^β$，与屈服应力$σ_{Y}$在很大程度上独立的加载方案。一个适当的重新缩放的HB参数允许描述与空间相关的应力的非均质流，基于协同性的概念，最近提出的软玻璃材料的应力松弛现象的非局部性的程度的特征。
We present an integrated experimental and quantitative theoretical study of the mechanics of self-crosslinked, neutral, repulsive pNIPAM microgel suspensions over concentration (c) range spanning the fluid, glassy and putative "soft jammed" regimes. In the glassy regime we measure a linear elastic dynamic shear modulus over 3 decades which follows an apparent power law concentration dependence G'~$c^{5.64}$, followed by a sharp crossover to a nearly linear growth at high concentrations. We formulate a theoretical approach to address all three regimes within a single conceptual Brownian dynamic…
Emergent odd viscoelasticity in chiral soft glassy materials
University of Göttingen（哥廷根大学）；Ecole Polytechnique de l’Université de Nantes, LTeN, U6607, Nantes Université（南特大学理工学院，LTeN，U6607）；King’s College London（伦敦国王学院）
We study theoretically the dynamics of soft glassy materials during the process of stress relaxation following the rapid imposition of a shear strain. By detailed numerical simulations of a mesoscopic soft glassy rheology model and three different simplified continuum fluidity models, we show that a dramatic shear localisation instability arises, in which the strain field suddenly becomes heterogeneous within the sample, accompanied by a precipitous drop in the stress. Remarkably, this instability can arise at extremely long delay times after the strain was applied, due to the long-term memory…
Rheological constitutive equation for model of soft glassy materials
我们精确地求解并详细地描述了泡沫、乳状液、泥浆等的低频剪切流变学的简化标量模型。Lequeux，P. Hebraud，M. E. Cates，Phys. Rev. Lett. 78，2020（1997）]。该模型将这种“软玻璃质材料”流变学的相似性归因于结构无序和亚稳性的共同特征。通过关注介观元素的动力学，它保留了一个通用的字符。相互作用由平均场噪声温度x表示，玻璃化转变发生在x=1（以适当的单位表示）。该模型的精确解采用将应力与应变历史相关联的本构方程的形式，从该本构方程可以导出所有流变性质。对于线性响应，我们发现储能模量G'和损耗模量G“都随频率ω^{x-1}（1<x<2）变化，在玻璃化转变附近变得平坦。在玻璃相，老化的模量预测。稳态剪切流动曲线显示x<2的幂律流体行为，玻璃相中具有非零屈服应力; Cox-Merz规则在该非牛顿状态下不成立。单阶和双阶应变进一步探讨了模型的非线性行为，这是不能很好地表示的BKZ关系。最后，我们考虑在有限应变幅γ下G'和G“的测量。在玻璃化转变附近，随着应变扫描中γ的增加，G“呈现最大值。由于非线性效应，它的值可能会被严重高估，即使当应力响应非常接近谐波时也会出现这种效应。在最大应变γ_c处，测量仍能探测到线性响应，这一点与频率无关。
Synthetic hectorite clay Laponite RD/XLG is composed of disk-shaped nanoparticles that acquire dissimilar charges when suspended in an aqueous media. Owing to their property to spontaneously self-assemble, Laponite is used as a rheology modifier in a variety of commercial water-based products. Particularly, aqueous dispersion of Laponite undergoes liquid - to - solid transition at about 1 volume % concentration. The evolution of the physical properties as dispersion transforms to solid state is reminiscent of physical aging in molecular as well as colloidal glasses. The corresponding soft glas…
We study theoretically shear banding in soft glassy materials subject to large amplitude time-periodic shear flows, considering separately the protocols of large amplitude oscillatory shear strain, large amplitude square or triangular or sawtooth strain rate, and large amplitude oscillatory shear stress. In each case, we find shear banding to be an important part of the material's flow response for a broad range of values of the frequency $ω$ and amplitude of the imposed oscillation. Crucially, and highly counterintuitively, in the glass phase this persists even to the lowest frequencies acces…
Soft glassy materials such as mayonnaise, wet clays, or dense microgels display under external shear a solid-to-liquid transition. Such a shear-induced transition is often associated with a non-monotonic stress response, in the form of a stress maximum referred to as "stress overshoot". This ubiquitous phenomenon is characterized by the coordinates of the maximum in terms of stress $σ_\text{M}$ and strain $γ_\text{M}$ that both increase as weak power laws of the applied shear rate. Here we rationalize such power-law scalings using a continuum model that predicts two different regimes in the li…
Confined glasses and their anomalous interfacial rheology raise important questions in fundamental research and numerous practical applications. In this Letter, we study the influence of interfacial air nanobubbles on the free surface of ultrathin high-molecular-weight glassy polystyrene films immersed in water, in ambient conditions. In particular, we reveal the counterintuitive fact that a soft nanobubble is able to deform the surface of a rigid glass, forming a nanocrater with a depth that increases with time. By combining in-situ atomic-force-microscopy measurements and a modified lubricat…
