Farain Kasra, Bonn Daniel
Van der Waals-Zeeman Institute, Institute of Physics, <a href="https://ror.org/04dkp9463">University of Amsterdam</a>, Science Park 904, 1098XH Amsterdam, The Netherlands.
Phys Rev Lett. 2024 Jul 12;133(2):028203. doi: 10.1103/PhysRevLett.133.028203.
Dry granular materials consist of a vast ensemble of discrete solid particles interacting through complex frictional forces at the contact points. The particles are so large that these systems are believed to be completely athermal. Here, we arrest the dynamics of a flowing granular material in a steady-state-flow configuration, enabling an isolated examination of aging at the particle contacts without granular rearrangements. Our findings reveal that the evolution of interparticle forces within the arrested athermal granular network results in the spontaneous increase of the system's yield stress. This strengthening process is logarithmic in time with a rate that depends on the temperature. We demonstrate that the material's stress relaxation exhibits similar time- and temperature-dependent behavior, suggesting a shared origin for aging and stress relaxation in these systems governed by thermal molecular processes at the scale of the grain contacts.
干燥颗粒材料由大量离散的固体颗粒组成，这些颗粒通过接触点处复杂的摩擦力相互作用。颗粒很大，以至于这些系统被认为是完全无热的。在这里，我们将流动的颗粒材料的动力学状态稳定在稳态流动配置中，从而能够在不发生颗粒重排的情况下，对颗粒接触处的老化进行单独研究。我们的研究结果表明，在静止的无热颗粒网络中，颗粒间力的演变会导致系统屈服应力的自发增加。这个强化过程在时间上是对数关系，其速率取决于温度。我们证明，材料的应力松弛表现出类似的时间和温度依赖性行为，这表明在这些由颗粒接触尺度上的热分子过程控制的系统中，老化和应力松弛有共同的起源。
