Poincloux Samuel, Takeuchi Kazumasa A
Department of Physics, The University of Tokyo, Bunkyo-ku 113-0033, Tokyo, Japan.
Institute for Physics of Intelligence, The University of Tokyo, Bunkyo-ku 113-0033, Tokyo, Japan.
Proc Natl Acad Sci U S A. 2024 Dec 3;121(49):e2408706121. doi: 10.1073/pnas.2408706121. Epub 2024 Nov 27.
A wide range of disordered materials, from biological to geological assemblies, feature discrete elements undergoing large shape changes. How significant geometrical variations at the microscopic scale affect the response of the assembly, in particular rigidity transitions, is an ongoing challenge in soft matter physics. However, the lack of a model granular-like experimental system featuring large and versatile particle deformability impedes advances. Here, we explore the oscillatory shear response of a sponge-like granular assembly composed of highly compressible elastic rings. We highlight a progressive rigidity transition, switching from a yielded phase to a solid one by increasing density or decreasing shear amplitude. The rearranging yielded state consists of crystal clusters separated by melted regions; in contrast, the solid state remains amorphous and absorbs all imposed shear elastically. We rationalize this transition by uncovering an effective, attractive shear force between rings that emerges from a friction-geometry interplay. If friction is sufficiently high, the extent of the contacts between rings, captured analytically by elementary geometry, controls the rigidity transition.
从生物聚集体到地质聚集体，各种各样的无序材料都具有经历大幅形状变化的离散元素。微观尺度上显著的几何变化如何影响聚集体的响应，尤其是刚度转变，是软物质物理学中一个持续存在的挑战。然而，缺乏一个具有大的且通用的颗粒可变形性的类颗粒实验系统阻碍了进展。在此，我们探究了由高度可压缩弹性环组成的海绵状颗粒聚集体的振荡剪切响应。我们突出了一种渐进的刚度转变，通过增加密度或减小剪切幅度，从屈服相转变为固相。重排的屈服态由被熔化区域分隔的晶体簇组成；相比之下，固态保持无定形并弹性吸收所有施加的剪切力。我们通过揭示由摩擦 - 几何相互作用产生的环之间有效的吸引剪切力来解释这种转变。如果摩擦力足够高，通过基本几何分析得出的环之间接触的程度控制着刚度转变。
