Laboratoire de Physique Statistique, Ecole Normale Supérieure, PSL Research University, Sorbonne University, CNRS, F-75231 Paris, France.
Université de Lyon, Ecole Normale Supérieure de Lyon, Université Claude Bernard, CNRS, Laboratoire de Physique, F-69342 Lyon, France.
Phys Rev Lett. 2018 Aug 3;121(5):058002. doi: 10.1103/PhysRevLett.121.058002.
Crackling noise, which occurs in a wide range of situations, is characterized by discrete events of various sizes, often correlated in the form of avalanches. We report experimental evidence that the mechanical response of a knitted fabric displays such broadly distributed events both in the force signal and in the deformation field, with statistics analogous to that of earthquakes or soft amorphous materials. A knit consists of a regular network of frictional contacts, linked by the elasticity of the yarn. When deformed, the fabric displays spatially extended avalanchelike yielding events resulting from collective interyarn contact slips. We measure the size distribution of these avalanches, at the stitch level from the analysis of nonelastic displacement fields and externally from force fluctuations. The two measurements yield consistent power law distributions reminiscent of those found in other avalanching systems. Our study shows that a knitted fabric is not only a thread-based metamaterial with highly sought after mechanical properties, but also an original, model system, with topologically protected structural order, where an intermittent, scale-invariant response emerges from minimal ingredients, and thus a significant landmark in the study of out-of-equilibrium universality.
噼啪声发生在广泛的情况下，其特征是具有各种大小的离散事件，这些事件通常以雪崩的形式相关联。我们报告了实验证据，表明针织织物的机械响应在力信号和变形场中都显示出这种广泛分布的事件，其统计特性类似于地震或软非晶材料。针织品由具有摩擦接触的规则网络组成，通过纱线的弹性连接在一起。当织物变形时，由于纱线之间的集体接触滑动，会出现空间扩展的类雪崩屈服事件。我们从非弹性位移场的分析和外部力波动测量这些雪崩的大小分布。这两种测量方法得到的幂律分布一致，使人联想到在其他雪崩系统中发现的分布。我们的研究表明，针织品不仅是一种具有高度理想机械性能的基于线的超材料，而且还是一种具有拓扑保护结构有序的原始模型系统，其中从最小的成分中出现间歇性、标度不变的响应，因此是研究非平衡普遍性的一个重要里程碑。
