Ripp Monica M, Démery Vincent, Zhang Teng, Paulsen Joseph D
Department of Physics, Syracuse University, Syracuse, NY 13244, USA.
Gulliver, CNRS, ESPCI Paris, PSL Research University, 10 rue Vauquelin, 75005 Paris, France.
Soft Matter. 2020 May 6;16(17):4121-4130. doi: 10.1039/d0sm00250j.
A basic paradigm underlying the Hookean mechanics of amorphous, isotropic solids is that small deformations are proportional to the magnitude of external forces. However, slender bodies may undergo large deformations even under minute forces, leading to nonlinear responses rooted in purely geometric effects. Here we study the indentation of a polymer film on a liquid bath. Our experiments and simulations support a recently-predicted stiffening response [D. Vella and B. Davidovitch, Phys. Rev. E, 2018, 98, 013003], and we show that the system softens at large slopes, in agreement with our theory that addresses small and large deflections. We show how stiffening and softening emanate from nontrivial yet generic features of the stress and displacement fields.
非晶态各向同性固体胡克力学的一个基本范式是，小变形与外力大小成正比。然而，细长物体即使在微小力作用下也可能发生大变形，从而导致源于纯几何效应的非线性响应。在此，我们研究聚合物薄膜在液池上的压痕。我们的实验和模拟支持了最近预测的硬化响应[D. 韦拉和B. 达维多维奇，《物理评论E》，2018年，98卷，013003]，并且我们表明，在大斜率下系统会软化，这与我们处理小挠度和大挠度的理论一致。我们展示了硬化和软化如何源于应力和位移场的非平凡但普遍的特征。
