Figure 5.

Analysis of two simple toy models reveals the origins of linear and nonlinear creep regimes. (A–C) Model in which network-spanning elements behave as simple linear springs. (A) Force-extension behavior of individual elements. Different colors indicate different force levels shown by the color scale located below. (B) From left to right, a schematic diagram illustrating the appearance, force buildup, and disappearance of individual elements during deformation. (C) Predicted relationship between a strain rate ($\dot{\epsilon }$) and applied stress (σ) for a network of simple linear springs. (D–F) Model in which the force-extension behavior for individual elements is nonlinear. (D) Force-extension behavior with weak linear dependence below a critical extension threshold and rapid increase above the threshold. (E) A schematic diagram during deformation. Only a small subset of highly extended elements support significant force. (F) Predicted dependence of $\dot{\epsilon }$ on σ is linear below a critical stress and constant above it (see Supporting Material for details). To see this figure in color, go online.