the stress heterogeneity would be even larger [@Dussi2020].

Because in the RSN the initial structure is homogeneous, stress concentration does not occur from the onset of deformation, but develops during deformation as bonds are ruptured. We can quantify this development via the difference between the failure threshold of a broken sacrificial bond $\lambda_{S,fail}$, a measure for the actual local extension, and the extension estimated from the global strain assuming all deformations are affine, $dl_{aff}$. We therefore define $\Lambda=\lambda_{S,fail}-dl_{aff}$. To compare with the MS model, it must be noted that in this model the stress is homogeneous, but the strain field is not. In fact, the microcracks take up additional strain to compensate for the absence of the sacrificial network. This means that the deformation of the remaining sacrificial bonds is less than the affine strain, so that $\Lambda$ is always smaller that 1 in the MS model (See dashed line in Fig. \[fig:StressConc\](e)). If at any time $\Lambda>0$, stress concentration must therefore be present.

This analysis reveals different modes of stress concentration during the failure of a RSN system as shown in in Fig. \[fig:StressConc\](e). At first nothing breaks, this regime coincides with the reversibly elastic regime found at the 