*2.3. Viscoelasticity*

Hysteresis is modeled by a single Maxwell element. The problem treated in this work requires only a narrow range of strain rates such that this procedure is justified. Viscoelastic stress is evolved according to the differential equation

$$\frac{d\sigma\_{\rm vis}}{dt} = -\frac{1}{\tau\_c} \sigma\_{\rm vis} + \frac{d\sigma\_{\rm el}}{dt} \tag{9}$$

where *σ*vis is the viscoelastic stress contribution, *τc* is the relaxation time scale, and *σ*el is the elastic Cauchy stress derived from the free energy density given by Equation (6).
