Figure 4.

Basis functions ${\varphi }_k\left(t\right)$ (12) of the relaxation modulus model $G_K\left(t\right)$ (11) for two time-scaling factors, $\alpha$: (a) $\alpha =0.001 \left[\mathrm{s}\right]$; (b) $\alpha =0.1 \left[\mathrm{s}\right]$; $k=1, 2, 5, 10, 100, 500$.