Fig. 5.

Geometry used in simulations (50 × 50 × 50 mm³) of waves superimposed on lengthening. Green dashed arrows represent harmonic loading in two perpendicular directions, which correspond to fast and slow shear wave polarizations for shear waves propagating along the negative Z-axis (red arrows). Blue solid lines are the mean fiber direction, where $\varphi =45\hspace{0.17em}\mathrm{deg}$. One fiber family in (a) the undeformed configuration ($\mathbf{a}=(\mathbf{j}+\mathbf{k})/\sqrt{2})$ and (b) after imposed stretch $\lambda$ in the Z-direction ($\mathbf{a}=(\frac{1}{\sqrt{\lambda }}\mathbf{j}+\lambda \mathbf{k})/\sqrt{{\lambda }^2+\frac{1}{\lambda }}$).