As for the compressible case, if kðtÞ is specified then the time-dependent tractions can be determined directly from these
equations. Alternatively, the usual physical situation is that the tractions are imposed. As such T12 would be given and
kðtÞ determined from the nonlinear Volterra integral equation, via the numerical scheme referred to above and given in
the appendix of De Pascalis et al., 2014. The Eq. (19) for shear stress is written as