herein, the relations are given explicitly in Eqs. (12) and (19), which are easily evaluated to find T12ðtÞ for a given kðtÞ. When
the stress profile is specified then these equations offer nonlinear Volterra integral equations to solve for k(t), which are easily
evaluated numerically as described in Sections 3 and 4.
The numerical results, discussed in the previous section, offer a number of points. First, whether the shear deformation
(strain) or shear stress is imposed, the results obtained by our model appear physically ‘reasonable’ (see Figs. 1 and 3).
Second, even though simple shear is isochoric (instantaneously volume preserving), material compressibility has an effect
through the memory of the past deformation. In general though, for the parameter values chosen in this article, the difference
between compressible and incompressible materials is small except at large shear values (see Fig. 2). Third, the effect of
compressibility is found to diminish as the ratio of relaxation times sð¼ sd=shÞ increases, although, as a fourth point, the
energy dissipated over a forcing cycle is found to be greater for a compressible material than the incompressible material
(see Fig. 4). Finally, the last figure reveals that the long-time dissipation over a single cycle increases monotonically at
low frequencies but tends to a constant value at mid to high frequencies.
The strength of the present model is its relative simplicity, so that it can be applied to inhomogeneous deformations. The
authors are currently applying the new method to the viscoelastic deformation around voids in rubber-like bodies subjected
to time-varying hydrostatic loading, where equilibrium has to be enforced as an extra constraint. The same approach is also
being utilised to study deformations of viscoelastic soft biological tissues, where insight can be gained as to the likely effect
of large stretch, impact or other trauma.