Of great value in a number of applications is the deformation of simple shear. In particular, the importance of this deformation
to the biomechanical community is associated with the study of brain tissue for which stress measurements have
been taken recently (Gilchrist, Rashid, Murphy, & Saccomandi, 2013; Rashid et al., 2012). For a general constitutive viscoelastic
Pipkin–Rogers law, the stress–strain equations have been presented in Wineman (2009). This, and a number of other
nonlinear viscoelastic models are, in practice, difficult to employ, and so Fung’s QLV approach is attractive. However, all past
applications of Fung’s QLV model to simple shear are, to the authors’ knowledge, deficient. It thus appears timely, from the
viewpoint of both Fung’s theory and applications in biomechanics and elsewhere, to study the classical problem of simple
shear by employing the authors’ new approach to QLV; this is therefore the aim of the present paper. We will carry out
the full analysis of the simple shear problem for both incompressible and compressible viscoelastic materials of quasilinear
type. Importantly, and unlike the case of simple shear of purely hyperelastic materials, even for isochoric deformations the
effects of compressibility can have an influence on the deformation due to the memory effect of the relaxation term
associated with hydrostatic compression.
The general form of the QLV constitutive equation can be written as