Incompressible viscoelastic liquid or solid

Note 3 The Finger strain tensor for a homogeneous orthogonal deformation or flow of incompressible, viscoelastic liquid or solid is... 

Equation relating stress and deformation in an incompressible viscoelastic liquid or solid. Note 1 A possible general form of constitutive equation when there is no dependence of stress on amount of strain is... 

Now we need to express s in terms of the stress in the liquid using a constitutive equation. Various authors have does this by using empirical (nonlinear elastic) equations [24,78], or by assuming elastic behavior with the solid and liquid phases compressible [63,58] or incompressible [79,64], or by allowing the network to be purely viscous [67] or viscoelastic [73,59,60,61,80] Biot [61] allows for anisotropy of the mechanical properties as well as for viscous dissipation within both the solid and liquid phases. 

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