A new constitutive equation for incompressible materials is obtained by assuming that the
stress tensor is an isotropic function of two kinematic quantities, namely, the rate-of-strain
tensor and the relative-rate-of-rotation tensor. A representation theorem is employed to
obtain the most general symmetric form of this function. The arising coefficients are assumed
to be functions of the second invariants of the two tensors only. Because the second
invariant of the relative-rate-of-rotation tensor is an indicator of the flow strength for several …