Universal relations for instantaneous deformations of viscoelastic fluids

The note considers viscoelastic fluids which undergo an instantaneous homogeneous deformation consisting of shear superposed on triaxial extension. Two relations involving the stress and deformation components are presented, which are valid for all such fluids, and hence are termed “universal relations”. The first contains the Lodge-Meissner relation as a special case; the second arises when a block is deformed by shear traction only. It relates dimensional changes to the amount of shear.