Relations Between Shear and Normal Stresses in a Step-Shear Experiment

The Lodge-Meissner step-shear relation for simple fluids is examined. It is demonstrated that the relation depends critically on two assumptions for the integral expansion of the simple fluid: First, the use of the Cauchy strain tensor as strain measure, and second, that the memory functions are bounded. It is pointed out that many simple differential and integral models do not satisfy these criteria and hence predict deviations from the Lodge-Meissner relation.