The relationship between viscosity, elasticity and plastic strength of a soft material as illustrated by some mechanical properties of flour dough.-III

The equation η = n. tr connects the viscosity, η, with the rigidity modulus, n, and the time of relaxa­tion, tr. In the case of simple fluids, for which the equation was originally given by Maxwell, the dissipation of shearing stress is so rapid that neither n nor tr has been measured, so that the relationship has only a theoretical interest. In the first paper of this series* it was shown that in flour dough stress dissipation proceeds at rates that can readily be followed experimentally. The “time of relaxation," tr, was given an extended significance, and defined in such a way as to be applicable to plastic materials like dough for which η is not a constant. A series of values for the viscosity was obtained with the aid of equation (i). RESP-865, 885, 910