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 .t r connects the viscosity, η, with the rigidity modulus,n , and the time of relaxation,t r . In the case of simple fluids, for which the equation was originally given by Maxwell, the dissipation of shearing stress is so rapid that neithern nort r 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,"t r , 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).