Dimensionless Groups Used to Plot Rheological Data

A deformation history that provides a critical test of constitutive equations is stress relaxation following double-step strain. In this experiment, a strain of is introduced at f = 0, and a second strain is introduced at t = such that the final total strain is The resulting stress is a function of four parameters, i.e., a= and is reported only for f fj. If it 

This relation, which Venerus et al. [22] call the Osaki-Lodge equation, has been found to be valid for entangled polystyrene solutions [22,42,43]. Another quantity of interest is the normal stress ratio defined as  

Tube models predict that this ratio is independent of both t and tp and Venerus et al. [22] found it to be valid with = 2 72 = 4 for a polystyrene solution. 

5 Dimensionless Groups Used to Plot Rheological Data 

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