(1)
This is a model of the Maxwell type. The complete Oldroyd was developed for the general case of large strains in three dimensions. Reduced to small shear strains, when the condition of linear viscoelasticity is observed; it yields for the dynamic moduli:
(1)
(2)
It happens that these expressions also describe a Maxwell element and dashpot in parallel, but with the redefinition of parameters:
(3)
(4)
(5)
In this form the model is alternatively known as the Jeffreys.
Figure 1: Oldroyd model written as combination of dashpot and Maxwell element.
Use this model to describe linear viscoelasticity with 3 model parameters only.
The Oldroyd model is not very common. Usually the 3 parameter Jeffrey model is used.
