ETH Polymer Physics seminar


2001-04-25
10:15 at ML J 37.1

Formulation of constitutive relations and material instability

Corneliu Balan

Department of Hydraulics, Polytechnical University of Bucharest, Romania

The work presents various formulations for differential constitutive relations which disclose non-monotonic steady flow curve, i.e. the steady dependence of the shear stress versus the strain rate, in simple shear flow. This specific family of constitutive relations exhibits material (intrinsic) instability since the steady state solution at the constant shear stress is dependent on the initial conditions for the shear rate, respectively on the initial conditions for normal stresses. The dynamics of the model is analyzed in the creeping motion and some comparison with experiments is made. The samples under investigations were lubricating greases, viscoelastic materials characterized by an internal network structure embedded into the liquid phase.


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