Paper Number
SA25 

Session
Self-assembled Systems and Gels

Title
The fluidity model for the mechanical description of thixotropic elasto-viscoplastic materials

Presentation Date and Time
October 14, 2015 (Wednesday) 3:10

Track / Room
Track 3 / Constellation E

Authors (Click on name to view author profile)

1. de Souza Mendes, Paulo R. (Pontifícia Universidade Católica-RJ, Mechanical Engineering)
2. Thompson, Roney L. (Universidade Federal Fluminense, Mechanical Engineering)
3. Abedi, Behbood (Pontifícia Universidade Católica-RJ, Mechanical Engineering)
4. Sica, Luiz R. (Pontifícia Universidade Católica-RJ, Mechanical Engineering)

Author and Affiliation Lines (in printed abstract book)
Paulo R. de Souza Mendes¹, Roney L. Thompson², Behbood Abedi¹, and Luiz R. Sica^1
1Mechanical Engineering, Pontifícia Universidade Católica-RJ, Rio de Janeiro, RJ 22453-900, Brazil; ²Mechanical Engineering, Universidade Federal Fluminense, Niterói, RJ, Brazil

Speaker / Presenter 
de Souza Mendes, Paulo R.

Text of Abstract
A constitutive model that accounts for thixotropy, viscoelasticity and yielding behavior is presented. It uses the fluidity to specify the microscopic state. The model is composed of two differential equations, one tensorial equation that relates the stress to the rate of strain and one scalar evolution equation for the fluidity. The equation for stress is a modified version of the Oldroyd-B model in which the relaxation and retardation times are functions of the fluidity. In contrast to the existing phenomenological models for thixotropic elasto-viscoplastic materials, the present one relies only on a few material functions that are directly measurable by means of three standard rheological tests. No fitting parameters are involved. The model predictions were compared with transient shear flow data pertaining to a laponite aqueous suspension, and the agreement turned out to be quite remarkable.