2022 Postdoctoral Fellow Poster Award

Understanding the transient large amplitude oscillatory shear (LAOS) behavior of yield stress fluids (YSFs)

1. Kamani, Krutarth M. (University of Illinois at Urbana-Champaign, Department of Chemical and Biomolecular Engineering)
2. Donley, Gavin J. (Georgetown University, Department of Physics)
3. Rao, Rekha (Sandia National Labs)
4. Grillet, Anne M. (Sandia National Laboratories)
5. Roberts, Christine (Sandia National Labs)
6. Shetty, Abhishek (Anton Paar USA Inc., Rheology Department, Advanced Technical Center)
7. Rogers, Simon A. (University of Illinois at Urbana-Champaign, Department of Chemical and Biomolecular Engineering)

Abstract

A full understanding of the sequence of processes exhibited by yield stress fluid under large amplitude oscillatory shearing (LAOS) is developed using multiple experimental and analytical approaches. A novel component rate Lissajous curve, unrecoverable rate vs recoverable rate is introduced and its utility is demonstrated by application to the analytical responses of four simple viscoelastic models. Using the component rate space, yielding behavior is investigated by comparing the experimental results with predictions from the elastic Bingham model that obeys the Oldroyd-Prager formalism and the recently proposed continuous model by Kamani et al. in which yielding is enhanced by rapid acquisition of elastic strain. The physical interpretation gained from the transient LAOS data is compared to the results from the analytical SPP framework and a novel time resolved Pipkin space. The component rate figures, therefore provide an independent test of the interpretations of the SPP analysis that can also be applied to other LAOS analysis frameworks. Each of these methods, the component rates, the SPP analysis, and the time-resolved Pipkin diagrams, unambiguously identifies the same material physics, showing that YSFs go through a sequence of physical processes that includes 1) elastic deformation 2) gradual yielding, and 3) plastic flow.