News

Big paper published on medium-amplitude rheology (Journal of Rheology)

Posted on by ewoldt@illinois.edu

Congratulations to Luca on his masterpiece work, just published in the Journal of Rheology:

“Continuous relaxation spectra for constitutive models in medium-amplitude oscillatory shear”
Martinetti, L., J. M. Soulages, and R. H. Ewoldt, Journal of Rheology, 62(5), 1271–1298

The work is a tour de force of new theoretical derivations, first-of-their-kind model fitting to experiments, and new molecular insights for a transient polymer network.

We employ the concept of a parameterized continuous spectrum, which can dramatically reduce the number of fit parameters of a model, resulting in a model that is more credible, and with more certainty on parameter values for inferring molecular information.

The framework can be applied generally to a vast library of existing mathematical models (Corotational, Giesekus, etc.). The work demonstrates the potential of using weakly nonlinear oscillations, a developing area of characterization also known as medium-amplitude oscillatory shear (MAOS), to understand complex fluid and soft matter rheology.

 

Journal of Mechanical Design Editors’ Choice Award

Posted on by ewoldt@illinois.edu

Congratulations to Jonathon and our collaborators Yong-Hoon Lee and James Allison (UIUC, ISE) on receiving a 2017 Journal of Mechanical Design Editors’ Choice Award – Honorable Mention.

The award was given in Quebec City, Canada, at the annual ASME International Design Engineering Technical Conference.

Our paper (DOI link) describes design optimization with viscous Newtonian fluids and arbitrary surface shapes for reducing friction in sliding contacts. The approach goes beyond simple textures considered in the literature (dimples, wedges, etc.) and instead considers an arbitrary continuous texture geometry represented using a two-dimensional cubic spline interpolation. This results in significant improvement in performance with the best designs, which are textures resembling a spiral blade.

The results have implications for thrust bearings, hydraulic systems, and anywhere that textured surfaces can be used to reduce friction and improve energy efficiency in engineered systems.

Collaboration with Moore group published in ACS Macro Letters

Posted on by ewoldt@illinois.edu

Congratulations to Arif on our recent collaborative paper with Liu et al. “Dynamic Remodeling of Covalent Networks via Ring-Opening Metathesis Polymerization” DOI link

Led by the Moore Group (UIUC, Chemistry), we report a fascinating system which reversibly changes from solid polymer network to liquid monomers, and back again, controlled by temperature. Rheology helps to characterize and understand the reversible process.

The ability to “remodel” a material is used throughout biology for resiliency and maintenance. Our work here represents a promising candidate for a synthetic engineered material that can remodel itself.