Paper Number
TM16 My Program
Session
Techniques and Methods: Rheometry, Tribometry, Spectroscopy and Microscopy
Title
Nonlinear chirp rheology
Presentation Date and Time
October 22, 2025 (Wednesday) 2:30
Track / Room
Track 7 / Sweeney Ballroom D
Authors
- Waeterloos, Jarno L. (KU Leuven, Department of Chemical Engineering)
- Clasen, Christian (KU Leuven, Department of Chemical Engineering)
Author and Affiliation Lines
Jarno L. Waeterloos and Christian Clasen
Department of Chemical Engineering, KU Leuven, Leuven, Flanders 3001, Belgium
Speaker / Presenter
Waeterloos, Jarno L.
Keywords
experimental methods; applied rheology; methods; rheometry; techniques
Text of Abstract
Chirp signals have proven to be highly efficient for acquiring small amplitude oscillatory shear (SAOS) data of viscoelastic materials sampling wider ranges of frequencies. By significantly reducing experimental times, chirps enable in particular the measurement of fast time-evolving systems. Recently, their popularity has grown with the development of chirp protocols which are directly implemented in both stress and strain controlled rheometers. While initially designed for measurements within the LVE regime, chirps are now also being considered for nonlinear rheological measurements where materials also undergo microstructural changes.
Advanced techniques like parallel and orthogonal superposition rheology allow the use of chirps for the characterization of nonlinearly deformed materials. In this work, we go further by demonstrating that chirps can directly be used to obtain nonlinear viscoelastic properties in medium amplitude oscillatory shear (MAOS) and large amplitude oscillatory shear (LAOS) measurements. Unlike single frequency sine waves, where the harmonics are easily separated by means of Fourier transform rheology, chirp signals present a challenge due to spectral overlap of the harmonics. In light of the recent development of Gaborheometry for the extraction of the Fourier-Tschebychev coefficients [1], a similar strategy is employed using the Gabor transform to extract the nonlinear viscoelastic harmonics from chirp signals. We show that additional corrections are required due to the inherent phase of the chirp waveform itself and demonstrate with simulations and experimental verification that with these corrections this method is highly efficient and reduces nonlinear measurement times by orders of magnitude. Finally, the possible use of the more extensive Frenet-Serret framework [2] is investigated for the determination of nonlinear viscoelastic moduli using chirp signals.
[1] Rathinaraj and McKinley, JOR 67, 2, 479 (2023).
[2] Rogers, Rheol Acta 56, 5, 501 (2017).