Paper Number
PO106 My Program
Session
Poster Session
Title
A novel calibration procedure for orthogonal superposition measurements
Presentation Date and Time
October 16, 2024 (Wednesday) 6:30
Track / Room
Poster Session / Waterloo 3 & 4
Authors
- Waeterloos, Jarno L. (KU Leuven, Chemical Engineering Department)
- Clasen, Christian (KU Leuven, Chemical Engineering Department)
Author and Affiliation Lines
Jarno L. Waeterloos and Christian Clasen
Chemical Engineering Department, KU Leuven, Leuven 3000, Belgium
Speaker / Presenter
Waeterloos, Jarno L.
Keywords
experimental methods; theoretical methods; methods; techniques
Text of Abstract
Many materials undergo transient microstructural evolutions when subjected to steady shear flows. Measurement methodologies include subjecting the material to a steady shear while simultaneously applying an oscillation either in the mutual direction (parallel superposition - PSP) or in the perpendicular direction (orthogonal superposition - OSP). While PSP has the disadvantage of coupled flow fields leading to convoluted results, OSP can easily be used to gain insight into the material behavior under flow and serves as a framework for the development of novel methods. Although both techniques are commercially available for the TA ARES-G2 rheometer, the calibration of such setups has received little attention to enable proper accuracy over the whole frequency range. Traditionally, the rheometer parameters are determined using suspended weights or calibrated springs and the results are fitted to a mass-spring-damper differential equation [1]. Effects from the slotted orthogonal double-walled Couette are corrected by so-called end-factors [2].
In this work, it is demonstrated that the abovementioned methodologies for calibration of the normal force transducer for OSP measurements are inherently flawed. The ARES-G2 becomes dynamically unstable under loading and the measurement results are well below the minimal force and displacement limits causing artefacts in the obtained parameters. Similar to the ERIC methodology for gelling systems [3], a unified method is developed using readily available Newtonian standards. Advantages of this novel method include a simple protocol, the simultaneous determination of both rheometer and geometry effects thus eliminating the need for multiple calibration procedures, and accurate parameter estimation. This novel method is also capable of correcting the standard SAOS data obtained with the same Couette geometry.
[1] Vermant et al., Rev Sci Instrum 68, 11 (1997)
[2] Tao et al. Rheol Acta 59, 2, 95 (2020)
[3] Hudson et al., Phys. Fluids 29, 121602 (2017)