Document Type
Thesis
Date of Award
12-31-2025
Degree Name
Master of Science in Chemical Engineering - (M.S.)
Department
Chemical and Materials Engineering
First Advisor
David C. Venerus
Second Advisor
Kathleen McEnnis
Third Advisor
Shawn Alexander Chester
Abstract
Yield stress measurement in non-Newtonian fluids, particularly under complex flow conditions such as equibiaxial elongation, remains a significant challenge in experimental rheology. This work presents the development of a novel method, Continuous Lubricated Squeezing Flow (CLSF), designed to quantify the normal yield stress of viscoelastic materials while minimizing boundary artifacts.
The CLSF method was implemented and validated using Carbopol 940, a model yield-stress gel, at concentrations of 1 wt% and 2 wt%. Comparative shear rheology was first performed to establish baseline yield stresses and verify sample integrity. CLSF experiments were then conducted over controlled flow rate increments and gap distances to examine the transition from elastic loading to viscous yielding. Results revealed distinct elastic, viscoelastic, and viscous regimes, with the force—time profiles exhibiting reproducible overshoot and collapse behavior characteristic of structural yielding.
The findings confirm that the CLSF technique accurately captures the intrinsic yield response of viscoelastic materials when compared to shear using the von Mises yield criterion. Although the setup requires precise control of gap thickness and surface uniformity, the method provides accurate yield stress values and supports the use of von Mises for yield stress fluids. The approach introduced here establishes a foundation for future extensions of CLSF toward time-dependent, temperature-controlled, and microstructurally resolved investigations of non-Newtonian materials.
Recommended Citation
Segal, Asher, "A novel rheological technique to measure the yield stress in equibiaxial elongation" (2025). Theses. 3346.
https://digitalcommons.njit.edu/theses/3346
