Paper Number
PO126 

Session
Poster Session

Title
Inertial limits for creep tests: We can help you to avoid creepy data

Presentation Date and Time
October 12, 2022 (Wednesday) 6:30

Track / Room
Poster Session / Riverwalk A

Authors (Click on name to view author profile)

1. Fernandes, Rubens R. (University of Illinois Urbana-Champaign, Department of Mechanical Science and Engineering)
2. Boehm, Michael W. (Motif FoodWorks, Inc.)
3. Baier, Stefan K. (Motif FoodWorks, Inc.)
4. Ewoldt, Randy H. (University of Illinois at Urbana-Champaign, Mechanical Science and Engineering)

Author and Affiliation Lines (in printed abstract book)
Rubens R. Fernandes¹, Michael W. Boehm², Stefan K. Baier² and Randy H. Ewoldt^1
1Department of Mechanical Science and Engineering, University of Illinois Urbana-Champaign, Urbana, IL 61801; ²Motif FoodWorks, Inc., Boston, MA

Speaker / Presenter 
Fernandes, Rubens R.

Keywords
experimental methods; rheometry techniques

Text of Abstract
A typical stress-controlled rotational rheometer has a combined motor-transducer unit that applies torque to a rotating measuring system with a finite moment of inertia, which rotates and applies a moving boundary condition to the sample. This means that a fraction of the torque applied by the rheometer results in acceleration of the measuring system, which can lead to false readings whenever the fraction of the torque employed to accelerate the moving parts is significant when compared to the material reaction torque. We derive analytical expressions to avoid these “bad data” which can be expressed as limit lines in plots of compliance and fluidity as a function of time. We also identified several examples from the literature in which the measuring geometry appears to accelerate faster than the expected result under free acceleration. This framework allows experimentalists to quickly identify data that do not correspond to realistic material responses in creep experiments.