Closed-loop controlled filament stretching and break-up of polymer solutions

A constant true (radial) strain rate filament stretching experiment has been the Holy Grail of extensional rheological studies. These experiments are performed on a Filament Stretching Extensional Rheometer (FiSER). A filament stretching experiment is the only direct way of measuring the extensional viscosity of a fluid. Previous attempts to achieve constant rate stretching have required tedious and iterative processes, which relied on the data of previous experiments to generate an axial profile that would result in a constant true strain rate experiment. This study presents a method to actively control the axial strains via the utilization of radial strain feedback. The first method we tried was an "Euler 1st order approximation," in which the ratio of the axial and radial strains is calculated at each time-step to determine the axial strain necessary at the next time-step to maintain a constant radial strain rate. This method worked, but was limited by how accurate this "ratio" of strains could be calculated. The "ratio" becomes unstable when the change in strain per time-step reaches the same order of noise. To fix this problem, we implemented a least squares linear regression scheme.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Mechanical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2005

Author dc:creator

• Yeh, Roger, 1980-

Advisor dc:contributor.advisor

• Gareth H. McKinley.

• Mechanical Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/33908

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/33908