Paper Number
PO77
Session
Poster Session
Title
Additively manufactured vanes with modified geometries for measurements of yield-stress fluids
Presentation Date and Time
October 17, 2018 (Wednesday) 6:30
Track / Room
Poster Session / Woodway II/III
Authors
- Owens, Crystal E. (Massachusetts Institute of Technology, Mechanical Engineering)
- Narayanan, Thaneer (Massachusetts Institute of Technology)
- Hart, A. John (Massachusetts Institute of Technology, Mechanical Engineering)
- McKinley, Gareth H. (Massachusetts Institute of Technology)
Author and Affiliation Lines
Crystal E. Owens, Thaneer Narayanan, A. John Hart, and Gareth H. McKinley
Massachusetts Institute of Technology, Cambridge, MA 02139
Speaker / Presenter
Owens, Crystal E.
Text of Abstract
We constructed vanes with typical and novel geometries for rheological measurements using stereolithographic (SLA) 3D printing (Form2, Formlabs Inc), which works by UV-crosslinking a methacrylate-based liquid photopolymer to build a solid object layer by layer. The SLA printing process permits straightforward creation of complex structures with dimensional resolution <200µm over several cm in length, from materials having wide chemical compatibility and high mechanical stability. In particular, we designed a series of vane geometries for measuring the yield stress and flow curves of complex fluids that exhibit a yield stress, and demonstrated their use with viscous Newtonian fluids, carbopol-based hair gel, and a jammed emulsion (mayonnaise). In addition, the low cost of production allows these vanes to be disposable for measurement of caustic materials such as battery slurries.
Enabled by the SLA process, we introduce novel geometries designed to improve the typical 4-armed vane by creating a more homogeneous shear profile in the unknown test material, with minimally displaced sample material when inserting the vane. Geometries include a fractal structure, a hollow ribbed cylinder, and vanes with an arbitrary number of arms. The end of each vane connects to the spindle of a rheometer (Discovery Hybrid, TA Instruments) via an M4 helicoil threaded insert, resulting in a diameter runout of 0.1 to 1.0 mm without further processing. A 3D printed cup with a ribbed inner surface holds the sample fluid, and disassembles for ease of cleaning.
Finally, we designed and compared conversion equations that translate measured torque to material shear stress as a function of the vane geometry, and measured viscosity of silicone oils to within 5% for all vanes. We reproduced material flow curves with mean average error below 2% when compared to baseline flow curves measured by a cone and plate geometry, showing ultimately that the designs are useful for experiments, and not just made in vane.