Paper Number
NF15 

Session
Non-Newtonian Fluid Mechanics & Instabilities

Title
Surface textures and non-Newtonian fluids for decreased friction

Presentation Date and Time
February 15, 2017 (Wednesday) 3:35

Track / Room
Track 2 / Audubon A

Authors (Click on name to view author profile)

1. Schuh, Jonathon K. (University of Illinois at Urbana-Champaign, Mechanical Science and Engineering)
2. Ewoldt, Randy H. (University of Illinois at Urbana-Champaign, Mechanical Science and Engineering)

Author and Affiliation Lines (in printed abstract book)
Jonathon K. Schuh and Randy H. Ewoldt
Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801

Speaker / Presenter 
Schuh, Jonathon K.

Text of Abstract
Surface texturing is used to reduce friction in lubricated sliding contact. Here we experimentally study the coupling of non-Newtonian fluid properties with varying texture profiles. Gap-controlled experiments with polymer solutions were performed on a tribo-rheometer configuration using textured parallel disks and gap separations below 300 µm. Gap control, rather than normal force control used in traditional tribology studies, is necessary to control the relevant dimensionless parameters of the experiment. These include the Reynolds Number, Weissenberg Number, and Deborah Number. The Deborah Number appears due to transient variations in the direction of flow due to surface texturing, whereas the Weissenberg Number is determined by the characteristic strength of flow (shear rate). We measure normal and shear loads up to a maximum Reynolds number with respect to gap height Reh=59.54. Previous experimental work tested with the rotating plate moving in only one direction. In our work here, we study bi-directional sliding motion to verify symmetry in the experimental setup and to study the directional-dependent normal and shear response. We show that the symmetry of the surface textures depth profiles must be broken to produce normal forces above the viscoelastic response, and that an optimal angle of asymmetry ß exists for decreasing friction with asymmetric surface textures and viscoelastic lubricants.