Jonathon Schuh: University of Illinois at Urbana-Champaign · Jonathon Schuh: University of...

Jonathon Schuh: University of Illinois at Urbana-Champaign

Yong Hoon Lee: University of Illinois at Urbana-Champaign

James Allison: University of Illinois at Urbana-Champaign

Randy Ewoldt: University of Illinois at Urbana-Champaign

Decrease friction in lubricated sliding contact

Decrease shear stress

Increase normal force

Approach: surface textures and Non-Newtonian fluids

Determine optimal design of surface textures and

lubricant

22015 Fluid Power Innovation & Research Conference

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[1] Pipkin. Lectures on Viscoelastic Theory. 1972.

No

n-lin

ear:

Am

plit

ud

edependent

pro

pert

ies

Viscoelastic: Time-dependent properties

Weissenberg

Deborah

De = l / tchar

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Controlled by geometry Geometry+Fluid

Pipkin space [1]

[1] Pipkin. Lectures on Viscoelastic Theory. 1972.

De = l / tchar

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Newtonian

Fluid

Generalized

Newtonian

Fluid

Linear Viscoelastic

Ordered

Fluid

Expansion

Non-linear models

Experimental precision and challenges

Experimental results surface textures and

Newtonian fluids

Origin of the Pipkin space

Experimental results surface textures and Non-

Newtonian fluids

Exploring more of Pipkin space

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Non-

dimensional

ratios govern

behavior [2]

[2] Johnston, King, and Ewoldt. Tribology International. 2015.

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2015 Fluid Power Innovation & Research Conference 10

Gap controlled rotational rheometer

DHR-3 by TA instruments

Precision aligned for tribo-rheometry [2]

Parallel disks D=40 mm

Top: flat (RRMS=3.33 μm), rotating, stainless

Bottom: textured, 1018 steel, attached with

Crystalbond

Key Challenges:

• Gap error

• Non-texture

normal forces[2] Johnston, King, and Ewoldt. Tribology International. 2015.

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h = ha + e

ha =ht

1+e

ha

1

ha

=1

ht

+e

ht

1

ha

Risk of misinterpreting shear stress

reduction that is not due to the

textures [3,4]

Gap zeroing calibration based on

contact force

Squeeze flow of air produces force

Calibrated ε=19.0±0.69 μm using

Newtonian oil with η=0.14 Pa s

[3] Connelly and Greener. Journal of Rheology. 1985.

[4] Pipe, Majmudar, and McKinley. Tribology Letters. 2008.

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F

N

Risk of misinterpreting normal

forces that are not due to the

surface textures [5-7]

a) Inertia:

b) Surface Tension:

c) Non-Parallelism:

[5] Andablo-Reyes, Hidalgo-Álvarez, de Vicente. Journal of Non-Newtonian Fluid Mechanics. 2010.

[6] Andablo-Reyes, de Vicente, and Hidalgo-Álvarez. Journal of Rheology. 2011.

[7] Macosko, C.W. Rheology: Principles, Measurements, and Applications. 1994

Fnp = WhR4

h20.256

a

h

æ

èçö

ø÷

FN = C

Finertia = -3 / 40prR4W2

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ha =2 ha + e( )

pR4

M

W

Real shear stress

reduction through

use of textures

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Asymmetric textures produce

forces above experimental limit

through viscous effects.

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m* ºFt

FN

=M / R

FN

Asymmetric textures

decrease friction.

Optimal β.

Surface textures decrease shear stress

Symmetry must be broken in order to produce

normal forces above experimental limit

Sign of force depends on direction of motion

Normal forces are produced by viscous effects

up to Reh=1.21

Optimal angle β exists for decreasing friction

with asymmetric surface textures

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Non-Newtonian?

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Polyisobutylene (PIB) has been used as an additive for enhancing mechanical

properties [8] and modifying viscosity [9]decrease temperature dependence of viscosity

Dissolves in mineral oil

0.5wt% PIB (MW~1,000,000) in mineral oil (highly refined, S6, η=9.62 mPa s)

c/c*=0.0774 (dilute solution)

[8] Fuks, Bakaleinikov, and Samgina. Chemistry and Technology of Fuels and Oils. 1974.

[9] Totten. Fuels and Lubricants Handbook: Technology, Properties, Performance, and Testing. 2003

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Surface textures

reduce viscosity

beyond shear thinning

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Asymmetric surface

textures produce normal

forces above viscoelastic

response

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m* ºFT

FN

=M / R

FN

Asymmetric textures

decrease friction.

Optimal β

Surface textures decrease shear stress beyond

shear thinning

Symmetry must be broken to produce normal

forces above viscoelastic response

Normal forces are always positive

Optimal angle β exists for decreasing friction

with asymmetric surface textures

Friction coefficient is smaller with Non-Newtonian

fluids than Newtonian

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Examine relaxation time scale effects

Change concentration of polymer in solution

Explore more of Pipkin space

Mathematically model surface textures

and Non-Newtonian fluids

2nd order fluid

3D flow theorem of Giesekus

with Reynolds equation solver

Determine optimal design of textures and fluid

Direct optimization with Reynolds equation

Adaptive surrogate modeling techniques [10]

Experimentally test optimal texture and fluid

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[10] Rao et. al. iDETC 2015.

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Ewoldt Research Group Funding

Specific PeopleMichael Johnston (MS UIUC, 2014)

Nathan Bristow (BS UIUC, 2014)

Nikita Dutta (REU summer 2014)

Feargus MacFhionnlaoich (REU summer 2015)

Jonathon Schuh (schuh4@illinois.edu)

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hD

R

Rc

Rtj

W

h,r

FN ,ha( ) = f h, R, Rc, Rt , D,j,h,r,W( )

By Buckingham Pi Theorem:

FN

pR2 hWR / h( ),ha

h

æ

èç

ö

ø÷= F j,

h

R,

h

Rc

,h

Rt

,h

D,rWh2

h

æ

èçö

ø÷

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h = 1.4 Pa s

r=846.4 kg/m3

h = 1.4 Pa s

r=846.4 kg/m3

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h = 1.4 Pa s

r=846.4 kg/m3

h = 1.4 Pa s

r=846.4 kg/m3

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m* ºFT

FN

=M / R

FN

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M =Ntex tqzdr rdq( )( )Ri

Ro

ò-j /2

j /2

ò r

ha =2 ha + e( )

p R4

M

W

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2015 Fluid Power Innovation & Research Conference 37