World Tribology Congress 2009, 6 – 11 September, Kyoto 1

Adrian Predescu1), Mircea D. Pascovici1), Traian Cicone1), Cristian S. Popescu1),

Constantin Grigoriu2), Dumitru Dragulinescu2)

1) Department of Machine Elements and Tribology, University POLITEHNICA of Bucharest 2) National Institute for Laser, Plasma and Radiation Physics, Bucharest

World Tribology Congress 2009, 6 – 11 September, Kyoto 2

PAPERS

STATE OF THE ART

GROOVED SURFACES

PIN- ON-DISC

Etsion, 2005 Glavatskih et al., 2005 Pettersson and Jacobson, 2003 – BL

Dobrica and Fillon, 2008 Costa and Hutchings, 2007 Kovalchenko et al., 2005

Cavallaro and Lubrecht, 2007

Anderson et al., 2007

Ning et al., 2007 Min-soo Suh et al., 2008

Min-soo Suh et al., 2008

Pascovici et al., 2009

World Tribology Congress 2009, 6 – 11 September, Kyoto 3

OBJECTIVES

• experimental assessment of hydrodynamic performances (load capacity and friction force) for parallel, partially textured, sliders and comparison with a similar step slider

• the comparison of the experimental data with numerical simulations and with the results obtained by the others in order to establish the new research directions

World Tribology Congress 2009, 6 – 11 September, Kyoto 4

LST TECHNOLOGY

1. Laser Nd:YVO4;2. Microscope objective mount;3. Microscope objective;4. X axis linear table;5. Y axis linear table.   

World Tribology Congress 2009, 6 – 11 September, Kyoto 5

TEST RIG AND SPECIMENS

World Tribology Congress 2009, 6 – 11 September, Kyoto 6

EXPERIMENTAL PROCEDURE

Pin-on-disk testing arrangement

textured pin

capacitive probe

thermocouple

Pin

Load, F

Rotating Disc

Lubricant

n

rm

Constant film thickness tests

World Tribology Congress 2009, 6 – 11 September, Kyoto 7

THE MODEL

Data used in experiments and numerical simulations

Constant Value Variable Value

d 6.3 mm U [0.157-0.942] m/s

s 0.01 mm hmin [0.008-0.012] mm

η 27 0.28 Pas

L 0.2 mm

U

s hmin

L

pi=0 pe=0

d

z

y

x

b

World Tribology Congress 2009, 6 – 11 September, Kyoto 8

RESULTS

Experiment

Load capacity variation vs. time Friction force variation vs. time

0

1

2

3

4

5

0 5 10 15 20 25

Time [sec]

No

rma

l fo

rce

[N

]

200

600

400

TEXTUREDh min = 8 m

s = 10 mmL = 100 mm= 0.5

20W50 =0.28Pa.s

0

0,1

0,2

0,3

0,4

0 5 10 15 20 25

Time [sec]F

ric

tio

n f

orc

e [

N]

TEXTUREDh min = 8 m

s = 10 mmL = 100 mm= 0.5

20W50 =0.28Pa.s

200

600

400

Lb /

World Tribology Congress 2009, 6 – 11 September, Kyoto 9

RESULTS

Experiment

0,05

0,07

0,09

0,11

0,13

0,15

0 5 10 15 20 25

Time [sec]

Fri

cti

on

co

efi

cie

nt,

20W50

=0.28Pa.s

TEXTUREDh min = 8 m

s = 10 mmL = 100 mm= 0.5

200

600

400

Friction coefficient variation vs. time

World Tribology Congress 2009, 6 – 11 September, Kyoto 10

RESULTS

Experiment

Dimensionless load capacity vs. dimensionless film thickness

0

5

10

15

1,7 1,9 2,1 2,3

H [ ]

Step Textured

400 rpm

200 rpm

310F

s = 10 mL = 100 mm = 0.5

20W50 =0.28Pa.s

0,1

0,2

0,3

0,4

1,7 1,9 2,1 2,3

H [ ]

Step Textured

400 rpm

200 rpm

610fF

s = 10 mL = 100 mm = 0.5

20W50 =0.28Pa.s

Dimensionless friction force vs. dimensionless film thickness

2

min

Ud

FhF f

3

2min

Ud

FhF

min

min

h

shH

World Tribology Congress 2009, 6 – 11 September, Kyoto 11

RESULTS

Experiment

0,00

0,02

0,04

0,06

0,08

0,10

1,7 1,9 2,1 2,3

H [ ]

[-]

Step Textured

400 rpm

200 rpm

s = 10 mL = 100 mm = 0.5

20W50 =0.28Pa.s

Friction coefficient vs. dimensionless film thickness

F

Ff

min

min

h

shH

World Tribology Congress 2009, 6 – 11 September, Kyoto 12

RESULTS

Numerical simulations

z

x

p

-3.15 mm 3.15 mm

-3.15 mm

3.15 mm

265822 Pa

-25327 Pa

Pressure distribution at h=0.01 mm, and U=0.314 m/s

The vectorial velocity distribution in film

World Tribology Congress 2009, 6 – 11 September, Kyoto 13

RESULTS

Experiment vs. Numerical

0

2

4

6

8

8 9 10 11 12

h min [m]

F [

N]

CFD Experiment

400 rpm

200 rpm

s = 10 mL = 100 mm = 0.5

20W50 =0.28Pa.s

Load capacity vs. film thickness, experiment and numerical

Friction force vs. film thickness, experiment and numerical

0,00

0,20

0,40

0,60

0,80

1,00

8 10 12h min [m]

Ff [

N]

CFD Experiment

400 rpm

200 rpm

s = 10 mL = 100 mm = 0.5

20W50 =0.28Pa.s

World Tribology Congress 2009, 6 – 11 September, Kyoto 14

CONCLUSIONS

• Original experimental setup for testing lubricated textured surfaces using a standard pin-on-disc machine specially instrumented.

• Original tests with a textured (grooved) pin on a flat disc.

• The preliminary results have clearly put in evidence the cumulative hydrodynamic effect of partially textured surfaces.

• Sources of differences between the numerical simulations and experiments: – relative positioning of the pin and the disc;

– the accuracy of the film thickness measurement;

– “wave effect”.

• The experimental results fairly agree with previously reported results.

• New tests will be performed for different configurations with improved surface accuracy.

• Stepped slider is better than grooved slider.

World Tribology Congress 2009, 6 – 11 September, Kyoto 15