friction evaluation of lubricated laser textured surfaces
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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
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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
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LST TECHNOLOGY
1. Laser Nd:YVO4;2. Microscope objective mount;3. Microscope objective;4. X axis linear table;5. Y axis linear table.
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TEST RIG AND SPECIMENS
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EXPERIMENTAL PROCEDURE
Pin-on-disk testing arrangement
textured pin
capacitive probe
thermocouple
Pin
Load, F
Rotating Disc
Lubricant
n
rm
Constant film thickness tests
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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
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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 /
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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
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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
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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
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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
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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
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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.
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