Optimization of the
Triboconditioning Process for Low
Friction Surfaces
Zlate Dimkovski
Int. workshop “Super-lubricity in the automotive real world”, May 5th 2015, Sao Paolo, Brazil
Outline
• A study on Triboconditioning process
on a valvetrain components
– Introduction
– Process/Friction Tests
– Surface Analysis
– Conclusions
• Triboconditioned liner surfaces
2Zlate Dimkovski, Halmstad University
Triboconditioningas a cost-effective process
F
n
Ring sample
Tool
sample
Wear
width
increases
Tool sample
asperities
flatten
WS2
Ring sample
5Zlate Dimkovski, Halmstad University
Process tests on tribometer
• Test variables:
– Load-F (180 & 360N)
– Speed-n (600 & 1200 rpm)
– Surface finish (Ground & Honed)
– Time: ~6 min
• Test outputs:
– Coef. of friction
– El. resistance
Block-on-ring module
F
nRing
Tool
6Zlate Dimkovski, Halmstad University
7
Friction (start-stop) tests
• Test variables:
– Load: F=3N
– Speed: n=0-714rpm
– Surface finish (Ground & Honed)
– 3 repetitions (3 diff. ring samples)
• Test outputs:
– Coef. of friction (COF)
– El. Resistance (R)
Block-on-ring module
F=3N
n
Ring sampleWidth=6mm
Block sampleWidth=3mm
Zlate Dimkovski, Halmstad University
8
Testing sequence (5min total test time)
5 5 5 5
Start-stop tests:
Zlate Dimkovski, Halmstad University
9
COF
&
R(resistence)
Signals
Analyzed interval
Rotational Speed V2=0-11.9 rev/s (0-714rpm)Zlate Dimkovski, Halmstad University
Functional friction (start-stop) tests
0,1084
0,1034 0,1033
0,0950
0,06
0,07
0,08
0,09
0,10
0,11
0,12
360/600 180/600 360/1200 180/1200
COF Honed
0,088
0,076
0,1087
0,0867
0,06
0,07
0,08
0,09
0,10
0,11
0,12
360/600 180/600 360/1200 180/1200
COF Ground
Load (N)/Speed(rpm) Load (N)/Speed(rpm)
10Zlate Dimkovski, Halmstad University
3D
ro
ug
hn
ess
pa
ram
ete
rsLoad/Speed Sq S10z Shv Sha Spk Sk Sk reduct.
N/rpm µm µm µm³ µm² µm µm %
180/360 Before 0,145 0,813 7,5 791,2 0,110 0,367
180/360 After 0,088 0,829 6,6 918,3 0,074 0,206
180/1200 Before 0,149 0,846 5,9 650,0 0,115 0,388
180/1200 After 0,098 0,914 7,1 771,2 0,082 0,225
360/600 Before 0,141 0,782 8,3 910,1 0,107 0,366
360/600 After 0,109 1,039 8,2 779,7 0,083 0,244
360/1200 Before 0,154 0,856 10,7 1101,4 0,135 0,358
360/1200 After 0,127 1,019 4,6 476,7 0,117 0,298
180/360 Before 0,084 0,785 3,9 306,9 0,061 0,195
180/360 After 0,076 0,877 5,9 619,7 0,056 0,142
180/1200 Before 0,102 0,897 3,8 263,0 0,093 0,231
180/1200 After 0,075 1,064 6,6 769,4 0,059 0,140
360/600 Before 0,081 0,725 4,2 337,3 0,054 0,185
360/600 After 0,079 0,897 4,4 526,9 0,073 0,121
360/1200 Before 0,083 0,757 4,2 331,9 0,058 0,195
360/1200 After 0,096 1,021 4,5 401,9 0,107 0,179
42,0
33,3
16,9
Ho
ne
dG
rou
nd
26,9
39,5
34,4
8,3
43,8
?11Zlate Dimkovski, Halmstad University
12
Morphological decomposition for 180N/600rpm
Ground Honed
(Before-After)/Before*100(Before-After)/Before*100
Multi-scale analysis:
Zlate Dimkovski, Halmstad University
13
Morphological decomposition for 180N/600rpm
Ground Honed
13
Roughness Waviness
Zoom on
Roughness
Scales
Roughness Waviness
Zoom on
Roughness
Scales
4 measurements/ring
Zlate Dimkovski, Halmstad University
Morphological decomposition (Averages of 3 samples)Increase/decrease percentage over all the scales
-500
-400
-300
-200
-100
0
100
1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61
180N/1200rpm
Ground
Honed
-500
-400
-300
-200
-100
0
100
1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61
180N/600rpm
Ground
Honed
-500
-400
-300
-200
-100
0
100
1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61
360N/600rpm
Ground
Honed
-500
-400
-300
-200
-100
0
100
1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61
360N/1200rpm
Ground
Honed
14
Sq
cha
ng
e [
%] (S
qb
efo
re –
Sq
aft
er)
/Sq
befo
re*1
00
Scales Scales
Scales Scales
Zlate Dimkovski, Halmstad University
Conclusions (Valvetrain surfaces)
• The lowest friction showed the ground surface treated
by low load/low speed process parameters
• Contrary to the ground rings, the longer wavelengths
of the honed surfaces increase during
triboconditioning
• The ground (rougher) surface before treatment better
than the honed (smooth) one due to the better
reduction of the waviness & core roughness
15Zlate Dimkovski, Halmstad University
Power Losses in IC Engines
(Richardson D. E. 2000)
17
Focus: Cylinder Liner – Twin Land Oil Control Ring
Zlate Dimkovski, Halmstad University
Triboconditioned Liner SurfacesCoated Uncoated
ISO 25178
Height Parameters
Sa 0.6387 µm
Sz 9.222 µm
Ssk -1.275
Sku 4.531
EUR 15178N
Functional Parameters
Sk 1.153 µm
Spk 0.2353 µm
Svk 1.608 µm
Sr1 5.263 %
Sr2 71.56 %
ISO 25178
Height Parameters
Sa 0.4087 µm
Sz 6.239 µm
Ssk -2.27
Sku 9.079
EUR 15178N
Functional Parameters
Sk 0.6115 µm
Spk 0.2293 µm
Svk 1.583 µm
Sr1 7.962 %
Sr2 77.81 %
SMOOTHER
PLATEAUSZlate Dimkovski, Halmstad University 18
Truck ring-liner tribotests
Testing parameters:
• 10mm wide liner samples: 2
• Load: 8N
• Speeds: 0.5Hz, 1Hz, 2Hz & 5Hz
• Stroke: 24mm
• Nominal contact pressure: 1.42 MPa
• Liner samples half-coated, half-uncoated
• New (TLOCR) Twin Land Oil Control Rings: 2
• Viscous engine oil: 20W50
• Room temperature
• Time: 10min
Zlate Dimkovski, Halmstad University 19
Setup
Stiffer suspension
in tangential direction
Force sensor
Zlate Dimkovski, Halmstad University 20
Obvious Friction Reduction in Boundary & Mixed
Lubrication Regime
COATED
Speed: 1Hz
Zlate Dimkovski, Halmstad University 25
Conclusions/Future work
(Liner Surfaces)
Conclusions
• Triboconditioned surfaces
reduce friction (more in
boundary/mixed regime).
• Coating/Surface topography
contribution?
Future work
• Novel
stratified/honed/textured
surfaces in production
• Coated (plasma/DLC) surfaces
with low viscosity oils
• Better
models/simulations/tribotests
26Zlate Dimkovski, Halmstad University
References
1. Dimkovski Z. et al, 2014, Int. Conference on
Metrology and Properties of Engineering
Surface, Charlotte, USA
2. Zhmud B., 2011, Tribology and Lubrication
Technology, 67, 42
3. Zhmud B., Tomanik E. and Xavier F.-A., 2014,
Lubrication Science, 26, 277
Zlate Dimkovski, Halmstad University 27
Acknowledgements
• Vinnova, Swedish Energy Foundation
• Volvo Groups Truck Technologies
• Volvo Cars
• Applied Nano Surfaces
• Gnutti Carlo Sweden
• Scania
• Digitalsurf, France
28Zlate Dimkovski, Halmstad University