The Influence of Lubricant Properties on ARKL Temperature Rise
Oct. 19, 2012S.W Yang, W.S. Kwon
Lubricants Lab / Global TechnologySK innovation
Overview
2
§ Transmission efficiency & the ARKL test:
§ Approach:
§ Experimental Techniques:
§ Regression analysis:
§ Results:
§ Conclusions:
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.000 10.000 20.000 30.000 40.000 50.000
AR
KL
EOTT
MTM Traction at s.r.r 0.94 % and 100 °C
80 °C
100 °C
120 °C
Boundary
EHL
Hydrodynamic
Churning
ARKL EOTT
ARKL = 81 + 2620MTM + 4.0HTHS
* Presented at STLE Annual Meeting 2012 by Siwon Yang, Tom Reddyhoff, Hugh Spikes.
Transmission Efficiency
§ FrictionTemperature increase
Efficiency losses
§ Additional problems associated with high temperatures:
§ Transmissions deliver engine power to axle
§ Aim: to develop a method of exploring & understanding the impact of lubricants on transmission efficiency
3
The ARKL Test
(Axial Groove-Ball-Bearing Test)
§ ARKL: Achsial-Rillen-Kugel-Lager
§ Operation: load and rotate bearing while monitoring temperature
§ Uses Shell four-ball apparatus
[PV 1454 Getriebeöle: Prüfung der Temperaturentwicklung im Axialrillenkugellager-Temperature-Adapter. 08/1988. VW. Wolfsburg.]
§ Developed by VW; correlates with 1.6 l, 55 kW VW Polo tests *
*
4
The ARKL Test
(Axial Groove-Ball-Bearing Test)
§ ARKL: Achsial-Rillen-Kugel-Lager
§ Operation: load and rotate bearing while monitoring temperature
§ Uses Shell four-ball apparatus
§ Developed by VW
§ Shell four-ball apparatus§ Bearing type: N° 51208§ Well-insulated Housing§ Test oil volume: 40 ml§ Speed: 4000 rpm § Load: 5000 N § Duration: 2 hours
§ EOTT: End of Test Temperature
5
Aims
§ ARKL EOTT does not aid understanding of origins of friction
ARKL EOTT Transmission efficiency
§ Sources of friction:
Boundary
EHL
Hydrodynamic
Churning
§ Possible solution: to regression fit ARKL data to lubricant properties.
§ What are the relative importance of these?
6
hN/P
I: Dry friction
II: Boundary lubrication
III: Mixed lubrication
IV: Elastohydrodynamic lubrication
V: Hydrodynamic lubrication
I II
IIIIV V
mStriebeck Curve
7
Regression Fitting - Previous Research
a) Benchaita, M.T. and Lockwood, F.E., Lubr. Sci. 5, pp. 259-281, (1993).b) Bovington, C. and Spikes, H.A., Int. Trib. Conference, Yokohama, Oct 1995, pp. 817-822, publ. JST, Tokyo (1996).c) Bovington, C. Anghel, V. and Spikes, H.A., SAE Tech. Paper 961142.d) Moore, A.J., SAE Techn. Paper 961138, (1996).e) Gangopadhyay, A.K., Sorab, J., Willermet, P.A. and Schriewer, K., SAE Techn. Paper 961140, (1996).f) Devlin, M.T., Lam, W.Y. and McDonnell, T.F., SAE Techn. Paper 982503, (1998).
§ Regression fitting has been used in the past to analyse the impact of lubricant properties on crankcase engine efficiency:
Traction
HTHS
Boundary
Contributions from lubricant regimes to Sequence V1, stage 2. (c)
Fuel efficiency vs. f(viscosity, EHD film thickness, boundary CoF). (a)
8
Approach
Film thickness
USVKVis & VI
Boundary friction
Density
EHL Traction
HTHS Thermal properties
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0 10 20 30 40 50 60
Film
thic
knes
s (n
m)
Mean rolling speed (m/s)
80 °C
100 °C
120 °C
0.1
1
10
100
1000
0.001 0.01 0.1 1 10
Film
thic
knes
s (n
m)
Mean rolling speed (m/s)
80°C
100°C
120°C
0 1000 2000 3000 4000 5000
0.0
0.1
0.2
HOSO_100튏HOSO+EC1%_40 튏HOSO+EC1%_100 튏
Fric
tion
Coe
ffici
ent
Rubbing Time (sec)
HOSO_40튏
0
2
4
6
8
10
12
14
0 2000000 4000000 6000000 8000000 10000000 12000000
Avg
Mea
sure
d Vi
scos
ity (c
P)
Avg Measured Shear Rate (1/s)
60°C
80°C
100°C
9
Test Lubricants
A to Z of lubricant samplesA B C D E F G H I J K L M N O P Q R S T U V W X Y Z1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
KV100 Target 2.0 5.5 7.5 12.0 5.5 5.5 5.5 5.5 7.5 7.5 7.5 7.5 5.5 5.5 5.5 5.5 5.5 5.5 5.5 5.5 5.5 5.5 5.5 5.5 5.5 5.5 KV 40 5.167 28.11 43.67 92.11 22.33 18.83 24.09 23.84 32.8 24.19 34.98 35.30 28.57 28.93 27.21 32.85 27.53 28.08 29.41 28.25 28.08 28.05 28.93 KV 100 1.730 5.500 7.462 12.23 5.515 5.548 5.519 5.432 7.420 7.548 7.534 7.508 5.501 5.515 5.510 5.514 5.420 5.616 4.759 5.501 5.489 5.507 5.625
VI n.a. 136 137 126 202 179 178 175 203 430 191 188 133 131 145 104 136 144 68 136 136 137 137HTHS 80°C 1.77 6.73 9.51 16.75 6.34 5.40 6.13 6.22 8.76 6.75 8.38 8.76 6.79 6.86 6.70 7.34 7.23 7.98 6.10 6.78 6.74 6.75 6.88HTHS 100°C 1.30 4.27 5.88 9.85 4.36 3.91 4.25 4.34 5.77 5.00 5.82 5.99 4.36 4.37 4.32 4.59 4.72 5.19 3.89 4.30 4.28 4.27 4.27HTHS 150°C 0.72 1.85 2.38 3.53 2.03 2.17 1.92 1.89 2.70 2.90 2.54 2.55 1.90 1.88 1.90 1.90 2.08 2.23 1.63 1.83 1.83 1.85 1.83
97.7 24.7 25.5 26.7 27.6 22.7 23.9 25.2 26.7 14.0 57.6 59.4 62.2 64.3 52.9 55.6 58.8 61.7 14.0 14.0 14.0 14.0 14.0 14.0 83.7 8.1 82.7 82.7 82.7 83.2 83.2 82.7
89.6 97.7
36.2 61.5
97.7 32.5 65.2
90.7 7.0
BalBal
97.797.7
PIB 97.715.4 22.1
12.8 18.2 PIB Polymer 8.8 13.7 OCP 5.8 9.3
EP P-ester 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3EP Inactive S 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0FM MoDTC 1.0FM Ethomeen 1.0FM Ethomeen 1.0AW Mixed ZDDP 0.5Det Ca-Sulphon 0.5Disp PIBSA/PAM 1.0
100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0
VMPAMA
Total, wt%
Raw Material
Base Oils
Group IV
Group III
Group III+
Group I
Group II
Ester
Varying base oil viscosity
Varying base oil type
All contain same mild AW/EPFM
10
Typical Data
ARKL EOTTIst-KV40°C
Ist-KV100°C
HTHS150°C
FilmThickness
80°C
FilmThickness
100°C
FilmThickness
120°C
HFRR 80°C full avg
HFRR100°C full
avg
HFRR120°C full
avg
HFRR80°C
2nd half
HFRR100°C
2nd half
102.55 5.167 1.730 0.72 28.5 21.9 16.6 0.126 0.120 0.105 0.124 0.117
101.9 28.11 5.500 1.85 66.3 47.6 37.9 0.116 0.108 0.105 0.113 0.109
106.75 43.67 7.462 2.38 84.5 58.4 44.2 0.114 0.116 0.103 0.110 0.114
114.15 92.11 12.23 3.53 131.6 83.8 62.7 0.105 0.110 0.101 0.100 0.107
109.6 22.33 5.515 2.03 51.8 40.1 33.0 0.121 0.115 0.105 0.118 0.115
107.45 18.83 5.548 2.17 50.4 40.3 36.6 0.127 0.117 0.104 0.126 0.117
109.15 24.09 5.519 1.92 59.1 42.8 31.5 0.121 0.117 0.102 0.120 0.116
109 23.84 5.432 1.89 63.4 44.1 30.8 0.122 0.118 0.105 0.122 0.118
114.3 32.8 7.420 2.70 58.2 45.0 37.5 0.117 0.113 0.105 0.112 0.114
112 24.19 7.548 2.90 51.4 36.9 28.2 0.123 0.117 0.107 0.122 0.117
113.5 34.98 7.534 2.54 61.4 47.9 32.6 0.114 0.115 0.108 0.111 0.116
113.9 35.30 7.508 2.55 58.4 45.5 33.8 0.123 0.111 0.108 0.123 0.112
112.65 28.57 5.501 1.90 68.1 47.4 37.7 0.117 0.117 0.099 0.114 0.114
109.45 28.93 5.515 1.88 73.7 51.5 37.1 0.119 0.107 0.099 0.117 0.101
108.5 27.21 5.510 1.90 65.9 48.6 40.1 0.117 0.101 0.104 0.114 0.101
128.75 32.85 5.514 1.90 75.5 49.5 35.8 0.122 0.105 0.104 0.121 0.099
117.55 32.2 5.512 1.91 71.3 41.0 29.5 0.125 0.109 0.109 0.123 0.109
113.4 27.53 5.420 2.08 68.3 47.9 34.8 0.123 0.123 0.113 0.121 0.123
105.3 28.08 5.616 2.23 67.3 43.2 33.6 0.111 0.107 0.113 0.110 0.105
142.6 29.41 4.759 1.63 84.5 60.5 40.2 0.126 0.125 0.107 0.125 0.123
100.95 28.25 5.501 1.83 73.2 50.4 39.5 0.087 0.107 0.105 0.093 0.107
ABCDEFGH
IJKLMNOPQRSTU
11
Regression Analysis
§ Used to correlate a dependent with independent variables
(ARKL EOTT) (traction, viscosity etc.)
0 = no correlation, 1 = perfect correlation
§ Use least square method§ Coefficient of Determination R2
Gives a measure of how well the model fits the data
EOTT = a0 + a1property1+ a2property2
f(Lubricant properties)
EOTT
12
Single Variable Correlation:
x1 a0 a1 R2
MTM80_0p23 89.80222847 2573.533687 0.748461928
MTM80_0p40 95.25909175 1011.452036 0.737730047
MTM80_0p30 94.0332151 1465.206419 0.730711558
MTM100_0p94 96.8654993 714.8223828 0.727383016
MTM100_1p25 95.95298755 659.8727791 0.726205294
MTM100_0p71 96.74106583 906.06729 0.722638212
MTM80_0p54 95.35478246 779.0137892 0.717628918
MTM80_0p71 94.60446166 679.3020485 0.707590428
Best correlation of all properties is given by MTM traction at 0.23% SRR
USV120_6 104.136 1.909207 0.02672
VI 113.9738 -0.022 0.021682
HTHS150 104.6033 2.725256 0.020479
KV100 105.501 0.795776 0.020421
USV120_10 105.9526 1.471658 0.010239
USV120_9 106.2973 1.349455 0.009052
EHD120 106.8971 0.08901 0.005247
SH 111.711 -0.93947 0.001353
X 110.5928 -2.69815 0.001221
1.
2.
3.
4.
5.
6.
7.
8.
133.
134.
135.
136.
137.
138.
139.
140.
141.
….
EOTT = 2573.5MTM + 89.802R² = 0.7485
80
90
100
110
120
130
140
150
0 0.005 0.01 0.015 0.02 0.025
AR
KL
EO
TT
MTM Traction at s.r.r 0.227 % and 80 °C13
x1 a0 a1 R2
MTM80_0p227 89.80222847 2573.533687 0.748461928
MTM80_0p402 95.25909175 1011.452036 0.737730047
MTM80_0p300 94.0332151 1465.206419 0.730711558
MTM100_0p940 96.8654993 714.8223828 0.727383016
MTM100_1p25 95.95298755 659.8727791 0.726205294
MTM100_0p708 96.74106583 906.06729 0.722638212
MTM80_0p536 95.35478246 779.0137892 0.717628918
MTM80_0p708 94.60446166 679.3020485 0.707590428
MTM120_0p708 98.66837256 1352.367819 0.702005429
MTM120_12p1 84.901509 738.5822122 0.699573836
MTM120_0p940 100.306924 818.7776334 0.69695606
MTM120_1p25 99.47771801 712.6159549 0.696731289
MTM80_0p940 93.55617951 636.0283262 0.695639703
MTM100_1p65 95.09044042 633.8616321 0.695463915
MTM120_1p65 98.3632249 671.9698971 0.694444573
MTM120_6p84 90.54890262 663.5732278 0.692378544
MTM80_1p25 92.21473327 623.3775555 0.689351191
MTM80_1p65 90.77373291 619.7931028 0.688704741
MTM EHL traction values all show better correlation than anything else
Single Variable Correlation:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
14
Effect of Traction Conditions
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0 10 20 30 40 50
R2
Slide-Roll Ratio
80 ̊C
100 ̊C
120 ̊C
(%)
15
Single Variable Correlation:
0.55
0.6
0.65
0.7
0.75
0.8
0 1 2 3 4
R2
n where (MTM Traction at s.r.r 0.227 % and 80 °C)n
(1.5, 0.757)
1.5
16
Two Variables:
x1 x2 a0 a1 a2 R2
MTM80_0p23 HTHS150 81.19433075 2619.827 3.975528 0.7918
MTM80_0p23 VI 82.17390922 2859.605 0.033959 0.78582
MTM80_0p23 HFRR100_2 78.88900473 2520.981 99.29387 0.784124
MTM80_0p23 HFRR100Avg 79.011687 2501.824 98.31748 0.779726
MTM80_0p23 USV120_1 83.47934638 2571.287 2.027124 0.778843
MTM80_0p23 HFRR120_2 77.11365954 2568.247 121.3063 0.778776
MTM80_0p23 KV100 84.09258032 2588.118 0.936954 0.776747
MTM80_0p23 USV120_9 80.81273629 2648.279 2.639776 0.776448
MTM80_0p23 USV120_2 83.77580451 2567.235 1.927672 0.776338
MTM80_0p23 HFRR120 76.38001828 2548.39 127.6703 0.775989
MTM80_0p23 USV120_10 80.84751076 2642.125 2.668215 0.775542
MTM80_0p23 USV120_3 83.82083735 2567.023 1.907671 0.775092
MTM80_0p23 USV120_4 84.06674681 2565.056 1.827617 0.773324
MTM80_0p23 USV100_1 84.84536893 2563.281 1.116792 0.771528
MTM80_0p23 USV120_5 84.25958767 2564.377 1.755492 0.770975
MTM80_0p23 USV120_7 84.5450449 2559.579 1.69528 0.768662
MTM80_0p23 X 90.78267172 2625.363 -11.019 0.768522
MTM80_0p23 USV120_6 84.60752177 2562.659 1.648608 0.768372
17
Two Variables
R² = 0.7918
90
100
110
120
130
140
150
90 100 110 120 130 140 150
AR
KL
EOTT
81.2 + 2620MTM + 3.98HTHS
18
Three Variables:
x1 x2 x3 a0 a1 a2 a3 R2MTM80_0p23 HTHS_150 EHD100 85.24193 3009.594 7.614183 -0.30135 0.849678
MTM80_0p23 HTHS_150 EHD120 86.58515 2797.654 7.380303 -0.36775 0.847424
MTM80_0p23 HTHS_150 EHD80 82.21859 3010.283 7.303062 -0.15854 0.837438
MTM80_0p23 HTHS_150 USV80_10 83.59428 2843.677 9.026733 -2.35551 0.833138
MTM80_0p23 HTHS_150 USV80_9 83.26994 2837.645 8.978108 -2.23671 0.830736
MTM80_0p23 HTHS_150 VI 72.94138 2903.836 5.328488 0.018119 0.829391
MTM80_0p23 HTHS_150 TC 120.993 2160.057 7.082792 -315.899 0.827302
MTM80_0p23 HTHS_150 USV120_9 74.54979 2841.25 9.369743 -2.17994 0.826288
MTM80_0p23 HTHS_150 USV120_10 74.66873 2843.599 9.265182 -2.1725 0.826169
MTM80_0p23 HTHS_150 USV80_7 79.84133 2769.779 8.60228 -1.38763 0.821321
MTM80_0p23 HTHS_150 HFRR100_2 71.89213 2568.642 3.686029 90.33923 0.82109
MTM80_0p23 HTHS_150 HFRR120_2 69.01778 2613.804 3.89987 117.9774 0.820457
MTM80_0p23 HTHS_150 USV80_8 79.97641 2776.004 8.556593 -1.43552 0.820429
MTM80_0p23 HTHS_150 USV80_6 79.53441 2767.978 8.495794 -1.27913 0.818285
MTM80_0p23 HTHS_150 HFRR100Avg 71.76872 2551.291 3.749032 90.34939 0.818061
MTM80_0p23 HTHS_150 HFRR120 68.6333 2594.512 3.861866 121.8198 0.816827
MTM80_0p23 HTHS_150 USV80_4 79.51007 2750.532 8.423449 -1.22393 0.814831
MTM80_0p23 HTHS_150 USV80_5 79.45059 2746.565 8.222816 -1.15379 0.814052
R² = 0.8497
90
100
110
120
130
140
150
90 100 110 120 130 140 150
AR
KL
EOTT
85.2 + 3010MTM + 7.61HTHS - 0.301EHL
19
ARKL EOTT = 81 + 21MTMnorm + 8.2HTHSnorm
Discussion
Low MTM traction,τ, and low HTHS gives low ARKL EOTT
§ In previous work carried out by Evonik, low EOTT was correlated withlow viscosity and high VI.(Dardin, A., et al., “Influence of Polyalkylmethacrylate Viscosity Index Improvers on the Efficiency of Lubricants,” SAE Technical Paper 2003-01-1967, 2003.)
§ Both are in agreement, since, (for same type of base oil):
Higher η Higher α Higher τ and vice versa
Lower VI Higher α Higher τ and vice versa
§ Also, some polymer molecules, e.g. PAMA, are flexible and so have low τ
R2 = 0.792
20
l Lower Traction
= Energy Savings
= Lower Oil Temperature
Trac
tion C
oef
fici
ent
@60
°C
Mean Speed, mm/s
0
0.01
0.02
0.03
0.04
0.05
0.06
0 1000 2000 3000 4000 5000
Group I & II
Group III
PAO
Traction Coefficient – across and within base oil group
21
Trac
tion C
oef
fici
ent@
60°C
Slide Rolling Ratio, % @1000mm/s0
0.01
0.02
0.03
0.04
0.05
0.06
0 10 20 30 40 50 60
PAO
22
l Lower Traction
= Energy Savings
= Lower Oil Temperature
Group I & II
Group III
Traction Coefficient – across and within base oil group
22
Conclusions
§ EHD traction is by far the most important lubricant property in determining EOTT in the ARKL test.
§ Viscosity at high shear rate also impacts slightly on ARKL EOTT.
§ This suggests that ARKL EOTT originates primarily from friction within the bearing/raceway contacts and secondarily from the viscous shear of lubricant in the inlet and sides of the contacts.
§ Boundary friction and thermal properties make little contribution.
§ Since ARKL EOTT is believed to correlate with transmission efficiency, the findings may be transferable to the design of transmission fluids
ARKL EOTT =81.2 + 2620MTM + 3.98HTHS
API group III, III+ and PAO are preferred base stocks in designing transmission fluid with energy efficiency
23
Acknowledgements
Coefficient of determination
The coefficient of determination is:
• The percentage of the variation that can be explained by the regression equation.• The explained variation divided by the total variation
Every sample has some variation in it (unless all the values are identical, and that's unlikely to happen).
The total variation is made up of two parts, the part that can be explained by the regression equation and the part that can't be explained by the regression equation.
The ratio of the explained variation to the total variation is a measure of how good the regression line is. If the regression line passed through every point on the scatter plot exactly, it would be able to explain all of the variation. The further the line is from the points, the less it is able to explain.