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.