Pressure viscosity sensitivity
Dynamic viscosity at atmospheric pressure η
0
10
-3
Pa
·s
Pressure viscosity coefficient α
10
-9
1/Pa
Pressure of interest p
10
6
Pa
Viscosity ratio Barus η/η
0
-
Viscosity ratio Roelands η/η
0
-
The Barus equation is accurate only for pressures up to 0.1 GPa. For higher pressure the Roelands equation gives the best result.
Lubricants
Dynamic visc η0
[mPa
·s]
Pressure-visc
coeff α [10
-9
m
2
/N]
30
60
100
30
60
100
High VI oils
Light machine oil
38
12.1
5.3
-
18.4
13.4
Heavy machine oil
153
34
9.1
23.7
20.5
15.8
Heavy machine oil
250
50.5
12.6
25.0
21.3
17.6
Cylinder oil
810
135
26.8
34.0
28.0
22.0
Medium VI oils
Spindle oil
18.6
6.3
2.4
20
16
13
Light machine oil
45
12
3.9
28
20
16
Medicinal white oil
107
23.3
6.4
29.6
22.8
17.8
Heavy machine oil
122
26.3
7.3
27.0
21.6
17.5
Heavy machine oil
171
31
7.5
28
23
18
Low VI oils
Spindle oil
30.7
8.6
3.1
25.7
20.3
15.4
Heavy machine oil
165
30.0
6.8
33.0
23.8
16.0
Heavy machine oil
310
44.2
9.4
34.6
26.3
19.5
Cylinder oil
2000
180
24.0
41.5
29.4
25.0
Other fluids / lub's
Water
0.90
0.47
0.28
0
0
0
Castor oil
360
80
18.0
15.9
14.4
12.3
Glycerol
535
73
13.9
5.9
5.5
3.6
PP glycol 750
82.3
17.8
PP glycol 1500
177
17.4
Tri-arylphosphate ester
25.5
31.6
Table adapted from page 21 Engineering Tribology Second Edition
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