The pressure viscosity coefficient α is used for the calculation of lubricant film thickness. If the film thickness should not be calculated, you can just enter zero.
According to (ISO/TR 1281-2, 2008) the pressure viscosity coefficient α can be calculated by the kinematic viscosity ν0 in cm2/s as
To calculate the reference viscosity ν1, a value of using ν in mm2/s and α in mm2/N is used according (Baalmann, 1994).
In the software, the proposal according (AGMA 925, 2003) is used, because different oil types are considered. The pressure viscosity coefficient is calculated as , where ηM is the dynamic viscosity at operating temperature. The factors k and s are given for different lubricant types as shown in the following table:
Oil type |
k |
s |
Mineral oil |
0.010471 |
0.1348 |
PAO based synthetic non-VI improved oil |
0.010326 |
0.0507 |
PAG based synthetic |
0.0047 |
0.1572 |
This formula is used if a lubricant from the list is selected. If ‘own input’ is selected, either the formula according to (ISO/TR 1281-2, 2008) 11.8 or according to (AGMA 925, 2003) or a direct input can be selected using the 
-button next to the input field.
