![]() ![]() If the lubricant is too viscous, it will require a large amount of energy to move (as in honey) if it is too thin, the surfaces will come in contact and friction will increase. Generally, the least viscous lubricant which still forces the two moving surfaces apart to achieve " fluid bearing" conditions is desired. ![]() The viscosity of a lubricant is closely related to its ability to reduce friction in solid body contacts. More is the Friction more is the amount of force required to move the layers this is. The internal forces or Friction of Fluid comes into play when one layer of Fluid is subjected to move over another layer. It is a measure of the internal forces of a Fluid. The VI was originally measured on a scale from 0 to 100 however, advancements in lubrication science have led to the development of oils with much higher VIs. Viscosity is the tendency of a Fluid to resist any change in its shape or Motion. g is a constant, which is 9.8 m/s2 (acceleration due to gravity) and v is the velocity of the ball falling through the liquid, and a is the radius of the ball. The higher the VI, the more stable the viscosity remains over some temperature range. The final equation youll need to calculate the liquids viscosity is this: Viscosity (2 x (ball density liquid density) x g x a2) รท (9 x v). The lower the VI, the more the viscosity is affected by changes in temperature. It is mostly used to characterize the viscosity-temperature behavior of lubricating oils. ![]() The viscosity index ( VI) is an arbitrary, unit-less measure of a fluid's change in viscosity relative to temperature change. ![]()
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