Gokhan
Thread starter
Originally Posted by Shannow
The question was with regard to "film strength".
So your thread title mentions ring wear, but neither of the papers offered that as a suggestion or conclusion?
Oil-film strength means the viscosity of the oil under pressure at a given temperature. So, it's the pressure - viscosity-coefficient-corrected (PVC-corrected) viscosity. You can also take the PVC to be the oil-film strength but remember to account for the ambient-pressure viscosity.
The main reason why the cavitation is studied is that it could cause wear or damage. That's why they are trying to minimize it. This is mentioned in the introduction of most papers, such as the beginning of the second paper:
"Elastohydrodynamic lubricated (EHL) machine elements working under reciprocating motions are very common in mechanical applications. The lubrication state of these machine elements is often influenced by cavitation phenomena, because after reversal of the rolling direction the outlet region becomes the new inlet region. This means that the cavity produced in the outlet region can be entrained into the conjunction, and break the fluid film, which may lead to surface failure."
More explanation of the phenomenon:
"The cavitation region shrinks considerably in the vicinity of the dead centres. However, it partly survives beyond the dead-centre reversal as a confined bubble at the leading edge of the contact. Although this bubble quickly shrinks being absorbed by the lubricant film, while located at the inlet, it depletes the available lubricant supply leading to starvation. Quickly after the dead centre, a new cavitation region forms at the trailing edge of the contact. Although these two cavitation regions only coexist for a brief period, together with a very low entrainment motion and high contact loads, lead to thinner films and higher friction forces."
Cavitation-induced starvation for piston-ring/liner tribological conjunction
The question was with regard to "film strength".
So your thread title mentions ring wear, but neither of the papers offered that as a suggestion or conclusion?
Oil-film strength means the viscosity of the oil under pressure at a given temperature. So, it's the pressure - viscosity-coefficient-corrected (PVC-corrected) viscosity. You can also take the PVC to be the oil-film strength but remember to account for the ambient-pressure viscosity.
The main reason why the cavitation is studied is that it could cause wear or damage. That's why they are trying to minimize it. This is mentioned in the introduction of most papers, such as the beginning of the second paper:
"Elastohydrodynamic lubricated (EHL) machine elements working under reciprocating motions are very common in mechanical applications. The lubrication state of these machine elements is often influenced by cavitation phenomena, because after reversal of the rolling direction the outlet region becomes the new inlet region. This means that the cavity produced in the outlet region can be entrained into the conjunction, and break the fluid film, which may lead to surface failure."
More explanation of the phenomenon:
"The cavitation region shrinks considerably in the vicinity of the dead centres. However, it partly survives beyond the dead-centre reversal as a confined bubble at the leading edge of the contact. Although this bubble quickly shrinks being absorbed by the lubricant film, while located at the inlet, it depletes the available lubricant supply leading to starvation. Quickly after the dead centre, a new cavitation region forms at the trailing edge of the contact. Although these two cavitation regions only coexist for a brief period, together with a very low entrainment motion and high contact loads, lead to thinner films and higher friction forces."
Cavitation-induced starvation for piston-ring/liner tribological conjunction