Theory 060/Engineering & Materials /Tribology
Starvation Begins at a Film Ratio
Starvation is blamed on too little oil. It can happen with a full sump.
Lubricant starvation begins when the film thickness ratio falls below a critical value set by the contact's inlet geometry, so starvation can occur at high speed with plenty of oil present.
01The evidence
Starvation has been observed at high entrainment speeds despite adequate supply, with the film collapsing where replenishment cannot keep pace.
02The tension
Starvation is treated as a supply problem, with the remedy being more oil or slower speed. The inlet replenishment time is rarely modelled as the constraint.
03The mechanism
Oil must be replenished at the inlet between passes. At high speed, the time available falls and the meniscus cannot reform, so the inlet film thins even though oil is abundant elsewhere.
That makes starvation a function of the film thickness relative to the inlet gap, and predicts a critical speed at which starvation begins regardless of supply volume.
04What this is not
Supply models add oil. This adds a replenishment constraint, which predicts starvation at high speed with full supply.
05Predictions
- P1Starvation should begin at a critical speed.
- P2More oil should not prevent it beyond a point.
- P3Inlet geometry should shift the threshold.
06Refutation
Starvation absent at high speed with abundant supply would remove the replenishment constraint.
07What it changes
It would change high-speed bearing design.