Lambda ratio / film parameter

Notes and assumptions

The film parameter is useful for screening, but TriboNet’s EHD film-thickness guidance stresses that roughness and operating conditions must be reported honestly. A lambda value alone does not summarize wear, friction, starvation, contamination, sliding, or transient starts.

• Use minimum film thickness when the goal is surface-separation screening.
• Use RMS roughness values from comparable measurement methods and directions.
• The detailed TriboNet article also lists overlapping classical regime ranges: partial lubrication around 1 to 5, elastohydrodynamic around 3 to 10, and hydrodynamic around 5 to 100.
• Related TriboNet references: EHD Film Thickness Explained and EHL Film Thickness in Practice.