Stretch effects in radial lip seals

Stretch effects in the surface may occur when full film lubricated surfaces experience tangential deformations. It is observed that a stationary rubber lip seal mounted against a sliding counterpart shows oscillatory displacements in the lip’s flattened contact with time. Beyond a critical value this oscillation speed yield a load carrying capacity which is larger than entrainment effects. Displacements of lip impurities in the contact between an axial lip seal and a flat optical glass disc were followed through a microscope and a camera, using white light, and analysed using image processing software. It was concluded that for this lip seal the stretch effect contributes to the film thickness, but that its contribution is an order of magnitude less than the roughness induced entrainment effect.