Study of lubricated impact using optical interferometry

An experimental study of lubricated impacts between a steel ball and a flat glass surface has been performed. The experimental set-up consists of a Ø70 mm ball mounted on a pendulum which impacts onto a lubricated glass disc. The contact region is studied by means of optical interferometry using a monochromatic light source, a microscope and a high-speed video recording equipment.

The lubricants are of PAO type and the viscosity ranges from 27 to 2600 mm² s⁻¹ at the test temperature. The impact velocity is varied between 0.08 and 0.29 m s⁻¹.

A dimple occurs at the centre of the contact where the lubricant is trapped. The influence of viscosity and impact velocity on the dimple's depth and diameter is studied.