Soft Elasto-Hydrodynamic Lubrication

This article examines the use of ferrofluids to control starvation in lubricated contacts. Starvation in a ball–plate contact is experimentally studied under sliding–rolling conditions using a Mini Traction Machine (MTM). Friction is measured and the experimental results are presented in the form of Stribeck curves. The volume of lubricant is controlled in such a way that no free bulk oil is present in the vicinity of the contact. An abrupt change in the slope of the Stribeck curve in the Hydrodynamic Lubrication zone is interpreted as the onset of starvation. It is then shown that the use of ferrofluids in the presence of a magnetic field distribution can change the conditions at which this onset of starvation occurs. Different magnetic field distributions are tested for different values of load and ferrofluid viscosity. It is proposed that ferrofluid lubricants in conjunction with a suitably positioned magnetic field can be used to promote replenishment, and thus control and reduce lubricant starvation.