Analysis of fluid film formation between contacting compliant solids

Industrial compliant surface bearings and dynamic seals sometimes suffer se vere damage during start up after long rest, and a similar problem is predi cted for joint prostheses with compliant artificial articular cartilage. In this study, fluid film developing between compliant solids by sliding is a nalyzed numerically using a modified elasto-hydrodynamic lubrication theory which permits direct contact and cavitation. The result shows that the for efront of the fluid film moves in the same direction with sliding while dir ect contact remains until the fluid film takes the place of the entire cont acting region. With an increase of compliance and the Stribeck number, the velocity of fluid film formation increases and approaches half of the slidi ng speed but never exceeds it. In other words, the minimum sliding distance for non-contacting condition is twice the initial contact width. Therefore , when a heavy load is applied to compliant surface bearings, the contact w idth will be large and the unlubricated region will remain long. Since a co mpliant material is not as strong as hard materials, it may be damaged duri ng start up after a long rest. As the study has thus clarified the mechanis m of damage which compliant surfaces experience during start up, effective methods to protect surfaces from damage will be found according to the theo retical backgrounds. (C) 1999 Elsevier Science Ltd. All rights reserved.