EFFECTS OF CARTILAGE STIFFNESS AND VISCOSITY ON A NON-POROUS COMPLIANT BEARING LUBRICATION MODEL FOR LIVING JOINTS

There are several possible lubrication mechanisms for living joints. One such mechanism, the squeeze film compliant bearing, is examined through the use of a computational model. The model is based on a finite element representation for the compliant surfaces. The lubricant is described by Reynold's equation. A minimization technique provides solutions to this inherently nonlinear problem, and alleviates difficulties in numerical convergence. In earlier work, the results of this model showed good correlation with both numerical results of another model and laboratory measurements for film thickness of a compliant sphere approaching a glass plate. In this paper, the model is used as a basis for conducting a parametric study of the influence of cartilage modulus and fluid viscosity on the lubrication characteristics. A load of 445 N was applied in the studies. Results of the compliant system are compared with those for a system with rigid surfaces representing a prosthesis. Based on the results obtained by the model and the ranges of parameters considered, it was found that changes in viscosity of the lubricant had a greater influence than changes in the cartilage modulus. The lubrication qualities of the compliant system were superior to those of the system with rigid surfaces if the same lubricant properties were used. However, lubrication viscosities could be found such that a compliant system with a low viscosity has poorer lubrication properties than a rigid system with a higher viscosity. © 1979.