A contact finite element formulation for biological soft hydrated tissues

As part of the highly complex numerical simulation of human joints, a finite element formulation for contact between layers of articular cartilage has been developed. A biphasic description of the cartilage is used, where the material is considered to be a porous, permeable solid matrix with fluid flowing through it. Governing equations and contact boundary conditions are summarized for this material before developing the finite element formulation from a Galerkin weighted residual statement. Lagrange multipliers are introduced to enforce the two kinetic continuity equations across the contact surface, and an iterative scheme is employed to determine the current contact area. Numerical examples are presented which demonstrate both that the appropriate continuity across the contact surface is enforced and that the contact surface definition is accurate.