An improved finite element contact model for anatomical simulations

This work focuses on the simulation of mechanical contact between nonlinearly elastic objects such as the components of the human body. The computation of the reaction forces that act on the contact surfaces (contact forces) is the key for designing a reliable contact handling algorithm. In traditional methods, contact forces are often defined as discontinuous functions of deformation, which leads to poor convergence characteristics. This problem becomes especially serious in areas with complicated self-contact such as skin folds.; I introduce a novel penalty method for finite element simulation based on the concept of material depth, which is the distance between a particle inside an object and the object's boundary. By linearly interpolating pre-computed material depths at node points, contact forces can be analytically integrated over contact surfaces without raising the computational cost. The continuity achieved by this formulation reduces oscillation and artificial acceleration resulting in a more reliable simulation algorithm.; This algorithm is implemented as part of an implicit finite element program for static, quasistatic and dynamic analysis of nonlinear viscoelastic solids. I demonstrate its effectiveness in an animation showing realistic effects such as folding skin and sliding contacts of tissues involved in knee flexion. The finite element model of the leg and its internal structures was derived from the Visible Human dataset.; With this method, it is now easier for engineers and scientists to simulate a wide variety of anatomical and tissue structures such as multiple adjacent organs and biomaterials made of intertwined protein fibers. This method also helps animators to use more anatomically accurate human and animal models to enhance the realism of the generated images.