Computer Simulation of Facial Expression. 2nd Report, Identification of In Vivo Mechanical Properties and Analysis of Wrinkling and Finite Deformation of Hyper Elastic Soft Tissue by the Finite-Element Method.

Abstract

It is the purpose of the investigation to clarify mechanisms of facial expressions and formation of wrinkles on a face with a hyper elastic skin. In the present study, parameters of mechanical properties are identified by using the results of both in vivo experiments and calculation by the finite-element method (FEM). We also carried out in vitro experiments for formation of wrinkles with a rabbit skin and conducted analysis of wrinkles, in which formulations of hyper elasticity and large deformation for a skin-fat composite were incrementally made as buckling and post-buckling problems, using the same model of the experiments. Furthermore, we carried out in vivo experiments and FEM analysis of wrinkles in the forehead skin of a human being. The validity of the analysis method proposed in this study and the usefulness of the developed FEM programs are demonstrated by comparison with the series of experimental results.