A model is described to simulate expressive wrinkles in 3D facial animation and skin aging. A plastic-visco-elastic skin surface is defined that can slide over an underlying layer. This layer constrains the skin surface by the spring force that simulates the connective fat tissue between skin and muscles. Muscle masks are constructed to characterize the muscular contractions that offer the tension to the skin and provide the facial movement. By choosing proper parameters for this physically based model, wrinkles in facial animation and skin aging are simulated through the elastic process assembled with visco and plastic units.